media: videobuf2: don't test db_attach in dma-contig prepare and finish

We moved cache management decision making to the upper layer and
rely on buffer's need_cache_sync flags and videobuf2 core. If the
upper layer (core) has decided to invoke ->prepare() or ->finish()
then we must sync.

For DMABUF ->need_cache_sync_on_prepare and ->need_cache_sync_on_flush
are always false so videobuf core does not call ->prepare() and
->finish() on such buffers.

Additionally, scratch the DMABUF comment.
Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

drivers/media/common/videobuf2/videobuf2-dma-contig.c

@@ -100,8 +100,7 @@ static void vb2_dc_prepare(void *buf_priv)
 	struct vb2_dc_buf *buf = buf_priv;
 	struct sg_table *sgt = buf->dma_sgt;
 
-	/* DMABUF exporter will flush the cache for us */
-	if (!sgt || buf->db_attach)
+	if (!sgt)
 		return;
 
 	dma_sync_sg_for_device(buf->dev, sgt->sgl, sgt->orig_nents,
@@ -113,8 +112,7 @@ static void vb2_dc_finish(void *buf_priv)
 	struct vb2_dc_buf *buf = buf_priv;
 	struct sg_table *sgt = buf->dma_sgt;
 
-	/* DMABUF exporter will flush the cache for us */
-	if (!sgt || buf->db_attach)
+	if (!sgt)
 		return;
 
 	dma_sync_sg_for_cpu(buf->dev, sgt->sgl, sgt->orig_nents, buf->dma_dir);

drivers/media/common/videobuf2/videobuf2-dma-sg.c

@@ -204,10 +204,6 @@ static void vb2_dma_sg_prepare(void *buf_priv)
 	struct vb2_dma_sg_buf *buf = buf_priv;
 	struct sg_table *sgt = buf->dma_sgt;
 
-	/* DMABUF exporter will flush the cache for us */
-	if (buf->db_attach)
-		return;
-
 	dma_sync_sg_for_device(buf->dev, sgt->sgl, sgt->orig_nents,
 			       buf->dma_dir);
 }
@@ -217,10 +213,6 @@ static void vb2_dma_sg_finish(void *buf_priv)
 	struct vb2_dma_sg_buf *buf = buf_priv;
 	struct sg_table *sgt = buf->dma_sgt;
 
-	/* DMABUF exporter will flush the cache for us */
-	if (buf->db_attach)
-		return;
-
 	dma_sync_sg_for_cpu(buf->dev, sgt->sgl, sgt->orig_nents, buf->dma_dir);
 }