From 657f8bd88cb5a968d907fd1c891cee52dc156caa Mon Sep 17 00:00:00 2001
From: Julia Lawall
Date: Sat, 21 May 2022 13:10:23 +0200
Subject: spi: fix typo in comment

Spelling mistake (triple letters) in comment.
Detected with the help of Coccinelle.

Signed-off-by: Julia Lawall <Julia.Lawall@inria.fr>
Link: https://lore.kernel.org/r/20220521111145.81697-13-Julia.Lawall@inria.fr
Signed-off-by: Mark Brown <broonie@kernel.org>
---
 include/linux/spi/spi.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

(limited to 'include')

diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h
index d361ba26203b..eadfd3ba3cbc 100644
--- a/include/linux/spi/spi.h
+++ b/include/linux/spi/spi.h
@@ -1127,7 +1127,7 @@ spi_max_transfer_size(struct spi_device *spi)
 	if (ctlr->max_transfer_size)
 		tr_max = ctlr->max_transfer_size(spi);
 
-	/* transfer size limit must not be greater than messsage size limit */
+	/* transfer size limit must not be greater than message size limit */
 	return min(tr_max, msg_max);
 }
 
-- 
cgit v1.2.3


From 6598b91b5ac32bc756d7c3000a31f775d4ead1c4 Mon Sep 17 00:00:00 2001
From: David Jander
Date: Tue, 24 May 2022 11:18:08 +0200
Subject: spi: spi.c: Convert statistics to per-cpu u64_stats_t

This change gives a dramatic performance improvement in the hot path,
since many costly spin_lock_irqsave() calls can be avoided.

On an i.MX8MM system with a MCP2518FD CAN controller connected via SPI,
the time the driver takes to handle interrupts, or in other words the time
the IRQ line of the CAN controller stays low is mainly dominated by the
time it takes to do 3 relatively short sync SPI transfers. The effect of
this patch is a reduction of this time from 136us down to only 98us.

Suggested-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David Jander <david@protonic.nl>
Link: https://lore.kernel.org/r/20220524091808.2269898-1-david@protonic.nl
Signed-off-by: Mark Brown <broonie@kernel.org>
---
 drivers/spi/spi.c       | 143 +++++++++++++++++++++++++++++++++---------------
 include/linux/spi/spi.h |  52 ++++++++++--------
 2 files changed, 127 insertions(+), 68 deletions(-)

(limited to 'include')

diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index ea09d1b42bf6..d94822bf3cec 100644
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -33,6 +33,7 @@
 #include <linux/idr.h>
 #include <linux/platform_data/x86/apple.h>
 #include <linux/ptp_clock_kernel.h>
+#include <linux/percpu.h>
 
 #define CREATE_TRACE_POINTS
 #include <trace/events/spi.h>
@@ -49,6 +50,7 @@ static void spidev_release(struct device *dev)
 
 	spi_controller_put(spi->controller);
 	kfree(spi->driver_override);
+	free_percpu(spi->pcpu_statistics);
 	kfree(spi);
 }
 
@@ -93,6 +95,47 @@ static ssize_t driver_override_show(struct device *dev,
 }
 static DEVICE_ATTR_RW(driver_override);
 
+static struct spi_statistics *spi_alloc_pcpu_stats(struct device *dev)
+{
+	struct spi_statistics __percpu *pcpu_stats;
+
+	if (dev)
+		pcpu_stats = devm_alloc_percpu(dev, struct spi_statistics);
+	else
+		pcpu_stats = alloc_percpu_gfp(struct spi_statistics, GFP_KERNEL);
+
+	if (pcpu_stats) {
+		int cpu;
+
+		for_each_possible_cpu(cpu) {
+			struct spi_statistics *stat;
+
+			stat = per_cpu_ptr(pcpu_stats, cpu);
+			u64_stats_init(&stat->syncp);
+		}
+	}
+	return pcpu_stats;
+}
+
+#define spi_pcpu_stats_totalize(ret, in, field)				\
+do {									\
+	int i;								\
+	ret = 0;							\
+	for_each_possible_cpu(i) {					\
+		const struct spi_statistics *pcpu_stats;		\
+		u64 inc;						\
+		unsigned int start;					\
+		pcpu_stats = per_cpu_ptr(in, i);			\
+		do {							\
+			start = u64_stats_fetch_begin_irq(		\
+					&pcpu_stats->syncp);		\
+			inc = u64_stats_read(&pcpu_stats->field);	\
+		} while (u64_stats_fetch_retry_irq(			\
+					&pcpu_stats->syncp, start));	\
+		ret += inc;						\
+	}								\
+} while (0)
+
 #define SPI_STATISTICS_ATTRS(field, file)				\
 static ssize_t spi_controller_##field##_show(struct device *dev,	\
 					     struct device_attribute *attr, \
@@ -100,7 +143,7 @@ static ssize_t spi_controller_##field##_show(struct device *dev,	\
 {									\
 	struct spi_controller *ctlr = container_of(dev,			\
 					 struct spi_controller, dev);	\
-	return spi_statistics_##field##_show(&ctlr->statistics, buf);	\
+	return spi_statistics_##field##_show(ctlr->pcpu_statistics, buf); \
 }									\
 static struct device_attribute dev_attr_spi_controller_##field = {	\
 	.attr = { .name = file, .mode = 0444 },				\
@@ -111,47 +154,46 @@ static ssize_t spi_device_##field##_show(struct device *dev,		\
 					char *buf)			\
 {									\
 	struct spi_device *spi = to_spi_device(dev);			\
-	return spi_statistics_##field##_show(&spi->statistics, buf);	\
+	return spi_statistics_##field##_show(spi->pcpu_statistics, buf); \
 }									\
 static struct device_attribute dev_attr_spi_device_##field = {		\
 	.attr = { .name = file, .mode = 0444 },				\
 	.show = spi_device_##field##_show,				\
 }
 
-#define SPI_STATISTICS_SHOW_NAME(name, file, field, format_string)	\
+#define SPI_STATISTICS_SHOW_NAME(name, file, field)			\
 static ssize_t spi_statistics_##name##_show(struct spi_statistics *stat, \
 					    char *buf)			\
 {									\
-	unsigned long flags;						\
 	ssize_t len;							\
-	spin_lock_irqsave(&stat->lock, flags);				\
-	len = sysfs_emit(buf, format_string "\n", stat->field);		\
-	spin_unlock_irqrestore(&stat->lock, flags);			\
+	u64 val;							\
+	spi_pcpu_stats_totalize(val, stat, field);			\
+	len = sysfs_emit(buf, "%llu\n", val);				\
 	return len;							\
 }									\
 SPI_STATISTICS_ATTRS(name, file)
 
-#define SPI_STATISTICS_SHOW(field, format_string)			\
+#define SPI_STATISTICS_SHOW(field)					\
 	SPI_STATISTICS_SHOW_NAME(field, __stringify(field),		\
-				 field, format_string)
+				 field)
 
-SPI_STATISTICS_SHOW(messages, "%lu");
-SPI_STATISTICS_SHOW(transfers, "%lu");
-SPI_STATISTICS_SHOW(errors, "%lu");
-SPI_STATISTICS_SHOW(timedout, "%lu");
+SPI_STATISTICS_SHOW(messages);
+SPI_STATISTICS_SHOW(transfers);
+SPI_STATISTICS_SHOW(errors);
+SPI_STATISTICS_SHOW(timedout);
 
-SPI_STATISTICS_SHOW(spi_sync, "%lu");
-SPI_STATISTICS_SHOW(spi_sync_immediate, "%lu");
-SPI_STATISTICS_SHOW(spi_async, "%lu");
+SPI_STATISTICS_SHOW(spi_sync);
+SPI_STATISTICS_SHOW(spi_sync_immediate);
+SPI_STATISTICS_SHOW(spi_async);
 
-SPI_STATISTICS_SHOW(bytes, "%llu");
-SPI_STATISTICS_SHOW(bytes_rx, "%llu");
-SPI_STATISTICS_SHOW(bytes_tx, "%llu");
+SPI_STATISTICS_SHOW(bytes);
+SPI_STATISTICS_SHOW(bytes_rx);
+SPI_STATISTICS_SHOW(bytes_tx);
 
 #define SPI_STATISTICS_TRANSFER_BYTES_HISTO(index, number)		\
 	SPI_STATISTICS_SHOW_NAME(transfer_bytes_histo##index,		\
 				 "transfer_bytes_histo_" number,	\
-				 transfer_bytes_histo[index],  "%lu")
+				 transfer_bytes_histo[index])
 SPI_STATISTICS_TRANSFER_BYTES_HISTO(0,  "0-1");
 SPI_STATISTICS_TRANSFER_BYTES_HISTO(1,  "2-3");
 SPI_STATISTICS_TRANSFER_BYTES_HISTO(2,  "4-7");
@@ -170,7 +212,7 @@ SPI_STATISTICS_TRANSFER_BYTES_HISTO(14, "16384-32767");
 SPI_STATISTICS_TRANSFER_BYTES_HISTO(15, "32768-65535");
 SPI_STATISTICS_TRANSFER_BYTES_HISTO(16, "65536+");
 
-SPI_STATISTICS_SHOW(transfers_split_maxsize, "%lu");
+SPI_STATISTICS_SHOW(transfers_split_maxsize);
 
 static struct attribute *spi_dev_attrs[] = {
 	&dev_attr_modalias.attr,
@@ -267,30 +309,30 @@ static const struct attribute_group *spi_master_groups[] = {
 	NULL,
 };
 
-static void spi_statistics_add_transfer_stats(struct spi_statistics *stats,
+static void spi_statistics_add_transfer_stats(struct spi_statistics *pcpu_stats,
 					      struct spi_transfer *xfer,
 					      struct spi_controller *ctlr)
 {
-	unsigned long flags;
 	int l2len = min(fls(xfer->len), SPI_STATISTICS_HISTO_SIZE) - 1;
+	struct spi_statistics *stats = this_cpu_ptr(pcpu_stats);
 
 	if (l2len < 0)
 		l2len = 0;
 
-	spin_lock_irqsave(&stats->lock, flags);
+	u64_stats_update_begin(&stats->syncp);
 
-	stats->transfers++;
-	stats->transfer_bytes_histo[l2len]++;
+	u64_stats_inc(&stats->transfers);
+	u64_stats_inc(&stats->transfer_bytes_histo[l2len]);
 
-	stats->bytes += xfer->len;
+	u64_stats_add(&stats->bytes, xfer->len);
 	if ((xfer->tx_buf) &&
 	    (xfer->tx_buf != ctlr->dummy_tx))
-		stats->bytes_tx += xfer->len;
+		u64_stats_add(&stats->bytes_tx, xfer->len);
 	if ((xfer->rx_buf) &&
 	    (xfer->rx_buf != ctlr->dummy_rx))
-		stats->bytes_rx += xfer->len;
+		u64_stats_add(&stats->bytes_rx, xfer->len);
 
-	spin_unlock_irqrestore(&stats->lock, flags);
+	u64_stats_update_end(&stats->syncp);
 }
 
 /*
@@ -519,14 +561,19 @@ struct spi_device *spi_alloc_device(struct spi_controller *ctlr)
 		return NULL;
 	}
 
