On Mon, May 26, 2014 at 02:46:29PM +0300, ville.syrjala@xxxxxxxxxxxxxxx wrote: > From: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx> > > When drm_vblank_on() is called the hardware vblank counter may have > been reset, so we can't trust that the old values sampled prior to > drm_vblank_off() have anything to do with the new values. > > So update the .last count in drm_vblank_on() to make the first > drm_vblank_enable() consider that as the reference point. This > will correct the user space visible counter to account for the > time between drm_vblank_on() and the first drm_vblank_enable() > calls. > > For extra safety subtract one from the .last count in drm_vblank_on() > to make sure that user space will never see the same counter value > before and after modeset. > > Signed-off-by: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx> Reviewed-by: Daniel Vetter <daniel.vetter@xxxxxxxx> > --- > drivers/gpu/drm/drm_irq.c | 12 ++++++++++++ > 1 file changed, 12 insertions(+) > > diff --git a/drivers/gpu/drm/drm_irq.c b/drivers/gpu/drm/drm_irq.c > index bb64f0f..54cb85d 100644 > --- a/drivers/gpu/drm/drm_irq.c > +++ b/drivers/gpu/drm/drm_irq.c > @@ -1095,6 +1095,18 @@ void drm_vblank_on(struct drm_device *dev, int crtc) > atomic_dec(&dev->vblank[crtc].refcount); > dev->vblank[crtc].inmodeset = 0; > } > + > + /* > + * sample the current counter to avoid random jumps > + * when drm_vblank_enable() applies the diff > + * > + * -1 to make sure user will never see the same > + * vblank counter value before and after a modeset > + */ > + dev->vblank[crtc].last = > + (dev->driver->get_vblank_counter(dev, crtc) - 1) & > + dev->max_vblank_count; > + > /* re-enable interrupts if there's are users left */ > if (atomic_read(&dev->vblank[crtc].refcount) != 0) > WARN_ON(drm_vblank_enable(dev, crtc)); > -- > 1.8.5.5 > > _______________________________________________ > Intel-gfx mailing list > Intel-gfx@xxxxxxxxxxxxxxxxxxxxx > http://lists.freedesktop.org/mailman/listinfo/intel-gfx -- Daniel Vetter Software Engineer, Intel Corporation +41 (0) 79 365 57 48 - http://blog.ffwll.ch _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/intel-gfx
