drm/exynos: restored kernel_fb_list when reiniting fb_helper

during recreating exynos_drm_fbdev as a new display device probes,
fb_helper is reinitialized but kernel fb is not changed
so kernel_fb_list should be restored after fb_helper is reinitialized.

Signed-off-by: Joonyoung Shim <jy0922.shim@samsung.com>
Signed-off-by: Inki Dae <inki.dae@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>

drivers/gpu/drm/exynos/exynos_drm_fbdev.c

@@ -405,6 +405,18 @@ int exynos_drm_fbdev_reinit(struct drm_device *dev)
 	fb_helper = private->fb_helper;
 
 	if (fb_helper) {
+		struct list_head temp_list;
+
+		INIT_LIST_HEAD(&temp_list);
+
+		/*
+		 * fb_helper is reintialized but kernel fb is reused
+		 * so kernel_fb_list need to be backuped and restored
+		 */
+		if (!list_empty(&fb_helper->kernel_fb_list))
+			list_replace_init(&fb_helper->kernel_fb_list,
+					&temp_list);
+
 		drm_fb_helper_fini(fb_helper);
 
 		ret = drm_fb_helper_init(dev, fb_helper,
@@ -414,6 +426,9 @@ int exynos_drm_fbdev_reinit(struct drm_device *dev)
 			return ret;
 		}
 
+		if (!list_empty(&temp_list))
+			list_replace(&temp_list, &fb_helper->kernel_fb_list);
+
 		ret = drm_fb_helper_single_add_all_connectors(fb_helper);
 		if (ret < 0) {
 			DRM_ERROR("failed to add fb helper to connectors\n");