Merge branch 'for-next' into for-linus

Merge 5.16-devel branch for upstreaming

Signed-off-by: Takashi Iwai <tiwai@suse.de>

48 files changed, 1606 insertions, 452 deletions

diff --git a/sound/core/Makefile b/sound/core/Makefile
index d774792850f3..350d704ced98 100644
--- a/sound/core/Makefile
+++ b/sound/core/Makefile
@@ -9,7 +9,9 @@ ifneq ($(CONFIG_SND_PROC_FS),)
 snd-y += info.o
 snd-$(CONFIG_SND_OSSEMUL) += info_oss.o
 endif
+ifneq ($(CONFIG_M68K),y)
 snd-$(CONFIG_ISA_DMA_API) += isadma.o
+endif
 snd-$(CONFIG_SND_OSSEMUL) += sound_oss.o
 snd-$(CONFIG_SND_VMASTER) += vmaster.o
 snd-$(CONFIG_SND_JACK)	  += ctljack.o jack.o
@@ -17,7 +19,6 @@ snd-$(CONFIG_SND_JACK)	  += ctljack.o jack.o
 snd-pcm-y := pcm.o pcm_native.o pcm_lib.o pcm_misc.o \
 		pcm_memory.o memalloc.o
 snd-pcm-$(CONFIG_SND_PCM_TIMER) += pcm_timer.o
-snd-pcm-$(CONFIG_SND_DMA_SGBUF) += sgbuf.o
 snd-pcm-$(CONFIG_SND_PCM_ELD) += pcm_drm_eld.o
 snd-pcm-$(CONFIG_SND_PCM_IEC958) += pcm_iec958.o
 
diff --git a/sound/core/memalloc.c b/sound/core/memalloc.c
index c7c943c661e6..99cd0f67daa1 100644
--- a/sound/core/memalloc.c
+++ b/sound/core/memalloc.c
@@ -10,6 +10,7 @@
 #include <linux/mm.h>
 #include <linux/dma-mapping.h>
 #include <linux/genalloc.h>
+#include <linux/highmem.h>
 #include <linux/vmalloc.h>
 #ifdef CONFIG_X86
 #include <asm/set_memory.h>
@@ -39,9 +40,11 @@ static void *__snd_dma_alloc_pages(struct snd_dma_buffer *dmab, size_t size)
 }
 
 /**
- * snd_dma_alloc_pages - allocate the buffer area according to the given type
+ * snd_dma_alloc_dir_pages - allocate the buffer area according to the given
+ *	type and direction
  * @type: the DMA buffer type
  * @device: the device pointer
+ * @dir: DMA direction
  * @size: the buffer size to allocate
  * @dmab: buffer allocation record to store the allocated data
  *
@@ -51,8 +54,9 @@ static void *__snd_dma_alloc_pages(struct snd_dma_buffer *dmab, size_t size)
  * Return: Zero if the buffer with the given size is allocated successfully,
  * otherwise a negative value on error.
  */
-int snd_dma_alloc_pages(int type, struct device *device, size_t size,
-			struct snd_dma_buffer *dmab)
+int snd_dma_alloc_dir_pages(int type, struct device *device,
+			    enum dma_data_direction dir, size_t size,
+			    struct snd_dma_buffer *dmab)
 {
 	if (WARN_ON(!size))
 		return -ENXIO;
@@ -62,6 +66,7 @@ int snd_dma_alloc_pages(int type, struct device *device, size_t size,
 	size = PAGE_ALIGN(size);
 	dmab->dev.type = type;
 	dmab->dev.dev = device;
+	dmab->dev.dir = dir;
 	dmab->bytes = 0;
 	dmab->addr = 0;
 	dmab->private_data = NULL;
@@ -71,7 +76,7 @@ int snd_dma_alloc_pages(int type, struct device *device, size_t size,
 	dmab->bytes = size;
 	return 0;
 }
-EXPORT_SYMBOL(snd_dma_alloc_pages);
+EXPORT_SYMBOL(snd_dma_alloc_dir_pages);
 
 /**
  * snd_dma_alloc_pages_fallback - allocate the buffer area according to the given type with fallback
@@ -129,9 +134,10 @@ static void __snd_release_pages(struct device *dev, void *res)
 }
 
 /**
- * snd_devm_alloc_pages - allocate the buffer and manage with devres
+ * snd_devm_alloc_dir_pages - allocate the buffer and manage with devres
  * @dev: the device pointer
  * @type: the DMA buffer type
+ * @dir: DMA direction
  * @size: the buffer size to allocate
  *
  * Allocate buffer pages depending on the given type and manage using devres.
@@ -144,7 +150,8 @@ static void __snd_release_pages(struct device *dev, void *res)
  * The function returns the snd_dma_buffer object at success, or NULL if failed.
  */
 struct snd_dma_buffer *
-snd_devm_alloc_pages(struct device *dev, int type, size_t size)
+snd_devm_alloc_dir_pages(struct device *dev, int type,
+			 enum dma_data_direction dir, size_t size)
 {
 	struct snd_dma_buffer *dmab;
 	int err;
@@ -157,7 +164,7 @@ snd_devm_alloc_pages(struct device *dev, int type, size_t size)
 	if (!dmab)
 		return NULL;
 
-	err = snd_dma_alloc_pages(type, dev, size, dmab);
+	err = snd_dma_alloc_dir_pages(type, dev, dir, size, dmab);
 	if (err < 0) {
 		devres_free(dmab);
 		return NULL;
@@ -166,7 +173,7 @@ snd_devm_alloc_pages(struct device *dev, int type, size_t size)
 	devres_add(dev, dmab);
 	return dmab;
 }
-EXPORT_SYMBOL_GPL(snd_devm_alloc_pages);
+EXPORT_SYMBOL_GPL(snd_devm_alloc_dir_pages);
 
 /**
  * snd_dma_buffer_mmap - perform mmap of the given DMA buffer
@@ -185,6 +192,26 @@ int snd_dma_buffer_mmap(struct snd_dma_buffer *dmab,
 }
 EXPORT_SYMBOL(snd_dma_buffer_mmap);
 
+#ifdef CONFIG_HAS_DMA
+/**
+ * snd_dma_buffer_sync - sync DMA buffer between CPU and device
+ * @dmab: buffer allocation information
+ * @mode: sync mode
+ */
+void snd_dma_buffer_sync(struct snd_dma_buffer *dmab,
+			 enum snd_dma_sync_mode mode)
+{
+	const struct snd_malloc_ops *ops;
+
+	if (!dmab || !dmab->dev.need_sync)
+		return;
+	ops = snd_dma_get_ops(dmab);
+	if (ops && ops->sync)
+		ops->sync(dmab, mode);
+}
+EXPORT_SYMBOL_GPL(snd_dma_buffer_sync);
+#endif /* CONFIG_HAS_DMA */
+
 /**
  * snd_sgbuf_get_addr - return the physical address at the corresponding offset
  * @dmab: buffer allocation information
@@ -468,6 +495,161 @@ static const struct snd_malloc_ops snd_dma_wc_ops = {
 	.mmap = snd_dma_wc_mmap,
 };
 #endif /* CONFIG_X86 */
+
+/*
+ * Non-contiguous pages allocator
+ */
+static void *snd_dma_noncontig_alloc(struct snd_dma_buffer *dmab, size_t size)
+{
+	struct sg_table *sgt;
+	void *p;
+
+	sgt = dma_alloc_noncontiguous(dmab->dev.dev, size, dmab->dev.dir,
+				      DEFAULT_GFP, 0);
+	if (!sgt)
+		return NULL;
+	dmab->dev.need_sync = dma_need_sync(dmab->dev.dev, dmab->dev.dir);
+	p = dma_vmap_noncontiguous(dmab->dev.dev, size, sgt);
+	if (p)
+		dmab->private_data = sgt;
+	else
+		dma_free_noncontiguous(dmab->dev.dev, size, sgt, dmab->dev.dir);
+	return p;
+}
+
+static void snd_dma_noncontig_free(struct snd_dma_buffer *dmab)
+{
+	dma_vunmap_noncontiguous(dmab->dev.dev, dmab->area);
+	dma_free_noncontiguous(dmab->dev.dev, dmab->bytes, dmab->private_data,
+			       dmab->dev.dir);
+}
+
+static int snd_dma_noncontig_mmap(struct snd_dma_buffer *dmab,
+				  struct vm_area_struct *area)
+{
+	return dma_mmap_noncontiguous(dmab->dev.dev, area,
+				      dmab->bytes, dmab->private_data);
+}
+
+static void snd_dma_noncontig_sync(struct snd_dma_buffer *dmab,
+				   enum snd_dma_sync_mode mode)
+{
+	if (mode == SNDRV_DMA_SYNC_CPU) {
+		if (dmab->dev.dir == DMA_TO_DEVICE)
+			return;
+		dma_sync_sgtable_for_cpu(dmab->dev.dev, dmab->private_data,
+					 dmab->dev.dir);
+		invalidate_kernel_vmap_range(dmab->area, dmab->bytes);
+	} else {
+		if (dmab->dev.dir == DMA_FROM_DEVICE)
+			return;
+		flush_kernel_vmap_range(dmab->area, dmab->bytes);
+		dma_sync_sgtable_for_device(dmab->dev.dev, dmab->private_data,
+					    dmab->dev.dir);
+	}
+}
+
+static const struct snd_malloc_ops snd_dma_noncontig_ops = {
+	.alloc = snd_dma_noncontig_alloc,
+	.free = snd_dma_noncontig_free,
+	.mmap = snd_dma_noncontig_mmap,
+	.sync = snd_dma_noncontig_sync,
+	/* re-use vmalloc helpers for get_* ops */
+	.get_addr = snd_dma_vmalloc_get_addr,
+	.get_page = snd_dma_vmalloc_get_page,
+	.get_chunk_size = snd_dma_vmalloc_get_chunk_size,
+};
+
+/* x86-specific SG-buffer with WC pages */
+#ifdef CONFIG_SND_DMA_SGBUF
+#define vmalloc_to_virt(v) (unsigned long)page_to_virt(vmalloc_to_page(v))
+
+static void *snd_dma_sg_wc_alloc(struct snd_dma_buffer *dmab, size_t size)
+{
+	void *p = snd_dma_noncontig_alloc(dmab, size);
+	size_t ofs;
+
+	if (!p)
+		return NULL;
+	for (ofs = 0; ofs < size; ofs += PAGE_SIZE)
+		set_memory_uc(vmalloc_to_virt(p + ofs), 1);
+	return p;
+}
+
+static void snd_dma_sg_wc_free(struct snd_dma_buffer *dmab)
+{
+	size_t ofs;
+
+	for (ofs = 0; ofs < dmab->bytes; ofs += PAGE_SIZE)
+		set_memory_wb(vmalloc_to_virt(dmab->area + ofs), 1);
+	snd_dma_noncontig_free(dmab);
+}
+
+static int snd_dma_sg_wc_mmap(struct snd_dma_buffer *dmab,
+			      struct vm_area_struct *area)
+{
+	area->vm_page_prot = pgprot_writecombine(area->vm_page_prot);
+	/* FIXME: dma_mmap_noncontiguous() works? */
+	return -ENOENT; /* continue with the default mmap handler */
+}
+
+const struct snd_malloc_ops snd_dma_sg_wc_ops = {
+	.alloc = snd_dma_sg_wc_alloc,
+	.free = snd_dma_sg_wc_free,
+	.mmap = snd_dma_sg_wc_mmap,
+	.sync = snd_dma_noncontig_sync,
+	.get_addr = snd_dma_vmalloc_get_addr,
+	.get_page = snd_dma_vmalloc_get_page,
+	.get_chunk_size = snd_dma_vmalloc_get_chunk_size,
+};
+#endif /* CONFIG_SND_DMA_SGBUF */
+
+/*
+ * Non-coherent pages allocator
+ */
+static void *snd_dma_noncoherent_alloc(struct snd_dma_buffer *dmab, size_t size)
+{
+	dmab->dev.need_sync = dma_need_sync(dmab->dev.dev, dmab->dev.dir);
+	return dma_alloc_noncoherent(dmab->dev.dev, size, &dmab->addr,
+				     dmab->dev.dir, DEFAULT_GFP);
+}
+
+static void snd_dma_noncoherent_free(struct snd_dma_buffer *dmab)
+{
+	dma_free_noncoherent(dmab->dev.dev, dmab->bytes, dmab->area,
+			     dmab->addr, dmab->dev.dir);
+}
+
+static int snd_dma_noncoherent_mmap(struct snd_dma_buffer *dmab,
+				    struct vm_area_struct *area)
+{
+	area->vm_page_prot = vm_get_page_prot(area->vm_flags);
+	return dma_mmap_pages(dmab->dev.dev, area,
+			      area->vm_end - area->vm_start,
+			      virt_to_page(dmab->area));
+}
+
+static void snd_dma_noncoherent_sync(struct snd_dma_buffer *dmab,
+				     enum snd_dma_sync_mode mode)
+{
+	if (mode == SNDRV_DMA_SYNC_CPU) {
+		if (dmab->dev.dir != DMA_TO_DEVICE)
+			dma_sync_single_for_cpu(dmab->dev.dev, dmab->addr,
+						dmab->bytes, dmab->dev.dir);
+	} else {
+		if (dmab->dev.dir != DMA_FROM_DEVICE)
+			dma_sync_single_for_device(dmab->dev.dev, dmab->addr,
+						   dmab->bytes, dmab->dev.dir);
+	}
+}
+
+static const struct snd_malloc_ops snd_dma_noncoherent_ops = {
+	.alloc = snd_dma_noncoherent_alloc,
+	.free = snd_dma_noncoherent_free,
+	.mmap = snd_dma_noncoherent_mmap,
+	.sync = snd_dma_noncoherent_sync,
+};
+
 #endif /* CONFIG_HAS_DMA */
 
 /*
@@ -479,14 +661,15 @@ static const struct snd_malloc_ops *dma_ops[] = {
 #ifdef CONFIG_HAS_DMA
 	[SNDRV_DMA_TYPE_DEV] = &snd_dma_dev_ops,
 	[SNDRV_DMA_TYPE_DEV_WC] = &snd_dma_wc_ops,
+	[SNDRV_DMA_TYPE_NONCONTIG] = &snd_dma_noncontig_ops,
+	[SNDRV_DMA_TYPE_NONCOHERENT] = &snd_dma_noncoherent_ops,
+#ifdef CONFIG_SND_DMA_SGBUF
+	[SNDRV_DMA_TYPE_DEV_WC_SG] = &snd_dma_sg_wc_ops,
+#endif
 #ifdef CONFIG_GENERIC_ALLOCATOR
 	[SNDRV_DMA_TYPE_DEV_IRAM] = &snd_dma_iram_ops,
 #endif /* CONFIG_GENERIC_ALLOCATOR */
 #endif /* CONFIG_HAS_DMA */
-#ifdef CONFIG_SND_DMA_SGBUF
-	[SNDRV_DMA_TYPE_DEV_SG] = &snd_dma_sg_ops,
-	[SNDRV_DMA_TYPE_DEV_WC_SG] = &snd_dma_sg_ops,
-#endif
 };
 
 static const struct snd_malloc_ops *snd_dma_get_ops(struct snd_dma_buffer *dmab)
diff --git a/sound/core/memalloc_local.h b/sound/core/memalloc_local.h
index 9f2e0a608b49..a6f3a87194da 100644
--- a/sound/core/memalloc_local.h
+++ b/sound/core/memalloc_local.h
@@ -10,6 +10,7 @@ struct snd_malloc_ops {
 	unsigned int (*get_chunk_size)(struct snd_dma_buffer *dmab,
 				       unsigned int ofs, unsigned int size);
 	int (*mmap)(struct snd_dma_buffer *dmab, struct vm_area_struct *area);
+	void (*sync)(struct snd_dma_buffer *dmab, enum snd_dma_sync_mode mode);
 };
 
 #ifdef CONFIG_SND_DMA_SGBUF
diff --git a/sound/core/pcm_compat.c b/sound/core/pcm_compat.c
index dfe5a64e19d2..e4e176854ce7 100644
--- a/sound/core/pcm_compat.c
+++ b/sound/core/pcm_compat.c
@@ -453,6 +453,8 @@ static int snd_pcm_ioctl_sync_ptr_x32(struct snd_pcm_substream *substream,
 	sstatus.suspended_state = status->suspended_state;
 	sstatus.audio_tstamp = status->audio_tstamp;
 	snd_pcm_stream_unlock_irq(substream);
+	if (!(sflags & SNDRV_PCM_SYNC_PTR_APPL))
+		snd_pcm_dma_buffer_sync(substream, SNDRV_DMA_SYNC_DEVICE);
 	if (put_user(sstatus.state, &src->s.status.state) ||
 	    put_user(sstatus.hw_ptr, &src->s.status.hw_ptr) ||
 	    put_user(sstatus.tstamp.tv_sec, &src->s.status.tstamp_sec) ||
@@ -533,6 +535,8 @@ static int snd_pcm_ioctl_sync_ptr_buggy(struct snd_pcm_substream *substream,
 	sync_ptr.s.status.suspended_state = status->suspended_state;
 	sync_ptr.s.status.audio_tstamp = status->audio_tstamp;
 	snd_pcm_stream_unlock_irq(substream);
+	if (!(sync_ptr.flags & SNDRV_PCM_SYNC_PTR_APPL))
+		snd_pcm_dma_buffer_sync(substream, SNDRV_DMA_SYNC_DEVICE);
 	if (copy_to_user(_sync_ptr, &sync_ptr, sizeof(sync_ptr)))
 		return -EFAULT;
 	return 0;
diff --git a/sound/core/pcm_lib.c b/sound/core/pcm_lib.c
index a144a3f68e9e..4f4b4739f987 100644
--- a/sound/core/pcm_lib.c
+++ b/sound/core/pcm_lib.c
@@ -106,6 +106,7 @@ void snd_pcm_playback_silence(struct snd_pcm_substream *substream, snd_pcm_ufram
 		frames -= transfer;
 		ofs = 0;
 	}
+	snd_pcm_dma_buffer_sync(substream, SNDRV_DMA_SYNC_DEVICE);
 }
 
 #ifdef CONFIG_SND_DEBUG
@@ -2256,8 +2257,12 @@ snd_pcm_sframes_t __snd_pcm_lib_xfer(struct snd_pcm_substream *substream,
 			goto _end_unlock;
 		}
 		snd_pcm_stream_unlock_irq(substream);
+		if (!is_playback)
+			snd_pcm_dma_buffer_sync(substream, SNDRV_DMA_SYNC_CPU);
 		err = writer(substream, appl_ofs, data, offset, frames,
 			     transfer);
+		if (is_playback)
+			snd_pcm_dma_buffer_sync(substream, SNDRV_DMA_SYNC_DEVICE);
 		snd_pcm_stream_lock_irq(substream);
 		if (err < 0)
 			goto _end_unlock;
diff --git a/sound/core/pcm_local.h b/sound/core/pcm_local.h
index fe9689b8a6a6..ecb21697ae3a 100644
--- a/sound/core/pcm_local.h
+++ b/sound/core/pcm_local.h
@@ -73,4 +73,11 @@ void snd_pcm_sync_stop(struct snd_pcm_substream *substream, bool sync_irq);
 		for ((subs) = (pcm)->streams[str].substream; (subs); \
 		     (subs) = (subs)->next)
 
+static inline void snd_pcm_dma_buffer_sync(struct snd_pcm_substream *substream,
+					   enum snd_dma_sync_mode mode)
+{
+	if (substream->runtime->info & SNDRV_PCM_INFO_EXPLICIT_SYNC)
+		snd_dma_buffer_sync(snd_pcm_get_dma_buf(substream), mode);
+}
+
 #endif	/* __SOUND_CORE_PCM_LOCAL_H */
diff --git a/sound/core/pcm_memory.c b/sound/core/pcm_memory.c
index 7fbd1ccbb5b0..b70ce3b69ab4 100644
--- a/sound/core/pcm_memory.c
+++ b/sound/core/pcm_memory.c
@@ -32,15 +32,20 @@ module_param(max_alloc_per_card, ulong, 0644);
 MODULE_PARM_DESC(max_alloc_per_card, "Max total allocation bytes per card.");
 
 static int do_alloc_pages(struct snd_card *card, int type, struct device *dev,
-			  size_t size, struct snd_dma_buffer *dmab)
+			  int str, size_t size, struct snd_dma_buffer *dmab)
 {
+	enum dma_data_direction dir;
 	int err;
 
 	if (max_alloc_per_card &&
 	    card->total_pcm_alloc_bytes + size > max_alloc_per_card)
 		return -ENOMEM;
 
