clk: handle NULL args in clk_set_parent()

NULL struct clk pointers should be treated just as the Linux kernel clk
driver does [1]. The reasoning should also apply to the parent clk
argument.

A NULL struct clk pointer can happen for example on the Freescale i.MX6
SABRE Smart Device Board if CONFIG_DRIVER_VIDEO_IMX_IPUV3 is disabled,
leading to assigned-clocks IMX6QDL_CLK_LDB_DI0_SEL and
IMX6QDL_CLK_LDB_DI1_SEL [2] being unavailable. Without this patch, the
board hangs while setting those assigned clock configurations since [3].

[1] 89ac8d7ae1cd ("clk: handle NULL struct clk gracefully")
[2] dts/src/arm/imx6qdl-sabresd.dtsi
[3] f5eb5fddb4 ("clk: fix of clk set defaults when dev is a clk provider")

Signed-off-by: Bastian Krause <bst@pengutronix.de>
Link: https://lore.barebox.org/20220511100911.2009482-1-bst@pengutronix.de
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

1 files changed, 6 insertions, 1 deletions

diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index 8e317b4b05..efb5d4ad4a 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -230,7 +230,10 @@ int clk_set_parent(struct clk *clk, struct clk *newparent)
 {
 	struct clk_hw *hw;
 	int i, ret;
-	struct clk *curparent = clk_get_parent(clk);
+	struct clk *curparent;
+
+	if (!clk || !newparent)
+		return 0;
 
 	if (IS_ERR(clk))
 		return PTR_ERR(clk);
@@ -254,6 +257,8 @@ int clk_set_parent(struct clk *clk, struct clk *newparent)
 	if (i == clk->num_parents)
 		return -EINVAL;
 
+	curparent = clk_get_parent(clk);
+
 	if (clk->enable_count)
 		clk_enable(newparent);