drm/msm: Add display components by parsing MDP ports

The kms driver currently identifies all the mdss components it needs by
parsing a phandle list from the 'connectors' DT property.

Instead of this, describe a list of ports that the MDP hardware provides
to the external world. These ports are linked to external encoder
interfaces such as DSI, HDMI. These are also the subcomponent devices
that we need add. This description of ports complies with the generic
graph bindings.

The LVDS port is a special case since it is a part of MDP4 itself, and
its output connects directly to the LVDS panel. In this case, we don't
try to add it as a component.
Signed-off-by: Archit Taneja <architt@codeaurora.org>
Signed-off-by: Rob Clark <robdclark@gmail.com>

drivers/gpu/drm/msm/msm_drv.c

@@ -823,10 +823,64 @@ static int add_components(struct device *dev, struct component_match **matchptr,
 	return 0;
 }
 
+/*
+ * Identify what components need to be added by parsing what remote-endpoints
+ * our MDP output ports are connected to. In the case of LVDS on MDP4, there
+ * is no external component that we need to add since LVDS is within MDP4
+ * itself.
+ */
+static int add_components_mdp(struct device *mdp_dev,
+			      struct component_match **matchptr)
+{
+	struct device_node *np = mdp_dev->of_node;
+	struct device_node *ep_node;
+
+	for_each_endpoint_of_node(np, ep_node) {
+		struct device_node *intf;
+		struct of_endpoint ep;
+		int ret;
+
+		ret = of_graph_parse_endpoint(ep_node, &ep);
+		if (ret) {
+			dev_err(mdp_dev, "unable to parse port endpoint\n");
+			of_node_put(ep_node);
+			return ret;
+		}
+
+		/*
+		 * The LCDC/LVDS port on MDP4 is a speacial case where the
+		 * remote-endpoint isn't a component that we need to add
+		 */
+		if (of_device_is_compatible(np, "qcom,mdp4") &&
+		    ep.port == 0) {
+			of_node_put(ep_node);
+			continue;
+		}
+
+		/*
+		 * It's okay if some of the ports don't have a remote endpoint
+		 * specified. It just means that the port isn't connected to
+		 * any external interface.
+		 */
+		intf = of_graph_get_remote_port_parent(ep_node);
+		if (!intf) {
+			of_node_put(ep_node);
+			continue;
+		}
+
+		component_match_add(mdp_dev, matchptr, compare_of, intf);
+
+		of_node_put(intf);
+		of_node_put(ep_node);
+	}
+
+	return 0;
+}
+
 static int add_display_components(struct device *dev,
 				  struct component_match **matchptr)
 {
-	return add_components(dev, matchptr, "connectors");
+	return add_components_mdp(dev, matchptr);
 }
 
 static int add_gpu_components(struct device *dev,