[PATCH 1/2] dmaengine: stm32-dma: fix stm32_dma_prep_slave_sg in case of MDMA chaining

[PATCH 1/2] dmaengine: stm32-dma: fix stm32_dma_prep_slave_sg in case of MDMA chaining

[Amelie Delaunay]

Current Target (CT) have to be reset when starting an MDMA chaining use
case, as Double Buffer mode is activated. It ensures the DMA will start
processing the first memory target (pointed with SxM0AR).

Fixes: 723795173ce1 ("dmaengine: stm32-dma: add support to trigger STM32 MDMA")
Signed-off-by: Amelie Delaunay <amelie.delaunay@foss.st.com>
Cc: stable@vger.kernel.org
---
 drivers/dma/stm32-dma.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/dma/stm32-dma.c b/drivers/dma/stm32-dma.c
index 5c36811aa134..7427acc82259 100644
--- a/drivers/dma/stm32-dma.c
+++ b/drivers/dma/stm32-dma.c
@@ -1113,8 +1113,10 @@ static struct dma_async_tx_descriptor *stm32_dma_prep_slave_sg(
 		chan->chan_reg.dma_scr &= ~STM32_DMA_SCR_PFCTRL;
 
 	/* Activate Double Buffer Mode if DMA triggers STM32 MDMA and more than 1 sg */
-	if (chan->trig_mdma && sg_len > 1)
+	if (chan->trig_mdma && sg_len > 1) {
 		chan->chan_reg.dma_scr |= STM32_DMA_SCR_DBM;
+		chan->chan_reg.dma_scr &= ~STM32_DMA_SCR_CT;
+	}
 
 	for_each_sg(sgl, sg, sg_len, i) {
 		ret = stm32_dma_set_xfer_param(chan, direction, &buswidth,
-- 
2.25.1

[PATCH 2/2] dmaengine: stm32-dma: fix residue in case of MDMA chaining

[Amelie Delaunay]

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: 723795173ce1 ("dmaengine: stm32-dma: add support to trigger STM32 MDMA")
Signed-off-by: Amelie Delaunay <amelie.delaunay@foss.st.com>
Cc: stable@vger.kernel.org
---
 drivers/dma/stm32-dma.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/dma/stm32-dma.c b/drivers/dma/stm32-dma.c
index 7427acc82259..0b30151fb45c 100644
--- a/drivers/dma/stm32-dma.c
+++ b/drivers/dma/stm32-dma.c
@@ -1389,11 +1389,12 @@ 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;
-		residue = sg_req->len;
+		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;
 
-- 
2.25.1

Re: [PATCH 1/2] dmaengine: stm32-dma: fix stm32_dma_prep_slave_sg in case of MDMA chaining

[Vinod Koul]

On Wed, 04 Oct 2023 17:50:23 +0200, Amelie Delaunay wrote:
> Current Target (CT) have to be reset when starting an MDMA chaining use
> case, as Double Buffer mode is activated. It ensures the DMA will start
> processing the first memory target (pointed with SxM0AR).
> 
> 

Applied, thanks!

[1/2] dmaengine: stm32-dma: fix stm32_dma_prep_slave_sg in case of MDMA chaining
      commit: 2df467e908ce463cff1431ca1b00f650f7a514b4
[2/2] dmaengine: stm32-dma: fix residue in case of MDMA chaining
      commit: 67e13e89742c3b21ce177f612bf9ef32caae6047

Best regards,
-- 
~Vinod