diff --git a/drivers/gpu/drm/vkms/vkms_crtc.c b/drivers/gpu/drm/vkms/vkms_crtc.c
index ac85e17428f8..d071c517480d 100644
--- a/drivers/gpu/drm/vkms/vkms_crtc.c
+++ b/drivers/gpu/drm/vkms/vkms_crtc.c
@@ -15,10 +15,17 @@ static enum hrtimer_restart vkms_vblank_simulate(struct hrtimer *timer)
 	struct vkms_crtc_state *state;
 	u64 ret_overrun;
 	bool ret;
+	const ktime_t interval = output->period_ns;
+	const ktime_t now = output->vblank_hrtimer.base->get_time();
 
 	ret_overrun = hrtimer_forward_now(&output->vblank_hrtimer,
-					  output->period_ns);
-	WARN_ON(ret_overrun != 1);
+					  interval);
+	if (ret_overrun != 1) {
+		printk(KERN_INFO "now=%llu interval=%llu ret_overrun=%llu\n",
+		       (unsigned long long) now, (unsigned long long) interval,
+		       (unsigned long long) ret_overrun);
+		WARN_ON(1);
+	}
 
 	spin_lock(&output->lock);
 	ret = drm_crtc_handle_vblank(crtc);