drm/i915: Reset state after a GPU reset or resume

Call drm_mode_config_reset() after an invalidation event to restore any
cached state to unknown.

Tested-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
index 66796bb..e517447 100644
--- a/drivers/gpu/drm/i915/i915_drv.c
+++ b/drivers/gpu/drm/i915/i915_drv.c
@@ -354,6 +354,7 @@
 		error = i915_gem_init_ringbuffer(dev);
 		mutex_unlock(&dev->struct_mutex);
 
+		drm_mode_config_reset(dev);
 		drm_irq_install(dev);
 
 		/* Resume the modeset for every activated CRTC */
@@ -542,6 +543,7 @@
 
 		mutex_unlock(&dev->struct_mutex);
 		drm_irq_uninstall(dev);
+		drm_mode_config_reset(dev);
 		drm_irq_install(dev);
 		mutex_lock(&dev->struct_mutex);
 	}