media: videobuf2: add begin/end cpu_access callbacks to dma-contig

Provide begin_cpu_access() and end_cpu_access() callbacks for
cache synchronisation on exported buffers.

The patch also adds a new helper function - vb2_dc_buffer_consistent(),
which returns true is if the buffer is consistent (DMA_ATTR_NON_CONSISTENT
bit cleared), so then we don't need to sync anything.
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

@@ -42,6 +42,11 @@ struct vb2_dc_buf {
 	struct dma_buf_attachment	*db_attach;
 };
 
+static inline bool vb2_dc_buffer_consistent(unsigned long attr)
+{
+	return !(attr & DMA_ATTR_NON_CONSISTENT);
+}
+
 /*********************************************/
 /*        scatterlist table functions        */
 /*********************************************/
@@ -335,6 +340,34 @@ static void vb2_dc_dmabuf_ops_release(struct dma_buf *dbuf)
 	vb2_dc_put(dbuf->priv);
 }
 
+static int
+vb2_dc_dmabuf_ops_begin_cpu_access(struct dma_buf *dbuf,
+				   enum dma_data_direction direction)
+{
+	struct vb2_dc_buf *buf = dbuf->priv;
+	struct sg_table *sgt = buf->dma_sgt;
+
+	if (vb2_dc_buffer_consistent(buf->attrs))
+		return 0;
+
+	dma_sync_sg_for_cpu(buf->dev, sgt->sgl, sgt->nents, buf->dma_dir);
+	return 0;
+}
+
+static int
+vb2_dc_dmabuf_ops_end_cpu_access(struct dma_buf *dbuf,
+				 enum dma_data_direction direction)
+{
+	struct vb2_dc_buf *buf = dbuf->priv;
+	struct sg_table *sgt = buf->dma_sgt;
+
+	if (vb2_dc_buffer_consistent(buf->attrs))
+		return 0;
+
+	dma_sync_sg_for_device(buf->dev, sgt->sgl, sgt->nents, buf->dma_dir);
+	return 0;
+}
+
 static void *vb2_dc_dmabuf_ops_vmap(struct dma_buf *dbuf)
 {
 	struct vb2_dc_buf *buf = dbuf->priv;
@@ -353,6 +386,8 @@ static const struct dma_buf_ops vb2_dc_dmabuf_ops = {
 	.detach = vb2_dc_dmabuf_ops_detach,
 	.map_dma_buf = vb2_dc_dmabuf_ops_map,
 	.unmap_dma_buf = vb2_dc_dmabuf_ops_unmap,
+	.begin_cpu_access = vb2_dc_dmabuf_ops_begin_cpu_access,
+	.end_cpu_access = vb2_dc_dmabuf_ops_end_cpu_access,
 	.vmap = vb2_dc_dmabuf_ops_vmap,
 	.mmap = vb2_dc_dmabuf_ops_mmap,
 	.release = vb2_dc_dmabuf_ops_release,