+	spi->pcpu_statistics = spi_alloc_pcpu_stats(NULL);
+	if (!spi->pcpu_statistics) {
+		kfree(spi);
+		spi_controller_put(ctlr);
+		return NULL;
+	}
+
 	spi->master = spi->controller = ctlr;
 	spi->dev.parent = &ctlr->dev;
 	spi->dev.bus = &spi_bus_type;
 	spi->dev.release = spidev_release;
 	spi->mode = ctlr->buswidth_override_bits;
 
-	spin_lock_init(&spi->statistics.lock);
-
 	device_initialize(&spi->dev);
 	return spi;
 }
@@ -1225,8 +1272,8 @@ static int spi_transfer_wait(struct spi_controller *ctlr,
 			     struct spi_message *msg,
 			     struct spi_transfer *xfer)
 {
-	struct spi_statistics *statm = &ctlr->statistics;
-	struct spi_statistics *stats = &msg->spi->statistics;
+	struct spi_statistics *statm = ctlr->pcpu_statistics;
+	struct spi_statistics *stats = msg->spi->pcpu_statistics;
 	u32 speed_hz = xfer->speed_hz;
 	unsigned long long ms;
 
@@ -1382,8 +1429,8 @@ static int spi_transfer_one_message(struct spi_controller *ctlr,
 	struct spi_transfer *xfer;
 	bool keep_cs = false;
 	int ret = 0;
-	struct spi_statistics *statm = &ctlr->statistics;
-	struct spi_statistics *stats = &msg->spi->statistics;
+	struct spi_statistics *statm = ctlr->pcpu_statistics;
+	struct spi_statistics *stats = msg->spi->pcpu_statistics;
 
 	spi_set_cs(msg->spi, true, false);
 
@@ -3029,7 +3076,11 @@ int spi_register_controller(struct spi_controller *ctlr)
 		}
 	}
 	/* add statistics */
-	spin_lock_init(&ctlr->statistics.lock);
+	ctlr->pcpu_statistics = spi_alloc_pcpu_stats(dev);
+	if (!ctlr->pcpu_statistics) {
+		dev_err(dev, "Error allocating per-cpu statistics\n");
+		goto destroy_queue;
+	}
 
 	mutex_lock(&board_lock);
 	list_add_tail(&ctlr->list, &spi_controller_list);
@@ -3042,6 +3093,8 @@ int spi_register_controller(struct spi_controller *ctlr)
 	acpi_register_spi_devices(ctlr);
 	return status;
 
+destroy_queue:
+	spi_destroy_queue(ctlr);
 free_bus_id:
 	mutex_lock(&board_lock);
 	idr_remove(&spi_master_idr, ctlr->bus_num);
@@ -3367,9 +3420,9 @@ static int __spi_split_transfer_maxsize(struct spi_controller *ctlr,
 	*xferp = &xfers[count - 1];
 
 	/* increment statistics counters */
-	SPI_STATISTICS_INCREMENT_FIELD(&ctlr->statistics,
+	SPI_STATISTICS_INCREMENT_FIELD(ctlr->pcpu_statistics,
 				       transfers_split_maxsize);
-	SPI_STATISTICS_INCREMENT_FIELD(&msg->spi->statistics,
+	SPI_STATISTICS_INCREMENT_FIELD(msg->spi->pcpu_statistics,
 				       transfers_split_maxsize);
 
 	return 0;
@@ -3760,8 +3813,8 @@ static int __spi_async(struct spi_device *spi, struct spi_message *message)
 
 	message->spi = spi;
 
-	SPI_STATISTICS_INCREMENT_FIELD(&ctlr->statistics, spi_async);
-	SPI_STATISTICS_INCREMENT_FIELD(&spi->statistics, spi_async);
+	SPI_STATISTICS_INCREMENT_FIELD(ctlr->pcpu_statistics, spi_async);
+	SPI_STATISTICS_INCREMENT_FIELD(spi->pcpu_statistics, spi_async);
 
 	trace_spi_message_submit(message);
 
@@ -3908,8 +3961,8 @@ static int __spi_sync(struct spi_device *spi, struct spi_message *message)
 	message->context = &done;
 	message->spi = spi;
 
-	SPI_STATISTICS_INCREMENT_FIELD(&ctlr->statistics, spi_sync);
-	SPI_STATISTICS_INCREMENT_FIELD(&spi->statistics, spi_sync);
+	SPI_STATISTICS_INCREMENT_FIELD(ctlr->pcpu_statistics, spi_sync);
+	SPI_STATISTICS_INCREMENT_FIELD(spi->pcpu_statistics, spi_sync);
 
 	/*
 	 * If we're not using the legacy transfer method then we will
@@ -3932,9 +3985,9 @@ static int __spi_sync(struct spi_device *spi, struct spi_message *message)
 	if (status == 0) {
 		/* Push out the messages in the calling context if we can */
 		if (ctlr->transfer == spi_queued_transfer) {
-			SPI_STATISTICS_INCREMENT_FIELD(&ctlr->statistics,
+			SPI_STATISTICS_INCREMENT_FIELD(ctlr->pcpu_statistics,
 						       spi_sync_immediate);
-			SPI_STATISTICS_INCREMENT_FIELD(&spi->statistics,
+			SPI_STATISTICS_INCREMENT_FIELD(spi->pcpu_statistics,
 						       spi_sync_immediate);
 			__spi_pump_messages(ctlr, false);
 		}
diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h
index eadfd3ba3cbc..eac8d3caf954 100644
--- a/include/linux/spi/spi.h
+++ b/include/linux/spi/spi.h
@@ -17,6 +17,7 @@
 
 #include <uapi/linux/spi/spi.h>
 #include <linux/acpi.h>
+#include <linux/u64_stats_sync.h>
 
 struct dma_chan;
 struct software_node;
@@ -59,37 +60,42 @@ extern struct bus_type spi_bus_type;
  *                 maxsize limit
  */
 struct spi_statistics {
-	spinlock_t		lock; /* lock for the whole structure */
+	struct u64_stats_sync	syncp;
 
-	unsigned long		messages;
-	unsigned long		transfers;
-	unsigned long		errors;
-	unsigned long		timedout;
+	u64_stats_t		messages;
+	u64_stats_t		transfers;
+	u64_stats_t		errors;
+	u64_stats_t		timedout;
 
-	unsigned long		spi_sync;
-	unsigned long		spi_sync_immediate;
-	unsigned long		spi_async;
+	u64_stats_t		spi_sync;
+	u64_stats_t		spi_sync_immediate;
+	u64_stats_t		spi_async;
 
-	unsigned long long	bytes;
-	unsigned long long	bytes_rx;
-	unsigned long long	bytes_tx;
+	u64_stats_t		bytes;
+	u64_stats_t		bytes_rx;
+	u64_stats_t		bytes_tx;
 
 #define SPI_STATISTICS_HISTO_SIZE 17
-	unsigned long transfer_bytes_histo[SPI_STATISTICS_HISTO_SIZE];
+	u64_stats_t	transfer_bytes_histo[SPI_STATISTICS_HISTO_SIZE];
 
-	unsigned long transfers_split_maxsize;
+	u64_stats_t	transfers_split_maxsize;
 };
 
-#define SPI_STATISTICS_ADD_TO_FIELD(stats, field, count)	\
-	do {							\
-		unsigned long flags;				\
-		spin_lock_irqsave(&(stats)->lock, flags);	\
-		(stats)->field += count;			\
-		spin_unlock_irqrestore(&(stats)->lock, flags);	\
+#define SPI_STATISTICS_ADD_TO_FIELD(pcpu_stats, field, count)		\
+	do {								\
+		struct spi_statistics *__lstats = this_cpu_ptr(pcpu_stats); \
+		u64_stats_update_begin(&__lstats->syncp);		\
+		u64_stats_add(&__lstats->field, count);			\
+		u64_stats_update_end(&__lstats->syncp);			\
 	} while (0)
 
-#define SPI_STATISTICS_INCREMENT_FIELD(stats, field)	\
-	SPI_STATISTICS_ADD_TO_FIELD(stats, field, 1)
+#define SPI_STATISTICS_INCREMENT_FIELD(pcpu_stats, field)		\
+	do {								\
+		struct spi_statistics *__lstats = this_cpu_ptr(pcpu_stats); \
+		u64_stats_update_begin(&__lstats->syncp);		\
+		u64_stats_inc(&__lstats->field);			\
+		u64_stats_update_end(&__lstats->syncp);			\
+	} while (0)
 
 /**
  * struct spi_delay - SPI delay information
@@ -194,7 +200,7 @@ struct spi_device {
 	struct spi_delay	cs_inactive;
 
 	/* the statistics */
-	struct spi_statistics	statistics;
+	struct spi_statistics __percpu	*pcpu_statistics;
 
 	/*
 	 * likely need more hooks for more protocol options affecting how
@@ -647,7 +653,7 @@ struct spi_controller {
 	s8			max_native_cs;
 
 	/* statistics */
-	struct spi_statistics	statistics;
+	struct spi_statistics __percpu	*pcpu_statistics;
 
 	/* DMA channels for use with core dmaengine helpers */
 	struct dma_chan		*dma_tx;
-- 
cgit v1.2.3


From 5dfac65b621733e69b789150a0a3f1bf2f9095a3 Mon Sep 17 00:00:00 2001
From: David Jander
Date: Wed, 8 Jun 2022 17:33:09 +0200
Subject: spi: <linux/spi/spi.h>: Add missing documentation for struct members

Fixes these "make htmldocs" warnings:

include/linux/spi/spi.h:82: warning: Function parameter or member 'syncp' not described in 'spi_statistics'
include/linux/spi/spi.h:213: warning: Function parameter or member 'pcpu_statistics' not described in 'spi_device'
include/linux/spi/spi.h:676: warning: Function parameter or member 'pcpu_statistics' not described in 'spi_controller'

Fixes: 6598b91b5ac3 ("spi: spi.c: Convert statistics to per-cpu u64_stats_t")
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: David Jander <david@protonic.nl>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Link: https://lore.kernel.org/r/20220608153309.2899565-1-david@protonic.nl
Signed-off-by: Mark Brown <broonie@kernel.org>
---
 include/linux/spi/spi.h | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

(limited to 'include')

diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h
index eac8d3caf954..2e63b4935deb 100644
--- a/include/linux/spi/spi.h
+++ b/include/linux/spi/spi.h
@@ -35,7 +35,8 @@ extern struct bus_type spi_bus_type;
 
 /**
  * struct spi_statistics - statistics for spi transfers
- * @lock:          lock protecting this structure
+ * @syncp:         seqcount to protect members in this struct for per-cpu udate
+ *                 on 32-bit systems
  *
  * @messages:      number of spi-messages handled
  * @transfers:     number of spi_transfers handled
@@ -155,7 +156,7 @@ extern int spi_delay_exec(struct spi_delay *_delay, struct spi_transfer *xfer);
  * @cs_inactive: delay to be introduced by the controller after CS is
  *	deasserted. If @cs_change_delay is used from @spi_transfer, then the
  *	two delays will be added up.
- * @statistics: statistics for the spi_device
+ * @pcpu_statistics: statistics for the spi_device
  *
  * A @spi_device is used to interchange data between an SPI slave
  * (usually a discrete chip) and CPU memory.
@@ -439,7 +440,7 @@ extern struct spi_device *spi_new_ancillary_device(struct spi_device *spi, u8 ch
  * @max_native_cs: When cs_gpiods is used, and this field is filled in,
  *	spi_register_controller() will validate all native CS (including the
  *	unused native CS) against this value.
- * @statistics: statistics for the spi_controller
+ * @pcpu_statistics: statistics for the spi_controller
  * @dma_tx: DMA transmit channel
  * @dma_rx: DMA receive channel
  * @dummy_rx: dummy receive buffer for full-duplex devices
-- 
cgit v1.2.3


