linux-kernel - Re: [PATCH v3 05/12] opp: Add dev_pm_opp_set

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Date:   Thu, 21 Jan 2021 00:57:04 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Viresh Kumar <viresh.kumar@...aro.org>
Cc:     Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Mark Brown <broonie@...nel.org>,
        Liam Girdwood <lgirdwood@...il.com>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Peter Geis <pgwipeout@...il.com>,
        Nicolas Chauvet <kwizart@...il.com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Kevin Hilman <khilman@...nel.org>,
        Peter De Schrijver <pdeschrijver@...dia.com>,
        Viresh Kumar <vireshk@...nel.org>,
        Stephen Boyd <sboyd@...nel.org>, Nishanth Menon <nm@...com>,
        Yangtao Li <tiny.windzz@...il.com>,
        Matt Merhar <mattmerhar@...tonmail.com>,
        linux-kernel@...r.kernel.org, linux-tegra@...r.kernel.org,
        linux-pm@...r.kernel.org
Subject: Re: [PATCH v3 05/12] opp: Add dev_pm_opp_set_voltage()

18.01.2021 22:14, Dmitry Osipenko пишет:
> 18.01.2021 12:52, Viresh Kumar пишет:
>> On 18-01-21, 03:55, Dmitry Osipenko wrote:
>>> diff --git a/drivers/opp/core.c b/drivers/opp/core.c
>>> index 99d18befc209..341484d58e6c 100644
>>> --- a/drivers/opp/core.c
>>> +++ b/drivers/opp/core.c
>>> @@ -2731,3 +2731,58 @@ int dev_pm_opp_sync_regulators(struct device *dev)
>>>  	return ret;
>>>  }
>>>  EXPORT_SYMBOL_GPL(dev_pm_opp_sync_regulators);
>>> +
>>> +/**
>>> + * dev_pm_opp_set_voltage() - Change voltage of regulators
>>> + * @dev:	device for which we do this operation
>>> + * @opp:	opp based on which the voltages are to be configured
>>> + *
>>> + * Change voltage of the OPP table regulators.
>>> + *
>>> + * Return: 0 on success or a negative error value.
>>> + */
>>> +int dev_pm_opp_set_voltage(struct device *dev, struct dev_pm_opp *opp)
>>
>> I think we should do better than this, will require some work from
>> your part though (or I can do it if you want).
>>
>> Basically what you wanted to do here is set the OPP for a device and
>> this means do whatever is required for setting the OPP. It is normally
>> frequency, which is not your case, but it is other things as well.
>> Like setting multiple regulators, bandwidth, required-opps, etc.
>>
>> I feel the right way of doing this would be to do this:
>>
>> Factor out dev_pm_opp_set_opp() from dev_pm_opp_set_rate() and make
>> the later call the former. And then we can just call
>> dev_pm_opp_set_opp() from your usecase. This will make sure we have a
>> single code path for all the set-opp stuff. What do you think ?
>>
> 
> Sounds like it could be a lot of code moving and some extra complexity
> will be added to the code. If nobody will ever need the universal
> dev_pm_opp_set_opp(), then it could become a wasted effort. I'd choose
> the easiest path, i.e. to defer the dev_pm_opp_set_opp() implementation
> until somebody will really need it.
> 
> But if it looks to you that it won't be a too much effort, then I'll
> appreciate if you could type the patch.
> 

Let's start with dev_pm_opp_set_voltage() for now. It shouldn't be a
problem at all to upgrade it to dev_pm_opp_set_opp() later on.

I'll make a v4 with the dev_pm_opp_set_voltage(), please let me know if
you have objections or more suggestions!