-	err = snd_dma_alloc_pages(type, dev, size, dmab);
+	if (str == SNDRV_PCM_STREAM_PLAYBACK)
+		dir = DMA_TO_DEVICE;
+	else
+		dir = DMA_FROM_DEVICE;
+	err = snd_dma_alloc_dir_pages(type, dev, dir, size, dmab);
 	if (!err) {
 		mutex_lock(&card->memory_mutex);
 		card->total_pcm_alloc_bytes += dmab->bytes;
@@ -77,7 +82,7 @@ static int preallocate_pcm_pages(struct snd_pcm_substream *substream,
 
 	do {
 		err = do_alloc_pages(card, dmab->dev.type, dmab->dev.dev,
-				     size, dmab);
+				     substream->stream, size, dmab);
 		if (err != -ENOMEM)
 			return err;
 		if (no_fallback)
@@ -177,6 +182,7 @@ static void snd_pcm_lib_preallocate_proc_write(struct snd_info_entry *entry,
 			if (do_alloc_pages(card,
 					   substream->dma_buffer.dev.type,
 					   substream->dma_buffer.dev.dev,
+					   substream->stream,
 					   size, &new_dmab) < 0) {
 				buffer->error = -ENOMEM;
 				pr_debug("ALSA pcmC%dD%d%c,%d:%s: cannot preallocate for size %zu\n",
@@ -418,6 +424,7 @@ int snd_pcm_lib_malloc_pages(struct snd_pcm_substream *substream, size_t size)
 		if (do_alloc_pages(card,
 				   substream->dma_buffer.dev.type,
 				   substream->dma_buffer.dev.dev,
+				   substream->stream,
 				   size, dmab) < 0) {
 			kfree(dmab);
 			pr_debug("ALSA pcmC%dD%d%c,%d:%s: cannot preallocate for size %zu\n",
diff --git a/sound/core/pcm_native.c b/sound/core/pcm_native.c
index d233cb3b41d8..621883e71194 100644
--- a/sound/core/pcm_native.c
+++ b/sound/core/pcm_native.c
@@ -2685,6 +2685,13 @@ int snd_pcm_open_substream(struct snd_pcm *pcm, int stream,
 		goto error;
 	}
 
+	/* automatically set EXPLICIT_SYNC flag in the managed mode whenever
+	 * the DMA buffer requires it
+	 */
+	if (substream->managed_buffer_alloc &&
+	    substream->dma_buffer.dev.need_sync)
+		substream->runtime->hw.info |= SNDRV_PCM_INFO_EXPLICIT_SYNC;
+
 	*rsubstream = substream;
 	return 0;
 
@@ -2912,6 +2919,8 @@ static snd_pcm_sframes_t snd_pcm_rewind(struct snd_pcm_substream *substream,
 		ret = rewind_appl_ptr(substream, frames,
 				      snd_pcm_hw_avail(substream));
 	snd_pcm_stream_unlock_irq(substream);
+	if (ret >= 0)
+		snd_pcm_dma_buffer_sync(substream, SNDRV_DMA_SYNC_DEVICE);
 	return ret;
 }
 
@@ -2929,35 +2938,31 @@ static snd_pcm_sframes_t snd_pcm_forward(struct snd_pcm_substream *substream,
 		ret = forward_appl_ptr(substream, frames,
 				       snd_pcm_avail(substream));
 	snd_pcm_stream_unlock_irq(substream);
+	if (ret >= 0)
+		snd_pcm_dma_buffer_sync(substream, SNDRV_DMA_SYNC_DEVICE);
 	return ret;
 }
 
-static int snd_pcm_hwsync(struct snd_pcm_substream *substream)
-{
-	int err;
-
-	snd_pcm_stream_lock_irq(substream);
-	err = do_pcm_hwsync(substream);
-	snd_pcm_stream_unlock_irq(substream);
-	return err;
-}
-		
 static int snd_pcm_delay(struct snd_pcm_substream *substream,
 			 snd_pcm_sframes_t *delay)
 {
 	int err;
-	snd_pcm_sframes_t n = 0;
 
 	snd_pcm_stream_lock_irq(substream);
 	err = do_pcm_hwsync(substream);
-	if (!err)
-		n = snd_pcm_calc_delay(substream);
+	if (delay && !err)
+		*delay = snd_pcm_calc_delay(substream);
 	snd_pcm_stream_unlock_irq(substream);
-	if (!err)
-		*delay = n;
+	snd_pcm_dma_buffer_sync(substream, SNDRV_DMA_SYNC_CPU);
+
 	return err;
 }
 		
+static inline int snd_pcm_hwsync(struct snd_pcm_substream *substream)
+{
+	return snd_pcm_delay(substream, NULL);
+}
+
 static int snd_pcm_sync_ptr(struct snd_pcm_substream *substream,
 			    struct snd_pcm_sync_ptr __user *_sync_ptr)
 {
@@ -3000,6 +3005,8 @@ static int snd_pcm_sync_ptr(struct snd_pcm_substream *substream,
 	sync_ptr.s.status.suspended_state = status->suspended_state;
 	sync_ptr.s.status.audio_tstamp = status->audio_tstamp;
 	snd_pcm_stream_unlock_irq(substream);
+	if (!(sync_ptr.flags & SNDRV_PCM_SYNC_PTR_APPL))
+		snd_pcm_dma_buffer_sync(substream, SNDRV_DMA_SYNC_DEVICE);
 	if (copy_to_user(_sync_ptr, &sync_ptr, sizeof(sync_ptr)))
 		return -EFAULT;
 	return 0;
@@ -3096,6 +3103,8 @@ static int snd_pcm_ioctl_sync_ptr_compat(struct snd_pcm_substream *substream,
 	sstatus.suspended_state = status->suspended_state;
 	sstatus.audio_tstamp = status->audio_tstamp;
 	snd_pcm_stream_unlock_irq(substream);
+	if (!(sflags & SNDRV_PCM_SYNC_PTR_APPL))
+		snd_pcm_dma_buffer_sync(substream, SNDRV_DMA_SYNC_DEVICE);
 	if (put_user(sstatus.state, &src->s.status.state) ||
 	    put_user(sstatus.hw_ptr, &src->s.status.hw_ptr) ||
 	    put_user(sstatus.tstamp.tv_sec, &src->s.status.tstamp_sec) ||
@@ -3218,6 +3227,9 @@ static int snd_pcm_common_ioctl(struct file *file,
 	if (PCM_RUNTIME_CHECK(substream))
 		return -ENXIO;
 
+	if (substream->runtime->status->state == SNDRV_PCM_STATE_DISCONNECTED)
+		return -EBADFD;
+
 	res = snd_power_wait(substream->pcm->card);
 	if (res < 0)
 		return res;
@@ -3272,7 +3284,7 @@ static int snd_pcm_common_ioctl(struct file *file,
 		return snd_pcm_hwsync(substream);
 	case SNDRV_PCM_IOCTL_DELAY:
 	{
-		snd_pcm_sframes_t delay;
+		snd_pcm_sframes_t delay = 0;
 		snd_pcm_sframes_t __user *res = arg;
 		int err;
 
@@ -3344,6 +3356,9 @@ int snd_pcm_kernel_ioctl(struct snd_pcm_substream *substream,
 	snd_pcm_uframes_t *frames = arg;
 	snd_pcm_sframes_t result;
 	
+	if (substream->runtime->status->state == SNDRV_PCM_STATE_DISCONNECTED)
+		return -EBADFD;
+
 	switch (cmd) {
 	case SNDRV_PCM_IOCTL_FORWARD:
 	{
@@ -3386,7 +3401,8 @@ static ssize_t snd_pcm_read(struct file *file, char __user *buf, size_t count,
 	if (PCM_RUNTIME_CHECK(substream))
 		return -ENXIO;
 	runtime = substream->runtime;
-	if (runtime->status->state == SNDRV_PCM_STATE_OPEN)
+	if (runtime->status->state == SNDRV_PCM_STATE_OPEN ||
+	    runtime->status->state == SNDRV_PCM_STATE_DISCONNECTED)
 		return -EBADFD;
 	if (!frame_aligned(runtime, count))
 		return -EINVAL;
@@ -3410,7 +3426,8 @@ static ssize_t snd_pcm_write(struct file *file, const char __user *buf,
 	if (PCM_RUNTIME_CHECK(substream))
 		return -ENXIO;
 	runtime = substream->runtime;
-	if (runtime->status->state == SNDRV_PCM_STATE_OPEN)
+	if (runtime->status->state == SNDRV_PCM_STATE_OPEN ||
+	    runtime->status->state == SNDRV_PCM_STATE_DISCONNECTED)
 		return -EBADFD;
 	if (!frame_aligned(runtime, count))
 		return -EINVAL;
@@ -3436,7 +3453,8 @@ static ssize_t snd_pcm_readv(struct kiocb *iocb, struct iov_iter *to)
 	if (PCM_RUNTIME_CHECK(substream))
 		return -ENXIO;
 	runtime = substream->runtime;
-	if (runtime->status->state == SNDRV_PCM_STATE_OPEN)
+	if (runtime->status->state == SNDRV_PCM_STATE_OPEN ||
+	    runtime->status->state == SNDRV_PCM_STATE_DISCONNECTED)
 		return -EBADFD;
 	if (!iter_is_iovec(to))
 		return -EINVAL;
@@ -3472,7 +3490,8 @@ static ssize_t snd_pcm_writev(struct kiocb *iocb, struct iov_iter *from)
 	if (PCM_RUNTIME_CHECK(substream))
 		return -ENXIO;
 	runtime = substream->runtime;
-	if (runtime->status->state == SNDRV_PCM_STATE_OPEN)
+	if (runtime->status->state == SNDRV_PCM_STATE_OPEN ||
+	    runtime->status->state == SNDRV_PCM_STATE_DISCONNECTED)
 		return -EBADFD;
 	if (!iter_is_iovec(from))
 		return -EINVAL;
@@ -3511,6 +3530,9 @@ static __poll_t snd_pcm_poll(struct file *file, poll_table *wait)
 		return ok | EPOLLERR;
 
 	runtime = substream->runtime;
+	if (runtime->status->state == SNDRV_PCM_STATE_DISCONNECTED)
+		return ok | EPOLLERR;
+
 	poll_wait(file, &runtime->sleep, wait);
 
 	mask = 0;
@@ -3820,6 +3842,8 @@ static int snd_pcm_mmap(struct file *file, struct vm_area_struct *area)
 	substream = pcm_file->substream;
 	if (PCM_RUNTIME_CHECK(substream))
 		return -ENXIO;
+	if (substream->runtime->status->state == SNDRV_PCM_STATE_DISCONNECTED)
+		return -EBADFD;
 
 	offset = area->vm_pgoff << PAGE_SHIFT;
 	switch (offset) {
@@ -3856,6 +3880,8 @@ static int snd_pcm_fasync(int fd, struct file * file, int on)
 	if (PCM_RUNTIME_CHECK(substream))
 		return -ENXIO;
 	runtime = substream->runtime;
+	if (runtime->status->state == SNDRV_PCM_STATE_DISCONNECTED)
+		return -EBADFD;
 	return fasync_helper(fd, file, on, &runtime->fasync);
 }
 
diff --git a/sound/core/sgbuf.c b/sound/core/sgbuf.c
deleted file mode 100644
index 8352a5cdb19f..000000000000
--- a/sound/core/sgbuf.c
+++ /dev/null
@@ -1,201 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0-or-later
-/*
- * Scatter-Gather buffer
- *
- *  Copyright (c) by Takashi Iwai <tiwai@suse.de>
- */
-
-#include <linux/slab.h>
-#include <linux/mm.h>
-#include <linux/vmalloc.h>
-#include <linux/export.h>
-#include <sound/memalloc.h>
-#include "memalloc_local.h"
-
-struct snd_sg_page {
-	void *buf;
-	dma_addr_t addr;
-};
-
-struct snd_sg_buf {
-	int size;	/* allocated byte size */
-	int pages;	/* allocated pages */
-	int tblsize;	/* allocated table size */
-	struct snd_sg_page *table;	/* address table */
-	struct page **page_table;	/* page table (for vmap/vunmap) */
-	struct device *dev;
-};
-
-/* table entries are align to 32 */
-#define SGBUF_TBL_ALIGN		32
-#define sgbuf_align_table(tbl)	ALIGN((tbl), SGBUF_TBL_ALIGN)
-
-static void snd_dma_sg_free(struct snd_dma_buffer *dmab)
-{
-	struct snd_sg_buf *sgbuf = dmab->private_data;
-	struct snd_dma_buffer tmpb;
-	int i;
-
-	if (!sgbuf)
-		return;
-
-	vunmap(dmab->area);
-	dmab->area = NULL;
-
-	tmpb.dev.type = SNDRV_DMA_TYPE_DEV;
-	if (dmab->dev.type == SNDRV_DMA_TYPE_DEV_WC_SG)
-		tmpb.dev.type = SNDRV_DMA_TYPE_DEV_WC;
-	tmpb.dev.dev = sgbuf->dev;
-	for (i = 0; i < sgbuf->pages; i++) {
-		if (!(sgbuf->table[i].addr & ~PAGE_MASK))
-			continue; /* continuous pages */
-		tmpb.area = sgbuf->table[i].buf;
-		tmpb.addr = sgbuf->table[i].addr & PAGE_MASK;
-		tmpb.bytes = (sgbuf->table[i].addr & ~PAGE_MASK) << PAGE_SHIFT;
-		snd_dma_free_pages(&tmpb);
-	}
-
-	kfree(sgbuf->table);
-	kfree(sgbuf->page_table);
-	kfree(sgbuf);
-	dmab->private_data = NULL;
-}
-
-#define MAX_ALLOC_PAGES		32
-
-static void *snd_dma_sg_alloc(struct snd_dma_buffer *dmab, size_t size)
-{
-	struct snd_sg_buf *sgbuf;
-	unsigned int i, pages, chunk, maxpages;
-	struct snd_dma_buffer tmpb;
-	struct snd_sg_page *table;
-	struct page **pgtable;
-	int type = SNDRV_DMA_TYPE_DEV;
-	pgprot_t prot = PAGE_KERNEL;
-	void *area;
-
-	dmab->private_data = sgbuf = kzalloc(sizeof(*sgbuf), GFP_KERNEL);
-	if (!sgbuf)
-		return NULL;
-	if (dmab->dev.type == SNDRV_DMA_TYPE_DEV_WC_SG) {
-		type = SNDRV_DMA_TYPE_DEV_WC;
-#ifdef pgprot_noncached
-		prot = pgprot_noncached(PAGE_KERNEL);
-#endif
-	}
-	sgbuf->dev = dmab->dev.dev;
-	pages = snd_sgbuf_aligned_pages(size);
-	sgbuf->tblsize = sgbuf_align_table(pages);
-	table = kcalloc(sgbuf->tblsize, sizeof(*table), GFP_KERNEL);
-	if (!table)
-		goto _failed;
-	sgbuf->table = table;
-	pgtable = kcalloc(sgbuf->tblsize, sizeof(*pgtable), GFP_KERNEL);
-	if (!pgtable)
-		goto _failed;
-	sgbuf->page_table = pgtable;
-
-	/* allocate pages */
-	maxpages = MAX_ALLOC_PAGES;
-	while (pages > 0) {
-		chunk = pages;
-		/* don't be too eager to take a huge chunk */
-		if (chunk > maxpages)
-			chunk = maxpages;
-		chunk <<= PAGE_SHIFT;
-		if (snd_dma_alloc_pages_fallback(type, dmab->dev.dev,
-						 chunk, &tmpb) < 0) {
-			if (!sgbuf->pages)
-				goto _failed;
-			size = sgbuf->pages * PAGE_SIZE;
-			break;
-		}
-		chunk = tmpb.bytes >> PAGE_SHIFT;
-		for (i = 0; i < chunk; i++) {
-			table->buf = tmpb.area;
-			table->addr = tmpb.addr;
-			if (!i)
-				table->addr |= chunk; /* mark head */
-			table++;
-			*pgtable++ = virt_to_page(tmpb.area);
-			tmpb.area += PAGE_SIZE;
-			tmpb.addr += PAGE_SIZE;
-		}
-		sgbuf->pages += chunk;
-		pages -= chunk;
-		if (chunk < maxpages)
-			maxpages = chunk;
-	}
-
-	sgbuf->size = size;
-	area = vmap(sgbuf->page_table, sgbuf->pages, VM_MAP, prot);
-	if (!area)
-		goto _failed;
-	return area;
-
- _failed:
-	snd_dma_sg_free(dmab); /* free the table */
-	return NULL;
-}
-
-static dma_addr_t snd_dma_sg_get_addr(struct snd_dma_buffer *dmab,
-				      size_t offset)
-{
-	struct snd_sg_buf *sgbuf = dmab->private_data;
-	dma_addr_t addr;
-
-	addr = sgbuf->table[offset >> PAGE_SHIFT].addr;
-	addr &= ~((dma_addr_t)PAGE_SIZE - 1);
-	return addr + offset % PAGE_SIZE;
-}
-
-static struct page *snd_dma_sg_get_page(struct snd_dma_buffer *dmab,
-					size_t offset)
-{
-	struct snd_sg_buf *sgbuf = dmab->private_data;
-	unsigned int idx = offset >> PAGE_SHIFT;
-
-	if (idx >= (unsigned int)sgbuf->pages)
-		return NULL;
-	return sgbuf->page_table[idx];
-}
-
-static unsigned int snd_dma_sg_get_chunk_size(struct snd_dma_buffer *dmab,
-					      unsigned int ofs,
-					      unsigned int size)
-{
-	struct snd_sg_buf *sg = dmab->private_data;
-	unsigned int start, end, pg;
-
-	start = ofs >> PAGE_SHIFT;
-	end = (ofs + size - 1) >> PAGE_SHIFT;
-	/* check page continuity */
-	pg = sg->table[start].addr >> PAGE_SHIFT;
-	for (;;) {
-		start++;
-		if (start > end)
-			break;
-		pg++;
-		if ((sg->table[start].addr >> PAGE_SHIFT) != pg)
-			return (start << PAGE_SHIFT) - ofs;
-	}
-	/* ok, all on continuous pages */
-	return size;
-}
-
-static int snd_dma_sg_mmap(struct snd_dma_buffer *dmab,
-			   struct vm_area_struct *area)
-{
-	if (dmab->dev.type == SNDRV_DMA_TYPE_DEV_WC_SG)
-		area->vm_page_prot = pgprot_writecombine(area->vm_page_prot);
-	return -ENOENT; /* continue with the default mmap handler */
-}
-
-const struct snd_malloc_ops snd_dma_sg_ops = {
-	.alloc = snd_dma_sg_alloc,
-	.free = snd_dma_sg_free,
-	.get_addr = snd_dma_sg_get_addr,
-	.get_page = snd_dma_sg_get_page,
-	.get_chunk_size = snd_dma_sg_get_chunk_size,
-	.mmap = snd_dma_sg_mmap,
-};
diff --git a/sound/firewire/motu/Makefile b/sound/firewire/motu/Makefile
index acdf66564fb0..3bef2a0b1e2e 100644
--- a/sound/firewire/motu/Makefile
+++ b/sound/firewire/motu/Makefile
@@ -4,5 +4,6 @@ CFLAGS_amdtp-motu.o	:= -I$(src)
 snd-firewire-motu-objs := motu.o amdtp-motu.o motu-transaction.o motu-stream.o \
 			  motu-proc.o motu-pcm.o motu-midi.o motu-hwdep.o \
 			  motu-protocol-v2.o motu-protocol-v3.o \
-			  motu-protocol-v1.o
+			  motu-protocol-v1.o motu-register-dsp-message-parser.o \
+			  motu-command-dsp-message-parser.o
 obj-$(CONFIG_SND_FIREWIRE_MOTU) += snd-firewire-motu.o
diff --git a/sound/firewire/motu/amdtp-motu.c b/sound/firewire/motu/amdtp-motu.c
index a18c2c033e83..2fb52f481d12 100644
--- a/sound/firewire/motu/amdtp-motu.c
+++ b/sound/firewire/motu/amdtp-motu.c
@@ -333,6 +333,7 @@ static unsigned int process_ir_ctx_payloads(struct amdtp_stream *s,
 					    unsigned int packets,
 					    struct snd_pcm_substream *pcm)
 {
+	struct snd_motu *motu = container_of(s, struct snd_motu, tx_stream);
 	struct amdtp_motu *p = s->protocol;
 	unsigned int pcm_frames = 0;
 	int i;
@@ -357,6 +358,14 @@ static unsigned int process_ir_ctx_payloads(struct amdtp_stream *s,
 			read_midi_messages(s, buf, data_blocks);
 	}
 
+	if (motu->spec->flags & SND_MOTU_SPEC_REGISTER_DSP) {
+		snd_motu_register_dsp_message_parser_parse(motu, descs, packets,
+							   s->data_block_quadlets);
+	} else if (motu->spec->flags & SND_MOTU_SPEC_COMMAND_DSP) {
+		snd_motu_command_dsp_message_parser_parse(motu, descs, packets,
+							  s->data_block_quadlets);
+	}
+
 	// For tracepoints.
 	if (trace_data_block_sph_enabled() ||
 	    trace_data_block_message_enabled())
@@ -415,8 +424,6 @@ static unsigned int process_it_ctx_payloads(struct amdtp_stream *s,
 		if (p->midi_ports)
 			write_midi_messages(s, buf, data_blocks);
 
