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Subject: Re: [PATCH v2 3/4] PM: domains: Drop/restore performance state votes
 for devices at runtime PM
From:   Dmitry Osipenko <digetx@gmail.com>
To:     Ulf Hansson <ulf.hansson@linaro.org>,
        "Rafael J . Wysocki" <rjw@rjwysocki.net>,
        Viresh Kumar <viresh.kumar@linaro.org>,
        linux-pm@vger.kernel.org
Cc:     Jonathan Hunter <jonathanh@nvidia.com>,
        Thierry Reding <thierry.reding@gmail.com>,
        Rajendra Nayak <rnayak@codeaurora.org>,
        Stephan Gerhold <stephan@gerhold.net>,
        Roja Rani Yarubandi <rojay@codeaurora.org>,
        Bjorn Andersson <bjorn.andersson@linaro.org>,
        Vincent Guittot <vincent.guittot@linaro.org>,
        Stephen Boyd <sboyd@kernel.org>, linux-kernel@vger.kernel.org
References: <20210603093438.138705-1-ulf.hansson@linaro.org>
 <20210603093438.138705-4-ulf.hansson@linaro.org>
 <a7f55fce-dd4a-22ab-f7e2-4821e765a634@gmail.com>
Message-ID: <1f71868c-7274-b4f8-e66d-dfb47cf44731@gmail.com>
Date:   Thu, 3 Jun 2021 22:08:43 +0300
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03.06.2021 22:02, Dmitry Osipenko пишет:
> 03.06.2021 12:34, Ulf Hansson пишет:
>> A subsystem/driver that need to manage OPPs for its device, should
>> typically drop its vote for the OPP when the device becomes runtime
>> suspended. In this way, the corresponding aggregation of the performance
>> state votes that is managed in genpd for the attached PM domain, may find
>> that the aggregated vote can be decreased. Hence, it may allow genpd to set
>> the lower performance state for the PM domain, thus avoiding to waste
>> energy.
>>
>> To accomplish this, typically a subsystem/driver would need to call
>> dev_pm_opp_set_rate|opp() for its device from its ->runtime_suspend()
>> callback, to drop the vote for the OPP. Accordingly, it needs another call
>> to dev_pm_opp_set_rate|opp() to restore the vote for the OPP from its
>> ->runtime_resume() callback.
>>
>> To avoid boilerplate code in subsystems/driver to deal with these things,
>> let's instead manage this internally in genpd.
>>
>> Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
>> ---
>>
>> Changes in v2:
>> 	- Rebased.
>> 	- A few minor cosmetic changes.
>> 	- Deal with the error path in genpd_runtime_resume().
> 
> I tested this on NVIDIA Tegra by removing the boilerplate code from
> drivers' RPM and haven't noticed any problems, the performance state is
> dropped/restored as expected. Thank you.
> 

Tested-by: Dmitry Osipenko <digetx@gmail.com>