Re: [PATCH V4 01/14] dt-bindings: cpufreq: mediatek: Add MediaTek CCI property

[Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>]

On 25/04/2022 12:20, Rex-BC Chen wrote:
>> However I am not sure if you solved your problem... see below:
>>
>>> For example:
>>> mediatek cci set 1.2V originally. When cpufreq want to adjust lower
>>> frequency adn set voltage to 1.0V.
>>> The framework will remain using 1.2V to prevent crash of mediatek
>>> cci.
>>
>> No, regulator_set_voltage() for proc_reg says:
>> "NOTE: If the regulator is shared between several devices then the
>> lowest
>>  request voltage that meets the system constraints will be used."
>>
>> Not the highest. So when your devfreq and cpufreq boots, calling
>> regulator_set_voltage will still cause high frequency and low
>> voltage.
>>
> 
> From the driver comment, I think it still needs to match "meets the
> system constraints".
> 
> From drivers, we can trace the driver and it finally to
> regulator_get_optimal_voltage().
> In [1], the framework will get max voltage while finding each device's
> voltage.
> 
> [1]: 
> https://elixir.bootlin.com/linux/latest/source/drivers/regulator/core.c#L3815

Right, actually in your case it's the regulator_check_consumers() above
that line, because you

I think it's quite generic problem, so would be worth solving for more
regulator consumers, but your approach is fine. At least I do not have
anything smarter, at the moment.

Best regards,
Krzysztof