drm: rcar-du: Keep plane to CRTC associations when disabling a plane
Changing the plane to CRTC associations requires restarting the CRTC
group, creating visible flicker. Mitigate the issue by changing plane
association only when a plane becomes enabled, not when it get disabled.
Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
diff --git a/drivers/gpu/drm/rcar-du/rcar_du_crtc.c b/drivers/gpu/drm/rcar-du/rcar_du_crtc.c
index 15f8d14..620a2c5 100644
--- a/drivers/gpu/drm/rcar-du/rcar_du_crtc.c
+++ b/drivers/gpu/drm/rcar-du/rcar_du_crtc.c
@@ -208,9 +208,10 @@
{
struct rcar_du_plane *planes[RCAR_DU_NUM_HW_PLANES];
unsigned int num_planes = 0;
+ unsigned int dptsr_planes;
+ unsigned int hwplanes = 0;
unsigned int prio = 0;
unsigned int i;
- u32 dptsr = 0;
u32 dspr = 0;
for (i = 0; i < ARRAY_SIZE(rcrtc->group->planes); ++i) {
@@ -238,37 +239,44 @@
prio -= 4;
dspr |= (index + 1) << prio;
- dptsr |= DPTSR_PnDK(index) | DPTSR_PnTS(index);
+ hwplanes |= 1 << index;
if (plane_format(plane)->planes == 2) {
index = (index + 1) % 8;
prio -= 4;
dspr |= (index + 1) << prio;
- dptsr |= DPTSR_PnDK(index) | DPTSR_PnTS(index);
+ hwplanes |= 1 << index;
}
}
- /* Select display timing and dot clock generator 2 for planes associated
- * with superposition controller 2.
+ /* Update the planes to display timing and dot clock generator
+ * associations.
+ *
+ * Updating the DPTSR register requires restarting the CRTC group,
+ * resulting in visible flicker. To mitigate the issue only update the
+ * association if needed by enabled planes. Planes being disabled will
+ * keep their current association.
+ *
+ * To mitigate the issue further we could pre-associate planes with
+ * CRTCs, either with a fixed 4/4 split, or through a module parameter.
*/
- if (rcrtc->index % 2) {
- /* The DPTSR register is updated when the display controller is
- * stopped. We thus need to restart the DU. Once again, sorry
- * for the flicker. One way to mitigate the issue would be to
- * pre-associate planes with CRTCs (either with a fixed 4/4
- * split, or through a module parameter). Flicker would then
- * occur only if we need to break the pre-association.
- */
- mutex_lock(&rcrtc->group->lock);
- if (rcar_du_group_read(rcrtc->group, DPTSR) != dptsr) {
- rcar_du_group_write(rcrtc->group, DPTSR, dptsr);
- if (rcrtc->group->used_crtcs)
- rcar_du_group_restart(rcrtc->group);
- }
- mutex_unlock(&rcrtc->group->lock);
+ mutex_lock(&rcrtc->group->lock);
+
+ dptsr_planes = rcrtc->index % 2 ? rcrtc->group->dptsr_planes | hwplanes
+ : rcrtc->group->dptsr_planes & ~hwplanes;
+
+ if (dptsr_planes != rcrtc->group->dptsr_planes) {
+ rcar_du_group_write(rcrtc->group, DPTSR,
+ (dptsr_planes << 16) | dptsr_planes);
+ rcrtc->group->dptsr_planes = dptsr_planes;
+
+ if (rcrtc->group->used_crtcs)
+ rcar_du_group_restart(rcrtc->group);
}
+ mutex_unlock(&rcrtc->group->lock);
+
rcar_du_group_write(rcrtc->group, rcrtc->index % 2 ? DS2PR : DS1PR,
dspr);
}