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authorMichel Dänzer <michel.daenzer@amd.com>2015-05-26 11:53:38 +0300
committerDaniel Vetter <daniel.vetter@ffwll.ch>2015-05-27 14:00:08 +0300
commit5ceecb2fa720c01a97e6fa2353c2b8f1e8d69f1f (patch)
tree4a9ad864ed2ff736c7138fa997875b7944601d6e /drivers/gpu/drm/drm_irq.c
parent60f207a5b6d8f23c2e8388b415e8d5c7311cc79d (diff)
downloadlinux-5ceecb2fa720c01a97e6fa2353c2b8f1e8d69f1f.tar.xz
drm: Fix off-by-one in vblank hardware counter wraparound handling
dev->max_vblank_count contains the largest value that can be represented by the hardware counter. When the hardware counter wraps around, we have to add that value + 1 to get the same value as if the hardware counter didn't wrap around. Signed-off-by: Michel Dänzer <michel.daenzer@amd.com> Reviewed-by: Christian König <christian.koenig@amd.com> Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Diffstat (limited to 'drivers/gpu/drm/drm_irq.c')
-rw-r--r--drivers/gpu/drm/drm_irq.c4
1 files changed, 2 insertions, 2 deletions
diff --git a/drivers/gpu/drm/drm_irq.c b/drivers/gpu/drm/drm_irq.c
index 1967e7fc9805..6f02b4b560b8 100644
--- a/drivers/gpu/drm/drm_irq.c
+++ b/drivers/gpu/drm/drm_irq.c
@@ -130,7 +130,7 @@ static void drm_update_vblank_count(struct drm_device *dev, int crtc)
/*
* Interrupts were disabled prior to this call, so deal with counter
* wrap if needed.
- * NOTE! It's possible we lost a full dev->max_vblank_count events
+ * NOTE! It's possible we lost a full dev->max_vblank_count + 1 events
* here if the register is small or we had vblank interrupts off for
* a long time.
*
@@ -147,7 +147,7 @@ static void drm_update_vblank_count(struct drm_device *dev, int crtc)
/* Deal with counter wrap */
diff = cur_vblank - vblank->last;
if (cur_vblank < vblank->last) {
- diff += dev->max_vblank_count;
+ diff += dev->max_vblank_count + 1;
DRM_DEBUG("last_vblank[%d]=0x%x, cur_vblank=0x%x => diff=0x%x\n",
crtc, vblank->last, cur_vblank, diff);