1 files changed, 9 insertions, 1 deletions

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;