clk: sync of_clk_get_parent_name with upstream

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@f8048050 and slowck,
respectively. So far, sckc@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@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

1 files changed, 44 insertions, 5 deletions

diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index 4386c95aa9..f2e459a760 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);
 }