[PATCH 6.1 070/131] dmaengine: stm32-dma: fix residue in case of MDMA chaining

Greg Kroah-Hartman
2023-10-16T09:02:25Z

From: Amelie Delaunay <amelie.delaunay@foss.st.com>

commit 67e13e89742c3b21ce177f612bf9ef32caae6047 upstream.

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
Link: https://lore.kernel.org/r/20231004155024.2609531-2-amelie.delaunay@foss.st.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.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;

--
2.42.0