drm: rcar-du: Restart the DU group when a plane source changes

Plane sources are configured by the VSPS bit in the PnDDCR4 register.
Although the datasheet states that the bit is updated during vertical
blanking, it seems that updates only occur when the DU group is held in
reset through the DSYSR.DRES bit. Restart the group if the source
changes.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>

1 files changed, 20 insertions, 2 deletions

diff --git a/drivers/gpu/drm/rcar-du/rcar_du_plane.c b/drivers/gpu/drm/rcar-du/rcar_du_plane.c
index cc383954e29a..2fa5745fca37 100644
--- a/drivers/gpu/drm/rcar-du/rcar_du_plane.c
+++ b/drivers/gpu/drm/rcar-du/rcar_du_plane.c
@@ -275,9 +275,27 @@ static void rcar_du_plane_atomic_update(struct drm_plane *plane,
 					struct drm_plane_state *old_state)
 {
 	struct rcar_du_plane *rplane = to_rcar_plane(plane);
+	struct rcar_du_plane_state *old_rstate;
+	struct rcar_du_plane_state *new_rstate;
 
-	if (plane->state->crtc)
-		rcar_du_plane_setup(rplane);
+	if (!plane->state->crtc)
+		return;
+
+	rcar_du_plane_setup(rplane);
+
+	/* Check whether the source has changed from memory to live source or
+	 * from live source to memory. The source has been configured by the
+	 * VSPS bit in the PnDDCR4 register. Although the datasheet states that
+	 * the bit is updated during vertical blanking, it seems that updates
+	 * only occur when the DU group is held in reset through the DSYSR.DRES
+	 * bit. We thus need to restart the group if the source changes.
+	 */
+	old_rstate = to_rcar_plane_state(old_state);
+	new_rstate = to_rcar_plane_state(plane->state);
+
+	if ((old_rstate->source == RCAR_DU_PLANE_MEMORY) !=
+	    (new_rstate->source == RCAR_DU_PLANE_MEMORY))
+		rplane->group->need_restart = true;
 }
 
 static const struct drm_plane_helper_funcs rcar_du_plane_helper_funcs = {