[PATCH] DRM: VBLANK: provide valid timestamp for EVENT_FLIP

[Eugeniy Paltsev]

If driver/HW doesn't support vblank functionality (for example
UDL driver, ARCPGU driver, ...) we always have vblank->time == 0.
In result we always provide zero timestamp for
DRM_EVENT_FLIP_COMPLETE. This breaks userspace apps (for example
weston) which relies on timestamp value.

Setup time to provide valid timestamp for DRM_EVENT_FLIP_COMPLETE
event.

Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Eugeniy Paltsev <Eugeniy.Paltsev@xxxxxxxxxxxx>
---
 drivers/gpu/drm/drm_vblank.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/gpu/drm/drm_vblank.c b/drivers/gpu/drm/drm_vblank.c
index 28cdcf76b6f9..0d19aca48782 100644
--- a/drivers/gpu/drm/drm_vblank.c
+++ b/drivers/gpu/drm/drm_vblank.c
@@ -911,6 +911,15 @@ void drm_crtc_send_vblank_event(struct drm_crtc *crtc,
 
 	if (dev->num_crtcs > 0) {
 		seq = drm_vblank_count_and_time(dev, pipe, &now);
+
+		/*
+		 * If driver/HW doesn't support vblank functionality we
+		 * always have vblank->time == 0. Setup time to provide valid
+		 * timestamp for DRM_EVENT_FLIP_COMPLETE event.
+		 */
+		if (!now && e->event.base.type == DRM_EVENT_FLIP_COMPLETE)
+			now = ktime_get();
+
 	} else {
 		seq = 0;
 
-- 
2.14.4