drm/exynos: fix null pointer dereference issue

This patch fixes null pointer dereference issue incurred
when ipp driver is enabled and Exynos drm driver is closed.

Non kms driver should register its own sub driver to setup necessary
resources, which is done by load(). So null pointer dereference
occurs when ipp driver is enabled and Exynos drm driver is closed
because ipp core device is registered after component_master_add_with_match
call.

This patch makes exynos_drm_device_subdrv_probe() to be called after all non
kms drivers are registered.

Signed-off-by: Inki Dae <inki.dae@samsung.com>

drivers/gpu/drm/exynos/exynos_drm_drv.c

@@ -108,11 +108,6 @@ static int exynos_drm_load(struct drm_device *dev, unsigned long flags)
 	if (ret)
 		goto err_unbind_all;
 
-	/* Probe non kms sub drivers and virtual display driver. */
-	ret = exynos_drm_device_subdrv_probe(dev);
-	if (ret)
-		goto err_cleanup_vblank;
-
 	/*
 	 * enable drm irq mode.
 	 * - with irq_enabled = true, we can use the vblank feature.
@@ -138,8 +133,6 @@ static int exynos_drm_load(struct drm_device *dev, unsigned long flags)
 
 	return 0;
 
-err_cleanup_vblank:
-	drm_vblank_cleanup(dev);
 err_unbind_all:
 	component_unbind_all(dev->dev, dev);
 err_mode_config_cleanup:
@@ -153,8 +146,6 @@ err_free_private:
 
 static int exynos_drm_unload(struct drm_device *dev)
 {
-	exynos_drm_device_subdrv_remove(dev);
-
 	exynos_drm_fbdev_fini(dev);
 	drm_kms_helper_poll_fini(dev);
 
@@ -636,9 +627,16 @@ static int exynos_drm_platform_probe(struct platform_device *pdev)
 		goto err_unregister_ipp_drv;
 #endif
 
+	/* Probe non kms sub drivers and virtual display driver. */
+	ret = exynos_drm_device_subdrv_probe(platform_get_drvdata(pdev));
+	if (ret)
+		goto err_unregister_resources;
+
 	return ret;
 
+err_unregister_resources:
 #ifdef CONFIG_DRM_EXYNOS_IPP
+	exynos_platform_device_ipp_unregister();
 err_unregister_ipp_drv:
 	platform_driver_unregister(&ipp_driver);
 err_unregister_gsc_drv:
@@ -691,6 +689,8 @@ err_unregister_fimd_drv:
 
 static int exynos_drm_platform_remove(struct platform_device *pdev)
 {
+	exynos_drm_device_subdrv_remove(platform_get_drvdata(pdev));
+
 #ifdef CONFIG_DRM_EXYNOS_IPP
 	exynos_platform_device_ipp_unregister();
 	platform_driver_unregister(&ipp_driver);