From 67b9d64139e13621d3ab8bb0daad7602e5fe0778 Mon Sep 17 00:00:00 2001
From: David Jander
Date: Thu, 9 Jun 2022 14:13:34 +0200
Subject: spi: Fix per-cpu stats access on 32 bit systems

On 32 bit systems, the following kernel BUG is hit:

BUG: using smp_processor_id() in preemptible [00000000] code: swapper/0/1
caller is debug_smp_processor_id+0x18/0x24
CPU: 1 PID: 1 Comm: swapper/0 Not tainted 5.19.0-rc1-00001-g6ae0aec8a366 #181
Hardware name: Freescale i.MX6 Quad/DualLite (Device Tree)
Backtrace:
 dump_backtrace from show_stack+0x20/0x24
 r7:81024ffd r6:00000000 r5:81024ffd r4:60000013
 show_stack from dump_stack_lvl+0x60/0x78
 dump_stack_lvl from dump_stack+0x14/0x1c
 r7:81024ffd r6:80f652de r5:80bec180 r4:819a2500
 dump_stack from check_preemption_disabled+0xc8/0xf0
 check_preemption_disabled from debug_smp_processor_id+0x18/0x24
 r8:8119b7e0 r7:81205534 r6:819f5c00 r5:819f4c00 r4:c083d724
 debug_smp_processor_id from __spi_sync+0x78/0x220
 __spi_sync from spi_sync+0x34/0x4c
 r10:bb7bf4e0 r9:c083d724 r8:00000007 r7:81a068c0 r6:822a83c0 r5:c083d724
 r4:819f4c00
 spi_sync from spi_mem_exec_op+0x338/0x370
 r5:000000b4 r4:c083d910
 spi_mem_exec_op from spi_nor_read_id+0x98/0xdc
 r10:bb7bf4e0 r9:00000000 r8:00000000 r7:00000000 r6:00000000 r5:82358040
 r4:819f7c40
 spi_nor_read_id from spi_nor_detect+0x38/0x114
 r7:82358040 r6:00000000 r5:819f7c40 r4:819f7c40
 spi_nor_detect from spi_nor_scan+0x11c/0xbec
 r10:bb7bf4e0 r9:00000000 r8:00000000 r7:c083da4c r6:00000000 r5:00010101
 r4:819f7c40
 spi_nor_scan from spi_nor_probe+0x10c/0x2d0
 r10:bb7bf4e0 r9:bb7bf4d0 r8:00000000 r7:819f4c00 r6:00000000 r5:00000000
 r4:819f7c40

per-cpu access needs to be guarded against preemption.

Fixes: 6598b91b5ac3 ("spi: spi.c: Convert statistics to per-cpu u64_stats_t")
Reported-by: Marc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: David Jander <david@protonic.nl>
Tested-by: Nícolas F. R. A. Prado <nfraprado@collabora.com>
Link: https://lore.kernel.org/r/20220609121334.2984808-1-david@protonic.nl
Signed-off-by: Mark Brown <broonie@kernel.org>
---
 drivers/spi/spi.c       |  5 ++++-
 include/linux/spi/spi.h | 10 ++++++++--
 2 files changed, 12 insertions(+), 3 deletions(-)

(limited to 'include')

diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index d94822bf3cec..ac61824b87b5 100644
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -314,11 +314,13 @@ static void spi_statistics_add_transfer_stats(struct spi_statistics *pcpu_stats,
 					      struct spi_controller *ctlr)
 {
 	int l2len = min(fls(xfer->len), SPI_STATISTICS_HISTO_SIZE) - 1;
-	struct spi_statistics *stats = this_cpu_ptr(pcpu_stats);
+	struct spi_statistics *stats;
 
 	if (l2len < 0)
 		l2len = 0;
 
+	get_cpu();
+	stats = this_cpu_ptr(pcpu_stats);
 	u64_stats_update_begin(&stats->syncp);
 
 	u64_stats_inc(&stats->transfers);
@@ -333,6 +335,7 @@ static void spi_statistics_add_transfer_stats(struct spi_statistics *pcpu_stats,
 		u64_stats_add(&stats->bytes_rx, xfer->len);
 
 	u64_stats_update_end(&stats->syncp);
+	put_cpu();
 }
 
 /*
diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h
index 2e63b4935deb..c96f526d9a20 100644
--- a/include/linux/spi/spi.h
+++ b/include/linux/spi/spi.h
@@ -84,18 +84,24 @@ struct spi_statistics {
 
 #define SPI_STATISTICS_ADD_TO_FIELD(pcpu_stats, field, count)		\
 	do {								\
-		struct spi_statistics *__lstats = this_cpu_ptr(pcpu_stats); \
+		struct spi_statistics *__lstats;			\
+		get_cpu();						\
+		__lstats = this_cpu_ptr(pcpu_stats);			\
 		u64_stats_update_begin(&__lstats->syncp);		\
 		u64_stats_add(&__lstats->field, count);			\
 		u64_stats_update_end(&__lstats->syncp);			\
+		put_cpu();						\
 	} while (0)
 
 #define SPI_STATISTICS_INCREMENT_FIELD(pcpu_stats, field)		\
 	do {								\
-		struct spi_statistics *__lstats = this_cpu_ptr(pcpu_stats); \
+		struct spi_statistics *__lstats;			\
+		get_cpu();						\
+		__lstats = this_cpu_ptr(pcpu_stats);			\
 		u64_stats_update_begin(&__lstats->syncp);		\
 		u64_stats_inc(&__lstats->field);			\
 		u64_stats_update_end(&__lstats->syncp);			\
+		put_cpu();						\
 	} while (0)
 
 /**
-- 
cgit v1.2.3


From 1714582a3a087eda8786d5a1b32b2ec86ca8a303 Mon Sep 17 00:00:00 2001
From: David Jander
Date: Tue, 21 Jun 2022 08:12:24 +0200
Subject: spi: Move ctlr->cur_msg_prepared to struct spi_message

This enables the possibility to transfer a message that is not at the
current tip of the async message queue.
This is in preparation of the next patch(es) which enable spi_sync messages
to skip the queue altogether.

Signed-off-by: David Jander <david@protonic.nl>
Link: https://lore.kernel.org/r/20220621061234.3626638-2-david@protonic.nl
Signed-off-by: Mark Brown <broonie@kernel.org>
---
 drivers/spi/spi.c       | 7 ++++---
 include/linux/spi/spi.h | 7 ++++---
 2 files changed, 8 insertions(+), 6 deletions(-)

(limited to 'include')

diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index c78d1ceeaa42..eb6360153fa1 100644
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -1684,7 +1684,7 @@ static void __spi_pump_messages(struct spi_controller *ctlr, bool in_kthread)
 			spi_finalize_current_message(ctlr);
 			goto out;
 		}
-		ctlr->cur_msg_prepared = true;
+		msg->prepared = true;
 	}
 
 	ret = spi_map_msg(ctlr, msg);
@@ -1926,7 +1926,7 @@ void spi_finalize_current_message(struct spi_controller *ctlr)
 	 */
 	spi_res_release(ctlr, mesg);
 
-	if (ctlr->cur_msg_prepared && ctlr->unprepare_message) {
+	if (mesg->prepared && ctlr->unprepare_message) {
 		ret = ctlr->unprepare_message(ctlr, mesg);
 		if (ret) {
 			dev_err(&ctlr->dev, "failed to unprepare message: %d\n",
@@ -1934,9 +1934,10 @@ void spi_finalize_current_message(struct spi_controller *ctlr)
 		}
 	}
 
+	mesg->prepared = false;
+
 	spin_lock_irqsave(&ctlr->queue_lock, flags);
 	ctlr->cur_msg = NULL;
-	ctlr->cur_msg_prepared = false;
 	ctlr->fallback = false;
 	kthread_queue_work(ctlr->kworker, &ctlr->pump_messages);
 	spin_unlock_irqrestore(&ctlr->queue_lock, flags);
diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h
index c96f526d9a20..1a75c26742f2 100644
--- a/include/linux/spi/spi.h
+++ b/include/linux/spi/spi.h
@@ -385,8 +385,6 @@ extern struct spi_device *spi_new_ancillary_device(struct spi_device *spi, u8 ch
  * @queue: message queue
  * @idling: the device is entering idle state
  * @cur_msg: the currently in-flight message
- * @cur_msg_prepared: spi_prepare_message was called for the currently
- *                    in-flight message
  * @cur_msg_mapped: message has been mapped for DMA
  * @last_cs: the last chip_select that is recorded by set_cs, -1 on non chip
  *           selected
@@ -621,7 +619,6 @@ struct spi_controller {
 	bool				running;
 	bool				rt;
 	bool				auto_runtime_pm;
-	bool                            cur_msg_prepared;
 	bool				cur_msg_mapped;
 	char				last_cs;
 	bool				last_cs_mode_high;
@@ -988,6 +985,7 @@ struct spi_transfer {
  * @queue: for use by whichever driver currently owns the message
  * @state: for use by whichever driver currently owns the message
  * @resources: for resource management when the spi message is processed
+ * @prepared: spi_prepare_message was called for the this message
  *
  * A @spi_message is used to execute an atomic sequence of data transfers,
  * each represented by a struct spi_transfer.  The sequence is "atomic"
@@ -1037,6 +1035,9 @@ struct spi_message {
 
 	/* list of spi_res reources when the spi message is processed */
 	struct list_head        resources;
+
+	/* spi_prepare_message was called for this message */
+	bool                    prepared;
 };
 
 static inline void spi_message_init_no_memset(struct spi_message *m)
-- 
cgit v1.2.3


From ae7d2346dc89ae89a6e0aabe6037591a11e593c0 Mon Sep 17 00:00:00 2001
From: David Jander
Date: Tue, 21 Jun 2022 08:12:25 +0200
Subject: spi: Don't use the message queue if possible in spi_sync

The interaction with the controller message queue and its corresponding
auxiliary flags and variables requires the use of the queue_lock which is
costly. Since spi_sync will transfer the complete message anyway, and not
return until it is finished, there is no need to put the message into the
queue if the queue is empty. This can save a lot of overhead.

As an example of how significant this is, when using the MCP2518FD SPI CAN
controller on a i.MX8MM SoC, the time during which the interrupt line
stays active (during 3 relatively short spi_sync messages), is reduced
from 98us to 72us by this patch.

