Commit 67e13e89 authored by Amelie Delaunay's avatar Amelie Delaunay Committed by Vinod Koul
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dmaengine: stm32-dma: fix residue in case of MDMA chaining 



In case of MDMA chaining, DMA is configured in Double-Buffer Mode (DBM)
with two periods, but if transfer has been prepared with _prep_slave_sg(),
the transfer is not marked cyclic (=!chan->desc->cyclic). However, as DBM
is activated for MDMA chaining, residue computation must take into account
cyclic constraints.

With only two periods in MDMA chaining, and no update due to Transfer
Complete interrupt masked, n_sg is always 0. If DMA current memory address
(depending on SxCR.CT and SxM0AR/SxM1AR) does not correspond, it means n_sg
should be increased.
Then, the residue of the current period is the one read from SxNDTR and
should not be overwritten with the full period length.

Fixes: 72379517 ("dmaengine: stm32-dma: add support to trigger STM32 MDMA")
Signed-off-by: default avatarAmelie Delaunay <amelie.delaunay@foss.st.com>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20231004155024.2609531-2-amelie.delaunay@foss.st.com


Signed-off-by: default avatarVinod Koul <vkoul@kernel.org>
parent 2df467e9

drivers/dma/stm32-dma.c

+4 −3
Original line number Diff line number Diff line
@@ -1389,10 +1389,11 @@ static size_t stm32_dma_desc_residue(struct stm32_dma_chan *chan, 


	residue = stm32_dma_get_remaining_bytes(chan);



	if (chan->desc->cyclic && !stm32_dma_is_current_sg(chan)) {

	if ((chan->desc->cyclic || chan->trig_mdma) && !stm32_dma_is_current_sg(chan)) {

		n_sg++;

		if (n_sg == chan->desc->num_sgs)

			n_sg = 0;

		if (!chan->trig_mdma)

			residue = sg_req->len;

	}
@@ -1403,7 +1404,7 @@ static size_t stm32_dma_desc_residue(struct stm32_dma_chan *chan, 
	 * residue = remaining bytes from NDTR + remaining

	 * periods/sg to be transferred

	 */

	if (!chan->desc->cyclic || n_sg != 0)

	if ((!chan->desc->cyclic && !chan->trig_mdma) || n_sg != 0)

		for (i = n_sg; i < desc->num_sgs; i++)

			residue += desc->sg_req[i].len;