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

[Ahmad Fatoum]

On 11.05.22 14:31, Bastian Krause wrote:
> 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>

Reviewed-by: Ahmad Fatoum <a.fatoum 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)


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