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

[Yang Xiwen]

On 3/20/2024 2:42 AM, Sam Protsenko wrote:
> 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!


Please be patient. The release cycle is quite long. My patch set for 
HiSilicon clk framework has been ignored for ~2months already.


>
>>   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
>>

-- 
Regards,
Yang Xiwen