Commit a4b306eb authored by Amelie Delaunay's avatar Amelie Delaunay Committed by Vinod Koul
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dmaengine: stm32-mdma: use Link Address Register to compute residue 



Current implementation relies on curr_hwdesc index. But to keep this index
up to date, Block Transfer interrupt (BTIE) has to be enabled.
If it is not, curr_hwdesc is not updated, and then residue is not reliable.
Rely on Link Address Register instead. And disable BTIE interrupt
in stm32_mdma_setup_xfer() because it is no more needed in case of
_prep_slave_sg() to maintain curr_hwdesc up to date.
It avoids extra interrupts and also ensures a reliable residue. These
improvements are required for STM32 DCMI camera capture use case, which
need STM32 DMA and MDMA chaining for good performance.

Fixes: 69687432 ("dmaengine: stm32-mdma: add support to be triggered by STM32 DMA")
Signed-off-by: default avatarAmelie Delaunay <amelie.delaunay@foss.st.com>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20231004163531.2864160-2-amelie.delaunay@foss.st.com


Signed-off-by: default avatarVinod Koul <vkoul@kernel.org>
parent 81337b9a

drivers/dma/stm32-mdma.c

+11 −4
Original line number Diff line number Diff line
@@ -777,8 +777,6 @@ static int stm32_mdma_setup_xfer(struct stm32_mdma_chan *chan, 
	/* Enable interrupts */

	ccr &= ~STM32_MDMA_CCR_IRQ_MASK;

	ccr |= STM32_MDMA_CCR_TEIE | STM32_MDMA_CCR_CTCIE;

	if (sg_len > 1)

		ccr |= STM32_MDMA_CCR_BTIE;

	desc->ccr = ccr;



	return 0;
@@ -1324,12 +1322,21 @@ static size_t stm32_mdma_desc_residue(struct stm32_mdma_chan *chan, 
{

	struct stm32_mdma_device *dmadev = stm32_mdma_get_dev(chan);

	struct stm32_mdma_hwdesc *hwdesc;

	u32 cbndtr, residue, modulo, burst_size;

	u32 cisr, clar, cbndtr, residue, modulo, burst_size;

	int i;



	cisr = stm32_mdma_read(dmadev, STM32_MDMA_CISR(chan->id));



	residue = 0;

	for (i = curr_hwdesc + 1; i < desc->count; i++) {

	/* Get the next hw descriptor to process from current transfer */

	clar = stm32_mdma_read(dmadev, STM32_MDMA_CLAR(chan->id));

	for (i = desc->count - 1; i >= 0; i--) {

		hwdesc = desc->node[i].hwdesc;



		if (hwdesc->clar == clar)

			break;/* Current transfer found, stop cumulating */



		/* Cumulate residue of unprocessed hw descriptors */

		residue += STM32_MDMA_CBNDTR_BNDT(hwdesc->cbndtr);

	}

	cbndtr = stm32_mdma_read(dmadev, STM32_MDMA_CBNDTR(chan->id));