drm/radeon: fix deferred page-flip detection logic on Avivo-based ASICs
This fixes page-flip-related flickering observed on Iconia Tab W500.
The update_pending status returned by radeon_page_flip is very accurate on
Avivo-based ASICs when vpos is negative.
Experiments were conducted on several ASIC generations ranging from RS690
to Cayman where the page flip was artificially timed to occur at a specific
vpos. With negative vpos, overriding update_pending always lead to
flickering.
The same experiment on RV380 and RV410 showed that update_pending is not
accurate with negative vpos. In most cases update_pending == 1 is returned
although the flip would complete before the start of the next frame.
Therefore I left the behaviour unchanged for pre-AVIVO ASICs for
performance reasons, although this may result in flickering in rare cases.
This change also makes the logic a little easier to understand.
Signed-off-by: Felix Kuehling <Felix.Kuehling@amd.com>
Reviewed-by: Mario Kleiner <mario.kleiner@tuebingen.mpg.de>
Signed-off-by: Dave Airlie <airlied@redhat.com>
diff --git a/drivers/gpu/drm/radeon/radeon_display.c b/drivers/gpu/drm/radeon/radeon_display.c
index 7cb062d..1f98e5f 100644
--- a/drivers/gpu/drm/radeon/radeon_display.c
+++ b/drivers/gpu/drm/radeon/radeon_display.c
@@ -303,8 +303,17 @@
if (update_pending &&
(DRM_SCANOUTPOS_VALID & radeon_get_crtc_scanoutpos(rdev->ddev, crtc_id,
&vpos, &hpos)) &&
- (vpos >=0) &&
- (vpos < (99 * rdev->mode_info.crtcs[crtc_id]->base.hwmode.crtc_vdisplay)/100)) {
+ ((vpos >= (99 * rdev->mode_info.crtcs[crtc_id]->base.hwmode.crtc_vdisplay)/100) ||
+ (vpos < 0 && !ASIC_IS_AVIVO(rdev)))) {
+ /* crtc didn't flip in this target vblank interval,
+ * but flip is pending in crtc. Based on the current
+ * scanout position we know that the current frame is
+ * (nearly) complete and the flip will (likely)
+ * complete before the start of the next frame.
+ */
+ update_pending = 0;
+ }
+ if (update_pending) {
/* crtc didn't flip in this target vblank interval,
* but flip is pending in crtc. It will complete it
* in next vblank interval, so complete the flip at