Signed-off-by: David Jander <david@protonic.nl>
Link: https://lore.kernel.org/r/20220621061234.3626638-3-david@protonic.nl
Signed-off-by: Mark Brown <broonie@kernel.org>
---
 drivers/spi/spi.c       | 246 +++++++++++++++++++++++++++++-------------------
 include/linux/spi/spi.h |  11 ++-
 2 files changed, 159 insertions(+), 98 deletions(-)

(limited to 'include')

diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index eb6360153fa1..2d057d03c4f7 100644
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -1549,6 +1549,80 @@ static void spi_idle_runtime_pm(struct spi_controller *ctlr)
 	}
 }
 
+static int __spi_pump_transfer_message(struct spi_controller *ctlr,
+		struct spi_message *msg, bool was_busy)
+{
+	struct spi_transfer *xfer;
+	int ret;
+
+	if (!was_busy && ctlr->auto_runtime_pm) {
+		ret = pm_runtime_get_sync(ctlr->dev.parent);
+		if (ret < 0) {
+			pm_runtime_put_noidle(ctlr->dev.parent);
+			dev_err(&ctlr->dev, "Failed to power device: %d\n",
+				ret);
+			return ret;
+		}
+	}
+
+	if (!was_busy)
+		trace_spi_controller_busy(ctlr);
+
+	if (!was_busy && ctlr->prepare_transfer_hardware) {
+		ret = ctlr->prepare_transfer_hardware(ctlr);
+		if (ret) {
+			dev_err(&ctlr->dev,
+				"failed to prepare transfer hardware: %d\n",
+				ret);
+
+			if (ctlr->auto_runtime_pm)
+				pm_runtime_put(ctlr->dev.parent);
+
+			msg->status = ret;
+			spi_finalize_current_message(ctlr);
+
+			return ret;
+		}
+	}
+
+	trace_spi_message_start(msg);
+
+	if (ctlr->prepare_message) {
+		ret = ctlr->prepare_message(ctlr, msg);
+		if (ret) {
+			dev_err(&ctlr->dev, "failed to prepare message: %d\n",
+				ret);
+			msg->status = ret;
+			spi_finalize_current_message(ctlr);
+			return ret;
+		}
+		msg->prepared = true;
+	}
+
+	ret = spi_map_msg(ctlr, msg);
+	if (ret) {
+		msg->status = ret;
+		spi_finalize_current_message(ctlr);
+		return ret;
+	}
+
+	if (!ctlr->ptp_sts_supported && !ctlr->transfer_one) {
+		list_for_each_entry(xfer, &msg->transfers, transfer_list) {
+			xfer->ptp_sts_word_pre = 0;
+			ptp_read_system_prets(xfer->ptp_sts);
+		}
+	}
+
+	ret = ctlr->transfer_one_message(ctlr, msg);
+	if (ret) {
+		dev_err(&ctlr->dev,
+			"failed to transfer one message from queue\n");
+		return ret;
+	}
+
+	return 0;
+}
+
 /**
  * __spi_pump_messages - function which processes spi message queue
  * @ctlr: controller to process queue for
@@ -1564,7 +1638,6 @@ static void spi_idle_runtime_pm(struct spi_controller *ctlr)
  */
 static void __spi_pump_messages(struct spi_controller *ctlr, bool in_kthread)
 {
-	struct spi_transfer *xfer;
 	struct spi_message *msg;
 	bool was_busy = false;
 	unsigned long flags;
@@ -1599,6 +1672,7 @@ static void __spi_pump_messages(struct spi_controller *ctlr, bool in_kthread)
 			    !ctlr->unprepare_transfer_hardware) {
 				spi_idle_runtime_pm(ctlr);
 				ctlr->busy = false;
+				ctlr->queue_empty = true;
 				trace_spi_controller_idle(ctlr);
 			} else {
 				kthread_queue_work(ctlr->kworker,
@@ -1625,6 +1699,7 @@ static void __spi_pump_messages(struct spi_controller *ctlr, bool in_kthread)
 
 		spin_lock_irqsave(&ctlr->queue_lock, flags);
 		ctlr->idling = false;
+		ctlr->queue_empty = true;
 		spin_unlock_irqrestore(&ctlr->queue_lock, flags);
 		return;
 	}
@@ -1641,75 +1716,7 @@ static void __spi_pump_messages(struct spi_controller *ctlr, bool in_kthread)
 	spin_unlock_irqrestore(&ctlr->queue_lock, flags);
 
 	mutex_lock(&ctlr->io_mutex);
-
-	if (!was_busy && ctlr->auto_runtime_pm) {
-		ret = pm_runtime_resume_and_get(ctlr->dev.parent);
-		if (ret < 0) {
-			dev_err(&ctlr->dev, "Failed to power device: %d\n",
-				ret);
-			mutex_unlock(&ctlr->io_mutex);
-			return;
-		}
-	}
-
-	if (!was_busy)
-		trace_spi_controller_busy(ctlr);
-
-	if (!was_busy && ctlr->prepare_transfer_hardware) {
-		ret = ctlr->prepare_transfer_hardware(ctlr);
-		if (ret) {
-			dev_err(&ctlr->dev,
-				"failed to prepare transfer hardware: %d\n",
-				ret);
-
-			if (ctlr->auto_runtime_pm)
-				pm_runtime_put(ctlr->dev.parent);
-
-			msg->status = ret;
-			spi_finalize_current_message(ctlr);
-
-			mutex_unlock(&ctlr->io_mutex);
-			return;
-		}
-	}
-
-	trace_spi_message_start(msg);
-
-	if (ctlr->prepare_message) {
-		ret = ctlr->prepare_message(ctlr, msg);
-		if (ret) {
-			dev_err(&ctlr->dev, "failed to prepare message: %d\n",
-				ret);
-			msg->status = ret;
-			spi_finalize_current_message(ctlr);
-			goto out;
-		}
-		msg->prepared = true;
-	}
-
-	ret = spi_map_msg(ctlr, msg);
-	if (ret) {
-		msg->status = ret;
-		spi_finalize_current_message(ctlr);
-		goto out;
-	}
-
-	if (!ctlr->ptp_sts_supported && !ctlr->transfer_one) {
-		list_for_each_entry(xfer, &msg->transfers, transfer_list) {
-			xfer->ptp_sts_word_pre = 0;
-			ptp_read_system_prets(xfer->ptp_sts);
-		}
-	}
-
-	ret = ctlr->transfer_one_message(ctlr, msg);
-	if (ret) {
-		dev_err(&ctlr->dev,
-			"failed to transfer one message from queue: %d\n",
-			ret);
-		goto out;
-	}
-
-out:
+	ret = __spi_pump_transfer_message(ctlr, msg, was_busy);
 	mutex_unlock(&ctlr->io_mutex);
 
 	/* Prod the scheduler in case transfer_one() was busy waiting */
@@ -1839,6 +1846,7 @@ static int spi_init_queue(struct spi_controller *ctlr)
 {
 	ctlr->running = false;
 	ctlr->busy = false;
+	ctlr->queue_empty = true;
 
 	ctlr->kworker = kthread_create_worker(0, dev_name(&ctlr->dev));
 	if (IS_ERR(ctlr->kworker)) {
@@ -1936,11 +1944,20 @@ void spi_finalize_current_message(struct spi_controller *ctlr)
 
 	mesg->prepared = false;
 
-	spin_lock_irqsave(&ctlr->queue_lock, flags);
-	ctlr->cur_msg = NULL;
-	ctlr->fallback = false;
-	kthread_queue_work(ctlr->kworker, &ctlr->pump_messages);
-	spin_unlock_irqrestore(&ctlr->queue_lock, flags);
+	if (!mesg->sync) {
+		/*
+		 * This message was sent via the async message queue. Handle
+		 * the queue and kick the worker thread to do the
+		 * idling/shutdown or send the next message if needed.
+		 */
+		spin_lock_irqsave(&ctlr->queue_lock, flags);
+		WARN(ctlr->cur_msg != mesg,
+			"Finalizing queued message that is not the current head of queue!");
+		ctlr->cur_msg = NULL;
+		ctlr->fallback = false;
+		kthread_queue_work(ctlr->kworker, &ctlr->pump_messages);
+		spin_unlock_irqrestore(&ctlr->queue_lock, flags);
+	}
 
 	trace_spi_message_done(mesg);
 
@@ -2043,6 +2060,7 @@ static int __spi_queued_transfer(struct spi_device *spi,
 	msg->status = -EINPROGRESS;
 
 	list_add_tail(&msg->queue, &ctlr->queue);
+	ctlr->queue_empty = false;
 	if (!ctlr->busy && need_pump)
 		kthread_queue_work(ctlr->kworker, &ctlr->pump_messages);
 
@@ -3938,6 +3956,39 @@ static int spi_async_locked(struct spi_device *spi, struct spi_message *message)
 
 }
 
+static void __spi_transfer_message_noqueue(struct spi_controller *ctlr, struct spi_message *msg)
+{
+	bool was_busy;
+	int ret;
+
+	mutex_lock(&ctlr->io_mutex);
+
+	/* If another context is idling the device then wait */
+	while (ctlr->idling)
+		usleep_range(10000, 11000);
+
+	was_busy = READ_ONCE(ctlr->busy);
+
+	ret = __spi_pump_transfer_message(ctlr, msg, was_busy);
+	if (ret)
+		goto out;
+
+	if (!was_busy) {
+		kfree(ctlr->dummy_rx);
+		ctlr->dummy_rx = NULL;
+		kfree(ctlr->dummy_tx);
+		ctlr->dummy_tx = NULL;
+		if (ctlr->unprepare_transfer_hardware &&
+		    ctlr->unprepare_transfer_hardware(ctlr))
+			dev_err(&ctlr->dev,
+				"failed to unprepare transfer hardware\n");
+		spi_idle_runtime_pm(ctlr);
+	}
+
+out:
+	mutex_unlock(&ctlr->io_mutex);
+}
+
 /*-------------------------------------------------------------------------*/
 
 /*
@@ -3956,51 +4007,52 @@ static int __spi_sync(struct spi_device *spi, struct spi_message *message)
 	DECLARE_COMPLETION_ONSTACK(done);
 	int status;
 	struct spi_controller *ctlr = spi->controller;
-	unsigned long flags;
 
 	status = __spi_validate(spi, message);
 	if (status != 0)
 		return status;
 
-	message->complete = spi_complete;
-	message->context = &done;
 	message->spi = spi;
 
 	SPI_STATISTICS_INCREMENT_FIELD(ctlr->pcpu_statistics, spi_sync);
 	SPI_STATISTICS_INCREMENT_FIELD(spi->pcpu_statistics, spi_sync);
 
 	/*
-	 * If we're not using the legacy transfer method then we will
-	 * try to transfer in the calling context so special case.
-	 * This code would be less tricky if we could remove the
-	 * support for driver implemented message queues.
+	 * Checking queue_empty here only guarantees async/sync message
+	 * ordering when coming from the same context. It does not need to
+	 * guard against reentrancy from a different context. The io_mutex
+	 * will catch those cases.
 	 */
-	if (ctlr->transfer == spi_queued_transfer) {
-		spin_lock_irqsave(&ctlr->bus_lock_spinlock, flags);
+	if (READ_ONCE(ctlr->queue_empty)) {
+		message->sync = true;
+		message->actual_length = 0;
+		message->status = -EINPROGRESS;
 
 		trace_spi_message_submit(message);
 
-		status = __spi_queued_transfer(spi, message, false);
+		SPI_STATISTICS_INCREMENT_FIELD(ctlr->pcpu_statistics, spi_sync_immediate);
+		SPI_STATISTICS_INCREMENT_FIELD(spi->pcpu_statistics, spi_sync_immediate);
 
-		spin_unlock_irqrestore(&ctlr->bus_lock_spinlock, flags);
-	} else {
-		status = spi_async_locked(spi, message);
+		__spi_transfer_message_noqueue(ctlr, message);
+
+		return message->status;
 	}
 
