[PATCH] clk: handle NULL args in clk_set_parent()

[Ahmad Fatoum]

Hello Bastian,

On 11.05.22 12:09, 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")

Thanks for your patch.

> 
> Signed-off-by: Bastian Krause <bst at pengutronix.de>
> ---
>  drivers/clk/clk.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> 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);

Linux clk_get_parent returns NULL if clk is NULL.
Can you teach barebox to do the same?

Linux clk_set_parent accepts a NULL parent to add a clock
to the orphan list. We don't seem to maintain an orphan
list in barebox, so early exist with return value zero
seems okay.

> +	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);
> +

With early-exiting clk_get_parent, you won't need to shift this code around.

Cheers,
Ahmad

>  	if (clk->enable_count)
>  		clk_enable(newparent);
>  


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