Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.37 as permitted sender) client-ip=23.128.96.37;
From:   Liu Ying <victor.liu@nxp.com>
To:     dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org
Cc:     andrzej.hajda@intel.com, neil.armstrong@linaro.org,
        rfoss@kernel.org, Laurent.pinchart@ideasonboard.com,
        jonas@kwiboo.se, jernej.skrabec@gmail.com,
        maarten.lankhorst@linux.intel.com, mripard@kernel.org,
        tzimmermann@suse.de, airlied@gmail.com, daniel@ffwll.ch,
        angelogioacchino.delregno@collabora.com, ulf.hansson@linaro.org,
        Linus Walleij <linus.walleij@linaro.org>
Subject: [PATCH] drm/bridge: panel: Check device dependency before managing device link
Date:   Thu, 23 Nov 2023 11:26:15 +0800
Message-Id: <20231123032615.3760488-1-victor.liu@nxp.com>
Content-Transfer-Encoding: 8bit
Content-Type: text/plain
MIME-Version: 1.0
X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?4mmKJCzHqihMxz8oc+ZMAsHRrA7P2CAqkxfcxdWS9/VKswy+MVmFO7R2J67d?=
 =?us-ascii?Q?T6xfP4vhH1rIiv7vAiDQYpYzCucHurEPkj7Y0ucN9Yj0Su2xZYsVJtfeAiPp?=
 =?us-ascii?Q?R1mP4Nq8yo6zDkQhvKsRrjHmfDTpowEgzibCvBhXOEZWn/JadF3GVwmzvx5V?=
 =?us-ascii?Q?6gel7/VrSKpLKOUkAk/jZ6dfwRno3cbbUzTSxHUL6JhXEaREfByHcvxk5yGR?=
 =?us-ascii?Q?KbsbtDAQed8HhMWaSGWTs9g+T8kFZZyxwZErgGxdjsh/IE8vHhXczhpigmay?=
 =?us-ascii?Q?sk3yHBDIhUBdJfcYjfOM1baBJQkDpdvWC9+qtopJESx2hc2LDfbc5I7yjBEm?=
 =?us-ascii?Q?4h+SEs7qf+wQavAOgdbuCsFIDma0Yu6qjIu5PO/STgsEBy1/f62AMyUaepzH?=
 =?us-ascii?Q?X9HzEVticKoTq5pgjhGtUqM0q0KrRJEXss7D1g3jZHrPlFPWGEc5vUsfCtXN?=
 =?us-ascii?Q?AZPPmYd1dPXR4sgm5gr8Opk7yv5ld2mt6AIlHOhGq0t+nNH1dZKH5Mo/KjJB?=
 =?us-ascii?Q?IWvMFjXAijtRc4NnMYissZdac1AFxWNXrtugGpEBKEv3Mc6jmtruvN9S1uxZ?=
 =?us-ascii?Q?3DdI6TkIRjba2JdcElcXBuhe8B0hjv5Q1M5s4tSoWeIU06sscWMK79Dyizax?=
 =?us-ascii?Q?DO8Vt+pHuEHvCkc/S+oaGaQCqrF7udIjvHsDr5Ji3zzNOaxaprE+DJwfAKrm?=
 =?us-ascii?Q?TeHt9Yt6EVgKwea70P1TMinR3llO30C5KL9MHOepbcpn3jCHNDxKlyVfvH6q?=
 =?us-ascii?Q?96GAjeyRQhWb+5rcQ6nsd9vrXVBNVbtNh0I24uYO5WIOH6DIJJOWPXfCT/UO?=
 =?us-ascii?Q?GgGaInfHYzxnC01UYmR+ja/Rqu0C+CCCdaarLmO5UnujWAqu3IiED/wSGujl?=
 =?us-ascii?Q?+OWNRiqYs9FGhIsHkMx7RfmZUY6j5//a2m/h8pe7vi7Ry6JmMCr9aumnFoVD?=
 =?us-ascii?Q?8YivWLUk1C540Yzzm+mA22qjKkdq4gC7H24spTZ5RDj5yvaclY/v1zQuyeIY?=
 =?us-ascii?Q?7uDyzw1YHDJdninLDzIL2N2kMY7KxDimCG42/67r9QlMDYTr8B8wONUy7B1p?=
 =?us-ascii?Q?a0NZCEtI2uWCV5qwtEOnMg+t+dGAtIHAXdkqKNWhuGLi2e8wvBAvjc+dr99w?=
 =?us-ascii?Q?qq8jVdatpySdxd+A/NxNWzSJ+PsuO2Tuo4KJ+Ta5COw1EQhIz4wRlXJsee0Y?=
 =?us-ascii?Q?DCthCvyJ4Rd9YNvQChUYLEsKk3py6dQqU8I0ueVVzuhmnzx+Fvz4sA0pqfA+?=
 =?us-ascii?Q?kw7gAidXZVCFs5A0shVeeqxdOurdqHX7+pvJBJGntxTM+OuDOSeyICNsAfpw?=
 =?us-ascii?Q?CQDuwpyf00YVnU4i176RQa8Dwf81fVBW5lbFYSaxvAZLFntkj8wwfk3I5JNd?=
 =?us-ascii?Q?8OCJXDJ1KkY0dK2tOpF337A8R76GSpwpQ6Vri8+vTKuTBmrrhrCvr+OkXHLK?=
 =?us-ascii?Q?vs3BDZD2LXYG+Nn1/qvq2pN8Fzsbsilu37hC8INuNGKZDakgYEpxa3WaB950?=
 =?us-ascii?Q?wktjUnlchVzJzimuNqzYRhvCAgoC6lvMbQGPTNyqaCu/zRKc3jOj+7ShbU6p?=
 =?us-ascii?Q?joFxo82/F607VkV26L1L8O5K6wDTZbtOPDT+TJ1V?=
X-OriginatorOrg: nxp.com
X-MS-Exchange-CrossTenant-Network-Message-Id: 82fe9da7-675b-402e-6f96-08dbebd35b87
X-MS-Exchange-CrossTenant-AuthSource: DB8PR04MB7051.eurprd04.prod.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 23 Nov 2023 03:22:01.3904
 (UTC)
X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted
X-MS-Exchange-CrossTenant-Id: 686ea1d3-bc2b-4c6f-a92c-d99c5c301635
X-MS-Exchange-CrossTenant-MailboxType: HOSTED
X-MS-Exchange-CrossTenant-UserPrincipalName: PPWRV4A92i6j9E042ULirVTl0lJraLjgZ10gA/QFpqh2vb0Vjk8gIO7gH6wpncu/2366PtAxQDFm1fPB94e+nQ==
X-MS-Exchange-Transport-CrossTenantHeadersStamped: DBAPR04MB7429
X-Spam-Status: No, score=-2.1 required=5.0 tests=BAYES_00,DKIM_SIGNED,
        DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_NONE,
        RCVD_IN_MSPIKE_H2,SPF_HELO_PASS,SPF_PASS,T_SCC_BODY_TEXT_LINE,
        URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.6
X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on
        lindbergh.monkeyblade.net
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org
X-Greylist: Sender passed SPF test, not delayed by milter-greylist-4.6.4 (snail.vger.email [0.0.0.0]); Wed, 22 Nov 2023 19:22:11 -0800 (PST)