+	/*
+	 * There are messages in the async queue that could have originated
+	 * from the same context, so we need to preserve ordering.
+	 * Therefor we send the message to the async queue and wait until they
+	 * are completed.
+	 */
+	message->complete = spi_complete;
+	message->context = &done;
+	status = spi_async_locked(spi, message);
 	if (status == 0) {
-		/* Push out the messages in the calling context if we can */
-		if (ctlr->transfer == spi_queued_transfer) {
-			SPI_STATISTICS_INCREMENT_FIELD(ctlr->pcpu_statistics,
-						       spi_sync_immediate);
-			SPI_STATISTICS_INCREMENT_FIELD(spi->pcpu_statistics,
-						       spi_sync_immediate);
-			__spi_pump_messages(ctlr, false);
-		}
-
 		wait_for_completion(&done);
 		status = message->status;
 	}
 	message->context = NULL;
+
 	return status;
 }
 
diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h
index 1a75c26742f2..74261a83b5fa 100644
--- a/include/linux/spi/spi.h
+++ b/include/linux/spi/spi.h
@@ -461,6 +461,8 @@ extern struct spi_device *spi_new_ancillary_device(struct spi_device *spi, u8 ch
  * @irq_flags: Interrupt enable state during PTP system timestamping
  * @fallback: fallback to pio if dma transfer return failure with
  *	SPI_TRANS_FAIL_NO_START.
+ * @queue_empty: signal green light for opportunistically skipping the queue
+ *	for spi_sync transfers.
  *
  * Each SPI controller can communicate with one or more @spi_device
  * children.  These make a small bus, sharing MOSI, MISO and SCK signals
@@ -677,6 +679,9 @@ struct spi_controller {
 
 	/* Interrupt enable state during PTP system timestamping */
 	unsigned long		irq_flags;
+
+	/* Flag for enabling opportunistic skipping of the queue in spi_sync */
+	bool			queue_empty;
 };
 
 static inline void *spi_controller_get_devdata(struct spi_controller *ctlr)
@@ -986,6 +991,7 @@ struct spi_transfer {
  * @state: for use by whichever driver currently owns the message
  * @resources: for resource management when the spi message is processed
  * @prepared: spi_prepare_message was called for the this message
+ * @sync: this message took the direct sync path skipping the async queue
  *
  * A @spi_message is used to execute an atomic sequence of data transfers,
  * each represented by a struct spi_transfer.  The sequence is "atomic"
@@ -1037,7 +1043,10 @@ struct spi_message {
 	struct list_head        resources;
 
 	/* spi_prepare_message was called for this message */
-	bool                    prepared;
+	bool			prepared;
+
+	/* this message is skipping the async queue */
+	bool			sync;
 };
 
 static inline void spi_message_init_no_memset(struct spi_message *m)
-- 
cgit v1.2.3


From 66a221593cb26dd6aabba63bcd18173f4e69c7ab Mon Sep 17 00:00:00 2001
From: David Jander
Date: Tue, 21 Jun 2022 08:12:30 +0200
Subject: spi: Remove the now unused ctlr->idling flag

The ctlr->idling flag is never checked now, so we don't need to set it
either.

Signed-off-by: David Jander <david@protonic.nl>
Link: https://lore.kernel.org/r/20220621061234.3626638-8-david@protonic.nl
Signed-off-by: Mark Brown <broonie@kernel.org>
---
 drivers/spi/spi.c       | 2 --
 include/linux/spi/spi.h | 2 --
 2 files changed, 4 deletions(-)

(limited to 'include')

diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index 71b767a9ad77..52736e339645 100644
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -1674,7 +1674,6 @@ static void __spi_pump_messages(struct spi_controller *ctlr, bool in_kthread)
 		}
 
 		ctlr->busy = false;
-		ctlr->idling = true;
 		spin_unlock_irqrestore(&ctlr->queue_lock, flags);
 
 		kfree(ctlr->dummy_rx);
@@ -1689,7 +1688,6 @@ static void __spi_pump_messages(struct spi_controller *ctlr, bool in_kthread)
 		trace_spi_controller_idle(ctlr);
 
 		spin_lock_irqsave(&ctlr->queue_lock, flags);
-		ctlr->idling = false;
 		ctlr->queue_empty = true;
 		goto out_unlock;
 	}
diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h
index 74261a83b5fa..c58f46be762f 100644
--- a/include/linux/spi/spi.h
+++ b/include/linux/spi/spi.h
@@ -383,7 +383,6 @@ extern struct spi_device *spi_new_ancillary_device(struct spi_device *spi, u8 ch
  * @pump_messages: work struct for scheduling work to the message pump
  * @queue_lock: spinlock to syncronise access to message queue
  * @queue: message queue
- * @idling: the device is entering idle state
  * @cur_msg: the currently in-flight message
  * @cur_msg_mapped: message has been mapped for DMA
  * @last_cs: the last chip_select that is recorded by set_cs, -1 on non chip
@@ -616,7 +615,6 @@ struct spi_controller {
 	spinlock_t			queue_lock;
 	struct list_head		queue;
 	struct spi_message		*cur_msg;
-	bool				idling;
 	bool				busy;
 	bool				running;
 	bool				rt;
-- 
cgit v1.2.3


From 69fa95905d40846756d22402690ddf5361a9d13b Mon Sep 17 00:00:00 2001
From: David Jander
Date: Tue, 21 Jun 2022 08:12:33 +0200
Subject: spi: Ensure the io_mutex is held until spi_finalize_current_message()

This patch introduces a completion that is completed in
spi_finalize_current_message() and waited for in
__spi_pump_transfer_message(). This way all manipulation of ctlr->cur_msg
is done with the io_mutex held and strictly ordered:
__spi_pump_transfer_message() will not return until
spi_finalize_current_message() is done using ctlr->cur_msg, and its
calling context is only touching ctlr->cur_msg after returning.
Due to this, we can safely drop the spin-locks around ctlr->cur_msg.

Signed-off-by: David Jander <david@protonic.nl>
Link: https://lore.kernel.org/r/20220621061234.3626638-11-david@protonic.nl
Signed-off-by: Mark Brown <broonie@kernel.org>
---
 drivers/spi/spi.c       | 32 ++++++++++++++------------------
 include/linux/spi/spi.h |  6 ++----
 2 files changed, 16 insertions(+), 22 deletions(-)

(limited to 'include')

diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index 3df84f43918c..db08cb868652 100644
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -1613,11 +1613,14 @@ static int __spi_pump_transfer_message(struct spi_controller *ctlr,
 		}
 	}
 
+	reinit_completion(&ctlr->cur_msg_completion);
 	ret = ctlr->transfer_one_message(ctlr, msg);
 	if (ret) {
 		dev_err(&ctlr->dev,
 			"failed to transfer one message from queue\n");
 		return ret;
+	} else {
+		wait_for_completion(&ctlr->cur_msg_completion);
 	}
 
 	return 0;
@@ -1704,6 +1707,12 @@ static void __spi_pump_messages(struct spi_controller *ctlr, bool in_kthread)
 	spin_unlock_irqrestore(&ctlr->queue_lock, flags);
 
 	ret = __spi_pump_transfer_message(ctlr, msg, was_busy);
+
+	if (!ret)
+		kthread_queue_work(ctlr->kworker, &ctlr->pump_messages);
+	ctlr->cur_msg = NULL;
+	ctlr->fallback = false;
+
 	mutex_unlock(&ctlr->io_mutex);
 
 	/* Prod the scheduler in case transfer_one() was busy waiting */
@@ -1897,12 +1906,9 @@ void spi_finalize_current_message(struct spi_controller *ctlr)
 {
 	struct spi_transfer *xfer;
 	struct spi_message *mesg;
-	unsigned long flags;
 	int ret;
 
-	spin_lock_irqsave(&ctlr->queue_lock, flags);
 	mesg = ctlr->cur_msg;
-	spin_unlock_irqrestore(&ctlr->queue_lock, flags);
 
 	if (!ctlr->ptp_sts_supported && !ctlr->transfer_one) {
 		list_for_each_entry(xfer, &mesg->transfers, transfer_list) {
@@ -1936,20 +1942,7 @@ void spi_finalize_current_message(struct spi_controller *ctlr)
 
 	mesg->prepared = false;
 
-	if (!mesg->sync) {
-		/*
-		 * This message was sent via the async message queue. Handle
-		 * the queue and kick the worker thread to do the
-		 * idling/shutdown or send the next message if needed.
-		 */
-		spin_lock_irqsave(&ctlr->queue_lock, flags);
-		WARN(ctlr->cur_msg != mesg,
-			"Finalizing queued message that is not the current head of queue!");
-		ctlr->cur_msg = NULL;
-		ctlr->fallback = false;
-		kthread_queue_work(ctlr->kworker, &ctlr->pump_messages);
-		spin_unlock_irqrestore(&ctlr->queue_lock, flags);
-	}
+	complete(&ctlr->cur_msg_completion);
 
 	trace_spi_message_done(mesg);
 
@@ -3036,6 +3029,7 @@ int spi_register_controller(struct spi_controller *ctlr)
 	}
 	ctlr->bus_lock_flag = 0;
 	init_completion(&ctlr->xfer_completion);
+	init_completion(&ctlr->cur_msg_completion);
 	if (!ctlr->max_dma_len)
 		ctlr->max_dma_len = INT_MAX;
 
@@ -3962,6 +3956,9 @@ static void __spi_transfer_message_noqueue(struct spi_controller *ctlr, struct s
 	if (ret)
 		goto out;
 
+	ctlr->cur_msg = NULL;
+	ctlr->fallback = false;
+
 	if (!was_busy) {
 		kfree(ctlr->dummy_rx);
 		ctlr->dummy_rx = NULL;
@@ -4013,7 +4010,6 @@ static int __spi_sync(struct spi_device *spi, struct spi_message *message)
 	 * will catch those cases.
 	 */
 	if (READ_ONCE(ctlr->queue_empty)) {
-		message->sync = true;
 		message->actual_length = 0;
 		message->status = -EINPROGRESS;
 
diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h
index c58f46be762f..c56e0d240a58 100644
--- a/include/linux/spi/spi.h
+++ b/include/linux/spi/spi.h
@@ -384,6 +384,7 @@ extern struct spi_device *spi_new_ancillary_device(struct spi_device *spi, u8 ch
  * @queue_lock: spinlock to syncronise access to message queue
  * @queue: message queue
  * @cur_msg: the currently in-flight message
+ * @cur_msg_completion: a completion for the current in-flight message
  * @cur_msg_mapped: message has been mapped for DMA
  * @last_cs: the last chip_select that is recorded by set_cs, -1 on non chip
  *           selected
@@ -615,6 +616,7 @@ struct spi_controller {
 	spinlock_t			queue_lock;
 	struct list_head		queue;
 	struct spi_message		*cur_msg;
+	struct completion               cur_msg_completion;
 	bool				busy;
 	bool				running;
 	bool				rt;
@@ -989,7 +991,6 @@ struct spi_transfer {
  * @state: for use by whichever driver currently owns the message
  * @resources: for resource management when the spi message is processed
  * @prepared: spi_prepare_message was called for the this message
- * @sync: this message took the direct sync path skipping the async queue
  *
  * A @spi_message is used to execute an atomic sequence of data transfers,
  * each represented by a struct spi_transfer.  The sequence is "atomic"
@@ -1042,9 +1043,6 @@ struct spi_message {
 
 	/* spi_prepare_message was called for this message */
 	bool			prepared;
-
-	/* this message is skipping the async queue */
-	bool			sync;
 };
 
 static inline void spi_message_init_no_memset(struct spi_message *m)
-- 
cgit v1.2.3


From dc3029056b02414c29b6627e3dd7b16624725ae9 Mon Sep 17 00:00:00 2001
From: David Jander
Date: Tue, 21 Jun 2022 08:12:34 +0200
Subject: spi: opportunistically skip ctlr->cur_msg_completion

There are only a few drivers that do not call
spi_finalize_current_message() in the context of transfer_one_message(),
and even for those cases the completion ctlr->cur_msg_completion is not
needed always. The calls to complete() and wait_for_completion() each
take a spin-lock, which is costly. This patch makes it possible to avoid
those calls in the big majority of cases, by introducing two flags that
with the help of ordering via barriers can avoid using the completion
safely. In case of a race with the context calling
spi_finalize_current_message(), the scheme errs on the safe side and takes
the completion.
The impact of this patch is worth the effort: On a i.MX8MM SoC, the time
the SPI bus is idle between two consecutive calls to spi_sync(), is
reduced from 19.6us to 16.8us... roughly 15%.

