DRM: Armada: implement lastclose() for fbhelper

Call drm_fb_helper_restore_fbdev_mode() upon last close so that in the
event of the X server crashing, we have some kind of mode restored.

Reviewed-by: Rob Clark <[e-mail]>
Reviewed-by: Thierry Reding <[e-mail]>
Signed-off-by: Russell King <[e-mail]>

drivers/gpu/drm/armada/armada_drm.h

···
 extern const struct drm_mode_config_funcs armada_drm_mode_config_funcs;
 
 int armada_fbdev_init(struct drm_device *);
+void armada_fbdev_lastclose(struct drm_device *);
 void armada_fbdev_fini(struct drm_device *);
 
 int armada_overlay_plane_create(struct drm_device *, unsigned long);

drivers/gpu/drm/armada/armada_drv.c

···
 		DRM_UNLOCKED),
 };
 
+static void armada_drm_lastclose(struct drm_device *dev)
+{
+	armada_fbdev_lastclose(dev);
+}
+
 static const struct file_operations armada_drm_fops = {
 	.owner			= THIS_MODULE,
 	.llseek			= no_llseek,
···
 	.open			= NULL,
 	.preclose		= NULL,
 	.postclose		= NULL,
-	.lastclose		= NULL,
+	.lastclose		= armada_drm_lastclose,
 	.unload			= armada_drm_unload,
 	.get_vblank_counter	= drm_vblank_count,
 	.enable_vblank		= armada_drm_enable_vblank,

drivers/gpu/drm/armada/armada_fbdev.c

···
 	return ret;
 }
 
+void armada_fbdev_lastclose(struct drm_device *dev)
+{
+	struct armada_private *priv = dev->dev_private;
+
+	drm_modeset_lock_all(dev);
+	if (priv->fbdev)
+		drm_fb_helper_restore_fbdev_mode(priv->fbdev);
+	drm_modeset_unlock_all(dev);
+}
+
 void armada_fbdev_fini(struct drm_device *dev)
 {
 	struct armada_private *priv = dev->dev_private;