-		// TODO: how to interact control messages between userspace?
-
 		write_sph(p->cache, buf, data_blocks, s->data_block_quadlets);
 	}
 
diff --git a/sound/firewire/motu/motu-command-dsp-message-parser.c b/sound/firewire/motu/motu-command-dsp-message-parser.c
new file mode 100644
index 000000000000..9efe4d364baf
--- /dev/null
+++ b/sound/firewire/motu/motu-command-dsp-message-parser.c
@@ -0,0 +1,181 @@
+// SPDX-License-Identifier: GPL-2.0-only
+//
+// motu-command-dsp-message-parser.c - a part of driver for MOTU FireWire series
+//
+// Copyright (c) 2021 Takashi Sakamoto <o-takashi@sakamocchi.jp>
+
+// Below models allow software to configure their DSP function by command transferred in
+// asynchronous transaction:
+//  * 828 mk3 (FireWire only and Hybrid)
+//  * 896 mk3 (FireWire only and Hybrid)
+//  * Ultralite mk3 (FireWire only and Hybrid)
+//  * Traveler mk3
+//  * Track 16
+//
+// Isochronous packets from the above models includes messages to report state of hardware meter.
+
+#include "motu.h"
+
+enum msg_parser_state {
+	INITIALIZED,
+	FRAGMENT_DETECTED,
+	AVAILABLE,
+};
+
+struct msg_parser {
+	spinlock_t lock;
+	enum msg_parser_state state;
+	unsigned int interval;
+	unsigned int message_count;
+	unsigned int fragment_pos;
+	unsigned int value_index;
+	u64 value;
+	struct snd_firewire_motu_command_dsp_meter meter;
+};
+
+int snd_motu_command_dsp_message_parser_new(struct snd_motu *motu)
+{
+	struct msg_parser *parser;
+
+	parser = devm_kzalloc(&motu->card->card_dev, sizeof(*parser), GFP_KERNEL);
+	if (!parser)
+		return -ENOMEM;
+	spin_lock_init(&parser->lock);
+	motu->message_parser = parser;
+
+	return 0;
+}
+
+int snd_motu_command_dsp_message_parser_init(struct snd_motu *motu, enum cip_sfc sfc)
+{
+	struct msg_parser *parser = motu->message_parser;
+
+	parser->state = INITIALIZED;
+
+	// All of data blocks don't have messages with meaningful information.
+	switch (sfc) {
+	case CIP_SFC_176400:
+	case CIP_SFC_192000:
+		parser->interval = 4;
+		break;
+	case CIP_SFC_88200:
+	case CIP_SFC_96000:
+		parser->interval = 2;
+		break;
+	case CIP_SFC_32000:
+	case CIP_SFC_44100:
+	case CIP_SFC_48000:
+	default:
+		parser->interval = 1;
+		break;
+	}
+
+	return 0;
+}
+
+#define FRAGMENT_POS			6
+#define MIDI_BYTE_POS			7
+#define MIDI_FLAG_POS			8
+// One value of hardware meter consists of 4 messages.
+#define FRAGMENTS_PER_VALUE		4
+#define VALUES_AT_IMAGE_END		0xffffffffffffffff
+
+void snd_motu_command_dsp_message_parser_parse(struct snd_motu *motu, const struct pkt_desc *descs,
+					unsigned int desc_count, unsigned int data_block_quadlets)
+{
+	struct msg_parser *parser = motu->message_parser;
+	unsigned int interval = parser->interval;
+	unsigned long flags;
+	int i;
+
+	spin_lock_irqsave(&parser->lock, flags);
+
+	for (i = 0; i < desc_count; ++i) {
+		const struct pkt_desc *desc = descs + i;
+		__be32 *buffer = desc->ctx_payload;
+		unsigned int data_blocks = desc->data_blocks;
+		int j;
+
+		for (j = 0; j < data_blocks; ++j) {
+			u8 *b = (u8 *)buffer;
+			buffer += data_block_quadlets;
+
+			switch (parser->state) {
+			case INITIALIZED:
+			{
+				u8 fragment = b[FRAGMENT_POS];
+
+				if (fragment > 0) {
+					parser->value = fragment;
+					parser->message_count = 1;
+					parser->state = FRAGMENT_DETECTED;
+				}
+				break;
+			}
+			case FRAGMENT_DETECTED:
+			{
+				if (parser->message_count % interval == 0) {
+					u8 fragment = b[FRAGMENT_POS];
+
+					parser->value >>= 8;
+					parser->value |= (u64)fragment << 56;
+
+					if (parser->value == VALUES_AT_IMAGE_END) {
+						parser->state = AVAILABLE;
+						parser->fragment_pos = 0;
+						parser->value_index = 0;
+						parser->message_count = 0;
+					}
+				}
+				++parser->message_count;
+				break;
+			}
+			case AVAILABLE:
+			default:
+			{
+				if (parser->message_count % interval == 0) {
+					u8 fragment = b[FRAGMENT_POS];
+
+					parser->value >>= 8;
+					parser->value |= (u64)fragment << 56;
+					++parser->fragment_pos;
+
+					if (parser->fragment_pos == 4) {
+						// Skip the last two quadlets since they could be
+						// invalid value (0xffffffff) as floating point
+						// number.
+						if (parser->value_index <
+						    SNDRV_FIREWIRE_MOTU_COMMAND_DSP_METER_COUNT - 2) {
+							u32 val = (u32)(parser->value >> 32);
+							parser->meter.data[parser->value_index] = val;
+						}
+						++parser->value_index;
+						parser->fragment_pos = 0;
+					}
+
+					if (parser->value == VALUES_AT_IMAGE_END) {
+						parser->value_index = 0;
+						parser->fragment_pos = 0;
+						parser->message_count = 0;
+					}
+				}
+				++parser->message_count;
+				break;
+			}
+			}
+		}
+	}
+
+	spin_unlock_irqrestore(&parser->lock, flags);
+}
+
+void snd_motu_command_dsp_message_parser_copy_meter(struct snd_motu *motu,
+					struct snd_firewire_motu_command_dsp_meter *meter)
+{
+	struct msg_parser *parser = motu->message_parser;
+	unsigned long flags;
+
+	spin_lock_irqsave(&parser->lock, flags);
+	memcpy(meter, &parser->meter, sizeof(*meter));
+	spin_unlock_irqrestore(&parser->lock, flags);
+}
diff --git a/sound/firewire/motu/motu-hwdep.c b/sound/firewire/motu/motu-hwdep.c
index b5ced5d27758..a900fc0e7644 100644
--- a/sound/firewire/motu/motu-hwdep.c
+++ b/sound/firewire/motu/motu-hwdep.c
@@ -16,6 +16,14 @@
 
 #include "motu.h"
 
+static bool has_dsp_event(struct snd_motu *motu)
+{
+	if (motu->spec->flags & SND_MOTU_SPEC_REGISTER_DSP)
+		return (snd_motu_register_dsp_message_parser_count_event(motu) > 0);
+	else
+		return false;
+}
+
 static long hwdep_read(struct snd_hwdep *hwdep, char __user *buf, long count,
 		       loff_t *offset)
 {
@@ -25,7 +33,7 @@ static long hwdep_read(struct snd_hwdep *hwdep, char __user *buf, long count,
 
 	spin_lock_irq(&motu->lock);
 
-	while (!motu->dev_lock_changed && motu->msg == 0) {
+	while (!motu->dev_lock_changed && motu->msg == 0 && !has_dsp_event(motu)) {
 		prepare_to_wait(&motu->hwdep_wait, &wait, TASK_INTERRUPTIBLE);
 		spin_unlock_irq(&motu->lock);
 		schedule();
@@ -40,20 +48,46 @@ static long hwdep_read(struct snd_hwdep *hwdep, char __user *buf, long count,
 		event.lock_status.type = SNDRV_FIREWIRE_EVENT_LOCK_STATUS;
 		event.lock_status.status = (motu->dev_lock_count > 0);
 		motu->dev_lock_changed = false;
+		spin_unlock_irq(&motu->lock);
 
-		count = min_t(long, count, sizeof(event.lock_status));
-	} else {
+		count = min_t(long, count, sizeof(event));
+		if (copy_to_user(buf, &event, count))
+			return -EFAULT;
+	} else if (motu->msg > 0) {
 		event.motu_notification.type = SNDRV_FIREWIRE_EVENT_MOTU_NOTIFICATION;
 		event.motu_notification.message = motu->msg;
 		motu->msg = 0;
+		spin_unlock_irq(&motu->lock);
 
-		count = min_t(long, count, sizeof(event.motu_notification));
-	}
+		count = min_t(long, count, sizeof(event));
+		if (copy_to_user(buf, &event, count))
+			return -EFAULT;
+	} else if (has_dsp_event(motu)) {
+		size_t consumed = 0;
+		u32 __user *ptr;
+		u32 ev;
 
-	spin_unlock_irq(&motu->lock);
+		spin_unlock_irq(&motu->lock);
 
-	if (copy_to_user(buf, &event, count))
-		return -EFAULT;
+		// Header is filled later.
+		consumed += sizeof(event.motu_register_dsp_change);
+
+		while (consumed < count &&
+		       snd_motu_register_dsp_message_parser_copy_event(motu, &ev)) {
+			ptr = (u32 __user *)(buf + consumed);
+			if (put_user(ev, ptr))
+				return -EFAULT;
+			consumed += sizeof(ev);
+		}
+
+		event.motu_register_dsp_change.type = SNDRV_FIREWIRE_EVENT_MOTU_REGISTER_DSP_CHANGE;
+		event.motu_register_dsp_change.count =
+			(consumed - sizeof(event.motu_register_dsp_change)) / 4;
+		if (copy_to_user(buf, &event, sizeof(event.motu_register_dsp_change)))
+			return -EFAULT;
+
+		count = consumed;
+	}
 
 	return count;
 }
@@ -67,7 +101,7 @@ static __poll_t hwdep_poll(struct snd_hwdep *hwdep, struct file *file,
 	poll_wait(file, &motu->hwdep_wait, wait);
 
 	spin_lock_irq(&motu->lock);
-	if (motu->dev_lock_changed || motu->msg)
+	if (motu->dev_lock_changed || motu->msg || has_dsp_event(motu))
 		events = EPOLLIN | EPOLLRDNORM;
 	else
 		events = 0;
@@ -155,6 +189,71 @@ static int hwdep_ioctl(struct snd_hwdep *hwdep, struct file *file,
 		return hwdep_lock(motu);
 	case SNDRV_FIREWIRE_IOCTL_UNLOCK:
 		return hwdep_unlock(motu);
+	case SNDRV_FIREWIRE_IOCTL_MOTU_REGISTER_DSP_METER:
+	{
+		struct snd_firewire_motu_register_dsp_meter *meter;
+		int err;
+
+		if (!(motu->spec->flags & SND_MOTU_SPEC_REGISTER_DSP))
+			return -ENXIO;
+
+		meter = kzalloc(sizeof(*meter), GFP_KERNEL);
+		if (!meter)
+			return -ENOMEM;
+
+		snd_motu_register_dsp_message_parser_copy_meter(motu, meter);
+
+		err = copy_to_user((void __user *)arg, meter, sizeof(*meter));
+		kfree(meter);
+
+		if (err)
+			return -EFAULT;
+
+		return 0;
+	}
+	case SNDRV_FIREWIRE_IOCTL_MOTU_COMMAND_DSP_METER:
+	{
+		struct snd_firewire_motu_command_dsp_meter *meter;
+		int err;
+
+		if (!(motu->spec->flags & SND_MOTU_SPEC_COMMAND_DSP))
+			return -ENXIO;
+
+		meter = kzalloc(sizeof(*meter), GFP_KERNEL);
+		if (!meter)
+			return -ENOMEM;
+
+		snd_motu_command_dsp_message_parser_copy_meter(motu, meter);
+
+		err = copy_to_user((void __user *)arg, meter, sizeof(*meter));
+		kfree(meter);
+
+		if (err)
+			return -EFAULT;
+
+		return 0;
+	}
+	case SNDRV_FIREWIRE_IOCTL_MOTU_REGISTER_DSP_PARAMETER:
+	{
+		struct snd_firewire_motu_register_dsp_parameter *param;
+		int err;
+
+		if (!(motu->spec->flags & SND_MOTU_SPEC_REGISTER_DSP))
+			return -ENXIO;
+
+		param = kzalloc(sizeof(*param), GFP_KERNEL);
+		if (!param)
+			return -ENOMEM;
+
+		snd_motu_register_dsp_message_parser_copy_parameter(motu, param);
+
+		err = copy_to_user((void __user *)arg, param, sizeof(*param));
+		kfree(param);
+		if (err)
+			return -EFAULT;
+
+		return 0;
+	}
 	default:
 		return -ENOIOCTLCMD;
 	}
@@ -193,5 +292,7 @@ int snd_motu_create_hwdep_device(struct snd_motu *motu)
 	hwdep->private_data = motu;
 	hwdep->exclusive = true;
 
+	motu->hwdep = hwdep;
+
 	return 0;
 }
diff --git a/sound/firewire/motu/motu-protocol-v2.c b/sound/firewire/motu/motu-protocol-v2.c
index 2bd4485e4bc7..a5f70efa2e88 100644
--- a/sound/firewire/motu/motu-protocol-v2.c
+++ b/sound/firewire/motu/motu-protocol-v2.c
@@ -275,7 +275,8 @@ const struct snd_motu_spec snd_motu_spec_828mk2 = {
 	.name = "828mk2",
 	.protocol_version = SND_MOTU_PROTOCOL_V2,
 	.flags = SND_MOTU_SPEC_RX_MIDI_2ND_Q |
-		 SND_MOTU_SPEC_TX_MIDI_2ND_Q,
+		 SND_MOTU_SPEC_TX_MIDI_2ND_Q |
+		 SND_MOTU_SPEC_REGISTER_DSP,
 	.tx_fixed_pcm_chunks = {14, 14, 0},
 	.rx_fixed_pcm_chunks = {14, 14, 0},
 };
@@ -283,7 +284,7 @@ const struct snd_motu_spec snd_motu_spec_828mk2 = {
 const struct snd_motu_spec snd_motu_spec_896hd = {
 	.name = "896HD",
 	.protocol_version = SND_MOTU_PROTOCOL_V2,
-	// No support for MIDI.
+	.flags = SND_MOTU_SPEC_REGISTER_DSP,
 	.tx_fixed_pcm_chunks = {14, 14, 8},
 	.rx_fixed_pcm_chunks = {14, 14, 8},
 };
@@ -292,7 +293,8 @@ const struct snd_motu_spec snd_motu_spec_traveler = {
 	.name = "Traveler",
 	.protocol_version = SND_MOTU_PROTOCOL_V2,
 	.flags = SND_MOTU_SPEC_RX_MIDI_2ND_Q |
-		 SND_MOTU_SPEC_TX_MIDI_2ND_Q,
+		 SND_MOTU_SPEC_TX_MIDI_2ND_Q |
+		 SND_MOTU_SPEC_REGISTER_DSP,
 	.tx_fixed_pcm_chunks = {14, 14, 8},
 	.rx_fixed_pcm_chunks = {14, 14, 8},
 };
@@ -301,7 +303,8 @@ const struct snd_motu_spec snd_motu_spec_ultralite = {
 	.name = "UltraLite",
 	.protocol_version = SND_MOTU_PROTOCOL_V2,
 	.flags = SND_MOTU_SPEC_RX_MIDI_2ND_Q |
-		 SND_MOTU_SPEC_TX_MIDI_2ND_Q,
+		 SND_MOTU_SPEC_TX_MIDI_2ND_Q |
+		 SND_MOTU_SPEC_REGISTER_DSP,
 	.tx_fixed_pcm_chunks = {14, 14, 0},
 	.rx_fixed_pcm_chunks = {14, 14, 0},
 };
@@ -310,7 +313,8 @@ const struct snd_motu_spec snd_motu_spec_8pre = {
 	.name = "8pre",
 	.protocol_version = SND_MOTU_PROTOCOL_V2,
 	.flags = SND_MOTU_SPEC_RX_MIDI_2ND_Q |
-		 SND_MOTU_SPEC_TX_MIDI_2ND_Q,
+		 SND_MOTU_SPEC_TX_MIDI_2ND_Q |
+		 SND_MOTU_SPEC_REGISTER_DSP,
 	// Two dummy chunks always in the end of data block.
 	.tx_fixed_pcm_chunks = {10, 10, 0},
 	.rx_fixed_pcm_chunks = {6, 6, 0},
diff --git a/sound/firewire/motu/motu-protocol-v3.c b/sound/firewire/motu/motu-protocol-v3.c
index 56e4504e7ec9..05608e8ca0bc 100644
--- a/sound/firewire/motu/motu-protocol-v3.c
+++ b/sound/firewire/motu/motu-protocol-v3.c
@@ -261,12 +261,12 @@ int snd_motu_protocol_v3_cache_packet_formats(struct snd_motu *motu)
 		return 0;
 }
 
