diff options
| -rw-r--r-- | drivers/dma/mxs-dma.c | 41 |
1 files changed, 35 insertions, 6 deletions
diff --git a/drivers/dma/mxs-dma.c b/drivers/dma/mxs-dma.c index f48f87feeca4..ead491346da7 100644 --- a/drivers/dma/mxs-dma.c +++ b/drivers/dma/mxs-dma.c @@ -119,7 +119,9 @@ struct mxs_dma_chan { int desc_count; enum dma_status status; unsigned int flags; + bool reset; #define MXS_DMA_SG_LOOP (1 << 0) +#define MXS_DMA_USE_SEMAPHORE (1 << 1) }; #define MXS_DMA_CHANNELS 16 @@ -205,7 +207,17 @@ static void mxs_dma_reset_chan(struct mxs_dma_chan *mxs_chan) struct mxs_dma_engine *mxs_dma = mxs_chan->mxs_dma; int chan_id = mxs_chan->chan.chan_id; - if (dma_is_apbh(mxs_dma) && apbh_is_old(mxs_dma)) { + /* + * mxs dma channel resets can cause a channel stall. To recover from a + * channel stall, we have to reset the whole DMA engine. To avoid this, + * we use cyclic DMA with semaphores, that are enhanced in + * mxs_dma_int_handler. To reset the channel, we can simply stop writing + * into the semaphore counter. + */ + if (mxs_chan->flags & MXS_DMA_USE_SEMAPHORE && + mxs_chan->flags & MXS_DMA_SG_LOOP) { + mxs_chan->reset = true; + } else if (dma_is_apbh(mxs_dma) && apbh_is_old(mxs_dma)) { writel(1 << (chan_id + BP_APBH_CTRL0_RESET_CHANNEL), mxs_dma->base + HW_APBHX_CTRL0 + STMP_OFFSET_REG_SET); } else { @@ -231,7 +243,6 @@ static void mxs_dma_reset_chan(struct mxs_dma_chan *mxs_chan) "Failed waiting for the DMA channel %d to leave state READ_FLUSH, trying to reset channel in READ_FLUSH state now\n", chan_id); - writel(1 << (chan_id + BP_APBHX_CHANNEL_CTRL_RESET_CHANNEL), mxs_dma->base + HW_APBHX_CHANNEL_CTRL + STMP_OFFSET_REG_SET); } @@ -249,7 +260,16 @@ static void mxs_dma_enable_chan(struct mxs_dma_chan *mxs_chan) mxs_dma->base + HW_APBHX_CHn_NXTCMDAR(mxs_dma, chan_id)); /* write 1 to SEMA to kick off the channel */ - writel(1, mxs_dma->base + HW_APBHX_CHn_SEMA(mxs_dma, chan_id)); + if (mxs_chan->flags & MXS_DMA_USE_SEMAPHORE && + mxs_chan->flags & MXS_DMA_SG_LOOP) { + /* A cyclic DMA consists of at least 2 segments, so initialize + * the semaphore with 2 so we have enough time to add 1 to the + * semaphore if we need to */ + writel(2, mxs_dma->base + HW_APBHX_CHn_SEMA(mxs_dma, chan_id)); + } else { + writel(1, mxs_dma->base + HW_APBHX_CHn_SEMA(mxs_dma, chan_id)); + } + mxs_chan->reset = false; } static void mxs_dma_disable_chan(struct mxs_dma_chan *mxs_chan) @@ -365,14 +385,21 @@ static irqreturn_t mxs_dma_int_handler(int irq, void *dev_id) mxs_chan->status = DMA_ERROR; mxs_dma_reset_chan(mxs_chan); } else if (mxs_chan->status != DMA_COMPLETE) { - if (mxs_chan->flags & MXS_DMA_SG_LOOP) + if (mxs_chan->flags & MXS_DMA_SG_LOOP) { mxs_chan->status = DMA_IN_PROGRESS; - else + if (mxs_chan->flags & MXS_DMA_USE_SEMAPHORE) + writel(1, mxs_dma->base + + HW_APBHX_CHn_SEMA(mxs_dma, chan)); + } else { mxs_chan->status = DMA_COMPLETE; + } } - if (mxs_chan->status == DMA_COMPLETE) + if (mxs_chan->status == DMA_COMPLETE) { + if (mxs_chan->reset) + return IRQ_HANDLED; dma_cookie_complete(&mxs_chan->desc); + } /* schedule tasklet on this channel */ tasklet_schedule(&mxs_chan->tasklet); @@ -576,6 +603,7 @@ static struct dma_async_tx_descriptor *mxs_dma_prep_dma_cyclic( mxs_chan->status = DMA_IN_PROGRESS; mxs_chan->flags |= MXS_DMA_SG_LOOP; + mxs_chan->flags |= MXS_DMA_USE_SEMAPHORE; if (num_periods > NUM_CCW) { dev_err(mxs_dma->dma_device.dev, @@ -607,6 +635,7 @@ static struct dma_async_tx_descriptor *mxs_dma_prep_dma_cyclic( ccw->bits |= CCW_IRQ; ccw->bits |= CCW_HALT_ON_TERM; ccw->bits |= CCW_TERM_FLUSH; + ccw->bits |= CCW_DEC_SEM; ccw->bits |= BF_CCW(direction == DMA_DEV_TO_MEM ? MXS_DMA_CMD_WRITE : MXS_DMA_CMD_READ, COMMAND); |