[PATCH RFC 3/3] media: rockchip-rga: attach dma_resv release fence at buf_queue

[Markus Fritsche]

Opt the Rockchip RGA driver into the new vb2 release-fence helper.

Same shape as the hantro patch: rga_buf_queue enqueues the buffer
in the driver's m2m queue via v4l2_m2m_buf_queue and additionally
attaches a release fence to each plane's dmabuf->resv via
vb2_buffer_attach_release_fence(). vb2_buffer_done signals the
fence when RGA completes the M2M operation.

Userspace consumers of RGA-produced dmabufs (image-processing
pipelines, screen-rotation servers, gstreamer flows on Rockchip
boards) get spec-clean implicit-sync semantics, matching what
hantro now does in the same patch series.

Signed-off-by: Markus Fritsche <mfritsche at reauktion.de>
---
 drivers/media/platform/rockchip/rga/rga-buf.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/media/platform/rockchip/rga/rga-buf.c b/drivers/media/platform/rockchip/rga/rga-buf.c
index 70808049d..5557ca632 100644
--- a/drivers/media/platform/rockchip/rga/rga-buf.c
+++ b/drivers/media/platform/rockchip/rga/rga-buf.c
@@ -153,6 +153,16 @@ static void rga_buf_queue(struct vb2_buffer *vb)
 	struct rga_ctx *ctx = vb2_get_drv_priv(vb->vb2_queue);
 
 	v4l2_m2m_buf_queue(ctx->fh.m2m_ctx, vbuf);
+
+	/*
+	 * Opt in to vb2's dma_resv release-fence path so userspace
+	 * consumers of RGA-produced dmabufs get a real producer fence
+	 * to wait on instead of the dma_buf core's stub fence. See
+	 * the leading patch in this series for rationale. Best-effort:
+	 * fence-allocation failure means we lose implicit-sync
+	 * precision but the m2m operation itself proceeds normally.
+	 */
+	(void)vb2_buffer_attach_release_fence(vb);
 }
 
 static void rga_buf_cleanup(struct vb2_buffer *vb)
-- 
2.47.3