[PATCH 1/2] clk: sync of_clk_get_parent_name with upstream

[Ahmad Fatoum]

Upstream of_clk_get_parent_name only resorts to node name as a fallback.
Instead, it uses the name supplied for registered clocks whenever
possible. On the sama5d2, this results in sckc at f8048050 and slowck,
respectively. So far, sckc at f8048050 in the parents array couldn't be
matched with any existing clock, leading to an inaccurate clock tree.

Port over the v5.8-rc1 state of the function to fix this.

Signed-off-by: Ahmad Fatoum <a.fatoum at pengutronix.de>
---
 drivers/clk/clk.c   | 49 ++++++++++++++++++++++++++++++++++++++++-----
 include/linux/clk.h |  2 +-
 2 files changed, 45 insertions(+), 6 deletions(-)

diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index 4386c95aa9ec..f2e459a76018 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -469,21 +469,60 @@ unsigned int of_clk_get_parent_count(struct device_node *np)
 }
 EXPORT_SYMBOL_GPL(of_clk_get_parent_count);
 
-char *of_clk_get_parent_name(struct device_node *np, unsigned int index)
+char *of_clk_get_parent_name(const struct device_node *np, int index)
 {
 	struct of_phandle_args clkspec;
+	struct property *prop;
 	const char *clk_name;
+	const __be32 *vp;
+	u32 pv;
 	int rc;
+	int count;
+	struct clk *clk;
 
 	rc = of_parse_phandle_with_args(np, "clocks", "#clock-cells", index,
-			&clkspec);
+					&clkspec);
 	if (rc)
 		return NULL;
 
+	index = clkspec.args_count ? clkspec.args[0] : 0;
+	count = 0;
+
+	/* if there is an indices property, use it to transfer the index
+	 * specified into an array offset for the clock-output-names property.
+	 */
+	of_property_for_each_u32(clkspec.np, "clock-indices", prop, vp, pv) {
+		if (index == pv) {
+			index = count;
+			break;
+		}
+		count++;
+	}
+	/* We went off the end of 'clock-indices' without finding it */
+	if (prop && !vp)
+		return NULL;
+
 	if (of_property_read_string_index(clkspec.np, "clock-output-names",
-				clkspec.args_count ? clkspec.args[0] : 0,
-				&clk_name) < 0)
-		clk_name = clkspec.np->name;
+					  index,
+					  &clk_name) < 0) {
+		/*
+		 * Best effort to get the name if the clock has been
+		 * registered with the framework. If the clock isn't
+		 * registered, we return the node name as the name of
+		 * the clock as long as #clock-cells = 0.
+		 */
+		clk = of_clk_get_from_provider(&clkspec);
+		if (IS_ERR(clk)) {
+			if (clkspec.args_count == 0)
+				clk_name = clkspec.np->name;
+			else
+				clk_name = NULL;
+		} else {
+			clk_name = __clk_get_name(clk);
+			clk_put(clk);
+		}
+	}
+
 
 	return xstrdup(clk_name);
 }
diff --git a/include/linux/clk.h b/include/linux/clk.h
index a005e7233de8..d14d8b96a342 100644
--- a/include/linux/clk.h
+++ b/include/linux/clk.h
@@ -556,7 +556,7 @@ struct string_list;
 
 int clk_name_complete(struct string_list *sl, char *instr);
 
-char *of_clk_get_parent_name(struct device_node *np, unsigned int index);
+char *of_clk_get_parent_name(const struct device_node *np, int index);
 
 static inline void clk_unregister(struct clk *clk)
 {
-- 
2.27.0