drm/vblank: Use abs64(diff_ns) for s64 diff_ns instead of abs(diff_ns)

Use of abs() wrongly wrapped diff_ns to 32 bit, which gives a 1/4000
probability of a missed vblank increment at each vblank irq reenable
if the kms driver doesn't support high precision vblank timestamping.
Not a big deal in practice, but let's make it nice.

Signed-off-by: Mario Kleiner <mario.kleiner@tuebingen.mpg.de>
Signed-off-by: Dave Airlie <airlied@redhat.com>

1 files changed, 2 insertions, 2 deletions

diff --git a/drivers/gpu/drm/drm_irq.c b/drivers/gpu/drm/drm_irq.c
index 3dadfa2a852..6d2d4faf867 100644
--- a/drivers/gpu/drm/drm_irq.c
+++ b/drivers/gpu/drm/drm_irq.c
@@ -164,7 +164,7 @@ static void vblank_disable_and_save(struct drm_device *dev, int crtc)
          * available. In that case we can't account for this and just
          * hope for the best.
          */
-        if ((vblrc > 0) && (abs(diff_ns) > 1000000))
+        if ((vblrc > 0) && (abs64(diff_ns) > 1000000))
                 atomic_inc(&dev->_vblank_count[crtc]);
 
         /* Invalidate all timestamps while vblank irq's are off. */
@@ -1293,7 +1293,7 @@ bool drm_handle_vblank(struct drm_device *dev, int crtc)
          * e.g., due to spurious vblank interrupts. We need to
          * ignore those for accounting.
          */
-        if (abs(diff_ns) > DRM_REDUNDANT_VBLIRQ_THRESH_NS) {
+        if (abs64(diff_ns) > DRM_REDUNDANT_VBLIRQ_THRESH_NS) {
                 /* Store new timestamp in ringbuffer. */
                 vblanktimestamp(dev, crtc, vblcount + 1) = tvblank;
                 smp_wmb();