-
 const struct snd_motu_spec snd_motu_spec_828mk3_fw = {
 	.name = "828mk3",
 	.protocol_version = SND_MOTU_PROTOCOL_V3,
 	.flags = SND_MOTU_SPEC_RX_MIDI_3RD_Q |
-		 SND_MOTU_SPEC_TX_MIDI_3RD_Q,
+		 SND_MOTU_SPEC_TX_MIDI_3RD_Q |
+		 SND_MOTU_SPEC_COMMAND_DSP,
 	.tx_fixed_pcm_chunks = {18, 18, 14},
 	.rx_fixed_pcm_chunks = {14, 14, 10},
 };
@@ -275,7 +275,8 @@ const struct snd_motu_spec snd_motu_spec_828mk3_hybrid = {
 	.name = "828mk3",
 	.protocol_version = SND_MOTU_PROTOCOL_V3,
 	.flags = SND_MOTU_SPEC_RX_MIDI_3RD_Q |
-		 SND_MOTU_SPEC_TX_MIDI_3RD_Q,
+		 SND_MOTU_SPEC_TX_MIDI_3RD_Q |
+		 SND_MOTU_SPEC_COMMAND_DSP,
 	.tx_fixed_pcm_chunks = {18, 18, 14},
 	.rx_fixed_pcm_chunks = {14, 14, 14},	// Additional 4 dummy chunks at higher rate.
 };
@@ -284,7 +285,8 @@ const struct snd_motu_spec snd_motu_spec_ultralite_mk3 = {
 	.name = "UltraLiteMk3",
 	.protocol_version = SND_MOTU_PROTOCOL_V3,
 	.flags = SND_MOTU_SPEC_RX_MIDI_3RD_Q |
-		 SND_MOTU_SPEC_TX_MIDI_3RD_Q,
+		 SND_MOTU_SPEC_TX_MIDI_3RD_Q |
+		 SND_MOTU_SPEC_COMMAND_DSP,
 	.tx_fixed_pcm_chunks = {18, 14, 10},
 	.rx_fixed_pcm_chunks = {14, 14, 14},
 };
@@ -293,7 +295,8 @@ const struct snd_motu_spec snd_motu_spec_audio_express = {
 	.name = "AudioExpress",
 	.protocol_version = SND_MOTU_PROTOCOL_V3,
 	.flags = SND_MOTU_SPEC_RX_MIDI_2ND_Q |
-		 SND_MOTU_SPEC_TX_MIDI_3RD_Q,
+		 SND_MOTU_SPEC_TX_MIDI_3RD_Q |
+		 SND_MOTU_SPEC_REGISTER_DSP,
 	.tx_fixed_pcm_chunks = {10, 10, 0},
 	.rx_fixed_pcm_chunks = {10, 10, 0},
 };
@@ -301,6 +304,7 @@ const struct snd_motu_spec snd_motu_spec_audio_express = {
 const struct snd_motu_spec snd_motu_spec_4pre = {
 	.name = "4pre",
 	.protocol_version = SND_MOTU_PROTOCOL_V3,
+	.flags = SND_MOTU_SPEC_REGISTER_DSP,
 	.tx_fixed_pcm_chunks = {10, 10, 0},
 	.rx_fixed_pcm_chunks = {10, 10, 0},
 };
diff --git a/sound/firewire/motu/motu-register-dsp-message-parser.c b/sound/firewire/motu/motu-register-dsp-message-parser.c
new file mode 100644
index 000000000000..0c587567540f
--- /dev/null
+++ b/sound/firewire/motu/motu-register-dsp-message-parser.c
@@ -0,0 +1,420 @@
+// SPDX-License-Identifier: GPL-2.0-only
+//
+// motu-register-dsp-message-parser.c - a part of driver for MOTU FireWire series
+//
+// Copyright (c) 2021 Takashi Sakamoto <o-takashi@sakamocchi.jp>
+
+// Below models allow software to configure their DSP functions by asynchronous transaction
+// to access their internal registers.
+// * 828 mk2
+// * 896hd
+// * Traveler
+// * 8 pre
+// * Ultralite
+// * 4 pre
+// * Audio Express
+//
+// Additionally, isochronous packets from the above models include messages to notify state of
+// DSP. The messages are two set of 3 byte data in 2nd and 3rd quadlet of data block. When user
+// operates hardware components such as dial and switch, corresponding messages are transferred.
+// The messages include Hardware metering and MIDI messages as well.
+
+#include "motu.h"
+
+#define MSG_FLAG_POS                    4
+#define MSG_FLAG_TYPE_MASK              0xf8
+#define MSG_FLAG_MIDI_MASK              0x01
+#define MSG_FLAG_MODEL_SPECIFIC_MASK    0x06
+#define   MSG_FLAG_8PRE                 0x00
+#define   MSG_FLAG_ULTRALITE            0x04
+#define   MSG_FLAG_TRAVELER             0x04
+#define   MSG_FLAG_828MK2               0x04
+#define   MSG_FLAG_896HD                0x04
+#define   MSG_FLAG_4PRE                 0x05 // MIDI mask is in 8th byte.
+#define   MSG_FLAG_AUDIOEXPRESS         0x05 // MIDI mask is in 8th byte.
+#define MSG_FLAG_TYPE_SHIFT             3
+#define MSG_VALUE_POS                   5
+#define MSG_MIDI_BYTE_POS		6
+#define MSG_METER_IDX_POS               7
+
+// In 4 pre and Audio express, meter index is in 6th byte. MIDI flag is in 8th byte and MIDI byte
+// is in 7th byte.
+#define MSG_METER_IDX_POS_4PRE_AE	6
+#define MSG_MIDI_BYTE_POS_4PRE_AE	7
+#define MSG_FLAG_MIDI_POS_4PRE_AE	8
+
+enum register_dsp_msg_type {
+	// Used for messages with no information.
+	INVALID = 0x00,
+	MIXER_SELECT = 0x01,
+	MIXER_SRC_GAIN = 0x02,
+	MIXER_SRC_PAN = 0x03,
+	MIXER_SRC_FLAG = 0x04,
+	MIXER_OUTPUT_PAIRED_VOLUME = 0x05,
+	MIXER_OUTPUT_PAIRED_FLAG = 0x06,
+	MAIN_OUTPUT_PAIRED_VOLUME = 0x07,
+	HP_OUTPUT_PAIRED_VOLUME = 0x08,
+	HP_OUTPUT_PAIRED_ASSIGNMENT = 0x09,
+	// Transferred by all models but the purpose is still unknown.
+	UNKNOWN_0 = 0x0a,
+	// Specific to 828mk2, 896hd, Traveler.
+	UNKNOWN_2 = 0x0c,
+	// Specific to 828mk2, Traveler, and 896hd (not functional).
+	LINE_INPUT_BOOST = 0x0d,
+	// Specific to 828mk2, Traveler, and 896hd (not functional).
+	LINE_INPUT_NOMINAL_LEVEL = 0x0e,
+	// Specific to Ultralite, 4 pre, Audio express, and 8 pre (not functional).
+	INPUT_GAIN_AND_INVERT = 0x15,
+	// Specific to 4 pre, and Audio express.
+	INPUT_FLAG = 0x16,
+	// Specific to 4 pre, and Audio express.
+	MIXER_SRC_PAIRED_BALANCE = 0x17,
+	// Specific to 4 pre, and Audio express.
+	MIXER_SRC_PAIRED_WIDTH = 0x18,
+	// Transferred by all models. This type of message interposes the series of the other
+	// messages. The message delivers signal level up to 96.0 kHz. In 828mk2, 896hd, and
+	// Traveler, one of physical outputs is selected for the message. The selection is done
+	// by LSB one byte in asynchronous write quadlet transaction to 0x'ffff'f000'0b2c.
+	METER = 0x1f,
+};
+
+#define EVENT_QUEUE_SIZE	16
+
+struct msg_parser {
+	spinlock_t lock;
+	struct snd_firewire_motu_register_dsp_meter meter;
+	bool meter_pos_quirk;
+
+	struct snd_firewire_motu_register_dsp_parameter param;
+	u8 prev_mixer_src_type;
+	u8 mixer_ch;
+	u8 mixer_src_ch;
+
+	u8 input_ch;
+	u8 prev_msg_type;
+
+	u32 event_queue[EVENT_QUEUE_SIZE];
+	unsigned int push_pos;
+	unsigned int pull_pos;
+};
+
+int snd_motu_register_dsp_message_parser_new(struct snd_motu *motu)
+{
+	struct msg_parser *parser;
+	parser = devm_kzalloc(&motu->card->card_dev, sizeof(*parser), GFP_KERNEL);
+	if (!parser)
+		return -ENOMEM;
+	spin_lock_init(&parser->lock);
+	if (motu->spec == &snd_motu_spec_4pre || motu->spec == &snd_motu_spec_audio_express)
+		parser->meter_pos_quirk = true;
+	motu->message_parser = parser;
+	return 0;
+}
+
+int snd_motu_register_dsp_message_parser_init(struct snd_motu *motu)
+{
+	struct msg_parser *parser = motu->message_parser;
+
+	parser->prev_mixer_src_type = INVALID;
+	parser->mixer_ch = 0xff;
+	parser->mixer_src_ch = 0xff;
+	parser->prev_msg_type = INVALID;
+
+	return 0;
+}
+
+// Rough implementaion of queue without overrun check.
+static void queue_event(struct snd_motu *motu, u8 msg_type, u8 identifier0, u8 identifier1, u8 val)
+{
+	struct msg_parser *parser = motu->message_parser;
+	unsigned int pos = parser->push_pos;
+	u32 entry;
+
+	if (!motu->hwdep || motu->hwdep->used == 0)
+		return;
+
+	entry = (msg_type << 24) | (identifier0 << 16) | (identifier1 << 8) | val;
+	parser->event_queue[pos] = entry;
+
+	++pos;
+	if (pos >= EVENT_QUEUE_SIZE)
+		pos = 0;
+	parser->push_pos = pos;
+}
+
+void snd_motu_register_dsp_message_parser_parse(struct snd_motu *motu, const struct pkt_desc *descs,
+					unsigned int desc_count, unsigned int data_block_quadlets)
+{
+	struct msg_parser *parser = motu->message_parser;
+	bool meter_pos_quirk = parser->meter_pos_quirk;
+	unsigned int pos = parser->push_pos;
+	unsigned long flags;
+	int i;
+
+	spin_lock_irqsave(&parser->lock, flags);
+
+	for (i = 0; i < desc_count; ++i) {
+		const struct pkt_desc *desc = descs + i;
+		__be32 *buffer = desc->ctx_payload;
+		unsigned int data_blocks = desc->data_blocks;
+		int j;
+
+		for (j = 0; j < data_blocks; ++j) {
+			u8 *b = (u8 *)buffer;
+			u8 msg_type = (b[MSG_FLAG_POS] & MSG_FLAG_TYPE_MASK) >> MSG_FLAG_TYPE_SHIFT;
+			u8 val = b[MSG_VALUE_POS];
+
+			buffer += data_block_quadlets;
+
+			switch (msg_type) {
+			case MIXER_SELECT:
+			{
+				u8 mixer_ch = val / 0x20;
+				if (mixer_ch < SNDRV_FIREWIRE_MOTU_REGISTER_DSP_MIXER_COUNT) {
+					parser->mixer_src_ch = 0;
+					parser->mixer_ch = mixer_ch;
+				}
+				break;
+			}
+			case MIXER_SRC_GAIN:
+			case MIXER_SRC_PAN:
+			case MIXER_SRC_FLAG:
+			case MIXER_SRC_PAIRED_BALANCE:
+			case MIXER_SRC_PAIRED_WIDTH:
+			{
+				struct snd_firewire_motu_register_dsp_parameter *param = &parser->param;
+				u8 mixer_ch = parser->mixer_ch;
+				u8 mixer_src_ch = parser->mixer_src_ch;
+
+				if (msg_type != parser->prev_mixer_src_type)
+					mixer_src_ch = 0;
+				else
+					++mixer_src_ch;
+				parser->prev_mixer_src_type = msg_type;
+
+				if (mixer_ch < SNDRV_FIREWIRE_MOTU_REGISTER_DSP_MIXER_COUNT &&
+				    mixer_src_ch < SNDRV_FIREWIRE_MOTU_REGISTER_DSP_MIXER_SRC_COUNT) {
+					u8 mixer_ch = parser->mixer_ch;
+
+					switch (msg_type) {
+					case MIXER_SRC_GAIN:
+						if (param->mixer.source[mixer_ch].gain[mixer_src_ch] != val) {
+							queue_event(motu, msg_type, mixer_ch, mixer_src_ch, val);
+							param->mixer.source[mixer_ch].gain[mixer_src_ch] = val;
+						}
+						break;
+					case MIXER_SRC_PAN:
+						if (param->mixer.source[mixer_ch].pan[mixer_src_ch] != val) {
+							queue_event(motu, msg_type, mixer_ch, mixer_src_ch, val);
+							param->mixer.source[mixer_ch].pan[mixer_src_ch] = val;
+						}
+						break;
+					case MIXER_SRC_FLAG:
+						if (param->mixer.source[mixer_ch].flag[mixer_src_ch] != val) {
+							queue_event(motu, msg_type, mixer_ch, mixer_src_ch, val);
+							param->mixer.source[mixer_ch].flag[mixer_src_ch] = val;
+						}
+						break;
+					case MIXER_SRC_PAIRED_BALANCE:
+						if (param->mixer.source[mixer_ch].paired_balance[mixer_src_ch] != val) {
+							queue_event(motu, msg_type, mixer_ch, mixer_src_ch, val);
+							param->mixer.source[mixer_ch].paired_balance[mixer_src_ch] = val;
+						}
+						break;
+					case MIXER_SRC_PAIRED_WIDTH:
+						if (param->mixer.source[mixer_ch].paired_width[mixer_src_ch] != val) {
+							queue_event(motu, msg_type, mixer_ch, mixer_src_ch, val);
+							param->mixer.source[mixer_ch].paired_width[mixer_src_ch] = val;
+						}
+						break;
+					default:
+						break;
+					}
+
+					parser->mixer_src_ch = mixer_src_ch;
+				}
+				break;
+			}
+			case MIXER_OUTPUT_PAIRED_VOLUME:
+			case MIXER_OUTPUT_PAIRED_FLAG:
+			{
+				struct snd_firewire_motu_register_dsp_parameter *param = &parser->param;
+				u8 mixer_ch = parser->mixer_ch;
+
+				if (mixer_ch < SNDRV_FIREWIRE_MOTU_REGISTER_DSP_MIXER_COUNT) {
+					switch (msg_type) {
+					case MIXER_OUTPUT_PAIRED_VOLUME:
+						if (param->mixer.output.paired_volume[mixer_ch] != val) {
+							queue_event(motu, msg_type, mixer_ch, 0, val);
+							param->mixer.output.paired_volume[mixer_ch] = val;
+						}
+						break;
+					case MIXER_OUTPUT_PAIRED_FLAG:
+						if (param->mixer.output.paired_flag[mixer_ch] != val) {
+							queue_event(motu, msg_type, mixer_ch, 0, val);
+							param->mixer.output.paired_flag[mixer_ch] = val;
+						}
+						break;
+					default:
+						break;
+					}
+				}
+				break;
+			}
+			case MAIN_OUTPUT_PAIRED_VOLUME:
+				if (parser->param.output.main_paired_volume != val) {
+					queue_event(motu, msg_type, 0, 0, val);
+					parser->param.output.main_paired_volume = val;
+				}
+				break;
+			case HP_OUTPUT_PAIRED_VOLUME:
+				if (parser->param.output.hp_paired_volume != val) {
+					queue_event(motu, msg_type, 0, 0, val);
+					parser->param.output.hp_paired_volume = val;
+				}
+				break;
+			case HP_OUTPUT_PAIRED_ASSIGNMENT:
+				if (parser->param.output.hp_paired_assignment != val) {
+					queue_event(motu, msg_type, 0, 0, val);
+					parser->param.output.hp_paired_assignment = val;
+				}
+				break;
+			case LINE_INPUT_BOOST:
+				if (parser->param.line_input.boost_flag != val) {
+					queue_event(motu, msg_type, 0, 0, val);
+					parser->param.line_input.boost_flag = val;
+				}
+				break;
+			case LINE_INPUT_NOMINAL_LEVEL:
+				if (parser->param.line_input.nominal_level_flag != val) {
+					queue_event(motu, msg_type, 0, 0, val);
+					parser->param.line_input.nominal_level_flag = val;
+				}
+				break;
+			case INPUT_GAIN_AND_INVERT:
+			case INPUT_FLAG:
+			{
+				struct snd_firewire_motu_register_dsp_parameter *param = &parser->param;
+				u8 input_ch = parser->input_ch;
+
+				if (parser->prev_msg_type != msg_type)
+					input_ch = 0;
+				else
+					++input_ch;
+
+				if (input_ch < SNDRV_FIREWIRE_MOTU_REGISTER_DSP_INPUT_COUNT) {
+					switch (msg_type) {
+					case INPUT_GAIN_AND_INVERT:
+						if (param->input.gain_and_invert[input_ch] != val) {
+							queue_event(motu, msg_type, input_ch, 0, val);
+							param->input.gain_and_invert[input_ch] = val;
+						}
+						break;
+					case INPUT_FLAG:
+						if (param->input.flag[input_ch] != val) {
+							queue_event(motu, msg_type, input_ch, 0, val);
+							param->input.flag[input_ch] = val;
+						}
+						break;
+					default:
+						break;
+					}
+					parser->input_ch = input_ch;
+				}
+				break;
+			}
+			case UNKNOWN_0:
+			case UNKNOWN_2:
+				break;
+			case METER:
+			{
+				u8 pos;
+
+				if (!meter_pos_quirk)
+					pos = b[MSG_METER_IDX_POS];
+				else
+					pos = b[MSG_METER_IDX_POS_4PRE_AE];
+
+				if (pos < SNDRV_FIREWIRE_MOTU_REGISTER_DSP_METER_INPUT_COUNT) {
+					parser->meter.data[pos] = val;
+				} else if (pos >= 0x80) {
+					pos -= (0x80 - SNDRV_FIREWIRE_MOTU_REGISTER_DSP_METER_INPUT_COUNT);
+
+					if (pos < SNDRV_FIREWIRE_MOTU_REGISTER_DSP_METER_COUNT)
+						parser->meter.data[pos] = val;
+				}
+
+				// The message for meter is interruptible to the series of other
+				// types of messages. Don't cache it.
+				fallthrough;
+			}
+			case INVALID:
+			default:
+				// Don't cache it.
+				continue;
+			}
+
+			parser->prev_msg_type = msg_type;
+		}
+	}
+
+	if (pos != parser->push_pos)
+		wake_up(&motu->hwdep_wait);
+
+	spin_unlock_irqrestore(&parser->lock, flags);
+}
+
+void snd_motu_register_dsp_message_parser_copy_meter(struct snd_motu *motu,
+						struct snd_firewire_motu_register_dsp_meter *meter)
+{
+	struct msg_parser *parser = motu->message_parser;
+	unsigned long flags;
+
+	spin_lock_irqsave(&parser->lock, flags);
+	memcpy(meter, &parser->meter, sizeof(*meter));
+	spin_unlock_irqrestore(&parser->lock, flags);
+}
+
+void snd_motu_register_dsp_message_parser_copy_parameter(struct snd_motu *motu,
+					struct snd_firewire_motu_register_dsp_parameter *param)
+{
+	struct msg_parser *parser = motu->message_parser;
+	unsigned long flags;
+
+	spin_lock_irqsave(&parser->lock, flags);
+	memcpy(param, &parser->param, sizeof(*param));
+	spin_unlock_irqrestore(&parser->lock, flags);
+}
+
+unsigned int snd_motu_register_dsp_message_parser_count_event(struct snd_motu *motu)
+{
+	struct msg_parser *parser = motu->message_parser;
+
+	if (parser->pull_pos > parser->push_pos)
+		return EVENT_QUEUE_SIZE - parser->pull_pos + parser->push_pos;
+	else
+		return parser->push_pos - parser->pull_pos;
+}
+
+bool snd_motu_register_dsp_message_parser_copy_event(struct snd_motu *motu, u32 *event)
+{
+	struct msg_parser *parser = motu->message_parser;
+	unsigned int pos = parser->pull_pos;
+	unsigned long flags;
+
+	if (pos == parser->push_pos)
+		return false;
+
+	spin_lock_irqsave(&parser->lock, flags);
+
+	*event = parser->event_queue[pos];
+
+	++pos;
+	if (pos >= EVENT_QUEUE_SIZE)
+		pos = 0;
+	parser->pull_pos = pos;
+
+	spin_unlock_irqrestore(&parser->lock, flags);
+
+	return true;
+}
diff --git a/sound/firewire/motu/motu-stream.c b/sound/firewire/motu/motu-stream.c
index 9e6ca39ebd7f..64aec9c3eefd 100644
--- a/sound/firewire/motu/motu-stream.c
+++ b/sound/firewire/motu/motu-stream.c
@@ -255,6 +255,16 @@ int snd_motu_stream_start_duplex(struct snd_motu *motu)
 		if (err < 0)
 			return err;
 
+		if (motu->spec->flags & SND_MOTU_SPEC_REGISTER_DSP) {
+			err = snd_motu_register_dsp_message_parser_init(motu);
+			if (err < 0)
+				return err;
+		} else if (motu->spec->flags & SND_MOTU_SPEC_COMMAND_DSP) {
+			err = snd_motu_command_dsp_message_parser_init(motu, motu->tx_stream.sfc);
+			if (err < 0)
+				return err;
+		}
+
 		err = begin_session(motu);
 		if (err < 0) {
 			dev_err(&motu->unit->device,
diff --git a/sound/firewire/motu/motu.c b/sound/firewire/motu/motu.c
index f65426238d4c..5fc7ae475537 100644
--- a/sound/firewire/motu/motu.c
+++ b/sound/firewire/motu/motu.c
@@ -112,6 +112,16 @@ static int motu_probe(struct fw_unit *unit, const struct ieee1394_device_id *ent
 	if (err < 0)
 		goto error;
 
+	if (motu->spec->flags & SND_MOTU_SPEC_REGISTER_DSP) {
+		err = snd_motu_register_dsp_message_parser_new(motu);
+		if (err < 0)
+			goto error;
+	} else if (motu->spec->flags & SND_MOTU_SPEC_COMMAND_DSP) {
+		err = snd_motu_command_dsp_message_parser_new(motu);
+		if (err < 0)
+			goto error;
+	}
+
 	err = snd_card_register(card);
 	if (err < 0)
 		goto error;
diff --git a/sound/firewire/motu/motu.h b/sound/firewire/motu/motu.h
index f1a830b358d4..79704ae6a73e 100644
--- a/sound/firewire/motu/motu.h
+++ b/sound/firewire/motu/motu.h
@@ -74,10 +74,13 @@ struct snd_motu {
 	int dev_lock_count;
 	bool dev_lock_changed;
 	wait_queue_head_t hwdep_wait;
+	struct snd_hwdep *hwdep;
 
 	struct amdtp_domain domain;
 
 	struct amdtp_motu_cache cache;
+
+	void *message_parser;
 };
 
 enum snd_motu_spec_flags {
@@ -85,6 +88,8 @@ enum snd_motu_spec_flags {
 	SND_MOTU_SPEC_RX_MIDI_3RD_Q	= 0x0002,
 	SND_MOTU_SPEC_TX_MIDI_2ND_Q	= 0x0004,
 	SND_MOTU_SPEC_TX_MIDI_3RD_Q	= 0x0008,
+	SND_MOTU_SPEC_REGISTER_DSP	= 0x0010,
+	SND_MOTU_SPEC_COMMAND_DSP	= 0x0020,
 };
 
 #define SND_MOTU_CLOCK_RATE_COUNT	6
@@ -270,4 +275,22 @@ static inline int snd_motu_protocol_cache_packet_formats(struct snd_motu *motu)
 		return -ENXIO;
 }
 
+int snd_motu_register_dsp_message_parser_new(struct snd_motu *motu);
+int snd_motu_register_dsp_message_parser_init(struct snd_motu *motu);
+void snd_motu_register_dsp_message_parser_parse(struct snd_motu *motu, const struct pkt_desc *descs,
+					unsigned int desc_count, unsigned int data_block_quadlets);
+void snd_motu_register_dsp_message_parser_copy_meter(struct snd_motu *motu,
+					struct snd_firewire_motu_register_dsp_meter *meter);
+void snd_motu_register_dsp_message_parser_copy_parameter(struct snd_motu *motu,
+					struct snd_firewire_motu_register_dsp_parameter *params);
+unsigned int snd_motu_register_dsp_message_parser_count_event(struct snd_motu *motu);
+bool snd_motu_register_dsp_message_parser_copy_event(struct snd_motu *motu, u32 *event);
+
+int snd_motu_command_dsp_message_parser_new(struct snd_motu *motu);
+int snd_motu_command_dsp_message_parser_init(struct snd_motu *motu, enum cip_sfc sfc);
+void snd_motu_command_dsp_message_parser_parse(struct snd_motu *motu, const struct pkt_desc *descs,
+					unsigned int desc_count, unsigned int data_block_quadlets);
+void snd_motu_command_dsp_message_parser_copy_meter(struct snd_motu *motu,
+					struct snd_firewire_motu_command_dsp_meter *meter);
+
 #endif
diff --git a/sound/firewire/oxfw/oxfw-stream.c b/sound/firewire/oxfw/oxfw-stream.c
index fff18b5d4e05..f4a702def397 100644
--- a/sound/firewire/oxfw/oxfw-stream.c
+++ b/sound/firewire/oxfw/oxfw-stream.c
@@ -9,7 +9,7 @@
 #include <linux/delay.h>
 
 #define AVC_GENERIC_FRAME_MAXIMUM_BYTES	512
-#define READY_TIMEOUT_MS	200
+#define READY_TIMEOUT_MS	600
 
