linux-kernel - Re: [PATCH v2 3/4] PM: domains: Drop/restore performance state votes for devices at runtime PM

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Date:   Fri, 4 Jun 2021 09:20:33 +0200
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     Dmitry Osipenko <digetx@...il.com>
Cc:     "Rafael J . Wysocki" <rjw@...ysocki.net>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Thierry Reding <thierry.reding@...il.com>,
        Rajendra Nayak <rnayak@...eaurora.org>,
        Stephan Gerhold <stephan@...hold.net>,
        Roja Rani Yarubandi <rojay@...eaurora.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Stephen Boyd <sboyd@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 3/4] PM: domains: Drop/restore performance state votes
 for devices at runtime PM

On Thu, 3 Jun 2021 at 21:08, Dmitry Osipenko <digetx@...il.com> wrote:
>
> 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@...aro.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@...il.com>

Thanks a lot, much appreciated!

Kind regards
Uffe