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Subject[PATCH] dmaengine: imx-dma: fix wrong callback invoke
Once the "ld_queue" list is not empty, next descriptor will migrate
into "ld_active" list. The "desc" variable will be overwritten
during that transition. And later the dmaengine_desc_get_callback_invoke()
will use it as an argument. As result we invoke wrong callback.

That behaviour was in place since:
commit fcaaba6c7136 ("dmaengine: imx-dma: fix callback path in tasklet").
But after commit 4cd13c21b207 ("softirq: Let ksoftirqd do its job")
things got worse, since possible delay between tasklet_schedule()
from DMA irq handler and actual tasklet function execution got bigger.
And that gave more time for new DMA request to be submitted and
to be put into "ld_queue" list.

It has been noticed that DMA issue is causing problems for "mxc-mmc"
driver. While stressing the system with heavy network traffic and
writing/reading to/from sd card simultaneously the timeout may happen:

10013000.sdhci: mxcmci_watchdog: read time out (status = 0x30004900)

That often lead to file system corruption.

Signed-off-by: Leonid Iziumtsev <>
drivers/dma/imx-dma.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/dma/imx-dma.c b/drivers/dma/imx-dma.c
index c2fff3f6c9ca..4a09af3cd546 100644
--- a/drivers/dma/imx-dma.c
+++ b/drivers/dma/imx-dma.c
@@ -618,7 +618,7 @@ static void imxdma_tasklet(unsigned long data)
struct imxdma_channel *imxdmac = (void *)data;
struct imxdma_engine *imxdma = imxdmac->imxdma;
- struct imxdma_desc *desc;
+ struct imxdma_desc *desc, *next_desc;
unsigned long flags;

spin_lock_irqsave(&imxdma->lock, flags);
@@ -648,10 +648,10 @@ static void imxdma_tasklet(unsigned long data)
list_move_tail(imxdmac->, &imxdmac->ld_free);

if (!list_empty(&imxdmac->ld_queue)) {
- desc = list_first_entry(&imxdmac->ld_queue, struct imxdma_desc,
- node);
+ next_desc = list_first_entry(&imxdmac->ld_queue,
+ struct imxdma_desc, node);
list_move_tail(imxdmac->, &imxdmac->ld_active);
- if (imxdma_xfer_desc(desc) < 0)
+ if (imxdma_xfer_desc(next_desc) < 0)
dev_warn(imxdma->dev, "%s: channel: %d couldn't xfer desc\n",
__func__, imxdmac->channel);
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