diff --git a/drivers/gpu/drm/drm_irq.c b/drivers/gpu/drm/drm_irq.c
index eba6337f5860..2151ea551d3b 100644
--- a/drivers/gpu/drm/drm_irq.c
+++ b/drivers/gpu/drm/drm_irq.c
@@ -616,10 +616,18 @@ int drm_control(struct drm_device *dev, void *data,
 void drm_calc_timestamping_constants(struct drm_crtc *crtc,
 				     const struct drm_display_mode *mode)
 {
-	struct drm_vblank_crtc *vblank = &crtc->dev->vblank[drm_crtc_index(crtc)];
+	struct drm_device *dev = crtc->dev;
+	unsigned int pipe = drm_crtc_index(crtc);
+	struct drm_vblank_crtc *vblank = &dev->vblank[pipe];
 	int linedur_ns = 0, framedur_ns = 0;
 	int dotclock = mode->crtc_clock;
 
+	if (!dev->num_crtcs)
+		return;
+
+	if (WARN_ON(pipe >= dev->num_crtcs))
+		return;
+
 	/* Valid dotclock? */
 	if (dotclock > 0) {
 		int frame_size = mode->crtc_htotal * mode->crtc_vtotal;