diff --git a/drivers/gpu/drm/drm_irq.c b/drivers/gpu/drm/drm_irq.c
index 33ee515..d80d952 100644
--- a/drivers/gpu/drm/drm_irq.c
+++ b/drivers/gpu/drm/drm_irq.c
@@ -219,7 +219,7 @@
 	for (i = 0; i < num_crtcs; i++)
 		init_waitqueue_head(&dev->vblank[i].queue);
 
-	DRM_INFO("Supports vblank timestamp caching Rev 1 (10.10.2010).\n");
+	DRM_INFO("Supports vblank timestamp caching Rev 2 (21.10.2013).\n");
 
 	/* Driver specific high-precision vblank timestamping supported? */
 	if (dev->driver->get_vblank_timestamp)
@@ -586,14 +586,17 @@
 	 * code gets preempted or delayed for some reason.
 	 */
 	for (i = 0; i < DRM_TIMESTAMP_MAXRETRIES; i++) {
-		/* Get system timestamp before query. */
-		stime = ktime_get();
+		/*
+		 * Get vertical and horizontal scanout position vpos, hpos,
+		 * and bounding timestamps stime, etime, pre/post query.
+		 */
+		vbl_status = dev->driver->get_scanout_position(dev, crtc, &vpos,
+							       &hpos, &stime, &etime);
 
-		/* Get vertical and horizontal scanout pos. vpos, hpos. */
-		vbl_status = dev->driver->get_scanout_position(dev, crtc, &vpos, &hpos);
-
-		/* Get system timestamp after query. */
-		etime = ktime_get();
+		/*
+		 * Get correction for CLOCK_MONOTONIC -> CLOCK_REALTIME if
+		 * CLOCK_REALTIME is requested.
+		 */
 		if (!drm_timestamp_monotonic)
 			mono_time_offset = ktime_get_monotonic_offset();
 
@@ -604,6 +607,7 @@
 			return -EIO;
 		}
 
+		/* Compute uncertainty in timestamp of scanout position query. */
 		duration_ns = ktime_to_ns(etime) - ktime_to_ns(stime);
 
 		/* Accept result with <  max_error nsecs timing uncertainty. */