From mboxrd@z Thu Jan 1 00:00:00 1970 From: mpa@pengutronix.de (Markus Pargmann) Date: Thu, 26 Sep 2013 17:06:35 +0200 Subject: [PATCH 2/3] dma: mxs-dma: Track number of irqs for callback In-Reply-To: <1380207996-27257-1-git-send-email-mpa@pengutronix.de> References: <1380207996-27257-1-git-send-email-mpa@pengutronix.de> Message-ID: <1380207996-27257-3-git-send-email-mpa@pengutronix.de> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Currently there is one tasklet scheduled for all interrupts between two mxs_dma_tasklet calls for one channel. With more than one interrupts, the tasklet is only called once. Using low latency audio playback, can lead to problems. When using sound/soc/soc-dmaengine-pcm.c, the dmaengine_pcm_dma_complete relies on being called for each interrupt that occures. This function is the callback which is called from the mxs-dma driver in mxs_dma_tasklet. This can cause wrong position counters and can lead to a wrong DMA buffer offset. In this situation the DMA engine and pcm lib may write and read from the same buffer segment. This patch adds a locked per-channel irq counter and calls the callback function in a loop for irq-counter times. Signed-off-by: Markus Pargmann --- drivers/dma/mxs-dma.c | 26 +++++++++++++++++++++++++- 1 file changed, 25 insertions(+), 1 deletion(-) diff --git a/drivers/dma/mxs-dma.c b/drivers/dma/mxs-dma.c index bfca8dc..13c7d83 100644 --- a/drivers/dma/mxs-dma.c +++ b/drivers/dma/mxs-dma.c @@ -115,6 +115,8 @@ struct mxs_dma_chan { int desc_count; enum dma_status status; unsigned int flags; + unsigned int nr_irqs; + spinlock_t lock; #define MXS_DMA_SG_LOOP (1 << 0) }; @@ -267,9 +269,21 @@ static dma_cookie_t mxs_dma_tx_submit(struct dma_async_tx_descriptor *tx) static void mxs_dma_tasklet(unsigned long data) { struct mxs_dma_chan *mxs_chan = (struct mxs_dma_chan *) data; + unsigned long flags; + spin_lock_irqsave(&mxs_chan->lock, flags); + + /* + * Some DMA users need exactly one call for each interrupt generated. + * This loop calls the callback nr_irqs times. + */ if (mxs_chan->desc.callback) - mxs_chan->desc.callback(mxs_chan->desc.callback_param); + for (; mxs_chan->nr_irqs; --mxs_chan->nr_irqs) + mxs_chan->desc.callback(mxs_chan->desc.callback_param); + else + mxs_chan->nr_irqs = 0; + + spin_unlock_irqrestore(&mxs_chan->lock, flags); } static int mxs_dma_irq_to_chan(struct mxs_dma_engine *mxs_dma, int irq) @@ -290,6 +304,7 @@ static irqreturn_t mxs_dma_int_handler(int irq, void *dev_id) u32 completed; u32 err; int chan = mxs_dma_irq_to_chan(mxs_dma, irq); + unsigned long flags; if (chan < 0) return IRQ_NONE; @@ -344,6 +359,13 @@ static irqreturn_t mxs_dma_int_handler(int irq, void *dev_id) if (mxs_chan->status == DMA_SUCCESS) dma_cookie_complete(&mxs_chan->desc); + /* + * Increase the number of irqs we saw for this channel. + */ + spin_lock_irqsave(&mxs_chan->lock, flags); + ++mxs_chan->nr_irqs; + spin_unlock_irqrestore(&mxs_chan->lock, flags); + /* schedule tasklet on this channel */ tasklet_schedule(&mxs_chan->tasklet); @@ -385,6 +407,8 @@ static int mxs_dma_alloc_chan_resources(struct dma_chan *chan) /* the descriptor is ready */ async_tx_ack(&mxs_chan->desc); + spin_lock_init(&mxs_chan->lock); + return 0; err_clk: -- 1.8.4.rc3