drm/radeon: Correctly clean up failed display probing

Improve the fbdev probing function to fully clean up if it failed.
Allows to remove special cases from fb_destroy as well.

This change is reorders the operations within radeonfb_probe(). It
first allocates a buffer object, then builds a DRM framebuffer for
the object and finally creates the fbdev device. If every step
succeeded, the probe function clears the framebuffer memory. This
is the optimal order to rollback any changes if any of the steps
fails.

No functional changes.
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/radeon/radeon_fb.c

@@ -177,17 +177,14 @@ static void radeon_fbdev_fb_destroy(struct fb_info *info)
 {
 	struct drm_fb_helper *fb_helper = info->par;
 	struct drm_framebuffer *fb = fb_helper->fb;
+	struct drm_gem_object *gobj = drm_gem_fb_get_obj(fb, 0);
 
-	if (fb) {
-		if (fb->obj[0]) {
-			radeon_fbdev_destroy_pinned_object(fb->obj[0]);
-			fb->obj[0] = NULL;
 	drm_framebuffer_unregister_private(fb);
 	drm_framebuffer_cleanup(fb);
-		}
 	kfree(fb);
 	fb_helper->fb = NULL;
-	}
+
+	radeon_fbdev_destroy_pinned_object(gobj);
 
 	drm_fb_helper_fini(fb_helper);
 }
@@ -213,11 +210,11 @@ static int radeon_fbdev_fb_helper_fb_probe(struct drm_fb_helper *fb_helper,
 					   struct drm_fb_helper_surface_size *sizes)
 {
 	struct radeon_device *rdev = fb_helper->dev->dev_private;
+	struct drm_mode_fb_cmd2 mode_cmd = { };
 	struct fb_info *info;
-	struct drm_framebuffer *fb = NULL;
-	struct drm_mode_fb_cmd2 mode_cmd;
-	struct drm_gem_object *gobj = NULL;
-	struct radeon_bo *rbo = NULL;
+	struct drm_gem_object *gobj;
+	struct radeon_bo *rbo;
+	struct drm_framebuffer *fb;
 	int ret;
 	unsigned long tmp;
 
@@ -236,45 +233,43 @@ static int radeon_fbdev_fb_helper_fb_probe(struct drm_fb_helper *fb_helper,
 		DRM_ERROR("failed to create fbcon object %d\n", ret);
 		return ret;
 	}
-
 	rbo = gem_to_radeon_bo(gobj);
 
-	/* okay we have an object now allocate the framebuffer */
-	info = drm_fb_helper_alloc_info(fb_helper);
-	if (IS_ERR(info)) {
-		ret = PTR_ERR(info);
-		goto out;
-	}
-
-	/* radeon resume is fragile and needs a vt switch to help it along */
-	info->skip_vt_switch = false;
-
 	fb = kzalloc(sizeof(*fb), GFP_KERNEL);
 	if (!fb) {
 		ret = -ENOMEM;
-		goto out;
+		goto err_radeon_fbdev_destroy_pinned_object;
 	}
-
 	ret = radeon_framebuffer_init(rdev->ddev, fb, &mode_cmd, gobj);
 	if (ret) {
 		DRM_ERROR("failed to initialize framebuffer %d\n", ret);
-		goto out;
+		goto err_kfree;
 	}
 
 	/* setup helper */
 	fb_helper->fb = fb;
 
-	memset_io(rbo->kptr, 0x0, radeon_bo_size(rbo));
+	/* okay we have an object now allocate the framebuffer */
+	info = drm_fb_helper_alloc_info(fb_helper);
+	if (IS_ERR(info)) {
+		ret = PTR_ERR(info);
+		goto err_drm_framebuffer_unregister_private;
+	}
 
 	info->fbops = &radeon_fbdev_fb_ops;
+	info->flags = FBINFO_DEFAULT;
+	/* radeon resume is fragile and needs a vt switch to help it along */
+	info->skip_vt_switch = false;
+
+	drm_fb_helper_fill_info(info, fb_helper, sizes);
 
 	tmp = radeon_bo_gpu_offset(rbo) - rdev->mc.vram_start;
 	info->fix.smem_start = rdev->mc.aper_base + tmp;
 	info->fix.smem_len = radeon_bo_size(rbo);
-	info->screen_base = rbo->kptr;
+	info->screen_base = (__force void __iomem *)rbo->kptr;
 	info->screen_size = radeon_bo_size(rbo);
 
-	drm_fb_helper_fill_info(info, fb_helper, sizes);
+	memset_io(info->screen_base, 0, info->screen_size);
 
 	/* Use default scratch pixmap (info->pixmap.flags = FB_PIXMAP_SYSTEM) */
 
@@ -287,13 +282,14 @@ static int radeon_fbdev_fb_helper_fb_probe(struct drm_fb_helper *fb_helper,
 	vga_switcheroo_client_fb_set(rdev->pdev, info);
 	return 0;
 
-out:
-	if (fb && ret) {
-		drm_gem_object_put(gobj);
+err_drm_framebuffer_unregister_private:
+	fb_helper->fb = NULL;
 	drm_framebuffer_unregister_private(fb);
 	drm_framebuffer_cleanup(fb);
+err_kfree:
 	kfree(fb);
-	}
+err_radeon_fbdev_destroy_pinned_object:
+	radeon_fbdev_destroy_pinned_object(gobj);
 	return ret;
 }