dmaengine: shdma: fix a race condition in __ld_cleanup()

This patch fixes a race condition about a list of shdma-base driver.
If we don't apply this patch, a dma slave driver (especially a usb
peripheral driver) may not be able to start the transfer.

If a dma slave driver has a callback, __ld_cleanup() will call
the callback before this driver removes the list. After the callback,
since the return value of __ld_cleanup() is not zero,
shdma_chan_ld_cleanup() calls __ld_cleanup() again. And, __ld_clean()
will removes the list.

At this time, if a dma slave driver calls dmaengine_submit() before
this driver removes the list, this driver will set schan->pm_state
to SHDMA_PM_PENDING in shdma_tx_submit(). And then, even if a dma
slave driver calls dma_async_issue_pending(), this driver don't
start the transfer because the schan->pm_state is SHDMA_PM_PENDING
in shdma_issue_pending().

So, this patch adds a new condition in __ld_clean() to check if the
schan->pm_state is SHDMA_PM_PENDING or not.

Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>

diff --git a/drivers/dma/sh/shdma-base.c b/drivers/dma/sh/shdma-base.c
index ed5b0993edfa794c0bd477a07dd74386aeb3554a..3a2adb131d462597c2ee07fe7819de75e4ef239e 100644 (file)
--- a/drivers/dma/sh/shdma-base.c
+++ b/drivers/dma/sh/shdma-base.c
@@ -391,6 +391,8 @@ static dma_async_tx_callback __ld_cleanup(struct shdma_chan *schan, bool all)
                                dev_dbg(schan->dev, "Bring down channel %d\n", schan->id);
                                pm_runtime_put(schan->dev);
                                schan->pm_state = SHDMA_PM_ESTABLISHED;
+                       } else if (schan->pm_state == SHDMA_PM_PENDING) {
+                               shdma_chan_xfer_ld_queue(schan);
                        }
                }
        }