drm: rcar-du: Consider plane to CRTC associations in the plane allocator
Hardware planes are driven by the timing generator of the CRTC they are
associated to. Changing the association requires restarting the CRTC
group that the plane belongs to, resulting in flicker on the other CRTC.
To avoid flicker as much as possible, try to allocate planes first from
the free planes already associated with the target CRTC. If allocation
fails then fall back to allocation from all free planes.
Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
diff --git a/drivers/gpu/drm/rcar-du/rcar_du_kms.c b/drivers/gpu/drm/rcar-du/rcar_du_kms.c
index ade1350..2c6cf69 100644
--- a/drivers/gpu/drm/rcar-du/rcar_du_kms.c
+++ b/drivers/gpu/drm/rcar-du/rcar_du_kms.c
@@ -383,6 +383,8 @@
for (i = 0; i < dev->mode_config.num_total_plane; ++i) {
struct rcar_du_plane_state *plane_state;
struct rcar_du_plane *plane;
+ unsigned int crtc_planes;
+ unsigned int free;
int idx;
if (!state->planes[i])
@@ -401,8 +403,21 @@
!rcar_du_plane_needs_realloc(plane, plane_state))
continue;
+ /* Try to allocate the plane from the free planes currently
+ * associated with the target CRTC to avoid restarting the CRTC
+ * group and thus minimize flicker. If it fails fall back to
+ * allocating from all free planes.
+ */
+ crtc_planes = to_rcar_crtc(plane_state->state.crtc)->index % 2
+ ? plane->group->dptsr_planes
+ : ~plane->group->dptsr_planes;
+ free = group_free_planes[plane->group->index];
+
idx = rcar_du_plane_hwalloc(plane_state->format->planes,
- group_free_planes[plane->group->index]);
+ free & crtc_planes);
+ if (idx < 0)
+ idx = rcar_du_plane_hwalloc(plane_state->format->planes,
+ free);
if (idx < 0) {
dev_dbg(rcdu->dev, "%s: no available hardware plane\n",
__func__);
@@ -749,6 +764,11 @@
rgrp->mmio_offset = mmio_offsets[i];
rgrp->index = i;
+ /* Pre-associate all hardware planes with the first CRTC in the
+ * group.
+ */
+ rgrp->dptsr_planes = 0;
+
ret = rcar_du_planes_init(rgrp);
if (ret < 0)
return ret;