[PATCH] media: vb2-dc: skip CPU sync in map/unmap dma_buf

[Lucas Stach <l.stach@pengutronix.de>]

This is rougly equivalent to ca0e68e21aae (drm/prime: skip CPU sync
in map/unmap dma_buf). The contig memory allocated is already device
coherent memory, so there is no point in doing a CPU sync when
mapping it to another device. Also most importers currently cache
the mapping so the CPU sync would only happen on the first import.
With that in mind we are better off with not pretending to do a
cache synchronization at all.

This gets rid of a lot of CPU overhead in uses where those dma-bufs
are regularily imported and detached again, like Weston is currently
doing in the DRM compositor.

Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
---
 drivers/media/common/videobuf2/videobuf2-dma-contig.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/media/common/videobuf2/videobuf2-dma-contig.c b/drivers/media/common/videobuf2/videobuf2-dma-contig.c
index aff0ab7bf83d..d38f097c14ae 100644
--- a/drivers/media/common/videobuf2/videobuf2-dma-contig.c
+++ b/drivers/media/common/videobuf2/videobuf2-dma-contig.c
@@ -273,8 +273,8 @@ static void vb2_dc_dmabuf_ops_detach(struct dma_buf *dbuf,
 
 	/* release the scatterlist cache */
 	if (attach->dma_dir != DMA_NONE)
-		dma_unmap_sg(db_attach->dev, sgt->sgl, sgt->orig_nents,
-			attach->dma_dir);
+		dma_unmap_sg_attrs(db_attach->dev, sgt->sgl, sgt->orig_nents,
+			attach->dma_dir, DMA_ATTR_SKIP_CPU_SYNC);
 	sg_free_table(sgt);
 	kfree(attach);
 	db_attach->priv = NULL;
@@ -305,8 +305,8 @@ static struct sg_table *vb2_dc_dmabuf_ops_map(
 	}
 
 	/* mapping to the client with new direction */
-	sgt->nents = dma_map_sg(db_attach->dev, sgt->sgl, sgt->orig_nents,
-				dma_dir);
+	sgt->nents = dma_map_sg_attrs(db_attach->dev, sgt->sgl, sgt->orig_nents,
+				dma_dir, DMA_ATTR_SKIP_CPU_SYNC);
 	if (!sgt->nents) {
 		pr_err("failed to map scatterlist\n");
 		mutex_unlock(lock);
-- 
2.20.1