 /*
  * According to datasheet of Oxford Semiconductor:
@@ -367,6 +367,11 @@ int snd_oxfw_stream_start_duplex(struct snd_oxfw *oxfw)
 				// Just after changing sampling transfer frequency, many cycles are
 				// skipped for packet transmission.
 				tx_init_skip_cycles = 400;
+			} else if (oxfw->quirks & SND_OXFW_QUIRK_VOLUNTARY_RECOVERY) {
+				// It takes a bit time for target device to adjust event frequency
+				// according to nominal event frequency in isochronous packets from
+				// ALSA oxfw driver.
+				tx_init_skip_cycles = 4000;
 			} else {
 				replay_seq = true;
 			}
diff --git a/sound/firewire/oxfw/oxfw.c b/sound/firewire/oxfw/oxfw.c
index daf731364695..b496f87841ae 100644
--- a/sound/firewire/oxfw/oxfw.c
+++ b/sound/firewire/oxfw/oxfw.c
@@ -25,6 +25,7 @@
 #define MODEL_SATELLITE		0x00200f
 #define MODEL_SCS1M		0x001000
 #define MODEL_DUET_FW		0x01dddd
+#define MODEL_ONYX_1640I	0x001640
 
 #define SPECIFIER_1394TA	0x00a02d
 #define VERSION_AVC		0x010001
@@ -192,6 +193,13 @@ static int detect_quirks(struct snd_oxfw *oxfw, const struct ieee1394_device_id
 		// OXFW971-based models may transfer events by blocking method.
 		if (!(oxfw->quirks & SND_OXFW_QUIRK_JUMBO_PAYLOAD))
 			oxfw->quirks |= SND_OXFW_QUIRK_BLOCKING_TRANSMISSION;
+
+		if (model == MODEL_ONYX_1640I) {
+			//Unless receiving packets without NOINFO packet, the device transfers
+			//mostly half of events in packets than expected.
+			oxfw->quirks |= SND_OXFW_QUIRK_IGNORE_NO_INFO_PACKET |
+					SND_OXFW_QUIRK_VOLUNTARY_RECOVERY;
+		}
 	}
 
 	return 0;
diff --git a/sound/firewire/oxfw/oxfw.h b/sound/firewire/oxfw/oxfw.h
index c13034f6c2ca..d728e451a25c 100644
--- a/sound/firewire/oxfw/oxfw.h
+++ b/sound/firewire/oxfw/oxfw.h
@@ -47,6 +47,11 @@ enum snd_oxfw_quirk {
 	// the device to process audio data even if the value is invalid in a point of
 	// IEC 61883-1/6.
 	SND_OXFW_QUIRK_IGNORE_NO_INFO_PACKET = 0x10,
+	// Loud Technologies Mackie Onyx 1640i seems to configure OXFW971 ASIC so that it decides
+	// event frequency according to events in received isochronous packets. The device looks to
+	// performs media clock recovery voluntarily. In the recovery, the packets with NO_INFO
+	// are ignored, thus driver should transfer packets with timestamp.
+	SND_OXFW_QUIRK_VOLUNTARY_RECOVERY = 0x20,
 };
 
 /* This is an arbitrary number for convinience. */
diff --git a/sound/hda/ext/hdac_ext_stream.c b/sound/hda/ext/hdac_ext_stream.c
index 0c005d67fa89..37154ed43bd5 100644
--- a/sound/hda/ext/hdac_ext_stream.c
+++ b/sound/hda/ext/hdac_ext_stream.c
@@ -106,20 +106,14 @@ void snd_hdac_stream_free_all(struct hdac_bus *bus)
 }
 EXPORT_SYMBOL_GPL(snd_hdac_stream_free_all);
 
-/**
- * snd_hdac_ext_stream_decouple - decouple the hdac stream
- * @bus: HD-audio core bus
- * @stream: HD-audio ext core stream object to initialize
- * @decouple: flag to decouple
- */
-void snd_hdac_ext_stream_decouple(struct hdac_bus *bus,
-				struct hdac_ext_stream *stream, bool decouple)
+void snd_hdac_ext_stream_decouple_locked(struct hdac_bus *bus,
+					 struct hdac_ext_stream *stream,
+					 bool decouple)
 {
 	struct hdac_stream *hstream = &stream->hstream;
 	u32 val;
 	int mask = AZX_PPCTL_PROCEN(hstream->index);
 
-	spin_lock_irq(&bus->reg_lock);
 	val = readw(bus->ppcap + AZX_REG_PP_PPCTL) & mask;
 
 	if (decouple && !val)
@@ -128,6 +122,20 @@ void snd_hdac_ext_stream_decouple(struct hdac_bus *bus,
 		snd_hdac_updatel(bus->ppcap, AZX_REG_PP_PPCTL, mask, 0);
 
 	stream->decoupled = decouple;
+}
+EXPORT_SYMBOL_GPL(snd_hdac_ext_stream_decouple_locked);
+
+/**
+ * snd_hdac_ext_stream_decouple - decouple the hdac stream
+ * @bus: HD-audio core bus
+ * @stream: HD-audio ext core stream object to initialize
+ * @decouple: flag to decouple
+ */
+void snd_hdac_ext_stream_decouple(struct hdac_bus *bus,
+				  struct hdac_ext_stream *stream, bool decouple)
+{
+	spin_lock_irq(&bus->reg_lock);
+	snd_hdac_ext_stream_decouple_locked(bus, stream, decouple);
 	spin_unlock_irq(&bus->reg_lock);
 }
 EXPORT_SYMBOL_GPL(snd_hdac_ext_stream_decouple);
@@ -252,6 +260,7 @@ hdac_ext_link_stream_assign(struct hdac_bus *bus,
 		return NULL;
 	}
 
+	spin_lock_irq(&bus->reg_lock);
 	list_for_each_entry(stream, &bus->stream_list, list) {
 		struct hdac_ext_stream *hstream = container_of(stream,
 						struct hdac_ext_stream,
@@ -266,17 +275,16 @@ hdac_ext_link_stream_assign(struct hdac_bus *bus,
 		}
 
 		if (!hstream->link_locked) {
-			snd_hdac_ext_stream_decouple(bus, hstream, true);
+			snd_hdac_ext_stream_decouple_locked(bus, hstream, true);
 			res = hstream;
 			break;
 		}
 	}
 	if (res) {
-		spin_lock_irq(&bus->reg_lock);
 		res->link_locked = 1;
 		res->link_substream = substream;
-		spin_unlock_irq(&bus->reg_lock);
 	}
+	spin_unlock_irq(&bus->reg_lock);
 	return res;
 }
 
@@ -292,6 +300,7 @@ hdac_ext_host_stream_assign(struct hdac_bus *bus,
 		return NULL;
 	}
 
+	spin_lock_irq(&bus->reg_lock);
 	list_for_each_entry(stream, &bus->stream_list, list) {
 		struct hdac_ext_stream *hstream = container_of(stream,
 						struct hdac_ext_stream,
@@ -301,18 +310,17 @@ hdac_ext_host_stream_assign(struct hdac_bus *bus,
 
 		if (!stream->opened) {
 			if (!hstream->decoupled)
-				snd_hdac_ext_stream_decouple(bus, hstream, true);
+				snd_hdac_ext_stream_decouple_locked(bus, hstream, true);
 			res = hstream;
 			break;
 		}
 	}
 	if (res) {
-		spin_lock_irq(&bus->reg_lock);
 		res->hstream.opened = 1;
 		res->hstream.running = 0;
 		res->hstream.substream = substream;
-		spin_unlock_irq(&bus->reg_lock);
 	}
+	spin_unlock_irq(&bus->reg_lock);
 
 	return res;
 }
@@ -378,15 +386,17 @@ void snd_hdac_ext_stream_release(struct hdac_ext_stream *stream, int type)
 		break;
 
 	case HDAC_EXT_STREAM_TYPE_HOST:
+		spin_lock_irq(&bus->reg_lock);
 		if (stream->decoupled && !stream->link_locked)
-			snd_hdac_ext_stream_decouple(bus, stream, false);
+			snd_hdac_ext_stream_decouple_locked(bus, stream, false);
+		spin_unlock_irq(&bus->reg_lock);
 		snd_hdac_stream_release(&stream->hstream);
 		break;
 
 	case HDAC_EXT_STREAM_TYPE_LINK:
-		if (stream->decoupled && !stream->hstream.opened)
-			snd_hdac_ext_stream_decouple(bus, stream, false);
 		spin_lock_irq(&bus->reg_lock);
+		if (stream->decoupled && !stream->hstream.opened)
+			snd_hdac_ext_stream_decouple_locked(bus, stream, false);
 		stream->link_locked = 0;
 		stream->link_substream = NULL;
 		spin_unlock_irq(&bus->reg_lock);
diff --git a/sound/hda/hdac_stream.c b/sound/hda/hdac_stream.c
index 1eb8563db2df..9867555883c3 100644
--- a/sound/hda/hdac_stream.c
+++ b/sound/hda/hdac_stream.c
@@ -296,6 +296,7 @@ struct hdac_stream *snd_hdac_stream_assign(struct hdac_bus *bus,
 	int key = (substream->pcm->device << 16) | (substream->number << 2) |
 		(substream->stream + 1);
 
+	spin_lock_irq(&bus->reg_lock);
 	list_for_each_entry(azx_dev, &bus->stream_list, list) {
 		if (azx_dev->direction != substream->stream)
 			continue;
@@ -309,13 +310,12 @@ struct hdac_stream *snd_hdac_stream_assign(struct hdac_bus *bus,
 			res = azx_dev;
 	}
 	if (res) {
-		spin_lock_irq(&bus->reg_lock);
 		res->opened = 1;
 		res->running = 0;
 		res->assigned_key = key;
 		res->substream = substream;
-		spin_unlock_irq(&bus->reg_lock);
 	}
+	spin_unlock_irq(&bus->reg_lock);
 	return res;
 }
 EXPORT_SYMBOL_GPL(snd_hdac_stream_assign);
diff --git a/sound/isa/Kconfig b/sound/isa/Kconfig
index 6ffa48dd5983..570b88e0b201 100644
--- a/sound/isa/Kconfig
+++ b/sound/isa/Kconfig
@@ -22,7 +22,7 @@ config SND_SB16_DSP
 menuconfig SND_ISA
 	bool "ISA sound devices"
 	depends on ISA || COMPILE_TEST
-	depends on ISA_DMA_API
+	depends on ISA_DMA_API && !M68K
 	default y
 	help
 	  Support for sound devices connected via the ISA bus.
diff --git a/sound/isa/gus/gus_dma.c b/sound/isa/gus/gus_dma.c
index a1c770d826dd..6d664dd8dde0 100644
--- a/sound/isa/gus/gus_dma.c
+++ b/sound/isa/gus/gus_dma.c
@@ -126,6 +126,8 @@ static void snd_gf1_dma_interrupt(struct snd_gus_card * gus)
 	}
 	block = snd_gf1_dma_next_block(gus);
 	spin_unlock(&gus->dma_lock);
+	if (!block)
+		return;
 	snd_gf1_dma_program(gus, block->addr, block->buf_addr, block->count, (unsigned short) block->cmd);
 	kfree(block);
 #if 0
diff --git a/sound/pci/Kconfig b/sound/pci/Kconfig
index 93bc9bef7641..41ce12597177 100644
--- a/sound/pci/Kconfig
+++ b/sound/pci/Kconfig
@@ -279,6 +279,7 @@ config SND_CS46XX_NEW_DSP
 config SND_CS5530
 	tristate "CS5530 Audio"
 	depends on ISA_DMA_API && (X86_32 || COMPILE_TEST)
+	depends on !M68K
 	select SND_SB16_DSP
 	help
 	  Say Y here to include support for audio on Cyrix/NatSemi CS5530 chips.
diff --git a/sound/pci/hda/hda_intel.c b/sound/pci/hda/hda_intel.c
index 4d22e7adeee8..7762718cf429 100644
--- a/sound/pci/hda/hda_intel.c
+++ b/sound/pci/hda/hda_intel.c
@@ -638,13 +638,17 @@ static int azx_position_check(struct azx *chip, struct azx_dev *azx_dev)
  * the update-IRQ timing.  The IRQ is issued before actually the
  * data is processed.  So, we need to process it afterwords in a
  * workqueue.
+ *
+ * Returns 1 if OK to proceed, 0 for delay handling, -1 for skipping update
  */
 static int azx_position_ok(struct azx *chip, struct azx_dev *azx_dev)
 {
 	struct snd_pcm_substream *substream = azx_dev->core.substream;
+	struct snd_pcm_runtime *runtime = substream->runtime;
 	int stream = substream->stream;
 	u32 wallclk;
 	unsigned int pos;
+	snd_pcm_uframes_t hwptr, target;
 
 	wallclk = azx_readl(chip, WALLCLK) - azx_dev->core.start_wallclk;
 	if (wallclk < (azx_dev->core.period_wallclk * 2) / 3)
@@ -681,6 +685,24 @@ static int azx_position_ok(struct azx *chip, struct azx_dev *azx_dev)
 		/* NG - it's below the first next period boundary */
 		return chip->bdl_pos_adj ? 0 : -1;
 	azx_dev->core.start_wallclk += wallclk;
+
+	if (azx_dev->core.no_period_wakeup)
+		return 1; /* OK, no need to check period boundary */
+
+	if (runtime->hw_ptr_base != runtime->hw_ptr_interrupt)
+		return 1; /* OK, already in hwptr updating process */
+
+	/* check whether the period gets really elapsed */
+	pos = bytes_to_frames(runtime, pos);
+	hwptr = runtime->hw_ptr_base + pos;
+	if (hwptr < runtime->status->hw_ptr)
+		hwptr += runtime->buffer_size;
+	target = runtime->hw_ptr_interrupt + runtime->period_size;
+	if (hwptr < target) {
+		/* too early wakeup, process it later */
+		return chip->bdl_pos_adj ? 0 : -1;
+	}
+
 	return 1; /* OK, it's fine */
 }
 
@@ -859,31 +881,6 @@ static int azx_get_delay_from_fifo(struct azx *chip, struct azx_dev *azx_dev,
 	return substream->runtime->delay;
 }
 
-static unsigned int azx_skl_get_dpib_pos(struct azx *chip,
-					 struct azx_dev *azx_dev)
-{
-	return _snd_hdac_chip_readl(azx_bus(chip),
-				    AZX_REG_VS_SDXDPIB_XBASE +
-				    (AZX_REG_VS_SDXDPIB_XINTERVAL *
-				     azx_dev->core.index));
-}
-
-/* get the current DMA position with correction on SKL+ chips */
-static unsigned int azx_get_pos_skl(struct azx *chip, struct azx_dev *azx_dev)
-{
-	/* DPIB register gives a more accurate position for playback */
-	if (azx_dev->core.substream->stream == SNDRV_PCM_STREAM_PLAYBACK)
-		return azx_skl_get_dpib_pos(chip, azx_dev);
-
-	/* For capture, we need to read posbuf, but it requires a delay
-	 * for the possible boundary overlap; the read of DPIB fetches the
-	 * actual posbuf
-	 */
-	udelay(20);
-	azx_skl_get_dpib_pos(chip, azx_dev);
-	return azx_get_pos_posbuf(chip, azx_dev);
-}
-
 static void __azx_shutdown_chip(struct azx *chip, bool skip_link_reset)
 {
 	azx_stop_chip(chip);
@@ -1573,7 +1570,7 @@ static void assign_position_fix(struct azx *chip, int fix)
 		[POS_FIX_POSBUF] = azx_get_pos_posbuf,
 		[POS_FIX_VIACOMBO] = azx_via_get_position,
 		[POS_FIX_COMBO] = azx_get_pos_lpib,
-		[POS_FIX_SKL] = azx_get_pos_skl,
+		[POS_FIX_SKL] = azx_get_pos_posbuf,
 		[POS_FIX_FIFO] = azx_get_pos_fifo,
 	};
 
diff --git a/sound/pci/hda/patch_realtek.c b/sound/pci/hda/patch_realtek.c
index e82d756ab850..6322fac9e694 100644
--- a/sound/pci/hda/patch_realtek.c
+++ b/sound/pci/hda/patch_realtek.c
@@ -8634,6 +8634,7 @@ static const struct snd_pci_quirk alc269_fixup_tbl[] = {
 		      ALC285_FIXUP_HP_GPIO_AMP_INIT),
 	SND_PCI_QUIRK(0x103c, 0x8783, "HP ZBook Fury 15 G7 Mobile Workstation",
 		      ALC285_FIXUP_HP_GPIO_AMP_INIT),
+	SND_PCI_QUIRK(0x103c, 0x8788, "HP OMEN 15", ALC285_FIXUP_HP_MUTE_LED),
 	SND_PCI_QUIRK(0x103c, 0x87c8, "HP", ALC287_FIXUP_HP_GPIO_LED),
 	SND_PCI_QUIRK(0x103c, 0x87e5, "HP ProBook 440 G8 Notebook PC", ALC236_FIXUP_HP_GPIO_LED),
 	SND_PCI_QUIRK(0x103c, 0x87e7, "HP ProBook 450 G8 Notebook PC", ALC236_FIXUP_HP_GPIO_LED),
diff --git a/sound/soc/sof/intel/hda-dai.c b/sound/soc/sof/intel/hda-dai.c
index c1f9f0f58464..6704dbcd101c 100644
--- a/sound/soc/sof/intel/hda-dai.c
+++ b/sound/soc/sof/intel/hda-dai.c
@@ -68,6 +68,7 @@ static struct hdac_ext_stream *
 		return NULL;
 	}
 
+	spin_lock_irq(&bus->reg_lock);
 	list_for_each_entry(stream, &bus->stream_list, list) {
 		struct hdac_ext_stream *hstream =
 			stream_to_hdac_ext_stream(stream);
@@ -107,12 +108,12 @@ static struct hdac_ext_stream *
 		 * is updated in snd_hdac_ext_stream_decouple().
 		 */
 		if (!res->decoupled)
-			snd_hdac_ext_stream_decouple(bus, res, true);
-		spin_lock_irq(&bus->reg_lock);
+			snd_hdac_ext_stream_decouple_locked(bus, res, true);
+
 		res->link_locked = 1;
 		res->link_substream = substream;
-		spin_unlock_irq(&bus->reg_lock);
 	}
+	spin_unlock_irq(&bus->reg_lock);
 
 	return res;
 }
diff --git a/sound/usb/6fire/comm.c b/sound/usb/6fire/comm.c
index 43a2a62d66f7..49629d4bb327 100644
--- a/sound/usb/6fire/comm.c
+++ b/sound/usb/6fire/comm.c
@@ -95,7 +95,7 @@ static int usb6fire_comm_send_buffer(u8 *buffer, struct usb_device *dev)
 	int actual_len;
 
 	ret = usb_interrupt_msg(dev, usb_sndintpipe(dev, COMM_EP),
-			buffer, buffer[1] + 2, &actual_len, HZ);
+			buffer, buffer[1] + 2, &actual_len, 1000);
 	if (ret < 0)
 		return ret;
 	else if (actual_len != buffer[1] + 2)
diff --git a/sound/usb/6fire/firmware.c b/sound/usb/6fire/firmware.c
index 8981e61f2da4..c51abc54d2f8 100644
--- a/sound/usb/6fire/firmware.c
+++ b/sound/usb/6fire/firmware.c
@@ -160,7 +160,7 @@ static int usb6fire_fw_ezusb_write(struct usb_device *device,
 {
 	return usb_control_msg_send(device, 0, type,
 				    USB_DIR_OUT | USB_TYPE_VENDOR | USB_RECIP_DEVICE,
-				    value, 0, data, len, HZ, GFP_KERNEL);
+				    value, 0, data, len, 1000, GFP_KERNEL);
 }
 
 static int usb6fire_fw_ezusb_read(struct usb_device *device,
@@ -168,7 +168,7 @@ static int usb6fire_fw_ezusb_read(struct usb_device *device,
 {
 	return usb_control_msg_recv(device, 0, type,
 				    USB_DIR_IN | USB_TYPE_VENDOR | USB_RECIP_DEVICE,
-				    value, 0, data, len, HZ, GFP_KERNEL);
+				    value, 0, data, len, 1000, GFP_KERNEL);
 }
 
 static int usb6fire_fw_fpga_write(struct usb_device *device,
@@ -178,7 +178,7 @@ static int usb6fire_fw_fpga_write(struct usb_device *device,
 	int ret;
 
 	ret = usb_bulk_msg(device, usb_sndbulkpipe(device, FPGA_EP), data, len,
-			&actual_len, HZ);
+			&actual_len, 1000);
 	if (ret < 0)
 		return ret;
 	else if (actual_len != len)
diff --git a/sound/usb/card.h b/sound/usb/card.h
index 5b19901f305a..87f042d06ce0 100644
--- a/sound/usb/card.h
+++ b/sound/usb/card.h
@@ -74,8 +74,9 @@ struct snd_usb_endpoint {
 
 	atomic_t state;		/* running state */
 
-	void (*prepare_data_urb) (struct snd_usb_substream *subs,
-				  struct urb *urb);
+	int (*prepare_data_urb) (struct snd_usb_substream *subs,
+				 struct urb *urb,
+				 bool in_stream_lock);
 	void (*retire_data_urb) (struct snd_usb_substream *subs,
 				 struct urb *urb);
 
