drm: bridge: simple-bridge: Delegate operations to next bridge

Instead of poking into the DT node of the next bridge for its DDC bus
and implementing the .get_modes() and .detect() connector operations
manually, retrieve the next bridge in the chain and delegate these
operations to it.
Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20200526011505.31884-7-laurent.pinchart+renesas@ideasonboard.com

drivers/gpu/drm/bridge/simple-bridge.c

@@ -29,7 +29,7 @@ struct simple_bridge {
 
 	const struct simple_bridge_info *info;
 
-	struct i2c_adapter	*ddc;
+	struct drm_bridge	*next_bridge;
 	struct regulator	*vdd;
 	struct gpio_desc	*enable;
 };
@@ -52,29 +52,28 @@ static int simple_bridge_get_modes(struct drm_connector *connector)
 	struct edid *edid;
 	int ret;
 
-	if (!sbridge->ddc)
-		goto fallback;
+	if (sbridge->next_bridge->ops & DRM_BRIDGE_OP_EDID) {
+		edid = drm_bridge_get_edid(sbridge->next_bridge, connector);
+		if (!edid)
+			DRM_INFO("EDID read failed. Fallback to standard modes\n");
+	} else {
+		edid = NULL;
+	}
 
-	edid = drm_get_edid(connector, sbridge->ddc);
 	if (!edid) {
-		DRM_INFO("EDID readout failed, falling back to standard modes\n");
-		goto fallback;
+		/*
+		 * In case we cannot retrieve the EDIDs (missing or broken DDC
+		 * bus from the next bridge), fallback on the XGA standards and
+		 * prefer a mode pretty much anyone can handle.
+		 */
+		ret = drm_add_modes_noedid(connector, 1920, 1200);
+		drm_set_preferred_mode(connector, 1024, 768);
+		return ret;
 	}
 
 	drm_connector_update_edid_property(connector, edid);
 	ret = drm_add_edid_modes(connector, edid);
 	kfree(edid);
-	return ret;
-
-fallback:
-	/*
-	 * In case we cannot retrieve the EDIDs (broken or missing i2c
-	 * bus), fallback on the XGA standards
-	 */
-	ret = drm_add_modes_noedid(connector, 1920, 1200);
-
-	/* And prefer a mode pretty much anyone can handle */
-	drm_set_preferred_mode(connector, 1024, 768);
 
 	return ret;
 }
@@ -88,16 +87,7 @@ simple_bridge_connector_detect(struct drm_connector *connector, bool force)
 {
 	struct simple_bridge *sbridge = drm_connector_to_simple_bridge(connector);
 
-	/*
-	 * Even if we have an I2C bus, we can't assume that the cable
-	 * is disconnected if drm_probe_ddc fails. Some cables don't
-	 * wire the DDC pins, or the I2C bus might not be working at
-	 * all.
-	 */
-	if (sbridge->ddc && drm_probe_ddc(sbridge->ddc))
-		return connector_status_connected;
-
-	return connector_status_unknown;
+	return drm_bridge_detect(sbridge->next_bridge);
 }
 
 static const struct drm_connector_funcs simple_bridge_con_funcs = {
@@ -120,6 +110,11 @@ static int simple_bridge_attach(struct drm_bridge *bridge,
 		return -EINVAL;
 	}
 
+	ret = drm_bridge_attach(bridge->encoder, sbridge->next_bridge, bridge,
+				DRM_BRIDGE_ATTACH_NO_CONNECTOR);
+	if (ret < 0)
+		return ret;
+
 	if (!bridge->encoder) {
 		DRM_ERROR("Missing encoder\n");
 		return -ENODEV;
@@ -130,7 +125,7 @@ static int simple_bridge_attach(struct drm_bridge *bridge,
 	ret = drm_connector_init_with_ddc(bridge->dev, &sbridge->connector,
 					  &simple_bridge_con_funcs,
 					  sbridge->info->connector_type,
-					  sbridge->ddc);
+					  sbridge->next_bridge->ddc);
 	if (ret) {
 		DRM_ERROR("Failed to initialize connector\n");
 		return ret;
@@ -172,31 +167,10 @@ static const struct drm_bridge_funcs simple_bridge_bridge_funcs = {
 	.disable	= simple_bridge_disable,
 };
 
-static struct i2c_adapter *simple_bridge_retrieve_ddc(struct device *dev)
-{
-	struct device_node *phandle, *remote;
-	struct i2c_adapter *ddc;
-
-	remote = of_graph_get_remote_node(dev->of_node, 1, -1);
-	if (!remote)
-		return ERR_PTR(-EINVAL);
-
-	phandle = of_parse_phandle(remote, "ddc-i2c-bus", 0);
-	of_node_put(remote);
-	if (!phandle)
-		return ERR_PTR(-ENODEV);
-
-	ddc = of_get_i2c_adapter_by_node(phandle);
-	of_node_put(phandle);
-	if (!ddc)
-		return ERR_PTR(-EPROBE_DEFER);
-
-	return ddc;
-}
-
 static int simple_bridge_probe(struct platform_device *pdev)
 {
 	struct simple_bridge *sbridge;
+	struct device_node *remote;
 
 	sbridge = devm_kzalloc(&pdev->dev, sizeof(*sbridge), GFP_KERNEL);
 	if (!sbridge)
@@ -205,6 +179,20 @@ static int simple_bridge_probe(struct platform_device *pdev)
 
 	sbridge->info = of_device_get_match_data(&pdev->dev);
 
+	/* Get the next bridge in the pipeline. */
+	remote = of_graph_get_remote_node(pdev->dev.of_node, 1, -1);
+	if (!remote)
+		return -EINVAL;
+
+	sbridge->next_bridge = of_drm_find_bridge(remote);
+	of_node_put(remote);
+
+	if (!sbridge->next_bridge) {
+		dev_dbg(&pdev->dev, "Next bridge not found, deferring probe\n");
+		return -EPROBE_DEFER;
+	}
+
+	/* Get the regulator and GPIO resources. */
 	sbridge->vdd = devm_regulator_get_optional(&pdev->dev, "vdd");
 	if (IS_ERR(sbridge->vdd)) {
 		int ret = PTR_ERR(sbridge->vdd);
@@ -222,18 +210,7 @@ static int simple_bridge_probe(struct platform_device *pdev)
 		return PTR_ERR(sbridge->enable);
 	}
 
-	sbridge->ddc = simple_bridge_retrieve_ddc(&pdev->dev);
-	if (IS_ERR(sbridge->ddc)) {
-		if (PTR_ERR(sbridge->ddc) == -ENODEV) {
-			dev_dbg(&pdev->dev,
-				"No i2c bus specified. Disabling EDID readout\n");
-			sbridge->ddc = NULL;
-		} else {
-			dev_err(&pdev->dev, "Couldn't retrieve i2c bus\n");
-			return PTR_ERR(sbridge->ddc);
-		}
-	}
-
+	/* Register the bridge. */
 	sbridge->bridge.funcs = &simple_bridge_bridge_funcs;
 	sbridge->bridge.of_node = pdev->dev.of_node;
 	sbridge->bridge.timings = sbridge->info->timings;
@@ -249,9 +226,6 @@ static int simple_bridge_remove(struct platform_device *pdev)
 
 	drm_bridge_remove(&sbridge->bridge);
 
-	if (sbridge->ddc)
-		i2c_put_adapter(sbridge->ddc);
-
 	return 0;
 }