[PATCH 10/33] dmaengine: at_hdmac: Fix premature completion of desc in issue_pending

Tudor Ambarus
2022-08-20T12:58:43Z

Multiple calls to atc_issue_pending() could result in a premature
completion of a descriptor from the atchan->active list, as the method
always completed the first active descriptor from the list. Instead,
issue_pending() should just take the first transaction descriptor from the
pending queue, move it to active_list and start the transfer.

Fixes: dc78baa2b90b ("dmaengine: at_hdmac: new driver for the Atmel AHB DMA Controller")
Reported-by: Peter Rosin <peda@axentia.se>
Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/lkml/13c6c9a2-6db5-c3bf-349b-4c127ad3496a@axentia.se/
---
drivers/dma/at_hdmac.c | 16 +++++++++++++---
1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/drivers/dma/at_hdmac.c b/drivers/dma/at_hdmac.c
index d9f492081e76..c445575f8646 100644
--- a/drivers/dma/at_hdmac.c
+++ b/drivers/dma/at_hdmac.c
@@ -1963,16 +1963,26 @@ atc_tx_status(struct dma_chan *chan,
}

/**
- * atc_issue_pending - try to finish work
+ * atc_issue_pending - takes the first transaction descriptor in the pending
+ * queue and starts the transfer.
* @chan: target DMA channel
*/
static void atc_issue_pending(struct dma_chan *chan)
{
- struct at_dma_chan *atchan = to_at_dma_chan(chan);
+ struct at_dma_chan *atchan = to_at_dma_chan(chan);
+ struct at_desc *desc;
+ unsigned long flags;

dev_vdbg(chan2dev(chan), "issue_pending\n");

- atc_advance_work(atchan);
+ spin_lock_irqsave(&atchan->lock, flags);
+ if (atc_chan_is_enabled(atchan) || list_empty(&atchan->queue))
+ return spin_unlock_irqrestore(&atchan->lock, flags);
+
+ desc = atc_first_queued(atchan);
+ list_move_tail(&desc->desc_node, &atchan->active_list);
+ atc_dostart(atchan, desc);
+ spin_unlock_irqrestore(&atchan->lock, flags);
}

/**
--
2.25.1