Signed-off-by: David Jander <david@protonic.nl>
Link: https://lore.kernel.org/r/20220621061234.3626638-12-david@protonic.nl
Signed-off-by: Mark Brown <broonie@kernel.org>
---
 drivers/spi/spi.c       | 27 +++++++++++++++++++++++++--
 include/linux/spi/spi.h |  8 ++++++++
 2 files changed, 33 insertions(+), 2 deletions(-)

(limited to 'include')

diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index db08cb868652..ef37f043fd17 100644
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -1613,14 +1613,34 @@ static int __spi_pump_transfer_message(struct spi_controller *ctlr,
 		}
 	}
 
+	/*
+	 * Drivers implementation of transfer_one_message() must arrange for
+	 * spi_finalize_current_message() to get called. Most drivers will do
+	 * this in the calling context, but some don't. For those cases, a
+	 * completion is used to guarantee that this function does not return
+	 * until spi_finalize_current_message() is done accessing
+	 * ctlr->cur_msg.
+	 * Use of the following two flags enable to opportunistically skip the
+	 * use of the completion since its use involves expensive spin locks.
+	 * In case of a race with the context that calls
+	 * spi_finalize_current_message() the completion will always be used,
+	 * due to strict ordering of these flags using barriers.
+	 */
+	WRITE_ONCE(ctlr->cur_msg_incomplete, true);
+	WRITE_ONCE(ctlr->cur_msg_need_completion, false);
 	reinit_completion(&ctlr->cur_msg_completion);
+	smp_wmb(); /* make these available to spi_finalize_current_message */
+
 	ret = ctlr->transfer_one_message(ctlr, msg);
 	if (ret) {
 		dev_err(&ctlr->dev,
 			"failed to transfer one message from queue\n");
 		return ret;
 	} else {
-		wait_for_completion(&ctlr->cur_msg_completion);
+		WRITE_ONCE(ctlr->cur_msg_need_completion, true);
+		smp_mb(); /* see spi_finalize_current_message()... */
+		if (READ_ONCE(ctlr->cur_msg_incomplete))
+			wait_for_completion(&ctlr->cur_msg_completion);
 	}
 
 	return 0;
@@ -1942,7 +1962,10 @@ void spi_finalize_current_message(struct spi_controller *ctlr)
 
 	mesg->prepared = false;
 
-	complete(&ctlr->cur_msg_completion);
+	WRITE_ONCE(ctlr->cur_msg_incomplete, false);
+	smp_mb(); /* See __spi_pump_transfer_message()... */
+	if (READ_ONCE(ctlr->cur_msg_need_completion))
+		complete(&ctlr->cur_msg_completion);
 
 	trace_spi_message_done(mesg);
 
diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h
index c56e0d240a58..eb0d316e3c36 100644
--- a/include/linux/spi/spi.h
+++ b/include/linux/spi/spi.h
@@ -385,6 +385,12 @@ extern struct spi_device *spi_new_ancillary_device(struct spi_device *spi, u8 ch
  * @queue: message queue
  * @cur_msg: the currently in-flight message
  * @cur_msg_completion: a completion for the current in-flight message
+ * @cur_msg_incomplete: Flag used internally to opportunistically skip
+ *	the @cur_msg_completion. This flag is used to check if the driver has
+ *	already called spi_finalize_current_message().
+ * @cur_msg_need_completion: Flag used internally to opportunistically skip
+ *	the @cur_msg_completion. This flag is used to signal the context that
+ *	is running spi_finalize_current_message() that it needs to complete()
  * @cur_msg_mapped: message has been mapped for DMA
  * @last_cs: the last chip_select that is recorded by set_cs, -1 on non chip
  *           selected
@@ -617,6 +623,8 @@ struct spi_controller {
 	struct list_head		queue;
 	struct spi_message		*cur_msg;
 	struct completion               cur_msg_completion;
+	bool				cur_msg_incomplete;
+	bool				cur_msg_need_completion;
 	bool				busy;
 	bool				running;
 	bool				rt;
-- 
cgit v1.2.3


From 95c8222f0e52b09b7607616274e7cae84d519a9b Mon Sep 17 00:00:00 2001
From: David Jander
Date: Wed, 29 Jun 2022 16:25:18 +0200
Subject: spi: spi.c: Fix comment style

Capitalize first word in comment where appropriate and add
parentheses to function names.

Reported-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: David Jander <david@protonic.nl>
Link: https://lore.kernel.org/r/20220629142519.3985486-3-david@protonic.nl
Signed-off-by: Mark Brown <broonie@kernel.org>
---
 drivers/spi/spi.c       | 94 ++++++++++++++++++++++++-------------------------
 include/linux/spi/spi.h | 82 +++++++++++++++++++++---------------------
 2 files changed, 88 insertions(+), 88 deletions(-)

(limited to 'include')

diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index 031606251b58..6d69f5dc62bc 100644
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -1354,7 +1354,7 @@ int spi_delay_to_ns(struct spi_delay *_delay, struct spi_transfer *xfer)
 		/* Nothing to do here */
 		break;
 	case SPI_DELAY_UNIT_SCK:
-		/* clock cycles need to be obtained from spi_transfer */
+		/* Clock cycles need to be obtained from spi_transfer */
 		if (!xfer)
 			return -EINVAL;
 		/*
@@ -1403,7 +1403,7 @@ static void _spi_transfer_cs_change_delay(struct spi_message *msg,
 	u32 unit = xfer->cs_change_delay.unit;
 	int ret;
 
-	/* return early on "fast" mode - for everything but USECS */
+	/* Return early on "fast" mode - for everything but USECS */
 	if (!delay) {
 		if (unit == SPI_DELAY_UNIT_USECS)
 			_spi_transfer_delay_ns(default_delay_ns);
@@ -1629,7 +1629,7 @@ static int __spi_pump_transfer_message(struct spi_controller *ctlr,
 	WRITE_ONCE(ctlr->cur_msg_incomplete, true);
 	WRITE_ONCE(ctlr->cur_msg_need_completion, false);
 	reinit_completion(&ctlr->cur_msg_completion);
-	smp_wmb(); /* make these available to spi_finalize_current_message */
+	smp_wmb(); /* Make these available to spi_finalize_current_message() */
 
 	ret = ctlr->transfer_one_message(ctlr, msg);
 	if (ret) {
@@ -1905,7 +1905,7 @@ struct spi_message *spi_get_next_queued_message(struct spi_controller *ctlr)
 	struct spi_message *next;
 	unsigned long flags;
 
-	/* get a pointer to the next message, if any */
+	/* Get a pointer to the next message, if any */
 	spin_lock_irqsave(&ctlr->queue_lock, flags);
 	next = list_first_entry_or_null(&ctlr->queue, struct spi_message,
 					queue);
@@ -2558,7 +2558,7 @@ struct spi_device *acpi_spi_device_alloc(struct spi_controller *ctlr,
 	acpi_dev_free_resource_list(&resource_list);
 
 	if (ret < 0)
-		/* found SPI in _CRS but it points to another controller */
+		/* Found SPI in _CRS but it points to another controller */
 		return ERR_PTR(-ENODEV);
 
 	if (!lookup.max_speed_hz &&
@@ -3014,7 +3014,7 @@ int spi_register_controller(struct spi_controller *ctlr)
 		return status;
 
 	if (ctlr->bus_num >= 0) {
-		/* devices with a fixed bus num must check-in with the num */
+		/* Devices with a fixed bus num must check-in with the num */
 		mutex_lock(&board_lock);
 		id = idr_alloc(&spi_master_idr, ctlr, ctlr->bus_num,
 			ctlr->bus_num + 1, GFP_KERNEL);
@@ -3023,7 +3023,7 @@ int spi_register_controller(struct spi_controller *ctlr)
 			return id == -ENOSPC ? -EBUSY : id;
 		ctlr->bus_num = id;
 	} else if (ctlr->dev.of_node) {
-		/* allocate dynamic bus number using Linux idr */
+		/* Allocate dynamic bus number using Linux idr */
 		id = of_alias_get_id(ctlr->dev.of_node, "spi");
 		if (id >= 0) {
 			ctlr->bus_num = id;
@@ -3082,7 +3082,7 @@ int spi_register_controller(struct spi_controller *ctlr)
 		goto free_bus_id;
 	}
 
-	/* setting last_cs to -1 means no chip selected */
+	/* Setting last_cs to -1 means no chip selected */
 	ctlr->last_cs = -1;
 
 	status = device_add(&ctlr->dev);
@@ -3106,7 +3106,7 @@ int spi_register_controller(struct spi_controller *ctlr)
 			goto free_bus_id;
 		}
 	}
-	/* add statistics */
+	/* Add statistics */
 	ctlr->pcpu_statistics = spi_alloc_pcpu_stats(dev);
 	if (!ctlr->pcpu_statistics) {
 		dev_err(dev, "Error allocating per-cpu statistics\n");
@@ -3209,7 +3209,7 @@ void spi_unregister_controller(struct spi_controller *ctlr)
 
 	device_del(&ctlr->dev);
 
-	/* free bus id */
+	/* Free bus id */
 	mutex_lock(&board_lock);
 	if (found == ctlr)
 		idr_remove(&spi_master_idr, id);
@@ -3268,14 +3268,14 @@ static void __spi_replace_transfers_release(struct spi_controller *ctlr,
 	struct spi_replaced_transfers *rxfer = res;
 	size_t i;
 
-	/* call extra callback if requested */
+	/* Call extra callback if requested */
 	if (rxfer->release)
 		rxfer->release(ctlr, msg, res);
 
-	/* insert replaced transfers back into the message */
+	/* Insert replaced transfers back into the message */
 	list_splice(&rxfer->replaced_transfers, rxfer->replaced_after);
 
-	/* remove the formerly inserted entries */
+	/* Remove the formerly inserted entries */
 	for (i = 0; i < rxfer->inserted; i++)
 		list_del(&rxfer->inserted_transfers[i].transfer_list);
 }
@@ -3308,7 +3308,7 @@ static struct spi_replaced_transfers *spi_replace_transfers(
 	struct spi_transfer *xfer;
 	size_t i;
 
