Resent, hopefully without html this time.

On September 22, 2015 11:10:15 PM GMT+02:00, Sakari Ailus [off-list ref] wrote:

Hi Tiffany,

(Robin and Hans cc'd.)

On Mon, Sep 21, 2015 at 08:26:11PM +0800, Tiffany Lin wrote:

quoted

vb2_dc_prepare use the number of SG entries dma_map_sg_attrs return.
But in dma_sync_sg_for_device, it use lengths of each SG entries
before dma_map_sg_attrs. dma_map_sg_attrs will concatenate
SGs until dma length > dma seg bundary. sgt->nents will less than
sgt->orig_nents. Using SG entries after dma_map_sg_attrs
in vb2_dc_prepare will make some SGs are not sync to device.
After add DMA_ATTR_SKIP_CPU_SYNC in vb2_dc_get_userptr to remove
sync data to device twice. Device randomly get incorrect data because
some SGs are not sync to device. Change to use number of SG entries
before dma_map_sg_attrs in vb2_dc_prepare to prevent this issue.

Signed-off-by: Tiffany Lin <tiffany.lin@mediatek.com>
---
 drivers/media/v4l2-core/videobuf2-dma-contig.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/media/v4l2-core/videobuf2-dma-contig.c

b/drivers/media/v4l2-core/videobuf2-dma-contig.c

quoted

index 2397ceb..c5d00bd 100644

--- a/drivers/media/v4l2-core/videobuf2-dma-contig.c
+++ b/drivers/media/v4l2-core/videobuf2-dma-contig.c

@@ -100,7 +100,7 @@ static void vb2_dc_prepare(void *buf_priv)
 	if (!sgt || buf->db_attach)
 		return;
 
-	dma_sync_sg_for_device(buf->dev, sgt->sgl, sgt->nents,

buf->dma_dir);

quoted

+	dma_sync_sg_for_device(buf->dev, sgt->sgl, sgt->orig_nents,

buf->dma_dir);

quoted

 }
 
 static void vb2_dc_finish(void *buf_priv)

@@ -112,7 +112,7 @@ static void vb2_dc_finish(void *buf_priv)
 	if (!sgt || buf->db_attach)
 		return;
 
-	dma_sync_sg_for_cpu(buf->dev, sgt->sgl, sgt->nents, buf->dma_dir);
+	dma_sync_sg_for_cpu(buf->dev, sgt->sgl, sgt->orig_nents,

buf->dma_dir);

quoted

 }
 
 /*********************************************/

Acked-by: Sakari Ailus <sakari.ailus@linux.intel.com>

Could you post a similar patch for videobuf2-dma-sg as well, please?
This
should probably go to stable (since when?).

videobuf-dma-sg appears to be broken, too, but the fix is more changes
than one or two lines.

-- 
Kind regards,

Sakari Ailus
e-mail: sakari.ailus at iki.fi	XMPP: sailus at retiisi.org.uk

Sakari, can you take a careful look at the vb2 code? If I remember correctly, the nents field receives the result of the map_sg function. I have no idea if that's correct.

BTW, don't spend too much time on vb1, nobody cares about that old framework, and vb1 drivers are rarely used on arm platforms. 

Regards,

Hans 

-- 
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