On Thu, Dec 02, 2021 at 10:11:55AM -0500, Mark Yacoub wrote: > From: Mark Yacoub <markyacoub@xxxxxxxxxx> > > [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@xxxxxxxxxxxx> > --- > 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); This doesn't look right. The timestamp corresponds to 'seq' not e->sequence (ie. whatever sequqnece number the user asked to wait for). > } > > if (crtc && crtc->funcs->get_vblank_timestamp) > -- > 2.34.0.rc2.393.gf8c9666880-goog -- Ville Syrjälä Intel
