[PATCH] clk: Propagate clk_set_rate() if CLK_SET_PARENT_RATE present

[Sam Protsenko]

On Thu, Mar 7, 2024 at 6:04 PM Sam Protsenko <semen.protsenko at linaro.org> wrote:
>
> Sometimes clocks provided to a consumer might not have .set_rate
> operation (like gate or mux clocks), but have CLK_SET_PARENT_RATE flag
> set. In that case it's usually possible to find a parent up the tree
> which is capable of setting the rate (div, pll, etc). Implement a simple
> lookup procedure for such cases, to traverse the clock tree until
> .set_rate capable parent is found, and use that parent to actually
> change the rate. The search will stop once the first .set_rate capable
> clock is found, which is usually enough to handle most cases.
>
> Signed-off-by: Sam Protsenko <semen.protsenko at linaro.org>
> ---

Hi Lukasz, Sean, Tom,

If this patch looks good to you and there are no outstanding comments,
can you please apply it? It's needed as a part of eMMC enablement for
E850-96 board, as eMMC gate (leaf) clock is specified as ciu clock in
dts, which requires further clock rate change propagation up to
divider clock.

Thanks!

>  drivers/clk/clk-uclass.c | 16 ++++++++++++++--
>  1 file changed, 14 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/clk/clk-uclass.c b/drivers/clk/clk-uclass.c
> index ed6e60bc4841..755f05f34669 100644
> --- a/drivers/clk/clk-uclass.c
> +++ b/drivers/clk/clk-uclass.c
> @@ -571,8 +571,20 @@ ulong clk_set_rate(struct clk *clk, ulong rate)
>                 return 0;
>         ops = clk_dev_ops(clk->dev);
>
> -       if (!ops->set_rate)
> -               return -ENOSYS;
> +       /* Try to find parents which can set rate */
> +       while (!ops->set_rate) {
> +               struct clk *parent;
> +
> +               if (!(clk->flags & CLK_SET_RATE_PARENT))
> +                       return -ENOSYS;
> +
> +               parent = clk_get_parent(clk);
> +               if (IS_ERR_OR_NULL(parent) || !clk_valid(parent))
> +                       return -ENODEV;
> +
> +               clk = parent;
> +               ops = clk_dev_ops(clk->dev);
> +       }
>
>         /* get private clock struct used for cache */
>         clk_get_priv(clk, &clkp);
> --
> 2.39.2
>