@@ -94,9 +95,9 @@ struct snd_usb_endpoint {
 	struct list_head ready_playback_urbs; /* playback URB FIFO for implicit fb */
 
 	unsigned int nurbs;		/* # urbs */
-	unsigned int nominal_queue_size; /* total buffer sizes in URBs */
 	unsigned long active_mask;	/* bitmask of active urbs */
 	unsigned long unlink_mask;	/* bitmask of unlinked urbs */
+	atomic_t submitted_urbs;	/* currently submitted urbs */
 	char *syncbuf;			/* sync buffer for all sync URBs */
 	dma_addr_t sync_dma;		/* DMA address of syncbuf */
 
@@ -125,6 +126,7 @@ struct snd_usb_endpoint {
 	int skip_packets;		/* quirks for devices to ignore the first n packets
 					   in a stream */
 	bool implicit_fb_sync;		/* syncs with implicit feedback */
+	bool lowlatency_playback;	/* low-latency playback mode */
 	bool need_setup;		/* (re-)need for configure? */
 
 	/* for hw constraints */
@@ -136,6 +138,7 @@ struct snd_usb_endpoint {
 	unsigned int cur_period_frames;
 	unsigned int cur_period_bytes;
 	unsigned int cur_buffer_periods;
+	unsigned char cur_clock;
 
 	spinlock_t lock;
 	struct list_head list;
@@ -188,7 +191,7 @@ struct snd_usb_substream {
 	} dsd_dop;
 
 	bool trigger_tstamp_pending_update; /* trigger timestamp being updated from initial estimate */
-	bool early_playback_start;	/* early start needed for playback? */
+	bool lowlatency_playback;	/* low-latency playback mode */
 	struct media_ctl *media_ctl;
 };
 
diff --git a/sound/usb/clock.c b/sound/usb/clock.c
index 81d5ce07d548..4dfe76416794 100644
--- a/sound/usb/clock.c
+++ b/sound/usb/clock.c
@@ -271,7 +271,7 @@ static int __uac_clock_find_source(struct snd_usb_audio *chip,
 		return -EINVAL;
 	}
 
-	/* first, see if the ID we're looking for is a clock source already */
+	/* first, see if the ID we're looking at is a clock source already */
 	source = snd_usb_find_clock_source(chip, entity_id, proto);
 	if (source) {
 		entity_id = GET_VAL(source, proto, bClockID);
@@ -297,7 +297,7 @@ static int __uac_clock_find_source(struct snd_usb_audio *chip,
 			goto find_source;
 		}
 
-		/* the entity ID we are looking for is a selector.
+		/* the entity ID we are looking at is a selector.
 		 * find out what it currently selects */
 		ret = uac_clock_selector_get_val(chip, clock_id);
 		if (ret < 0) {
@@ -496,6 +496,10 @@ int snd_usb_set_sample_rate_v2v3(struct snd_usb_audio *chip,
 	union uac23_clock_source_desc *cs_desc;
 
 	cs_desc = snd_usb_find_clock_source(chip, clock, fmt->protocol);
+
+	if (!cs_desc)
+		return 0;
+
 	if (fmt->protocol == UAC_VERSION_3)
 		bmControls = le32_to_cpu(cs_desc->v3.bmControls);
 	else
diff --git a/sound/usb/endpoint.c b/sound/usb/endpoint.c
index 533919a28856..743b8287cfcd 100644
--- a/sound/usb/endpoint.c
+++ b/sound/usb/endpoint.c
@@ -148,18 +148,23 @@ int snd_usb_endpoint_implicit_feedback_sink(struct snd_usb_endpoint *ep)
  * This won't be used for implicit feedback which takes the packet size
  * returned from the sync source
  */
-static int slave_next_packet_size(struct snd_usb_endpoint *ep)
+static int slave_next_packet_size(struct snd_usb_endpoint *ep,
+				  unsigned int avail)
 {
 	unsigned long flags;
+	unsigned int phase;
 	int ret;
 
 	if (ep->fill_max)
 		return ep->maxframesize;
 
 	spin_lock_irqsave(&ep->lock, flags);
-	ep->phase = (ep->phase & 0xffff)
-		+ (ep->freqm << ep->datainterval);
-	ret = min(ep->phase >> 16, ep->maxframesize);
+	phase = (ep->phase & 0xffff) + (ep->freqm << ep->datainterval);
+	ret = min(phase >> 16, ep->maxframesize);
+	if (avail && ret >= avail)
+		ret = -EAGAIN;
+	else
+		ep->phase = phase;
 	spin_unlock_irqrestore(&ep->lock, flags);
 
 	return ret;
@@ -169,20 +174,25 @@ static int slave_next_packet_size(struct snd_usb_endpoint *ep)
  * Return the number of samples to be sent in the next packet
  * for adaptive and synchronous endpoints
  */
-static int next_packet_size(struct snd_usb_endpoint *ep)
+static int next_packet_size(struct snd_usb_endpoint *ep, unsigned int avail)
 {
+	unsigned int sample_accum;
 	int ret;
 
 	if (ep->fill_max)
 		return ep->maxframesize;
 
-	ep->sample_accum += ep->sample_rem;
-	if (ep->sample_accum >= ep->pps) {
-		ep->sample_accum -= ep->pps;
+	sample_accum = ep->sample_accum + ep->sample_rem;
+	if (sample_accum >= ep->pps) {
+		sample_accum -= ep->pps;
 		ret = ep->packsize[1];
 	} else {
 		ret = ep->packsize[0];
 	}
+	if (avail && ret >= avail)
+		ret = -EAGAIN;
+	else
+		ep->sample_accum = sample_accum;
 
 	return ret;
 }
@@ -190,16 +200,27 @@ static int next_packet_size(struct snd_usb_endpoint *ep)
 /*
  * snd_usb_endpoint_next_packet_size: Return the number of samples to be sent
  * in the next packet
+ *
+ * If the size is equal or exceeds @avail, don't proceed but return -EAGAIN
+ * Exception: @avail = 0 for skipping the check.
  */
 int snd_usb_endpoint_next_packet_size(struct snd_usb_endpoint *ep,
-				      struct snd_urb_ctx *ctx, int idx)
+				      struct snd_urb_ctx *ctx, int idx,
+				      unsigned int avail)
 {
-	if (ctx->packet_size[idx])
-		return ctx->packet_size[idx];
-	else if (ep->sync_source)
-		return slave_next_packet_size(ep);
+	unsigned int packet;
+
+	packet = ctx->packet_size[idx];
+	if (packet) {
+		if (avail && packet >= avail)
+			return -EAGAIN;
+		return packet;
+	}
+
+	if (ep->sync_source)
+		return slave_next_packet_size(ep, avail);
 	else
-		return next_packet_size(ep);
+		return next_packet_size(ep, avail);
 }
 
 static void call_retire_callback(struct snd_usb_endpoint *ep,
@@ -263,7 +284,7 @@ static void prepare_silent_urb(struct snd_usb_endpoint *ep,
 		unsigned int length;
 		int counts;
 
-		counts = snd_usb_endpoint_next_packet_size(ep, ctx, i);
+		counts = snd_usb_endpoint_next_packet_size(ep, ctx, i, 0);
 		length = counts * ep->stride; /* number of silent bytes */
 		offset = offs * ep->stride + extra * i;
 		urb->iso_frame_desc[i].offset = offset;
@@ -286,8 +307,9 @@ static void prepare_silent_urb(struct snd_usb_endpoint *ep,
 /*
  * Prepare a PLAYBACK urb for submission to the bus.
  */
-static void prepare_outbound_urb(struct snd_usb_endpoint *ep,
-				 struct snd_urb_ctx *ctx)
+static int prepare_outbound_urb(struct snd_usb_endpoint *ep,
+				struct snd_urb_ctx *ctx,
+				bool in_stream_lock)
 {
 	struct urb *urb = ctx->urb;
 	unsigned char *cp = urb->transfer_buffer;
@@ -299,9 +321,9 @@ static void prepare_outbound_urb(struct snd_usb_endpoint *ep,
 	case SND_USB_ENDPOINT_TYPE_DATA:
 		data_subs = READ_ONCE(ep->data_subs);
 		if (data_subs && ep->prepare_data_urb)
-			ep->prepare_data_urb(data_subs, urb);
-		else /* no data provider, so send silence */
-			prepare_silent_urb(ep, ctx);
+			return ep->prepare_data_urb(data_subs, urb, in_stream_lock);
+		/* no data provider, so send silence */
+		prepare_silent_urb(ep, ctx);
 		break;
 
 	case SND_USB_ENDPOINT_TYPE_SYNC:
@@ -330,13 +352,14 @@ static void prepare_outbound_urb(struct snd_usb_endpoint *ep,
 
 		break;
 	}
+	return 0;
 }
 
 /*
  * Prepare a CAPTURE or SYNC urb for submission to the bus.
  */
-static inline void prepare_inbound_urb(struct snd_usb_endpoint *ep,
-				       struct snd_urb_ctx *urb_ctx)
+static int prepare_inbound_urb(struct snd_usb_endpoint *ep,
+			       struct snd_urb_ctx *urb_ctx)
 {
 	int i, offs;
 	struct urb *urb = urb_ctx->urb;
@@ -361,6 +384,7 @@ static inline void prepare_inbound_urb(struct snd_usb_endpoint *ep,
 		urb->iso_frame_desc[0].offset = 0;
 		break;
 	}
+	return 0;
 }
 
 /* notify an error as XRUN to the assigned PCM data substream */
@@ -396,6 +420,16 @@ next_packet_fifo_dequeue(struct snd_usb_endpoint *ep)
 	return p;
 }
 
+static void push_back_to_ready_list(struct snd_usb_endpoint *ep,
+				    struct snd_urb_ctx *ctx)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&ep->lock, flags);
+	list_add_tail(&ctx->ready_list, &ep->ready_playback_urbs);
+	spin_unlock_irqrestore(&ep->lock, flags);
+}
+
 /*
  * Send output urbs that have been prepared previously. URBs are dequeued
  * from ep->ready_playback_urbs and in case there aren't any available
@@ -406,12 +440,14 @@ next_packet_fifo_dequeue(struct snd_usb_endpoint *ep)
  * is that host controllers don't guarantee the order in which they return
  * inbound and outbound packets to their submitters.
  *
- * This function is only used for implicit feedback endpoints. For endpoints
- * driven by dedicated sync endpoints, URBs are immediately re-submitted
- * from their completion handler.
+ * This function is used both for implicit feedback endpoints and in low-
+ * latency playback mode.
  */
-static void queue_pending_output_urbs(struct snd_usb_endpoint *ep)
+void snd_usb_queue_pending_output_urbs(struct snd_usb_endpoint *ep,
+				       bool in_stream_lock)
 {
+	bool implicit_fb = snd_usb_endpoint_implicit_feedback_sink(ep);
+
 	while (ep_state_running(ep)) {
 
 		unsigned long flags;
@@ -420,14 +456,14 @@ static void queue_pending_output_urbs(struct snd_usb_endpoint *ep)
 		int err, i;
 
 		spin_lock_irqsave(&ep->lock, flags);
-		if (ep->next_packet_queued > 0 &&
+		if ((!implicit_fb || ep->next_packet_queued > 0) &&
 		    !list_empty(&ep->ready_playback_urbs)) {
 			/* take URB out of FIFO */
 			ctx = list_first_entry(&ep->ready_playback_urbs,
 					       struct snd_urb_ctx, ready_list);
 			list_del_init(&ctx->ready_list);
-
-			packet = next_packet_fifo_dequeue(ep);
+			if (implicit_fb)
+				packet = next_packet_fifo_dequeue(ep);
 		}
 		spin_unlock_irqrestore(&ep->lock, flags);
 
@@ -435,11 +471,24 @@ static void queue_pending_output_urbs(struct snd_usb_endpoint *ep)
 			return;
 
 		/* copy over the length information */
-		for (i = 0; i < packet->packets; i++)
-			ctx->packet_size[i] = packet->packet_size[i];
+		if (implicit_fb) {
+			for (i = 0; i < packet->packets; i++)
+				ctx->packet_size[i] = packet->packet_size[i];
+		}
 
 		/* call the data handler to fill in playback data */
-		prepare_outbound_urb(ep, ctx);
+		err = prepare_outbound_urb(ep, ctx, in_stream_lock);
+		/* can be stopped during prepare callback */
+		if (unlikely(!ep_state_running(ep)))
+			break;
+		if (err < 0) {
+			/* push back to ready list again for -EAGAIN */
+			if (err == -EAGAIN)
+				push_back_to_ready_list(ep, ctx);
+			else
+				notify_xrun(ep);
+			return;
+		}
 
 		err = usb_submit_urb(ctx->urb, GFP_ATOMIC);
 		if (err < 0) {
@@ -451,6 +500,7 @@ static void queue_pending_output_urbs(struct snd_usb_endpoint *ep)
 		}
 
 		set_bit(ctx->index, &ep->active_mask);
+		atomic_inc(&ep->submitted_urbs);
 	}
 }
 
@@ -461,7 +511,6 @@ static void snd_complete_urb(struct urb *urb)
 {
 	struct snd_urb_ctx *ctx = urb->context;
 	struct snd_usb_endpoint *ep = ctx->ep;
-	unsigned long flags;
 	int err;
 
 	if (unlikely(urb->status == -ENOENT ||		/* unlinked */
@@ -482,16 +531,20 @@ static void snd_complete_urb(struct urb *urb)
 		if (unlikely(!ep_state_running(ep)))
 			goto exit_clear;
 
-		if (snd_usb_endpoint_implicit_feedback_sink(ep)) {
-			spin_lock_irqsave(&ep->lock, flags);
-			list_add_tail(&ctx->ready_list, &ep->ready_playback_urbs);
+		/* in low-latency and implicit-feedback modes, push back the
+		 * URB to ready list at first, then process as much as possible
+		 */
+		if (ep->lowlatency_playback ||
+		     snd_usb_endpoint_implicit_feedback_sink(ep)) {
+			push_back_to_ready_list(ep, ctx);
 			clear_bit(ctx->index, &ep->active_mask);
-			spin_unlock_irqrestore(&ep->lock, flags);
-			queue_pending_output_urbs(ep);
+			snd_usb_queue_pending_output_urbs(ep, false);
+			atomic_dec(&ep->submitted_urbs); /* decrement at last */
 			return;
 		}
 
-		prepare_outbound_urb(ep, ctx);
+		/* in non-lowlatency mode, no error handling for prepare */
+		prepare_outbound_urb(ep, ctx, false);
 		/* can be stopped during prepare callback */
 		if (unlikely(!ep_state_running(ep)))
 			goto exit_clear;
@@ -513,6 +566,7 @@ static void snd_complete_urb(struct urb *urb)
 
 exit_clear:
 	clear_bit(ctx->index, &ep->active_mask);
+	atomic_dec(&ep->submitted_urbs);
 }
 
 /*
@@ -596,6 +650,7 @@ int snd_usb_add_endpoint(struct snd_usb_audio *chip, int ep_num, int type)
 	ep->type = type;
 	ep->ep_num = ep_num;
 	INIT_LIST_HEAD(&ep->ready_playback_urbs);
+	atomic_set(&ep->submitted_urbs, 0);
 
 	is_playback = ((ep_num & USB_ENDPOINT_DIR_MASK) == USB_DIR_OUT);
 	ep_num &= USB_ENDPOINT_NUMBER_MASK;
@@ -722,6 +777,7 @@ snd_usb_endpoint_open(struct snd_usb_audio *chip,
 		ep->cur_period_frames = params_period_size(params);
 		ep->cur_period_bytes = ep->cur_period_frames * ep->cur_frame_bytes;
 		ep->cur_buffer_periods = params_periods(params);
+		ep->cur_clock = fp->clock;
 
 		if (ep->type == SND_USB_ENDPOINT_TYPE_SYNC)
 			endpoint_set_syncinterval(chip, ep);
@@ -781,14 +837,19 @@ void snd_usb_endpoint_set_sync(struct snd_usb_audio *chip,
  * Pass NULL to deactivate each callback.
  */
 void snd_usb_endpoint_set_callback(struct snd_usb_endpoint *ep,
-				   void (*prepare)(struct snd_usb_substream *subs,
-						   struct urb *urb),
+				   int (*prepare)(struct snd_usb_substream *subs,
+						  struct urb *urb,
+						  bool in_stream_lock),
 				   void (*retire)(struct snd_usb_substream *subs,
 						  struct urb *urb),
 				   struct snd_usb_substream *data_subs)
 {
 	ep->prepare_data_urb = prepare;
 	ep->retire_data_urb = retire;
+	if (data_subs)
+		ep->lowlatency_playback = data_subs->lowlatency_playback;
+	else
+		ep->lowlatency_playback = false;
 	WRITE_ONCE(ep->data_subs, data_subs);
 }
 
@@ -833,6 +894,7 @@ void snd_usb_endpoint_close(struct snd_usb_audio *chip,
 		ep->altsetting = 0;
 		ep->cur_audiofmt = NULL;
 		ep->cur_rate = 0;
+		ep->cur_clock = 0;
 		ep->iface_ref = NULL;
 		usb_audio_dbg(chip, "EP 0x%x closed\n", ep->ep_num);
 	}
@@ -859,7 +921,7 @@ static int wait_clear_urbs(struct snd_usb_endpoint *ep)
 		return 0;
 
 	do {
-		alive = bitmap_weight(&ep->active_mask, ep->nurbs);
+		alive = atomic_read(&ep->submitted_urbs);
 		if (!alive)
 			break;
 
@@ -893,9 +955,10 @@ void snd_usb_endpoint_sync_pending_stop(struct snd_usb_endpoint *ep)
  *
  * This function moves the EP to STOPPING state if it's being RUNNING.
  */
-static int stop_urbs(struct snd_usb_endpoint *ep, bool force)
+static int stop_urbs(struct snd_usb_endpoint *ep, bool force, bool keep_pending)
 {
 	unsigned int i;
+	unsigned long flags;
 
 	if (!force && atomic_read(&ep->running))
 		return -EBUSY;
@@ -903,9 +966,14 @@ static int stop_urbs(struct snd_usb_endpoint *ep, bool force)
 	if (!ep_state_update(ep, EP_STATE_RUNNING, EP_STATE_STOPPING))
 		return 0;
 
+	spin_lock_irqsave(&ep->lock, flags);
 	INIT_LIST_HEAD(&ep->ready_playback_urbs);
 	ep->next_packet_head = 0;
 	ep->next_packet_queued = 0;
+	spin_unlock_irqrestore(&ep->lock, flags);
+
+	if (keep_pending)
+		return 0;
 
 	for (i = 0; i < ep->nurbs; i++) {
 		if (test_bit(i, &ep->active_mask)) {
@@ -930,7 +998,7 @@ static int release_urbs(struct snd_usb_endpoint *ep, bool force)
 	snd_usb_endpoint_set_callback(ep, NULL, NULL, NULL);
 
 	/* stop and unlink urbs */
-	err = stop_urbs(ep, force);
+	err = stop_urbs(ep, force, false);
 	if (err)
 		return err;
 
@@ -1132,10 +1200,6 @@ static int data_ep_set_params(struct snd_usb_endpoint *ep)
 		INIT_LIST_HEAD(&u->ready_list);
 	}
 
-	/* total buffer bytes of all URBs plus the next queue;
-	 * referred in pcm.c
-	 */
-	ep->nominal_queue_size = maxsize * urb_packs * (ep->nurbs + 1);
 	return 0;
 
 out_of_memory:
@@ -1340,6 +1404,25 @@ unlock:
 	return err;
 }
 
+/* get the current rate set to the given clock by any endpoint */
+int snd_usb_endpoint_get_clock_rate(struct snd_usb_audio *chip, int clock)
+{
+	struct snd_usb_endpoint *ep;
+	int rate = 0;
+
+	if (!clock)
+		return 0;
+	mutex_lock(&chip->mutex);
+	list_for_each_entry(ep, &chip->ep_list, list) {
+		if (ep->cur_clock == clock && ep->cur_rate) {
+			rate = ep->cur_rate;
+			break;
+		}
+	}
+	mutex_unlock(&chip->mutex);
+	return rate;
+}
+
 /**
  * snd_usb_endpoint_start: start an snd_usb_endpoint
  *
@@ -1355,6 +1438,7 @@ unlock:
  */
 int snd_usb_endpoint_start(struct snd_usb_endpoint *ep)
 {
+	bool is_playback = usb_pipeout(ep->pipe);
 	int err;
 	unsigned int i;
 
@@ -1391,13 +1475,9 @@ int snd_usb_endpoint_start(struct snd_usb_endpoint *ep)
 
 	if (snd_usb_endpoint_implicit_feedback_sink(ep) &&
 	    !(ep->chip->quirk_flags & QUIRK_FLAG_PLAYBACK_FIRST)) {
-		for (i = 0; i < ep->nurbs; i++) {
-			struct snd_urb_ctx *ctx = ep->urb + i;
-			list_add_tail(&ctx->ready_list, &ep->ready_playback_urbs);
-		}
-
 		usb_audio_dbg(ep->chip, "No URB submission due to implicit fb sync\n");
-		return 0;
+		i = 0;
+		goto fill_rest;
 	}
 
 	for (i = 0; i < ep->nurbs; i++) {
@@ -1406,10 +1486,18 @@ int snd_usb_endpoint_start(struct snd_usb_endpoint *ep)
 		if (snd_BUG_ON(!urb))
 			goto __error;
 
