From: Michel Dänzer Date: Tue, 26 May 2015 08:53:38 +0000 (+0900) Subject: drm: Fix off-by-one in vblank hardware counter wraparound handling X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=5ceecb2fa720c01a97e6fa2353c2b8f1e8d69f1f;p=linux-beck.git 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 Reviewed-by: Christian König Signed-off-by: Daniel Vetter --- 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);