Some panel devices already depend on DRM device, like the panel in
arch/arm/boot/dts/st/ste-ux500-samsung-skomer.dts, because DRM device is
the ancestor of those panel devices.  device_link_add() would fail by
returning a NULL pointer for those panel devices because of the existing
dependency.  So, check the dependency by calling device_is_dependent()
before adding or deleting device link between panel device and DRM device
so that the link is managed only for independent panel devices.

Fixes: 887878014534 ("drm/bridge: panel: Fix device link for DRM_BRIDGE_ATTACH_NO_CONNECTOR")
Fixes: 199cf07ebd2b ("drm/bridge: panel: Add a device link between drm device and panel device")
Reported-by: Linus Walleij <linus.walleij@linaro.org>
Closes: https://lore.kernel.org/lkml/CACRpkdaGzXD6HbiX7mVUNJAJtMEPG00Pp6+nJ1P0JrfJ-ArMvQ@mail.gmail.com/T/
Tested-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Liu Ying <victor.liu@nxp.com>
---
 drivers/gpu/drm/bridge/panel.c | 27 ++++++++++++++++++---------
 1 file changed, 18 insertions(+), 9 deletions(-)

diff --git a/drivers/gpu/drm/bridge/panel.c b/drivers/gpu/drm/bridge/panel.c
index e48823a4f1ed..5e8980023407 100644
--- a/drivers/gpu/drm/bridge/panel.c
+++ b/drivers/gpu/drm/bridge/panel.c
@@ -23,6 +23,7 @@ struct panel_bridge {
 	struct drm_panel *panel;
 	struct device_link *link;
 	u32 connector_type;
+	bool is_independent;
 };
 
 static inline struct panel_bridge *
@@ -67,12 +68,17 @@ static int panel_bridge_attach(struct drm_bridge *bridge,
 	struct drm_device *drm_dev = bridge->dev;
 	int ret;
 
-	panel_bridge->link = device_link_add(drm_dev->dev, panel->dev,
-					     DL_FLAG_STATELESS);
-	if (!panel_bridge->link) {
-		DRM_ERROR("Failed to add device link between %s and %s\n",
-			  dev_name(drm_dev->dev), dev_name(panel->dev));
-		return -EINVAL;
+	panel_bridge->is_independent = !device_is_dependent(drm_dev->dev,
+							    panel->dev);
+
+	if (panel_bridge->is_independent) {
+		panel_bridge->link = device_link_add(drm_dev->dev, panel->dev,
+						     DL_FLAG_STATELESS);
+		if (!panel_bridge->link) {
+			DRM_ERROR("Failed to add device link between %s and %s\n",
+				  dev_name(drm_dev->dev), dev_name(panel->dev));
+			return -EINVAL;
+		}
 	}
 
 	if (flags & DRM_BRIDGE_ATTACH_NO_CONNECTOR)
@@ -80,7 +86,8 @@ static int panel_bridge_attach(struct drm_bridge *bridge,
 
 	if (!bridge->encoder) {
 		DRM_ERROR("Missing encoder\n");
-		device_link_del(panel_bridge->link);
+		if (panel_bridge->is_independent)
+			device_link_del(panel_bridge->link);
 		return -ENODEV;
 	}
 
@@ -92,7 +99,8 @@ static int panel_bridge_attach(struct drm_bridge *bridge,
 				 panel_bridge->connector_type);
 	if (ret) {
 		DRM_ERROR("Failed to initialize connector\n");
-		device_link_del(panel_bridge->link);
+		if (panel_bridge->is_independent)
+			device_link_del(panel_bridge->link);
 		return ret;
 	}
 
@@ -115,7 +123,8 @@ static void panel_bridge_detach(struct drm_bridge *bridge)
 	struct panel_bridge *panel_bridge = drm_bridge_to_panel_bridge(bridge);
 	struct drm_connector *connector = &panel_bridge->connector;
 
-	device_link_del(panel_bridge->link);
+	if (panel_bridge->is_independent)
+		device_link_del(panel_bridge->link);
 
 	/*
 	 * Cleanup the connector if we know it was initialized.
-- 
2.37.1