-		if (usb_pipeout(ep->pipe)) {
-			prepare_outbound_urb(ep, urb->context);
-		} else {
-			prepare_inbound_urb(ep, urb->context);
+		if (is_playback)
+			err = prepare_outbound_urb(ep, urb->context, true);
+		else
+			err = prepare_inbound_urb(ep, urb->context);
+		if (err < 0) {
+			/* stop filling at applptr */
+			if (err == -EAGAIN)
+				break;
+			usb_audio_dbg(ep->chip,
+				      "EP 0x%x: failed to prepare urb: %d\n",
+				      ep->ep_num, err);
+			goto __error;
 		}
 
 		err = usb_submit_urb(urb, GFP_ATOMIC);
@@ -1420,14 +1508,29 @@ int snd_usb_endpoint_start(struct snd_usb_endpoint *ep)
 			goto __error;
 		}
 		set_bit(i, &ep->active_mask);
+		atomic_inc(&ep->submitted_urbs);
+	}
+
+	if (!i) {
+		usb_audio_dbg(ep->chip, "XRUN at starting EP 0x%x\n",
+			      ep->ep_num);
+		goto __error;
 	}
 
 	usb_audio_dbg(ep->chip, "%d URBs submitted for EP 0x%x\n",
-		      ep->nurbs, ep->ep_num);
+		      i, ep->ep_num);
+
+ fill_rest:
+	/* put the remaining URBs to ready list */
+	if (is_playback) {
+		for (; i < ep->nurbs; i++)
+			push_back_to_ready_list(ep, ep->urb + i);
+	}
+
 	return 0;
 
 __error:
-	snd_usb_endpoint_stop(ep);
+	snd_usb_endpoint_stop(ep, false);
 	return -EPIPE;
 }
 
@@ -1435,6 +1538,7 @@ __error:
  * snd_usb_endpoint_stop: stop an snd_usb_endpoint
  *
  * @ep: the endpoint to stop (may be NULL)
+ * @keep_pending: keep in-flight URBs
  *
  * A call to this function will decrement the running count of the endpoint.
  * In case the last user has requested the endpoint stop, the URBs will
@@ -1445,7 +1549,7 @@ __error:
  * The caller needs to synchronize the pending stop operation via
  * snd_usb_endpoint_sync_pending_stop().
  */
-void snd_usb_endpoint_stop(struct snd_usb_endpoint *ep)
+void snd_usb_endpoint_stop(struct snd_usb_endpoint *ep, bool keep_pending)
 {
 	if (!ep)
 		return;
@@ -1460,7 +1564,7 @@ void snd_usb_endpoint_stop(struct snd_usb_endpoint *ep)
 	if (!atomic_dec_return(&ep->running)) {
 		if (ep->sync_source)
 			WRITE_ONCE(ep->sync_source->sync_sink, NULL);
-		stop_urbs(ep, false);
+		stop_urbs(ep, false, keep_pending);
 	}
 }
 
@@ -1575,7 +1679,7 @@ static void snd_usb_handle_sync_urb(struct snd_usb_endpoint *ep,
 		}
 
 		spin_unlock_irqrestore(&ep->lock, flags);
-		queue_pending_output_urbs(ep);
+		snd_usb_queue_pending_output_urbs(ep, false);
 
 		return;
 	}
diff --git a/sound/usb/endpoint.h b/sound/usb/endpoint.h
index a668f675b52b..6a9af04cf175 100644
--- a/sound/usb/endpoint.h
+++ b/sound/usb/endpoint.h
@@ -19,6 +19,7 @@ void snd_usb_endpoint_close(struct snd_usb_audio *chip,
 			    struct snd_usb_endpoint *ep);
 int snd_usb_endpoint_configure(struct snd_usb_audio *chip,
 			       struct snd_usb_endpoint *ep);
+int snd_usb_endpoint_get_clock_rate(struct snd_usb_audio *chip, int clock);
 
 bool snd_usb_endpoint_compatible(struct snd_usb_audio *chip,
 				 struct snd_usb_endpoint *ep,
@@ -29,14 +30,15 @@ void snd_usb_endpoint_set_sync(struct snd_usb_audio *chip,
 			       struct snd_usb_endpoint *data_ep,
 			       struct snd_usb_endpoint *sync_ep);
 void snd_usb_endpoint_set_callback(struct snd_usb_endpoint *ep,
-				   void (*prepare)(struct snd_usb_substream *subs,
-						   struct urb *urb),
+				   int (*prepare)(struct snd_usb_substream *subs,
+						  struct urb *urb,
+						  bool in_stream_lock),
 				   void (*retire)(struct snd_usb_substream *subs,
 						  struct urb *urb),
 				   struct snd_usb_substream *data_subs);
 
 int snd_usb_endpoint_start(struct snd_usb_endpoint *ep);
-void snd_usb_endpoint_stop(struct snd_usb_endpoint *ep);
+void snd_usb_endpoint_stop(struct snd_usb_endpoint *ep, bool keep_pending);
 void snd_usb_endpoint_sync_pending_stop(struct snd_usb_endpoint *ep);
 void snd_usb_endpoint_suspend(struct snd_usb_endpoint *ep);
 int  snd_usb_endpoint_activate(struct snd_usb_endpoint *ep);
@@ -45,6 +47,9 @@ void snd_usb_endpoint_free_all(struct snd_usb_audio *chip);
 
 int snd_usb_endpoint_implicit_feedback_sink(struct snd_usb_endpoint *ep);
 int snd_usb_endpoint_next_packet_size(struct snd_usb_endpoint *ep,
-				      struct snd_urb_ctx *ctx, int idx);
+				      struct snd_urb_ctx *ctx, int idx,
+				      unsigned int avail);
+void snd_usb_queue_pending_output_urbs(struct snd_usb_endpoint *ep,
+				       bool in_stream_lock);
 
 #endif /* __USBAUDIO_ENDPOINT_H */
diff --git a/sound/usb/implicit.c b/sound/usb/implicit.c
index 23767a14d126..70319c822c10 100644
--- a/sound/usb/implicit.c
+++ b/sound/usb/implicit.c
@@ -54,8 +54,6 @@ static const struct snd_usb_implicit_fb_match playback_implicit_fb_quirks[] = {
 
 	/* Fixed EP */
 	/* FIXME: check the availability of generic matching */
-	IMPLICIT_FB_FIXED_DEV(0x1397, 0x0001, 0x81, 1), /* Behringer UFX1604 */
-	IMPLICIT_FB_FIXED_DEV(0x1397, 0x0002, 0x81, 1), /* Behringer UFX1204 */
 	IMPLICIT_FB_FIXED_DEV(0x2466, 0x8010, 0x81, 2), /* Fractal Audio Axe-Fx III */
 	IMPLICIT_FB_FIXED_DEV(0x31e9, 0x0001, 0x81, 2), /* Solid State Logic SSL2 */
 	IMPLICIT_FB_FIXED_DEV(0x31e9, 0x0002, 0x81, 2), /* Solid State Logic SSL2+ */
diff --git a/sound/usb/line6/driver.c b/sound/usb/line6/driver.c
index 9602929b7de9..59faa5a9a714 100644
--- a/sound/usb/line6/driver.c
+++ b/sound/usb/line6/driver.c
@@ -113,12 +113,12 @@ int line6_send_raw_message(struct usb_line6 *line6, const char *buffer,
 			retval = usb_interrupt_msg(line6->usbdev,
 						usb_sndintpipe(line6->usbdev, properties->ep_ctrl_w),
 						(char *)frag_buf, frag_size,
-						&partial, LINE6_TIMEOUT * HZ);
+						&partial, LINE6_TIMEOUT);
 		} else {
 			retval = usb_bulk_msg(line6->usbdev,
 						usb_sndbulkpipe(line6->usbdev, properties->ep_ctrl_w),
 						(char *)frag_buf, frag_size,
-						&partial, LINE6_TIMEOUT * HZ);
+						&partial, LINE6_TIMEOUT);
 		}
 
 		if (retval) {
@@ -347,7 +347,7 @@ int line6_read_data(struct usb_line6 *line6, unsigned address, void *data,
 	ret = usb_control_msg_send(usbdev, 0, 0x67,
 				   USB_TYPE_VENDOR | USB_RECIP_DEVICE | USB_DIR_OUT,
 				   (datalen << 8) | 0x21, address, NULL, 0,
-				   LINE6_TIMEOUT * HZ, GFP_KERNEL);
+				   LINE6_TIMEOUT, GFP_KERNEL);
 	if (ret) {
 		dev_err(line6->ifcdev, "read request failed (error %d)\n", ret);
 		goto exit;
@@ -360,7 +360,7 @@ int line6_read_data(struct usb_line6 *line6, unsigned address, void *data,
 		ret = usb_control_msg_recv(usbdev, 0, 0x67,
 					   USB_TYPE_VENDOR | USB_RECIP_DEVICE | USB_DIR_IN,
 					   0x0012, 0x0000, &len, 1,
-					   LINE6_TIMEOUT * HZ, GFP_KERNEL);
+					   LINE6_TIMEOUT, GFP_KERNEL);
 		if (ret) {
 			dev_err(line6->ifcdev,
 				"receive length failed (error %d)\n", ret);
@@ -387,7 +387,7 @@ int line6_read_data(struct usb_line6 *line6, unsigned address, void *data,
 	/* receive the result: */
 	ret = usb_control_msg_recv(usbdev, 0, 0x67,
 				   USB_TYPE_VENDOR | USB_RECIP_DEVICE | USB_DIR_IN,
-				   0x0013, 0x0000, data, datalen, LINE6_TIMEOUT * HZ,
+				   0x0013, 0x0000, data, datalen, LINE6_TIMEOUT,
 				   GFP_KERNEL);
 	if (ret)
 		dev_err(line6->ifcdev, "read failed (error %d)\n", ret);
@@ -417,7 +417,7 @@ int line6_write_data(struct usb_line6 *line6, unsigned address, void *data,
 
 	ret = usb_control_msg_send(usbdev, 0, 0x67,
 				   USB_TYPE_VENDOR | USB_RECIP_DEVICE | USB_DIR_OUT,
-				   0x0022, address, data, datalen, LINE6_TIMEOUT * HZ,
+				   0x0022, address, data, datalen, LINE6_TIMEOUT,
 				   GFP_KERNEL);
 	if (ret) {
 		dev_err(line6->ifcdev,
@@ -430,7 +430,7 @@ int line6_write_data(struct usb_line6 *line6, unsigned address, void *data,
 
 		ret = usb_control_msg_recv(usbdev, 0, 0x67,
 					   USB_TYPE_VENDOR | USB_RECIP_DEVICE | USB_DIR_IN,
-					   0x0012, 0x0000, status, 1, LINE6_TIMEOUT * HZ,
+					   0x0012, 0x0000, status, 1, LINE6_TIMEOUT,
 					   GFP_KERNEL);
 		if (ret) {
 			dev_err(line6->ifcdev,
diff --git a/sound/usb/line6/driver.h b/sound/usb/line6/driver.h
index 71d3da1db8c8..ecf3a2b39c7e 100644
--- a/sound/usb/line6/driver.h
+++ b/sound/usb/line6/driver.h
@@ -27,7 +27,7 @@
 #define LINE6_FALLBACK_INTERVAL 10
 #define LINE6_FALLBACK_MAXPACKETSIZE 16
 
-#define LINE6_TIMEOUT 1
+#define LINE6_TIMEOUT 1000
 #define LINE6_BUFSIZE_LISTEN 64
 #define LINE6_MIDI_MESSAGE_MAXLEN 256
 
diff --git a/sound/usb/line6/podhd.c b/sound/usb/line6/podhd.c
index 28794a35949d..b24bc82f89e3 100644
--- a/sound/usb/line6/podhd.c
+++ b/sound/usb/line6/podhd.c
@@ -190,7 +190,7 @@ static int podhd_dev_start(struct usb_line6_podhd *pod)
 	ret = usb_control_msg_send(usbdev, 0,
 					0x67, USB_TYPE_VENDOR | USB_RECIP_DEVICE | USB_DIR_OUT,
 					0x11, 0,
-					NULL, 0, LINE6_TIMEOUT * HZ, GFP_KERNEL);
+					NULL, 0, LINE6_TIMEOUT, GFP_KERNEL);
 	if (ret) {
 		dev_err(pod->line6.ifcdev, "read request failed (error %d)\n", ret);
 		goto exit;
@@ -200,7 +200,7 @@ static int podhd_dev_start(struct usb_line6_podhd *pod)
 	ret = usb_control_msg_recv(usbdev, 0, 0x67,
 					USB_TYPE_VENDOR | USB_RECIP_DEVICE | USB_DIR_IN,
 					0x11, 0x0,
-					init_bytes, 3, LINE6_TIMEOUT * HZ, GFP_KERNEL);
+					init_bytes, 3, LINE6_TIMEOUT, GFP_KERNEL);
 	if (ret) {
 		dev_err(pod->line6.ifcdev,
 			"receive length failed (error %d)\n", ret);
@@ -220,7 +220,7 @@ static int podhd_dev_start(struct usb_line6_podhd *pod)
 					USB_REQ_SET_FEATURE,
 					USB_TYPE_STANDARD | USB_RECIP_DEVICE | USB_DIR_OUT,
 					1, 0,
-					NULL, 0, LINE6_TIMEOUT * HZ, GFP_KERNEL);
+					NULL, 0, LINE6_TIMEOUT, GFP_KERNEL);
 exit:
 	return ret;
 }
diff --git a/sound/usb/line6/toneport.c b/sound/usb/line6/toneport.c
index 4e5693c97aa4..e33df58740a9 100644
--- a/sound/usb/line6/toneport.c
+++ b/sound/usb/line6/toneport.c
@@ -128,7 +128,7 @@ static int toneport_send_cmd(struct usb_device *usbdev, int cmd1, int cmd2)
 
 	ret = usb_control_msg_send(usbdev, 0, 0x67,
 				   USB_TYPE_VENDOR | USB_RECIP_DEVICE | USB_DIR_OUT,
-				   cmd1, cmd2, NULL, 0, LINE6_TIMEOUT * HZ,
+				   cmd1, cmd2, NULL, 0, LINE6_TIMEOUT,
 				   GFP_KERNEL);
 
 	if (ret) {
diff --git a/sound/usb/misc/ua101.c b/sound/usb/misc/ua101.c
index 5834d1dc317e..4f6b20ed29dd 100644
--- a/sound/usb/misc/ua101.c
+++ b/sound/usb/misc/ua101.c
@@ -1000,7 +1000,7 @@ static int detect_usb_format(struct ua101 *ua)
 		fmt_playback->bSubframeSize * ua->playback.channels;
 
 	epd = &ua->intf[INTF_CAPTURE]->altsetting[1].endpoint[0].desc;
-	if (!usb_endpoint_is_isoc_in(epd)) {
+	if (!usb_endpoint_is_isoc_in(epd) || usb_endpoint_maxp(epd) == 0) {
 		dev_err(&ua->dev->dev, "invalid capture endpoint\n");
 		return -ENXIO;
 	}
@@ -1008,7 +1008,7 @@ static int detect_usb_format(struct ua101 *ua)
 	ua->capture.max_packet_bytes = usb_endpoint_maxp(epd);
 
 	epd = &ua->intf[INTF_PLAYBACK]->altsetting[1].endpoint[0].desc;
-	if (!usb_endpoint_is_isoc_out(epd)) {
+	if (!usb_endpoint_is_isoc_out(epd) || usb_endpoint_maxp(epd) == 0) {
 		dev_err(&ua->dev->dev, "invalid playback endpoint\n");
 		return -ENXIO;
 	}
diff --git a/sound/usb/mixer.c b/sound/usb/mixer.c
index 8e030b1c061a..6e7bac8203ba 100644
--- a/sound/usb/mixer.c
+++ b/sound/usb/mixer.c
@@ -361,9 +361,8 @@ static int get_ctl_value_v2(struct usb_mixer_elem_info *cval, int request,
 
 	memset(buf, 0, sizeof(buf));
 
-	ret = snd_usb_lock_shutdown(chip) ? -EIO : 0;
-	if (ret)
-		goto error;
+	if (snd_usb_lock_shutdown(chip))
+		return -EIO;
 
 	idx = mixer_ctrl_intf(cval->head.mixer) | (cval->head.id << 8);
 	ret = snd_usb_ctl_msg(chip->dev, usb_rcvctrlpipe(chip->dev, 0), bRequest,
@@ -372,8 +371,7 @@ static int get_ctl_value_v2(struct usb_mixer_elem_info *cval, int request,
 	snd_usb_unlock_shutdown(chip);
 
 	if (ret < 0) {
-error:
-		usb_audio_err(chip,
+		usb_audio_dbg(chip,
 			"cannot get ctl value: req = %#x, wValue = %#x, wIndex = %#x, type = %d\n",
 			request, validx, idx, cval->val_type);
 		return ret;
@@ -1208,12 +1206,32 @@ static void volume_control_quirks(struct usb_mixer_elem_info *cval,
 	}
 }
 
+/* forcibly initialize the current mixer value; if GET_CUR fails, set to
+ * the minimum as default
+ */
+static void init_cur_mix_raw(struct usb_mixer_elem_info *cval, int ch, int idx)
+{
+	int val, err;
+
+	err = snd_usb_get_cur_mix_value(cval, ch, idx, &val);
+	if (!err)
+		return;
+	if (!cval->head.mixer->ignore_ctl_error)
+		usb_audio_warn(cval->head.mixer->chip,
+			       "%d:%d: failed to get current value for ch %d (%d)\n",
+			       cval->head.id, mixer_ctrl_intf(cval->head.mixer),
+			       ch, err);
+	snd_usb_set_cur_mix_value(cval, ch, idx, cval->min);
+}
+
 /*
  * retrieve the minimum and maximum values for the specified control
  */
 static int get_min_max_with_quirks(struct usb_mixer_elem_info *cval,
 				   int default_min, struct snd_kcontrol *kctl)
 {
+	int i, idx;
+
 	/* for failsafe */
 	cval->min = default_min;
 	cval->max = cval->min + 1;
@@ -1226,7 +1244,6 @@ static int get_min_max_with_quirks(struct usb_mixer_elem_info *cval,
 	} else {
 		int minchn = 0;
 		if (cval->cmask) {
-			int i;
 			for (i = 0; i < MAX_CHANNELS; i++)
 				if (cval->cmask & (1 << i)) {
 					minchn = i + 1;
@@ -1327,6 +1344,19 @@ no_res_check:
 		}
 	}
 
+	/* initialize all elements */
+	if (!cval->cmask) {
+		init_cur_mix_raw(cval, 0, 0);
+	} else {
+		idx = 0;
+		for (i = 0; i < MAX_CHANNELS; i++) {
+			if (cval->cmask & (1 << i)) {
+				init_cur_mix_raw(cval, i + 1, idx);
+				idx++;
+			}
+		}
+	}
+
 	return 0;
 }
 
diff --git a/sound/usb/mixer_quirks.c b/sound/usb/mixer_quirks.c
index 46082dc57be0..d489c1de3bae 100644
--- a/sound/usb/mixer_quirks.c
+++ b/sound/usb/mixer_quirks.c
@@ -2795,6 +2795,7 @@ static int snd_bbfpro_controls_create(struct usb_mixer_interface *mixer)
 #define SND_DJM_750_IDX		0x1
 #define SND_DJM_850_IDX		0x2
 #define SND_DJM_900NXS2_IDX	0x3
+#define SND_DJM_750MK2_IDX	0x4
 
 
 #define SND_DJM_CTL(_name, suffix, _default_value, _windex) { \
@@ -2984,10 +2985,40 @@ static const struct snd_djm_ctl snd_djm_ctls_900nxs2[] = {
 	SND_DJM_CTL("Ch5 Input",   900nxs2_cap5, 3, SND_DJM_WINDEX_CAP)
 };
 
