of: call __of_parse_phandle_with_args from of_parse_phandle

The simplest case of __of_parse_phandle_with_args() now implements the
semantics of of_parse_phandle(). Rewrite of_parse_phandle() to call
__of_parse_phandle_with_args() rather than open-coding the simple case.

Optimize __of_parse_phandle_with_args() so that it doesn't call
of_find_node_by_phandle() except when it's strictly needed. This avoids
introducing too much overhead when replacing of_parse_phandle().
Signed-off-by: Stephen Warren <swarren@nvidia.com>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Grant Likely <grant.likely@linaro.org>

drivers/of/base.c

@@ -1111,14 +1111,21 @@ static int __of_parse_phandle_with_args(const struct device_node *np,
 		if (phandle) {
 			/*
 			 * Find the provider node and parse the #*-cells
-			 * property to determine the argument length
+			 * property to determine the argument length.
+			 *
+			 * This is not needed if the cell count is hard-coded
+			 * (i.e. cells_name not set, but cell_count is set),
+			 * except when we're going to return the found node
+			 * below.
 			 */
+			if (cells_name || cur_index == index) {
 				node = of_find_node_by_phandle(phandle);
 				if (!node) {
 					pr_err("%s: could not find phandle\n",
 						np->full_name);
 					goto err;
 				}
+			}
 
 			if (cells_name) {
 				if (of_property_read_u32(node, cells_name,
@@ -1202,14 +1209,16 @@ static int __of_parse_phandle_with_args(const struct device_node *np,
 struct device_node *of_parse_phandle(const struct device_node *np,
 				     const char *phandle_name, int index)
 {
-	const __be32 *phandle;
-	int size;
+	struct of_phandle_args args;
+
+	if (index < 0)
+		return NULL;
 
-	phandle = of_get_property(np, phandle_name, &size);
-	if ((!phandle) || (size < sizeof(*phandle) * (index + 1)))
+	if (__of_parse_phandle_with_args(np, phandle_name, NULL, 0,
+					 index, &args))
 		return NULL;
 
-	return of_find_node_by_phandle(be32_to_cpup(phandle + index));
+	return args.np;
 }
 EXPORT_SYMBOL(of_parse_phandle);