On Tue, Apr 12, 2016 at 04:32:19PM +0200, Maarten Lankhorst wrote: > This function is useful for gen2 intel devices which have no frame > counter, but need a way to determine the current vblank count without > racing with the vblank interrupt handler. > > intel_pipe_update_start checks if no vblank interrupt will occur > during vblank evasion, but cannot check whether the vblank handler has > run to completion. This function uses the timestamps to determine > when the last vblank has happened, and interpolates from there. > > Changes since v1: > - Take vblank_time_lock and don't use drm_vblank_count_and_time. > Changes since v2: > - Don't return time of last vblank. > > Cc: Mario Kleiner <mario.kleiner.de@xxxxxxxxx> > Cc: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx> > Signed-off-by: Maarten Lankhorst <maarten.lankhorst@xxxxxxxxxxxxxxx> > --- > diff --git a/drivers/gpu/drm/drm_irq.c b/drivers/gpu/drm/drm_irq.c > index 3c1a6f18e71c..32bfa4bb8f41 100644 > --- a/drivers/gpu/drm/drm_irq.c > +++ b/drivers/gpu/drm/drm_irq.c > @@ -303,6 +303,32 @@ static void drm_update_vblank_count(struct drm_device *dev, unsigned int pipe, > store_vblank(dev, pipe, diff, &t_vblank, cur_vblank); > } > > +/** > + * drm_accurate_vblank_count - retrieve the master vblank counter > + * @crtc: which counter to retrieve > + * @tv_ret: last time counter was updated > + * > + * This function is similar to @drm_crtc_vblank_count but this > + * function interpolates to handle a race with vblank irq's. > + */ > + > +u32 drm_accurate_vblank_count(struct drm_crtc *crtc) > +{ > + struct drm_device *dev = crtc->dev; > + u32 vblank, pipe = drm_crtc_index(crtc); pipe should be 'unsigned int' for consistency. > + unsigned long flags; > + > + spin_lock_irqsave(&dev->vblank_time_lock, flags); > + > + drm_update_vblank_count(dev, pipe, 0); One thing that came to mind is some callers might end up doing the update twice if the irq wasn't yet enabled when drm_vblank_get() was called. Eg. drm_wait_one_vblank() might do that. So it might be a bit more efficient to add a drm_vblank_get_and_update() instead, or something like that. But I don't really care too much. Reviewed-by: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx> > + vblank = dev->vblank[pipe].count; > + > + spin_unlock_irqrestore(&dev->vblank_time_lock, flags); > + > + return vblank; > +} > +EXPORT_SYMBOL(drm_accurate_vblank_count); > + > /* > * Disable vblank irq's on crtc, make sure that last vblank count > * of hardware and corresponding consistent software vblank counter > diff --git a/include/drm/drmP.h b/include/drm/drmP.h > index 31483c2fef51..747c80da70e5 100644 > --- a/include/drm/drmP.h > +++ b/include/drm/drmP.h > @@ -995,6 +995,7 @@ extern void drm_crtc_vblank_off(struct drm_crtc *crtc); > extern void drm_crtc_vblank_reset(struct drm_crtc *crtc); > extern void drm_crtc_vblank_on(struct drm_crtc *crtc); > extern void drm_vblank_cleanup(struct drm_device *dev); > +extern u32 drm_accurate_vblank_count(struct drm_crtc *crtc); > extern u32 drm_vblank_no_hw_counter(struct drm_device *dev, unsigned int pipe); > > extern int drm_calc_vbltimestamp_from_scanoutpos(struct drm_device *dev, -- Ville Syrjälä Intel OTC _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel