From: Mark Yacoub markyacoub@google.com
[Why] drm_handle_vblank_events loops over vblank_event_list to send any event that is current or has passed. More than 1 event could be pending with past sequence time that need to be send. This can be a side effect of drivers without hardware vblank counter and they depend on the difference in the timestamps and the frame/field duration calculated in drm_update_vblank_count. This can lead to 1 vblirq being ignored due to very small diff, resulting in a subsequent vblank with 2 pending vblank events to be sent, each with a unique sequence expected by user space.
[How] Send each pending vblank event with the sequence it's waiting on instead of assigning the current sequence to all of them.
Fixes igt@kms_flip "Unexpected frame sequence" Tested on Jacuzzi (MT8183)
Signed-off-by: Mark Yacoub markyacoub@chromium.org --- drivers/gpu/drm/drm_vblank.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/drm_vblank.c b/drivers/gpu/drm/drm_vblank.c index 3417e1ac79185..47da8056abc14 100644 --- a/drivers/gpu/drm/drm_vblank.c +++ b/drivers/gpu/drm/drm_vblank.c @@ -1902,7 +1902,7 @@ static void drm_handle_vblank_events(struct drm_device *dev, unsigned int pipe)
list_del(&e->base.link); drm_vblank_put(dev, pipe); - send_vblank_event(dev, e, seq, now); + send_vblank_event(dev, e, e->sequence, now); }
if (crtc && crtc->funcs->get_vblank_timestamp)