drm: Don't clear vblank timestamps when vblank interrupt is disabled

Clearing the timestamps causes us to send zeroed timestamps to userspace
if they get sent out in response to the drm_vblank_off(). It's better
to send the very latest timestamp and count instead.

Testcase: igt/kms_flip/modeset-vs-vblank-race
Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

diff --git a/drivers/gpu/drm/drm_irq.c b/drivers/gpu/drm/drm_irq.c
index b16a636..65d2da9 100644 (file)
--- a/drivers/gpu/drm/drm_irq.c
+++ b/drivers/gpu/drm/drm_irq.c
@@ -56,14 +56,6 @@
 #define DRM_REDUNDANT_VBLIRQ_THRESH_NS 1000000
 
 /*
- * Clear vblank timestamp buffer for a crtc.
- */
-static void clear_vblank_timestamps(struct drm_device *dev, int crtc)
-{
-       memset(dev->vblank[crtc].time, 0, sizeof(dev->vblank[crtc].time));
-}
-
-/*
  * Disable vblank irq's on crtc, make sure that last vblank count
  * of hardware and corresponding consistent software vblank counter
  * are preserved, even if there are any spurious vblank irq's after
@@ -131,9 +123,6 @@ static void vblank_disable_and_save(struct drm_device *dev, int crtc)
                smp_mb__after_atomic();
        }
 
-       /* Invalidate all timestamps while vblank irq's are off. */
-       clear_vblank_timestamps(dev, crtc);
-
        spin_unlock_irqrestore(&dev->vblank_time_lock, irqflags);
 }