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Subject: Re: [PATCH v2 3/4] PM: domains: Drop/restore performance state votes
 for devices at runtime PM
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>
From:   Dmitry Osipenko <digetx@gmail.com>
Message-ID: <a7f55fce-dd4a-22ab-f7e2-4821e765a634@gmail.com>
Date:   Thu, 3 Jun 2021 22:02:59 +0300
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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.