dmaengine: imx-sdma: fix cyclic buffer race condition

Assign buffer ownership to SDMA after invoking descriptor callback to
make sure that SDMA does not write to the buffer before it is read by
the CPU.

Signed-off-by: Tomasz Moń <tomasz.mon@camlingroup.com>
Link: https://lore.kernel.org/r/20220117091955.1038937-2-tomasz.mon@camlingroup.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>

diff --git a/drivers/dma/imx-sdma.c b/drivers/dma/imx-sdma.c
index 330ff41cd6143da8cbf952225ec0e92b6f015309..8cc5103193c3cac0c476e306807a2f2dd533c30a 100644 (file)
--- a/drivers/dma/imx-sdma.c
+++ b/drivers/dma/imx-sdma.c
@@ -847,7 +847,6 @@ static void sdma_update_channel_loop(struct sdma_channel *sdmac)
                */
 
                desc->chn_real_count = bd->mode.count;
-               bd->mode.status |= BD_DONE;
                bd->mode.count = desc->period_len;
                desc->buf_ptail = desc->buf_tail;
                desc->buf_tail = (desc->buf_tail + 1) % desc->num_bd;
@@ -862,6 +861,9 @@ static void sdma_update_channel_loop(struct sdma_channel *sdmac)
                dmaengine_desc_get_callback_invoke(&desc->vd.tx, NULL);
                spin_lock(&sdmac->vc.lock);
 
+               /* Assign buffer ownership to SDMA */
+               bd->mode.status |= BD_DONE;
+
                if (error)
                        sdmac->status = old_status;
        }