drivers: gpu: drm: cix: Fixed potential NULL pointer issue.

This issue was caused by interface changes introduced by upstream:
9880702

Signed-off-by: Guomin.chen <Guomin.chen@cixtech.com>

Author: Guomin.chen

drivers/gpu/drm/cix/dptx/trilin_dptx_cix.c

@@ -95,7 +95,7 @@ static uint32_t drm_acpi_crtc_port_mask(struct drm_device *dev,
 	return 0;
 }
 
-static uint32_t drm_acpi_find_possible_crtcs(struct drm_device *dev,
+static uint32_t __maybe_unused drm_acpi_find_possible_crtcs(struct drm_device *dev,
 					     struct fwnode_handle *port)
 {
 	struct fwnode_handle *remote_port, *ep;
@@ -133,7 +133,7 @@ static int trilin_dptx_cix_bind(struct device *comp, struct device *master,
 	encoder = &cix_dptx->encoder;
 	if (has_acpi_companion(comp)) {
 		np = comp->fwnode;
-		encoder->possible_crtcs = drm_acpi_find_possible_crtcs(drm, np);
+		encoder->possible_crtcs = 0x3; // always port@0,port@1 possible
 	} else {
 		np = comp->of_node;
 		encoder->possible_crtcs = drm_of_find_possible_crtcs(drm, np);

drivers/gpu/drm/cix/linlon-dp/linlondp_dev.c

@@ -26,6 +26,7 @@ fwnode_graph_get_remote_node(const struct fwnode_handle *fwnode, u32 port_id,
 			     u32 endpoint_id)
 {
 	struct fwnode_handle *endpoint = NULL;
+	struct fwnode_reference_args args;
 
 	while ((endpoint = fwnode_graph_get_next_endpoint(fwnode, endpoint))) {
 		struct fwnode_endpoint fwnode_ep;
@@ -39,10 +40,17 @@ fwnode_graph_get_remote_node(const struct fwnode_handle *fwnode, u32 port_id,
 		if (fwnode_ep.port != port_id || fwnode_ep.id != endpoint_id)
 			continue;
 
+		memset(&args, 0, sizeof(args));
+		ret = acpi_node_get_property_reference(endpoint, "remote-endpoint", 0, &args);
+		if (!ret && is_acpi_device_node(args.fwnode)) {
+			pr_info("%s:%d get remote-endpoint device %s\n", __func__, __LINE__,
+					dev_name(&to_acpi_device_node(args.fwnode)->dev));
+			return args.fwnode;
+		}
+
 		remote = fwnode_graph_get_remote_port_parent(endpoint);
 		if (!remote)
 			return NULL;
-
 		return fwnode_device_is_available(remote) ? remote : NULL;
 	}
 

drivers/gpu/drm/cix/linlon-dp/linlondp_drv.c

@@ -190,7 +190,10 @@ static int linlondp_platform_probe(struct platform_device *pdev)
 					   LINLONDP_OF_PORT_OUTPUT, 1);
 		}
 	}
-	pr_info("%s end. match=%p\n", __func__, match);
+	if (!match) {
+		pr_err("%s end. add slave component_match failed!\n", __func__);
+		return -EINVAL;
+	}
 	return component_master_add_with_match(dev, &linlondp_master_ops,
 					       match);
 #else