media: videobuf2: do not sync caches when we are allowed not to

Skip ->prepare() or/and ->finish() cache synchronisation if
user-space requested us to do so (or when queue dma direction
permits us to skip cache syncs).
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-core.c

@@ -304,8 +304,11 @@ static void __vb2_buf_mem_prepare(struct vb2_buffer *vb)
 {
 	unsigned int plane;
 
+	if (vb->need_cache_sync_on_prepare) {
 		for (plane = 0; plane < vb->num_planes; ++plane)
-		call_void_memop(vb, prepare, vb->planes[plane].mem_priv);
+			call_void_memop(vb, prepare,
+					vb->planes[plane].mem_priv);
+	}
 	vb->synced = 1;
 }
 
@@ -317,8 +320,11 @@ static void __vb2_buf_mem_finish(struct vb2_buffer *vb)
 {
 	unsigned int plane;
 
+	if (vb->need_cache_sync_on_finish) {
 		for (plane = 0; plane < vb->num_planes; ++plane)
-		call_void_memop(vb, finish, vb->planes[plane].mem_priv);
+			call_void_memop(vb, finish,
+					vb->planes[plane].mem_priv);
+	}
 	vb->synced = 0;
 }