drm/rockchip: analogix_dp: make panel detect to an optional action

Some boards don't need to declare a panel device node, like the
display interface is DP monitors, so it's necessary to make the
panel detect to an optional action.
Signed-off-by: Yakir Yang <ykk@rock-chips.com>
Acked-by: Mark Yao <mark.yao@rock-chips.com>
Reviewed-by: Tomasz Figa <tomasz.figa@chromium.com>
Reviewed-by: Sean Paul <seanpaul@chromium.org>

drivers/gpu/drm/rockchip/analogix_dp-rockchip.c

@@ -329,38 +329,33 @@ static int rockchip_dp_probe(struct platform_device *pdev)
 {
 	struct device *dev = &pdev->dev;
 	struct device_node *panel_node, *port, *endpoint;
+	struct drm_panel *panel = NULL;
 	struct rockchip_dp_device *dp;
-	struct drm_panel *panel;
 
 	port = of_graph_get_port_by_id(dev->of_node, 1);
-	if (!port) {
-		dev_err(dev, "can't find output port\n");
-		return -EINVAL;
-	}
-
-	endpoint = of_get_child_by_name(port, "endpoint");
-	of_node_put(port);
-	if (!endpoint) {
-		dev_err(dev, "no output endpoint found\n");
-		return -EINVAL;
-	}
-
-	panel_node = of_graph_get_remote_port_parent(endpoint);
-	of_node_put(endpoint);
-	if (!panel_node) {
-		dev_err(dev, "no output node found\n");
-		return -EINVAL;
-	}
-
-	panel = of_drm_find_panel(panel_node);
-	if (!panel) {
-		DRM_ERROR("failed to find panel\n");
+	if (port) {
+		endpoint = of_get_child_by_name(port, "endpoint");
+		of_node_put(port);
+		if (!endpoint) {
+			dev_err(dev, "no output endpoint found\n");
+			return -EINVAL;
+		}
+
+		panel_node = of_graph_get_remote_port_parent(endpoint);
+		of_node_put(endpoint);
+		if (!panel_node) {
+			dev_err(dev, "no output node found\n");
+			return -EINVAL;
+		}
+
+		panel = of_drm_find_panel(panel_node);
 		of_node_put(panel_node);
-		return -EPROBE_DEFER;
+		if (!panel) {
+			DRM_ERROR("failed to find panel\n");
+			return -EPROBE_DEFER;
+		}
 	}
 
-	of_node_put(panel_node);
-
 	dp = devm_kzalloc(dev, sizeof(*dp), GFP_KERNEL);
 	if (!dp)
 		return -ENOMEM;