-	/* allocate the structure using spi_res */
+	/* Allocate the structure using spi_res */
 	rxfer = spi_res_alloc(msg->spi, __spi_replace_transfers_release,
 			      struct_size(rxfer, inserted_transfers, insert)
 			      + extradatasize,
@@ -3316,15 +3316,15 @@ static struct spi_replaced_transfers *spi_replace_transfers(
 	if (!rxfer)
 		return ERR_PTR(-ENOMEM);
 
-	/* the release code to invoke before running the generic release */
+	/* The release code to invoke before running the generic release */
 	rxfer->release = release;
 
-	/* assign extradata */
+	/* Assign extradata */
 	if (extradatasize)
 		rxfer->extradata =
 			&rxfer->inserted_transfers[insert];
 
-	/* init the replaced_transfers list */
+	/* Init the replaced_transfers list */
 	INIT_LIST_HEAD(&rxfer->replaced_transfers);
 
 	/*
@@ -3333,7 +3333,7 @@ static struct spi_replaced_transfers *spi_replace_transfers(
 	 */
 	rxfer->replaced_after = xfer_first->transfer_list.prev;
 
-	/* remove the requested number of transfers */
+	/* Remove the requested number of transfers */
 	for (i = 0; i < remove; i++) {
 		/*
 		 * If the entry after replaced_after it is msg->transfers
@@ -3343,14 +3343,14 @@ static struct spi_replaced_transfers *spi_replace_transfers(
 		if (rxfer->replaced_after->next == &msg->transfers) {
 			dev_err(&msg->spi->dev,
 				"requested to remove more spi_transfers than are available\n");
-			/* insert replaced transfers back into the message */
+			/* Insert replaced transfers back into the message */
 			list_splice(&rxfer->replaced_transfers,
 				    rxfer->replaced_after);
 
-			/* free the spi_replace_transfer structure */
+			/* Free the spi_replace_transfer structure... */
 			spi_res_free(rxfer);
 
-			/* and return with an error */
+			/* ...and return with an error */
 			return ERR_PTR(-EINVAL);
 		}
 
@@ -3367,26 +3367,26 @@ static struct spi_replaced_transfers *spi_replace_transfers(
 	 * based on the first transfer to get removed.
 	 */
 	for (i = 0; i < insert; i++) {
-		/* we need to run in reverse order */
+		/* We need to run in reverse order */
 		xfer = &rxfer->inserted_transfers[insert - 1 - i];
 
-		/* copy all spi_transfer data */
+		/* Copy all spi_transfer data */
 		memcpy(xfer, xfer_first, sizeof(*xfer));
 
-		/* add to list */
+		/* Add to list */
 		list_add(&xfer->transfer_list, rxfer->replaced_after);
 
-		/* clear cs_change and delay for all but the last */
+		/* Clear cs_change and delay for all but the last */
 		if (i) {
 			xfer->cs_change = false;
 			xfer->delay.value = 0;
 		}
 	}
 
-	/* set up inserted */
+	/* Set up inserted... */
 	rxfer->inserted = insert;
 
-	/* and register it with spi_res/spi_message */
+	/* ...and register it with spi_res/spi_message */
 	spi_res_add(msg, rxfer);
 
 	return rxfer;
@@ -3403,10 +3403,10 @@ static int __spi_split_transfer_maxsize(struct spi_controller *ctlr,
 	size_t offset;
 	size_t count, i;
 
-	/* calculate how many we have to replace */
+	/* Calculate how many we have to replace */
 	count = DIV_ROUND_UP(xfer->len, maxsize);
 
-	/* create replacement */
+	/* Create replacement */
 	srt = spi_replace_transfers(msg, xfer, 1, count, NULL, 0, gfp);
 	if (IS_ERR(srt))
 		return PTR_ERR(srt);
@@ -3429,9 +3429,9 @@ static int __spi_split_transfer_maxsize(struct spi_controller *ctlr,
 	 */
 	xfers[0].len = min_t(size_t, maxsize, xfer[0].len);
 
-	/* all the others need rx_buf/tx_buf also set */
+	/* All the others need rx_buf/tx_buf also set */
 	for (i = 1, offset = maxsize; i < count; offset += maxsize, i++) {
-		/* update rx_buf, tx_buf and dma */
+		/* Update rx_buf, tx_buf and dma */
 		if (xfers[i].rx_buf)
 			xfers[i].rx_buf += offset;
 		if (xfers[i].rx_dma)
@@ -3441,7 +3441,7 @@ static int __spi_split_transfer_maxsize(struct spi_controller *ctlr,
 		if (xfers[i].tx_dma)
 			xfers[i].tx_dma += offset;
 
-		/* update length */
+		/* Update length */
 		xfers[i].len = min(maxsize, xfers[i].len - offset);
 	}
 
@@ -3451,7 +3451,7 @@ static int __spi_split_transfer_maxsize(struct spi_controller *ctlr,
 	 */
 	*xferp = &xfers[count - 1];
 
-	/* increment statistics counters */
+	/* Increment statistics counters */
 	SPI_STATISTICS_INCREMENT_FIELD(ctlr->pcpu_statistics,
 				       transfers_split_maxsize);
 	SPI_STATISTICS_INCREMENT_FIELD(msg->spi->pcpu_statistics,
@@ -3713,7 +3713,7 @@ static int __spi_validate(struct spi_device *spi, struct spi_message *message)
 			return ret;
 
 		list_for_each_entry(xfer, &message->transfers, transfer_list) {
-			/* don't change cs_change on the last entry in the list */
+			/* Don't change cs_change on the last entry in the list */
 			if (list_is_last(&xfer->transfer_list, &message->transfers))
 				break;
 			xfer->cs_change = 1;
@@ -3806,7 +3806,7 @@ static int __spi_validate(struct spi_device *spi, struct spi_message *message)
 				!(spi->mode & SPI_TX_QUAD))
 				return -EINVAL;
 		}
-		/* check transfer rx_nbits */
+		/* Check transfer rx_nbits */
 		if (xfer->rx_buf) {
 			if (spi->mode & SPI_NO_RX)
 				return -EINVAL;
@@ -4144,7 +4144,7 @@ int spi_bus_lock(struct spi_controller *ctlr)
 	ctlr->bus_lock_flag = 1;
 	spin_unlock_irqrestore(&ctlr->bus_lock_spinlock, flags);
 
-	/* mutex remains locked until spi_bus_unlock is called */
+	/* Mutex remains locked until spi_bus_unlock() is called */
 
 	return 0;
 }
@@ -4173,7 +4173,7 @@ int spi_bus_unlock(struct spi_controller *ctlr)
 }
 EXPORT_SYMBOL_GPL(spi_bus_unlock);
 
-/* portable code must never pass more than 32 bytes */
+/* Portable code must never pass more than 32 bytes */
 #define	SPI_BUFSIZ	max(32, SMP_CACHE_BYTES)
 
 static u8	*buf;
@@ -4239,7 +4239,7 @@ int spi_write_then_read(struct spi_device *spi,
 	x[0].tx_buf = local_buf;
 	x[1].rx_buf = local_buf + n_tx;
 
-	/* do the i/o */
+	/* Do the i/o */
 	status = spi_sync(spi, &message);
 	if (status == 0)
 		memcpy(rxbuf, x[1].rx_buf, n_rx);
@@ -4256,7 +4256,7 @@ EXPORT_SYMBOL_GPL(spi_write_then_read);
 /*-------------------------------------------------------------------------*/
 
 #if IS_ENABLED(CONFIG_OF_DYNAMIC)
-/* must call put_device() when done with returned spi_device device */
+/* Must call put_device() when done with returned spi_device device */
 static struct spi_device *of_find_spi_device_by_node(struct device_node *node)
 {
 	struct device *dev = bus_find_device_by_of_node(&spi_bus_type, node);
@@ -4264,7 +4264,7 @@ static struct spi_device *of_find_spi_device_by_node(struct device_node *node)
 	return dev ? to_spi_device(dev) : NULL;
 }
 
-/* the spi controllers are not using spi_bus, so we find it with another way */
+/* The spi controllers are not using spi_bus, so we find it with another way */
 static struct spi_controller *of_find_spi_controller_by_node(struct device_node *node)
 {
 	struct device *dev;
@@ -4275,7 +4275,7 @@ static struct spi_controller *of_find_spi_controller_by_node(struct device_node
 	if (!dev)
 		return NULL;
 
-	/* reference got in class_find_device */
+	/* Reference got in class_find_device */
 	return container_of(dev, struct spi_controller, dev);
 }
 
@@ -4290,7 +4290,7 @@ static int of_spi_notify(struct notifier_block *nb, unsigned long action,
 	case OF_RECONFIG_CHANGE_ADD:
 		ctlr = of_find_spi_controller_by_node(rd->dn->parent);
 		if (ctlr == NULL)
-			return NOTIFY_OK;	/* not for us */
+			return NOTIFY_OK;	/* Not for us */
 
 		if (of_node_test_and_set_flag(rd->dn, OF_POPULATED)) {
 			put_device(&ctlr->dev);
@@ -4309,19 +4309,19 @@ static int of_spi_notify(struct notifier_block *nb, unsigned long action,
 		break;
 
 	case OF_RECONFIG_CHANGE_REMOVE:
-		/* already depopulated? */
+		/* Already depopulated? */
 		if (!of_node_check_flag(rd->dn, OF_POPULATED))
 			return NOTIFY_OK;
 
-		/* find our device by node */
+		/* Find our device by node */
 		spi = of_find_spi_device_by_node(rd->dn);
 		if (spi == NULL)
-			return NOTIFY_OK;	/* no? not meant for us */
+			return NOTIFY_OK;	/* No? not meant for us */
 
-		/* unregister takes one ref away */
+		/* Unregister takes one ref away */
 		spi_unregister_device(spi);
 
-		/* and put the reference of the find */
+		/* And put the reference of the find */
 		put_device(&spi->dev);
 		break;
 	}
diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h
index eb0d316e3c36..e6c73d5ff1a8 100644
--- a/include/linux/spi/spi.h
+++ b/include/linux/spi/spi.h
@@ -176,13 +176,13 @@ extern int spi_delay_exec(struct spi_delay *_delay, struct spi_transfer *xfer);
 struct spi_device {
 	struct device		dev;
 	struct spi_controller	*controller;
-	struct spi_controller	*master;	/* compatibility layer */
+	struct spi_controller	*master;	/* Compatibility layer */
 	u32			max_speed_hz;
 	u8			chip_select;
 	u8			bits_per_word;
 	bool			rt;
-#define SPI_NO_TX	BIT(31)		/* no transmit wire */
-#define SPI_NO_RX	BIT(30)		/* no receive wire */
+#define SPI_NO_TX	BIT(31)		/* No transmit wire */
+#define SPI_NO_RX	BIT(30)		/* No receive wire */
 	/*
 	 * All bits defined above should be covered by SPI_MODE_KERNEL_MASK.
 	 * The SPI_MODE_KERNEL_MASK has the SPI_MODE_USER_MASK counterpart,
@@ -199,14 +199,14 @@ struct spi_device {
 	void			*controller_data;
 	char			modalias[SPI_NAME_SIZE];
 	const char		*driver_override;
-	struct gpio_desc	*cs_gpiod;	/* chip select gpio desc */
-	struct spi_delay	word_delay; /* inter-word delay */
+	struct gpio_desc	*cs_gpiod;	/* Chip select gpio desc */
+	struct spi_delay	word_delay; /* Inter-word delay */
 	/* CS delays */
 	struct spi_delay	cs_setup;
 	struct spi_delay	cs_hold;
 	struct spi_delay	cs_inactive;
 
