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

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

1 files changed, 9 insertions, 6 deletions

diff --git a/drivers/gpu/drm/drm_irq.c b/drivers/gpu/drm/drm_irq.c
index cb3794a00f98..4d3760c63964 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;