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-rw-r--r--linux-core/drm_irq.c13
1 files changed, 10 insertions, 3 deletions
diff --git a/linux-core/drm_irq.c b/linux-core/drm_irq.c
index e2f106e4..ccb3ca89 100644
--- a/linux-core/drm_irq.c
+++ b/linux-core/drm_irq.c
@@ -360,9 +360,16 @@ void drm_update_vblank_count(struct drm_device *dev, int crtc)
cur_vblank = dev->driver->get_vblank_counter(dev, crtc);
spin_lock_irqsave(&dev->vbl_lock, irqflags);
if (cur_vblank < dev->last_vblank[crtc]) {
- diff = dev->max_vblank_count -
- dev->last_vblank[crtc];
- diff += cur_vblank;
+ if (cur_vblank == dev->last_vblank[crtc] - 1) {
+ diff = 0;
+ } else {
+ diff = dev->max_vblank_count -
+ dev->last_vblank[crtc];
+ diff += cur_vblank;
+ }
+
+ DRM_DEBUG("last_vblank[%d]=0x%x, cur_vblank=0x%x => diff=0x%x\n",
+ crtc, dev->last_vblank[crtc], cur_vblank, diff);
} else {
diff = cur_vblank - dev->last_vblank[crtc];
}