1 files changed, 15 insertions, 7 deletions

diff --git a/drivers/gpu/drm/drm_irq.c b/drivers/gpu/drm/drm_irq.c
index cb3794a00f98..68b756253f9f 100644
--- a/drivers/gpu/drm/drm_irq.c
+++ b/drivers/gpu/drm/drm_irq.c
@@ -407,13 +407,16 @@ int drm_irq_uninstall(struct drm_device *dev)
         /*
          * Wake up any waiters so they don't hang.
          */
-        spin_lock_irqsave(&dev->vbl_lock, irqflags);
-        for (i = 0; i < dev->num_crtcs; i++) {
-                DRM_WAKEUP(&dev->vbl_queue[i]);
-                dev->vblank_enabled[i] = 0;
-                dev->last_vblank[i] = dev->driver->get_vblank_counter(dev, i);
+        if (dev->num_crtcs) {
+                spin_lock_irqsave(&dev->vbl_lock, irqflags);
+                for (i = 0; i < dev->num_crtcs; i++) {
+                        DRM_WAKEUP(&dev->vbl_queue[i]);
+                        dev->vblank_enabled[i] = 0;
+                        dev->last_vblank[i] =
+                                dev->driver->get_vblank_counter(dev, i);
+                }
+                spin_unlock_irqrestore(&dev->vbl_lock, irqflags);
         }
-        spin_unlock_irqrestore(&dev->vbl_lock, irqflags);
 
         if (!irq_enabled)
                 return -EINVAL;
@@ -1125,6 +1128,7 @@ static int drm_queue_vblank_event(struct drm_device *dev, int pipe,
                 trace_drm_vblank_event_delivered(current->pid, pipe,
                                                  vblwait->request.sequence);
         } else {
+                /* drm_handle_vblank_events will call drm_vblank_put */
                 list_add_tail(&e->base.link, &dev->vblank_event_list);
                 vblwait->reply.sequence = vblwait->request.sequence;
         }
@@ -1205,8 +1209,12 @@ int drm_wait_vblank(struct drm_device *dev, void *data,
                 goto done;
         }
 
-        if (flags & _DRM_VBLANK_EVENT)
+        if (flags & _DRM_VBLANK_EVENT) {
+                /* must hold on to the vblank ref until the event fires
+                 * drm_vblank_put will be called asynchronously
+                 */
                 return drm_queue_vblank_event(dev, crtc, vblwait, file_priv);
+        }
 
         if ((flags & _DRM_VBLANK_NEXTONMISS) &&
             (seq - vblwait->request.sequence) <= (1<<23)) {