+// DJM-750MK2
+static const u16 snd_djm_opts_750mk2_cap1[] = {
+	0x0100, 0x0102, 0x0103, 0x0106, 0x0107, 0x0108, 0x0109, 0x010a };
+static const u16 snd_djm_opts_750mk2_cap2[] = {
+	0x0200, 0x0202, 0x0203, 0x0206, 0x0207, 0x0208, 0x0209, 0x020a };
+static const u16 snd_djm_opts_750mk2_cap3[] = {
+	0x0300, 0x0302, 0x0303, 0x0306, 0x0307, 0x0308, 0x0309, 0x030a };
+static const u16 snd_djm_opts_750mk2_cap4[] = {
+	0x0400, 0x0402, 0x0403, 0x0406, 0x0407, 0x0408, 0x0409, 0x040a };
+static const u16 snd_djm_opts_750mk2_cap5[] = {
+	0x0507, 0x0508, 0x0509, 0x050a, 0x0511, 0x0512, 0x0513, 0x0514 };
+
+static const u16 snd_djm_opts_750mk2_pb1[] = { 0x0100, 0x0101, 0x0104 };
+static const u16 snd_djm_opts_750mk2_pb2[] = { 0x0200, 0x0201, 0x0204 };
+static const u16 snd_djm_opts_750mk2_pb3[] = { 0x0300, 0x0301, 0x0304 };
+
+
+static const struct snd_djm_ctl snd_djm_ctls_750mk2[] = {
+	SND_DJM_CTL("Capture Level", cap_level, 0, SND_DJM_WINDEX_CAPLVL),
+	SND_DJM_CTL("Ch1 Input",   750mk2_cap1, 2, SND_DJM_WINDEX_CAP),
+	SND_DJM_CTL("Ch2 Input",   750mk2_cap2, 2, SND_DJM_WINDEX_CAP),
+	SND_DJM_CTL("Ch3 Input",   750mk2_cap3, 2, SND_DJM_WINDEX_CAP),
+	SND_DJM_CTL("Ch4 Input",   750mk2_cap4, 2, SND_DJM_WINDEX_CAP),
+	SND_DJM_CTL("Ch5 Input",   750mk2_cap5, 3, SND_DJM_WINDEX_CAP),
+	SND_DJM_CTL("Ch1 Output",   750mk2_pb1, 0, SND_DJM_WINDEX_PB),
+	SND_DJM_CTL("Ch2 Output",   750mk2_pb2, 1, SND_DJM_WINDEX_PB),
+	SND_DJM_CTL("Ch3 Output",   750mk2_pb3, 2, SND_DJM_WINDEX_PB)
+};
+
 
 static const struct snd_djm_device snd_djm_devices[] = {
 	SND_DJM_DEVICE(250mk2),
 	SND_DJM_DEVICE(750),
+	SND_DJM_DEVICE(750mk2),
 	SND_DJM_DEVICE(850),
 	SND_DJM_DEVICE(900nxs2)
 };
@@ -3235,6 +3266,9 @@ int snd_usb_mixer_apply_create_quirk(struct usb_mixer_interface *mixer)
 	case USB_ID(0x08e4, 0x017f): /* Pioneer DJ DJM-750 */
 		err = snd_djm_controls_create(mixer, SND_DJM_750_IDX);
 		break;
+	case USB_ID(0x2b73, 0x001b): /* Pioneer DJ DJM-750MK2 */
+		err = snd_djm_controls_create(mixer, SND_DJM_750MK2_IDX);
+		break;
 	case USB_ID(0x08e4, 0x0163): /* Pioneer DJ DJM-850 */
 		err = snd_djm_controls_create(mixer, SND_DJM_850_IDX);
 		break;
diff --git a/sound/usb/pcm.c b/sound/usb/pcm.c
index 5dc9266180e3..95ec8eec1bb0 100644
--- a/sound/usb/pcm.c
+++ b/sound/usb/pcm.c
@@ -219,16 +219,16 @@ int snd_usb_init_pitch(struct snd_usb_audio *chip,
 	return 0;
 }
 
-static bool stop_endpoints(struct snd_usb_substream *subs)
+static bool stop_endpoints(struct snd_usb_substream *subs, bool keep_pending)
 {
 	bool stopped = 0;
 
 	if (test_and_clear_bit(SUBSTREAM_FLAG_SYNC_EP_STARTED, &subs->flags)) {
-		snd_usb_endpoint_stop(subs->sync_endpoint);
+		snd_usb_endpoint_stop(subs->sync_endpoint, keep_pending);
 		stopped = true;
 	}
 	if (test_and_clear_bit(SUBSTREAM_FLAG_DATA_EP_STARTED, &subs->flags)) {
-		snd_usb_endpoint_stop(subs->data_endpoint);
+		snd_usb_endpoint_stop(subs->data_endpoint, keep_pending);
 		stopped = true;
 	}
 	return stopped;
@@ -261,7 +261,7 @@ static int start_endpoints(struct snd_usb_substream *subs)
 	return 0;
 
  error:
-	stop_endpoints(subs);
+	stop_endpoints(subs, false);
 	return err;
 }
 
@@ -437,7 +437,7 @@ static int configure_endpoints(struct snd_usb_audio *chip,
 
 	if (subs->data_endpoint->need_setup) {
 		/* stop any running stream beforehand */
-		if (stop_endpoints(subs))
+		if (stop_endpoints(subs, false))
 			sync_pending_stops(subs);
 		err = snd_usb_endpoint_configure(chip, subs->data_endpoint);
 		if (err < 0)
@@ -572,7 +572,7 @@ static int snd_usb_hw_free(struct snd_pcm_substream *substream)
 	subs->cur_audiofmt = NULL;
 	mutex_unlock(&chip->mutex);
 	if (!snd_usb_lock_shutdown(chip)) {
-		if (stop_endpoints(subs))
+		if (stop_endpoints(subs, false))
 			sync_pending_stops(subs);
 		close_endpoints(chip, subs);
 		snd_usb_unlock_shutdown(chip);
@@ -581,6 +581,26 @@ static int snd_usb_hw_free(struct snd_pcm_substream *substream)
 	return 0;
 }
 
+/* check whether early start is needed for playback stream */
+static int lowlatency_playback_available(struct snd_pcm_runtime *runtime,
+					 struct snd_usb_substream *subs)
+{
+	struct snd_usb_audio *chip = subs->stream->chip;
+
+	if (subs->direction == SNDRV_PCM_STREAM_CAPTURE)
+		return false;
+	/* disabled via module option? */
+	if (!chip->lowlatency)
+		return false;
+	/* free-wheeling mode? (e.g. dmix) */
+	if (runtime->stop_threshold > runtime->buffer_size)
+		return false;
+	/* implicit feedback mode has own operation mode */
+	if (snd_usb_endpoint_implicit_feedback_sink(subs->data_endpoint))
+		return false;
+	return true;
+}
+
 /*
  * prepare callback
  *
@@ -614,13 +634,8 @@ static int snd_usb_pcm_prepare(struct snd_pcm_substream *substream)
 	subs->period_elapsed_pending = 0;
 	runtime->delay = 0;
 
-	/* check whether early start is needed for playback stream */
-	subs->early_playback_start =
-		subs->direction == SNDRV_PCM_STREAM_PLAYBACK &&
-		(!chip->lowlatency ||
-		 (subs->data_endpoint->nominal_queue_size >= subs->buffer_bytes));
-
-	if (subs->early_playback_start)
+	subs->lowlatency_playback = lowlatency_playback_available(runtime, subs);
+	if (!subs->lowlatency_playback)
 		ret = start_endpoints(subs);
 
  unlock:
@@ -734,6 +749,7 @@ static int hw_rule_rate(struct snd_pcm_hw_params *params,
 			struct snd_pcm_hw_rule *rule)
 {
 	struct snd_usb_substream *subs = rule->private;
+	struct snd_usb_audio *chip = subs->stream->chip;
 	const struct audioformat *fp;
 	struct snd_interval *it = hw_param_interval(params, SNDRV_PCM_HW_PARAM_RATE);
 	unsigned int rmin, rmax, r;
@@ -745,6 +761,14 @@ static int hw_rule_rate(struct snd_pcm_hw_params *params,
 	list_for_each_entry(fp, &subs->fmt_list, list) {
 		if (!hw_check_valid_format(subs, params, fp))
 			continue;
+		r = snd_usb_endpoint_get_clock_rate(chip, fp->clock);
+		if (r > 0) {
+			if (!snd_interval_test(it, r))
+				continue;
+			rmin = min(rmin, r);
+			rmax = max(rmax, r);
+			continue;
+		}
 		if (fp->rate_table && fp->nr_rates) {
 			for (i = 0; i < fp->nr_rates; i++) {
 				r = fp->rate_table[i];
@@ -1056,6 +1080,13 @@ static int setup_hw_info(struct snd_pcm_runtime *runtime, struct snd_usb_substre
 	if (err < 0)
 		return err;
 
+	list_for_each_entry(fp, &subs->fmt_list, list) {
+		if (fp->implicit_fb) {
+			runtime->hw.info |= SNDRV_PCM_INFO_JOINT_DUPLEX;
+			break;
+		}
+	}
+
 	return 0;
 }
 
@@ -1068,6 +1099,10 @@ static int snd_usb_pcm_open(struct snd_pcm_substream *substream)
 	int ret;
 
 	runtime->hw = snd_usb_hardware;
+	/* need an explicit sync to catch applptr update in low-latency mode */
+	if (direction == SNDRV_PCM_STREAM_PLAYBACK &&
+	    as->chip->lowlatency)
+		runtime->hw.info |= SNDRV_PCM_INFO_SYNC_APPLPTR;
 	runtime->private_data = subs;
 	subs->pcm_substream = substream;
 	/* runtime PM is also done there */
@@ -1320,44 +1355,66 @@ static unsigned int copy_to_urb_quirk(struct snd_usb_substream *subs,
 	return bytes;
 }
 
-static void prepare_playback_urb(struct snd_usb_substream *subs,
-				 struct urb *urb)
+static int prepare_playback_urb(struct snd_usb_substream *subs,
+				struct urb *urb,
+				bool in_stream_lock)
 {
 	struct snd_pcm_runtime *runtime = subs->pcm_substream->runtime;
 	struct snd_usb_endpoint *ep = subs->data_endpoint;
 	struct snd_urb_ctx *ctx = urb->context;
-	unsigned int counts, frames, bytes;
+	unsigned int frames, bytes;
+	int counts;
+	unsigned int transfer_done, frame_limit, avail = 0;
 	int i, stride, period_elapsed = 0;
 	unsigned long flags;
+	int err = 0;
 
 	stride = ep->stride;
 
 	frames = 0;
 	ctx->queued = 0;
 	urb->number_of_packets = 0;
+
 	spin_lock_irqsave(&subs->lock, flags);
-	subs->frame_limit += ep->max_urb_frames;
+	frame_limit = subs->frame_limit + ep->max_urb_frames;
+	transfer_done = subs->transfer_done;
+
+	if (subs->lowlatency_playback &&
+	    runtime->status->state != SNDRV_PCM_STATE_DRAINING) {
+		unsigned int hwptr = subs->hwptr_done / stride;
+
+		/* calculate the byte offset-in-buffer of the appl_ptr */
+		avail = (runtime->control->appl_ptr - runtime->hw_ptr_base)
+			% runtime->buffer_size;
+		if (avail <= hwptr)
+			avail += runtime->buffer_size;
+		avail -= hwptr;
+	}
+
 	for (i = 0; i < ctx->packets; i++) {
-		counts = snd_usb_endpoint_next_packet_size(ep, ctx, i);
+		counts = snd_usb_endpoint_next_packet_size(ep, ctx, i, avail);
+		if (counts < 0)
+			break;
 		/* set up descriptor */
 		urb->iso_frame_desc[i].offset = frames * stride;
 		urb->iso_frame_desc[i].length = counts * stride;
 		frames += counts;
+		avail -= counts;
 		urb->number_of_packets++;
-		subs->transfer_done += counts;
-		if (subs->transfer_done >= runtime->period_size) {
-			subs->transfer_done -= runtime->period_size;
-			subs->frame_limit = 0;
+		transfer_done += counts;
+		if (transfer_done >= runtime->period_size) {
+			transfer_done -= runtime->period_size;
+			frame_limit = 0;
 			period_elapsed = 1;
 			if (subs->fmt_type == UAC_FORMAT_TYPE_II) {
-				if (subs->transfer_done > 0) {
+				if (transfer_done > 0) {
 					/* FIXME: fill-max mode is not
 					 * supported yet */
-					frames -= subs->transfer_done;
-					counts -= subs->transfer_done;
+					frames -= transfer_done;
+					counts -= transfer_done;
 					urb->iso_frame_desc[i].length =
 						counts * stride;
-					subs->transfer_done = 0;
+					transfer_done = 0;
 				}
 				i++;
 				if (i < ctx->packets) {
@@ -1371,13 +1428,19 @@ static void prepare_playback_urb(struct snd_usb_substream *subs,
 			}
 		}
 		/* finish at the period boundary or after enough frames */
-		if ((period_elapsed ||
-				subs->transfer_done >= subs->frame_limit) &&
+		if ((period_elapsed || transfer_done >= frame_limit) &&
 		    !snd_usb_endpoint_implicit_feedback_sink(ep))
 			break;
 	}
-	bytes = frames * stride;
 
+	if (!frames) {
+		err = -EAGAIN;
+		goto unlock;
+	}
+
+	bytes = frames * stride;
+	subs->transfer_done = transfer_done;
+	subs->frame_limit = frame_limit;
 	if (unlikely(ep->cur_format == SNDRV_PCM_FORMAT_DSD_U16_LE &&
 		     subs->cur_audiofmt->dsd_dop)) {
 		fill_playback_urb_dsd_dop(subs, urb, bytes);
@@ -1403,14 +1466,23 @@ static void prepare_playback_urb(struct snd_usb_substream *subs,
 		subs->trigger_tstamp_pending_update = false;
 	}
 
-	if (period_elapsed && !subs->running && !subs->early_playback_start) {
+	if (period_elapsed && !subs->running && subs->lowlatency_playback) {
 		subs->period_elapsed_pending = 1;
 		period_elapsed = 0;
 	}
+
+ unlock:
 	spin_unlock_irqrestore(&subs->lock, flags);
+	if (err < 0)
+		return err;
 	urb->transfer_buffer_length = bytes;
-	if (period_elapsed)
-		snd_pcm_period_elapsed(subs->pcm_substream);
+	if (period_elapsed) {
+		if (in_stream_lock)
+			snd_pcm_period_elapsed_under_stream_lock(subs->pcm_substream);
+		else
+			snd_pcm_period_elapsed(subs->pcm_substream);
+	}
+	return 0;
 }
 
 /*
@@ -1442,6 +1514,27 @@ static void retire_playback_urb(struct snd_usb_substream *subs,
 		snd_pcm_period_elapsed(subs->pcm_substream);
 }
 
+/* PCM ack callback for the playback stream;
+ * this plays a role only when the stream is running in low-latency mode.
+ */
+static int snd_usb_pcm_playback_ack(struct snd_pcm_substream *substream)
+{
+	struct snd_usb_substream *subs = substream->runtime->private_data;
+	struct snd_usb_endpoint *ep;
+
+	if (!subs->lowlatency_playback || !subs->running)
+		return 0;
+	ep = subs->data_endpoint;
+	if (!ep)
+		return 0;
+	/* When no more in-flight URBs available, try to process the pending
+	 * outputs here
+	 */
+	if (!ep->active_mask)
+		snd_usb_queue_pending_output_urbs(ep, true);
+	return 0;
+}
+
 static int snd_usb_substream_playback_trigger(struct snd_pcm_substream *substream,
 					      int cmd)
 {
@@ -1457,7 +1550,7 @@ static int snd_usb_substream_playback_trigger(struct snd_pcm_substream *substrea
 					      prepare_playback_urb,
 					      retire_playback_urb,
 					      subs);
-		if (!subs->early_playback_start &&
+		if (subs->lowlatency_playback &&
 		    cmd == SNDRV_PCM_TRIGGER_START) {
 			err = start_endpoints(subs);
 			if (err < 0) {
@@ -1473,7 +1566,7 @@ static int snd_usb_substream_playback_trigger(struct snd_pcm_substream *substrea
 		return 0;
 	case SNDRV_PCM_TRIGGER_SUSPEND:
 	case SNDRV_PCM_TRIGGER_STOP:
-		stop_endpoints(subs);
+		stop_endpoints(subs, substream->runtime->status->state == SNDRV_PCM_STATE_DRAINING);
 		snd_usb_endpoint_set_callback(subs->data_endpoint,
 					      NULL, NULL, NULL);
 		subs->running = 0;
@@ -1521,7 +1614,7 @@ static int snd_usb_substream_capture_trigger(struct snd_pcm_substream *substream
 		return 0;
 	case SNDRV_PCM_TRIGGER_SUSPEND:
 	case SNDRV_PCM_TRIGGER_STOP:
-		stop_endpoints(subs);
+		stop_endpoints(subs, false);
 		fallthrough;
 	case SNDRV_PCM_TRIGGER_PAUSE_PUSH:
 		snd_usb_endpoint_set_callback(subs->data_endpoint,
@@ -1545,6 +1638,7 @@ static const struct snd_pcm_ops snd_usb_playback_ops = {
 	.trigger =	snd_usb_substream_playback_trigger,
 	.sync_stop =	snd_usb_pcm_sync_stop,
 	.pointer =	snd_usb_pcm_pointer,
+	.ack =		snd_usb_pcm_playback_ack,
 };
 
 static const struct snd_pcm_ops snd_usb_capture_ops = {
diff --git a/sound/usb/quirks-table.h b/sound/usb/quirks-table.h
index 2af8c68fac27..b1522e43173e 100644
--- a/sound/usb/quirks-table.h
+++ b/sound/usb/quirks-table.h
@@ -3894,6 +3894,64 @@ YAMAHA_DEVICE(0x7010, "UB99"),
 },
 {
 	/*
+	 * Pioneer DJ DJM-750MK2
+	 * 10 channels playback & 12 channels capture @ 48kHz S24LE
+	 */
+	USB_DEVICE_VENDOR_SPEC(0x2b73, 0x001b),
+	.driver_info = (unsigned long) &(const struct snd_usb_audio_quirk) {
+		.ifnum = QUIRK_ANY_INTERFACE,
+		.type = QUIRK_COMPOSITE,
+		.data = (const struct snd_usb_audio_quirk[]) {
+			{
+				.ifnum = 0,
+				.type = QUIRK_AUDIO_FIXED_ENDPOINT,
+				.data = &(const struct audioformat) {
+					.formats = SNDRV_PCM_FMTBIT_S24_3LE,
+					.channels = 10,
+					.iface = 0,
+					.altsetting = 1,
+					.altset_idx = 1,
+					.endpoint = 0x01,
+					.ep_attr = USB_ENDPOINT_XFER_ISOC|
+					    USB_ENDPOINT_SYNC_ASYNC,
+					.rates = SNDRV_PCM_RATE_48000,
+					.rate_min = 48000,
+					.rate_max = 48000,
+					.nr_rates = 1,
+					.rate_table = (unsigned int[]) {
+						48000
+					}
+				}
+			},
+			{
+				.ifnum = 0,
+				.type = QUIRK_AUDIO_FIXED_ENDPOINT,
+				.data = &(const struct audioformat) {
+					.formats = SNDRV_PCM_FMTBIT_S24_3LE,
+					.channels = 12,
+					.iface = 0,
+					.altsetting = 1,
+					.altset_idx = 1,
+					.endpoint = 0x82,
+					.ep_idx = 1,
+					.ep_attr = USB_ENDPOINT_XFER_ISOC|
+						USB_ENDPOINT_SYNC_ASYNC|
+						USB_ENDPOINT_USAGE_IMPLICIT_FB,
+					.rates = SNDRV_PCM_RATE_48000,
+					.rate_min = 48000,
+					.rate_max = 48000,
+					.nr_rates = 1,
+					.rate_table = (unsigned int[]) { 48000 }
+				}
+			},
+			{
+				.ifnum = -1
+			}
+		}
+	}
+},
+{
+	/*
 	 * Pioneer DJ DJM-850
 	 * 8 channels playback and 8 channels capture @ 44.1/48/96kHz S24LE
 	 * Playback on EP 0x05
diff --git a/sound/usb/usx2y/usbusx2yaudio.c b/sound/usb/usx2y/usbusx2yaudio.c
index c39cc6851e2d..cfc1ea53978d 100644
--- a/sound/usb/usx2y/usbusx2yaudio.c
+++ b/sound/usb/usx2y/usbusx2yaudio.c
@@ -668,14 +668,15 @@ static void i_usx2y_04int(struct urb *urb)
 
 static int usx2y_rate_set(struct usx2ydev *usx2y, int rate)
 {
-	int			err = 0, i;
-	struct snd_usx2y_urb_seq	*us = NULL;
-	int			*usbdata = NULL;
-	const struct s_c2	*ra = rate == 48000 ? setrate_48000 : setrate_44100;
+	int err = 0, i;
+	struct snd_usx2y_urb_seq *us = NULL;
+	int *usbdata = NULL;
+	const struct s_c2 *ra = rate == 48000 ? setrate_48000 : setrate_44100;
 	struct urb *urb;
 
 	if (usx2y->rate != rate) {
-		us = kzalloc(sizeof(*us) + sizeof(struct urb *) * NOOF_SETRATE_URBS, GFP_KERNEL);
+		us = kzalloc(struct_size(us, urb, NOOF_SETRATE_URBS),
+			     GFP_KERNEL);
 		if (!us) {
 			err = -ENOMEM;
 			goto cleanup;
diff --git a/sound/virtio/virtio_pcm_msg.c b/sound/virtio/virtio_pcm_msg.c
index f88c8f29cbd8..aca2dc1989ba 100644
--- a/sound/virtio/virtio_pcm_msg.c
+++ b/sound/virtio/virtio_pcm_msg.c
@@ -20,7 +20,7 @@ struct virtio_pcm_msg {
 	struct virtio_snd_pcm_xfer xfer;
 	struct virtio_snd_pcm_status status;
 	size_t length;
-	struct scatterlist sgs[0];
+	struct scatterlist sgs[];
 };
 
 /**
@@ -146,8 +146,7 @@ int virtsnd_pcm_msg_alloc(struct virtio_pcm_substream *vss,
 		int sg_num = virtsnd_pcm_sg_num(data, period_bytes);
 		struct virtio_pcm_msg *msg;
 
-		msg = kzalloc(sizeof(*msg) + sizeof(*msg->sgs) * (sg_num + 2),
-			      GFP_KERNEL);
+		msg = kzalloc(struct_size(msg, sgs, sg_num + 2), GFP_KERNEL);
 		if (!msg)
 			return -ENOMEM;