+ /* 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;
+ }
+ }
+