1 files changed, 26 insertions, 3 deletions

diff --git a/drivers/gpu/drm/radeon/radeon_display.c b/drivers/gpu/drm/radeon/radeon_display.c
index 7ea647b84733..d680608f6f5b 100644
--- a/drivers/gpu/drm/radeon/radeon_display.c
+++ b/drivers/gpu/drm/radeon/radeon_display.c
@@ -306,7 +306,7 @@ void radeon_crtc_handle_flip(struct radeon_device *rdev, int crtc_id)
          * to complete in this vblank?
          */
         if (update_pending &&
-            (DRM_SCANOUTPOS_VALID & radeon_get_crtc_scanoutpos(rdev->ddev, crtc_id,
+            (DRM_SCANOUTPOS_VALID & radeon_get_crtc_scanoutpos(rdev->ddev, crtc_id, 0,
                                                                &vpos, &hpos, NULL, NULL)) &&
             ((vpos >= (99 * rdev->mode_info.crtcs[crtc_id]->base.hwmode.crtc_vdisplay)/100) ||
              (vpos < 0 && !ASIC_IS_AVIVO(rdev)))) {
@@ -1610,6 +1610,7 @@ bool radeon_crtc_scaling_mode_fixup(struct drm_crtc *crtc,
  *
  * \param dev Device to query.
  * \param crtc Crtc to query.
+ * \param flags Flags from caller (DRM_CALLED_FROM_VBLIRQ or 0).
  * \param *vpos Location where vertical scanout position should be stored.
  * \param *hpos Location where horizontal scanout position should go.
  * \param *stime Target location for timestamp taken immediately before
@@ -1631,8 +1632,8 @@ bool radeon_crtc_scaling_mode_fixup(struct drm_crtc *crtc,
  * unknown small number of scanlines wrt. real scanout position.
  *
  */
-int radeon_get_crtc_scanoutpos(struct drm_device *dev, int crtc, int *vpos, int *hpos,
-                               ktime_t *stime, ktime_t *etime)
+int radeon_get_crtc_scanoutpos(struct drm_device *dev, int crtc, unsigned int flags,
+                               int *vpos, int *hpos, ktime_t *stime, ktime_t *etime)
 {
         u32 stat_crtc = 0, vbl = 0, position = 0;
         int vbl_start, vbl_end, vtotal, ret = 0;
@@ -1774,5 +1775,27 @@ int radeon_get_crtc_scanoutpos(struct drm_device *dev, int crtc, int *vpos, int
         if (in_vbl)
                 ret |= DRM_SCANOUTPOS_INVBL;
 
+        /* Is vpos outside nominal vblank area, but less than
+         * 1/100 of a frame height away from start of vblank?
+         * If so, assume this isn't a massively delayed vblank
+         * interrupt, but a vblank interrupt that fired a few
+         * microseconds before true start of vblank. Compensate
+         * by adding a full frame duration to the final timestamp.
+         * Happens, e.g., on ATI R500, R600.
+         *
+         * We only do this if DRM_CALLED_FROM_VBLIRQ.
+         */
+        if ((flags & DRM_CALLED_FROM_VBLIRQ) && !in_vbl) {
+                vbl_start = rdev->mode_info.crtcs[crtc]->base.hwmode.crtc_vdisplay;
+                vtotal = rdev->mode_info.crtcs[crtc]->base.hwmode.crtc_vtotal;
+
+                if (vbl_start - *vpos < vtotal / 100) {
+                        *vpos -= vtotal;
+
+                        /* Signal this correction as "applied". */
+                        ret |= 0x8;
+                }
+        }
+
         return ret;
 }