This patch fixes an issue that a race condition happens between a client
driver and the rcar-dmac driver:

- The rcar_dmac_isr_transfer_end() is called.
 - The done list appears, and desc.running is the next active list.
- rcar_dmac_chan_get_residue() is called by a client driver before
  rcar_dmac_isr_channel_thread() is called.
 - The rcar_dmac_chan_get_residue() will not find any descriptors.
 - And, the following WARNING happens:
        WARN(1, "No descriptor for cookie!");

The sh-sci driver with HSCIF (921,600bps) on R-Car H3 can cause this
So, this patch checks the done lists in rcar_dmac_chan_get_residue()
and returns zero if the done lists has the argument cookie.

Tested-by: Nguyen Viet Dung <>
Signed-off-by: Yoshihiro Shimoda <>
 drivers/dma/sh/rcar-dmac.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/dma/sh/rcar-dmac.c b/drivers/dma/sh/rcar-dmac.c
index 2b2c7db..f748be6 100644
--- a/drivers/dma/sh/rcar-dmac.c
+++ b/drivers/dma/sh/rcar-dmac.c
@@ -1264,8 +1264,17 @@ static unsigned int rcar_dmac_chan_get_residue(struct 
rcar_dmac_chan *chan,
         * If the cookie doesn't correspond to the currently running transfer
         * then the descriptor hasn't been processed yet, and the residue is
         * equal to the full descriptor size.
+        * Also, a client driver is possible to call this function before
+        * rcar_dmac_isr_channel_thread() runs. In this case, the "desc.running"
+        * will be the next descriptor, and the done list will appear. So, if
+        * the argument cookie matches the done list's cookie, we can assume
+        * the residue is zero.
        if (cookie != desc->async_tx.cookie) {
+               list_for_each_entry(desc, &chan->desc.done, node) {
+                       if (cookie == desc->async_tx.cookie)
+                               return 0;
+               }
                list_for_each_entry(desc, &chan->desc.pending, node) {
                        if (cookie == desc->async_tx.cookie)
                                return desc->size;

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