[PATCH 6/6] dmaengine: imx-sdma: avoid stopping channel in the middle of a BD transfer

[Shawn Guo]

When STOP register bit gets set, SDMA hardware will immediately stop
the channel once the current burst other than buffer descriptor
transfer is done.

* Change sdma_disable_channel() to only set STOP register bit after
  polling the current BD done, so that the current BD transfer
  corruption could be avoided.

* Increment buf_tail in mxc_sdma_handle_channel_normal() as well as
  sdma_handle_channel_loop(), since buf_tail now is used in
  sdma_disable_channel() which could be called in both sg and cyclic
  cases.

* Return DMA_SUCCESS other than DMA_ERROR in sdma_disable_channel().

Signed-off-by: Shawn Guo <shawn.guo at freescale.com>
---
 drivers/dma/imx-sdma.c |    9 ++++++++-
 1 files changed, 8 insertions(+), 1 deletions(-)

diff --git a/drivers/dma/imx-sdma.c b/drivers/dma/imx-sdma.c
index fa63ace..ae87287 100644
--- a/drivers/dma/imx-sdma.c
+++ b/drivers/dma/imx-sdma.c
@@ -481,6 +481,8 @@ static void mxc_sdma_handle_channel_normal(struct sdma_channel *sdmac)
 	else
 		sdmac->status = DMA_SUCCESS;
 
+	sdmac->buf_tail++;
+
 	if (sdmac->desc.callback)
 		sdmac->desc.callback(sdmac->desc.callback_param);
 	sdmac->last_completed = sdmac->desc.cookie;
@@ -655,9 +657,14 @@ static void sdma_disable_channel(struct sdma_channel *sdmac)
 {
 	struct sdma_engine *sdma = sdmac->sdma;
 	int channel = sdmac->channel;
+	struct sdma_buffer_descriptor *bd = &sdmac->bd[sdmac->buf_tail];
+
+	while (bd->mode.status & BD_DONE)
+		cpu_relax();
 
 	__raw_writel(1 << channel, sdma->regs + SDMA_H_STATSTOP);
-	sdmac->status = DMA_ERROR;
+
+	sdmac->status = DMA_SUCCESS;
 }
 
 static int sdma_config_channel(struct sdma_channel *sdmac)
-- 
1.7.1