[PATCH v2] clk: handle NULL args in clk_{g,s}et_parent()

[Bastian Krause]

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 at pengutronix.de>
---
Changes since (implicit) v1:
- make clk_get_parent(NULL) return NULL
- undo shifting call to clk_get_parent() in clk_set_parent()
---
 drivers/clk/clk.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index 8e317b4b05..52e309e877 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -232,6 +232,9 @@ int clk_set_parent(struct clk *clk, struct clk *newparent)
 	int i, ret;
 	struct clk *curparent = clk_get_parent(clk);
 
+	if (!clk || !newparent)
+		return 0;
+
 	if (IS_ERR(clk))
 		return PTR_ERR(clk);
 	if (IS_ERR(newparent))
@@ -287,7 +290,7 @@ struct clk *clk_get_parent(struct clk *clk)
 	struct clk_hw *hw;
 	int idx;
 
-	if (IS_ERR(clk))
+	if (IS_ERR_OR_NULL(clk))
 		return clk;
 
 	if (!clk->num_parents)
-- 
2.30.2