dma: imx-sdma: buf_tail should be initialize in prepare function

This fix audio underrun issue. When SNDRV_PCM_TRIGGER_STOP
and SNDRV_PCM_TRIGGER_START, it calls prepare again. buf_tail
should be reset to zero.
So move buf_tail initialization into prepare function.

Signed-off-by: Richard Zhao <richard.zhao@freescale.com>
Acked-by: Shawn Guo <shawn.guo@linaro.org>
Signed-off-by: Vinod Koul <vinod.koul@linux.intel.com>

1 files changed, 4 insertions, 2 deletions

diff --git a/drivers/dma/imx-sdma.c b/drivers/dma/imx-sdma.c
index fb4f4990f5eb..1dc2a4ad0026 100644
--- a/drivers/dma/imx-sdma.c
+++ b/drivers/dma/imx-sdma.c
@@ -815,8 +815,6 @@ static int sdma_request_channel(struct sdma_channel *sdmac)
 
         init_completion(&sdmac->done);
 
-        sdmac->buf_tail = 0;
-
         return 0;
 out:
 
@@ -927,6 +925,8 @@ static struct dma_async_tx_descriptor *sdma_prep_slave_sg(
 
         sdmac->flags = 0;
 
+        sdmac->buf_tail = 0;
+
         dev_dbg(sdma->dev, "setting up %d entries for channel %d.\n",
                         sg_len, channel);
 
@@ -1027,6 +1027,8 @@ static struct dma_async_tx_descriptor *sdma_prep_dma_cyclic(
 
         sdmac->status = DMA_IN_PROGRESS;
 
+        sdmac->buf_tail = 0;
+
         sdmac->flags |= IMX_DMA_SG_LOOP;
         sdmac->direction = direction;
         ret = sdma_load_context(sdmac);