-	/* the statistics */
+	/* The statistics */
 	struct spi_statistics __percpu	*pcpu_statistics;
 
 	/*
@@ -228,7 +228,7 @@ static inline struct spi_device *to_spi_device(struct device *dev)
 	return dev ? container_of(dev, struct spi_device, dev) : NULL;
 }
 
-/* most drivers won't need to care about device refcounting */
+/* Most drivers won't need to care about device refcounting */
 static inline struct spi_device *spi_dev_get(struct spi_device *spi)
 {
 	return (spi && get_device(&spi->dev)) ? spi : NULL;
@@ -251,7 +251,7 @@ static inline void spi_set_ctldata(struct spi_device *spi, void *state)
 	spi->controller_state = state;
 }
 
-/* device driver data */
+/* Device driver data */
 
 static inline void spi_set_drvdata(struct spi_device *spi, void *data)
 {
@@ -318,7 +318,7 @@ static inline void spi_unregister_driver(struct spi_driver *sdrv)
 
 extern struct spi_device *spi_new_ancillary_device(struct spi_device *spi, u8 chip_select);
 
-/* use a define to avoid include chaining to get THIS_MODULE */
+/* Use a define to avoid include chaining to get THIS_MODULE */
 #define spi_register_driver(driver) \
 	__spi_register_driver(THIS_MODULE, driver)
 
@@ -486,7 +486,7 @@ struct spi_controller {
 
 	struct list_head list;
 
-	/* other than negative (== assign one dynamically), bus_num is fully
+	/* Other than negative (== assign one dynamically), bus_num is fully
 	 * board-specific.  usually that simplifies to being SOC-specific.
 	 * example:  one SOC has three SPI controllers, numbered 0..2,
 	 * and one board's schematics might show it using SPI-2.  software
@@ -499,7 +499,7 @@ struct spi_controller {
 	 */
 	u16			num_chipselect;
 
-	/* some SPI controllers pose alignment requirements on DMAable
+	/* Some SPI controllers pose alignment requirements on DMAable
 	 * buffers; let protocol drivers know about these requirements.
 	 */
 	u16			dma_alignment;
@@ -510,29 +510,29 @@ struct spi_controller {
 	/* spi_device.mode flags override flags for this controller */
 	u32			buswidth_override_bits;
 
-	/* bitmask of supported bits_per_word for transfers */
+	/* Bitmask of supported bits_per_word for transfers */
 	u32			bits_per_word_mask;
 #define SPI_BPW_MASK(bits) BIT((bits) - 1)
 #define SPI_BPW_RANGE_MASK(min, max) GENMASK((max) - 1, (min) - 1)
 
-	/* limits on transfer speed */
+	/* Limits on transfer speed */
 	u32			min_speed_hz;
 	u32			max_speed_hz;
 
-	/* other constraints relevant to this driver */
+	/* Other constraints relevant to this driver */
 	u16			flags;
-#define SPI_CONTROLLER_HALF_DUPLEX	BIT(0)	/* can't do full duplex */
-#define SPI_CONTROLLER_NO_RX		BIT(1)	/* can't do buffer read */
-#define SPI_CONTROLLER_NO_TX		BIT(2)	/* can't do buffer write */
-#define SPI_CONTROLLER_MUST_RX		BIT(3)	/* requires rx */
-#define SPI_CONTROLLER_MUST_TX		BIT(4)	/* requires tx */
+#define SPI_CONTROLLER_HALF_DUPLEX	BIT(0)	/* Can't do full duplex */
+#define SPI_CONTROLLER_NO_RX		BIT(1)	/* Can't do buffer read */
+#define SPI_CONTROLLER_NO_TX		BIT(2)	/* Can't do buffer write */
+#define SPI_CONTROLLER_MUST_RX		BIT(3)	/* Requires rx */
+#define SPI_CONTROLLER_MUST_TX		BIT(4)	/* Requires tx */
 
 #define SPI_MASTER_GPIO_SS		BIT(5)	/* GPIO CS must select slave */
 
-	/* flag indicating if the allocation of this struct is devres-managed */
+	/* Flag indicating if the allocation of this struct is devres-managed */
 	bool			devm_allocated;
 
-	/* flag indicating this is an SPI slave controller */
+	/* Flag indicating this is an SPI slave controller */
 	bool			slave;
 
 	/*
@@ -548,11 +548,11 @@ struct spi_controller {
 	/* Used to avoid adding the same CS twice */
 	struct mutex		add_lock;
 
-	/* lock and mutex for SPI bus locking */
+	/* Lock and mutex for SPI bus locking */
 	spinlock_t		bus_lock_spinlock;
 	struct mutex		bus_lock_mutex;
 
-	/* flag indicating that the SPI bus is locked for exclusive use */
+	/* Flag indicating that the SPI bus is locked for exclusive use */
 	bool			bus_lock_flag;
 
 	/* Setup mode and clock, etc (spi driver may call many times).
@@ -573,7 +573,7 @@ struct spi_controller {
 	 */
 	int (*set_cs_timing)(struct spi_device *spi);
 
-	/* bidirectional bulk transfers
+	/* Bidirectional bulk transfers
 	 *
 	 * + The transfer() method may not sleep; its main role is
 	 *   just to add the message to the queue.
@@ -595,7 +595,7 @@ struct spi_controller {
 	int			(*transfer)(struct spi_device *spi,
 						struct spi_message *mesg);
 
-	/* called on release() to free memory provided by spi_controller */
+	/* Called on release() to free memory provided by spi_controller */
 	void			(*cleanup)(struct spi_device *spi);
 
 	/*
@@ -666,14 +666,14 @@ struct spi_controller {
 	s8			unused_native_cs;
 	s8			max_native_cs;
 
-	/* statistics */
+	/* Statistics */
 	struct spi_statistics __percpu	*pcpu_statistics;
 
 	/* DMA channels for use with core dmaengine helpers */
 	struct dma_chan		*dma_tx;
 	struct dma_chan		*dma_rx;
 
-	/* dummy data for full duplex devices */
+	/* Dummy data for full duplex devices */
 	void			*dummy_rx;
 	void			*dummy_tx;
 
@@ -738,7 +738,7 @@ void spi_take_timestamp_post(struct spi_controller *ctlr,
 			     struct spi_transfer *xfer,
 			     size_t progress, bool irqs_off);
 
-/* the spi driver core manages memory for the spi_controller classdev */
+/* The spi driver core manages memory for the spi_controller classdev */
 extern struct spi_controller *__spi_alloc_controller(struct device *host,
 						unsigned int size, bool slave);
 
@@ -808,7 +808,7 @@ typedef void (*spi_res_release_t)(struct spi_controller *ctlr,
 struct spi_res {
 	struct list_head        entry;
 	spi_res_release_t       release;
-	unsigned long long      data[]; /* guarantee ull alignment */
+	unsigned long long      data[]; /* Guarantee ull alignment */
 };
 
 /*---------------------------------------------------------------------------*/
@@ -941,7 +941,7 @@ struct spi_res {
  * and its transfers, ignore them until its completion callback.
  */
 struct spi_transfer {
-	/* it's ok if tx_buf == rx_buf (right?)
+	/* It's ok if tx_buf == rx_buf (right?)
 	 * for MicroWire, one buffer must be null
 	 * buffers must work with dma_*map_single() calls, unless
 	 *   spi_message.is_dma_mapped reports a pre-existing mapping
@@ -1032,24 +1032,24 @@ struct spi_message {
 	 * tell them about such special cases.
 	 */
 
-	/* completion is reported through a callback */
+	/* Completion is reported through a callback */
 	void			(*complete)(void *context);
 	void			*context;
 	unsigned		frame_length;
 	unsigned		actual_length;
 	int			status;
 
-	/* for optional use by whatever driver currently owns the
+	/* For optional use by whatever driver currently owns the
 	 * spi_message ...  between calls to spi_async and then later
 	 * complete(), that's the spi_controller controller driver.
 	 */
 	struct list_head	queue;
 	void			*state;
 
-	/* list of spi_res reources when the spi message is processed */
+	/* List of spi_res reources when the spi message is processed */
 	struct list_head        resources;
 
-	/* spi_prepare_message was called for this message */
+	/* spi_prepare_message() was called for this message */
 	bool			prepared;
 };
 
@@ -1154,7 +1154,7 @@ spi_max_transfer_size(struct spi_device *spi)
 	if (ctlr->max_transfer_size)
 		tr_max = ctlr->max_transfer_size(spi);
 
-	/* transfer size limit must not be greater than message size limit */
+	/* Transfer size limit must not be greater than message size limit */
 	return min(tr_max, msg_max);
 }
 
@@ -1305,7 +1305,7 @@ spi_read(struct spi_device *spi, void *buf, size_t len)
 	return spi_sync_transfer(spi, &t, 1);
 }
 
-/* this copies txbuf and rxbuf data; for small transfers only! */
+/* This copies txbuf and rxbuf data; for small transfers only! */
 extern int spi_write_then_read(struct spi_device *spi,
 		const void *txbuf, unsigned n_tx,
 		void *rxbuf, unsigned n_rx);
@@ -1328,7 +1328,7 @@ static inline ssize_t spi_w8r8(struct spi_device *spi, u8 cmd)
 
 	status = spi_write_then_read(spi, &cmd, 1, &result, 1);
 
-	/* return negative errno or unsigned value */
+	/* Return negative errno or unsigned value */
 	return (status < 0) ? status : result;
 }
 
@@ -1353,7 +1353,7 @@ static inline ssize_t spi_w8r16(struct spi_device *spi, u8 cmd)
 
 	status = spi_write_then_read(spi, &cmd, 1, &result, 2);
 
-	/* return negative errno or unsigned value */
+	/* Return negative errno or unsigned value */
 	return (status < 0) ? status : result;
 }
 
@@ -1433,7 +1433,7 @@ static inline ssize_t spi_w8r16be(struct spi_device *spi, u8 cmd)
  * are active in some dynamic board configuration models.
  */
 struct spi_board_info {
-	/* the device name and module name are coupled, like platform_bus;
+	/* The device name and module name are coupled, like platform_bus;
 	 * "modalias" is normally the driver name.
 	 *
 	 * platform_data goes to spi_device.dev.platform_data,
@@ -1446,7 +1446,7 @@ struct spi_board_info {
 	void		*controller_data;
 	int		irq;
 
-	/* slower signaling on noisy or low voltage boards */
+	/* Slower signaling on noisy or low voltage boards */
 	u32		max_speed_hz;
 
 
@@ -1475,7 +1475,7 @@ struct spi_board_info {
 extern int
 spi_register_board_info(struct spi_board_info const *info, unsigned n);
 #else
-/* board init code may ignore whether SPI is configured or not */
+/* Board init code may ignore whether SPI is configured or not */
 static inline int
 spi_register_board_info(struct spi_board_info const *info, unsigned n)
 	{ return 0; }
-- 
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