drm: make sure drm_vblank_init() has been called before touching vbl_lock

Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

diff --git a/drivers/gpu/drm/drm_irq.c b/drivers/gpu/drm/drm_irq.c
index cb3794a00f98c541264404164f0eba269736126b..4d3760c63964c466097a0675566ebde9990e776a 100644 (file)
--- 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;