drm/etnaviv: Add a helper to get the first available GPU device node

This patch make the code in the etnaviv_pdev_probe() less twisted, and it
also make it easier to drop the reference to device node after finished.
Before apply this patch, there is no call to of_node_put() when done. We
should call of_node_put() when done.
Signed-off-by: Sui Jingfeng <suijingfeng@loongson.cn>
Signed-off-by: Lucas Stach <l.stach@pengutronix.de>

drivers/gpu/drm/etnaviv/etnaviv_drv.c

@@ -29,6 +29,17 @@
  * DRM operations:
  */
 
+static struct device_node *etnaviv_of_first_available_node(void)
+{
+	struct device_node *np;
+
+	for_each_compatible_node(np, NULL, "vivante,gc") {
+		if (of_device_is_available(np))
+			return np;
+	}
+
+	return NULL;
+}
 
 static void load_gpu(struct drm_device *dev)
 {
@@ -597,9 +608,6 @@ static int etnaviv_pdev_probe(struct platform_device *pdev)
 			if (!of_device_is_available(core_node))
 				continue;
 
-			if (!first_node)
-				first_node = core_node;
-
 			drm_of_component_match_add(&pdev->dev, &match,
 						   component_compare_of, core_node);
 		}
@@ -634,8 +642,11 @@ static int etnaviv_pdev_probe(struct platform_device *pdev)
 	 * device as the GPU we found. This assumes that all Vivante
 	 * GPUs in the system share the same DMA constraints.
 	 */
-	if (first_node)
+	first_node = etnaviv_of_first_available_node();
+	if (first_node) {
 		of_dma_configure(&pdev->dev, first_node, true);
+		of_node_put(first_node);
+	}
 
 	return component_master_add_with_match(dev, &etnaviv_master_ops, match);
 }
@@ -709,16 +720,13 @@ static int __init etnaviv_init(void)
 	 * If the DT contains at least one available GPU device, instantiate
 	 * the DRM platform device.
 	 */
-	for_each_compatible_node(np, NULL, "vivante,gc") {
-		if (!of_device_is_available(np))
-			continue;
+	np = etnaviv_of_first_available_node();
+	if (np) {
 		of_node_put(np);
 
 		ret = etnaviv_create_platform_device("etnaviv", &etnaviv_drm);
 		if (ret)
 			goto unregister_platform_driver;
-
-		break;
 	}
 
 	return 0;