[PATCH 6.1 186/232] dma: dma-axi-dmac: fix SW cyclic transfers

Sasha Levin
2026-02-28T18:14:07Z

From: Nuno Sá <nuno.sa@analog.com>

[ Upstream commit 9bd257181fd5c996d922e9991500ad27987cfbf4 ]

If 'hw_cyclic' is false we should still be able to do cyclic transfers in
"software". That was not working for the case where 'desc->num_sgs' is 1
because 'chan->next_desc' is never set with the current desc which means
that the cyclic transfer only runs once and in the next SOT interrupt we
do nothing since vchan_next_desc() will return NULL.

Fix it by setting 'chan->next_desc' as soon as we get a new desc via
vchan_next_desc().

Fixes: 0e3b67b348b8 ("dmaengine: Add support for the Analog Devices AXI-DMAC DMA controller")
Signed-off-by: Nuno Sá <nuno.sa@analog.com>
base-commit: 398035178503bf662281bbffb4bebce1460a4bc5
change-id: 20251104-axi-dmac-fixes-and-improvs-e3ad512a329c
Acked-by: Michael Hennerich <michael.hennerich@analog.com>
Link: https://patch.msgid.link/20251104-axi-dmac-fixes-and-improvs-v1-1-3e6fd9328f72@analog.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/dma/dma-axi-dmac.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/dma/dma-axi-dmac.c b/drivers/dma/dma-axi-dmac.c
index 176cf3665a185..ac73c3b59d268 100644
--- a/drivers/dma/dma-axi-dmac.c
+++ b/drivers/dma/dma-axi-dmac.c
@@ -225,6 +225,7 @@ static void axi_dmac_start_transfer(struct axi_dmac_chan *chan)
return;
list_move_tail(&vdesc->node, &chan->active_descs);
desc = to_axi_dmac_desc(vdesc);
+ chan->next_desc = desc;
}
sg = &desc->sg[desc->num_submitted];

@@ -242,8 +243,6 @@ static void axi_dmac_start_transfer(struct axi_dmac_chan *chan)
else
chan->next_desc = NULL;
flags |= AXI_DMAC_FLAG_LAST;
- } else {
- chan->next_desc = desc;
}

sg->id = axi_dmac_read(dmac, AXI_DMAC_REG_TRANSFER_ID);
--
2.51.0