Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
MIME-Version: 1.0
References: <20210603093438.138705-1-ulf.hansson@linaro.org>
 <20210603093438.138705-4-ulf.hansson@linaro.org> <a7f55fce-dd4a-22ab-f7e2-4821e765a634@gmail.com>
 <1f71868c-7274-b4f8-e66d-dfb47cf44731@gmail.com>
In-Reply-To: <1f71868c-7274-b4f8-e66d-dfb47cf44731@gmail.com>
From:   Ulf Hansson <ulf.hansson@linaro.org>
Date:   Fri, 4 Jun 2021 09:20:33 +0200
Message-ID: <CAPDyKFrLcVQQ4pH3wyjCu8Ysjr6=Bjjd=WDwTiOagAZe2ohWMQ@mail.gmail.com>
Subject: Re: [PATCH v2 3/4] PM: domains: Drop/restore performance state votes
 for devices at runtime PM
To:     Dmitry Osipenko <digetx@gmail.com>
Cc:     "Rafael J . Wysocki" <rjw@rjwysocki.net>,
        Viresh Kumar <viresh.kumar@linaro.org>,
        Linux PM <linux-pm@vger.kernel.org>,
        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 Mailing List <linux-kernel@vger.kernel.org>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
Precedence: bulk

On Thu, 3 Jun 2021 at 21:08, Dmitry Osipenko <digetx@gmail.com> wrote:
>
> 03.06.2021 22:02, Dmitry Osipenko =D0=BF=D0=B8=D1=88=D0=B5=D1=82:
> > 03.06.2021 12:34, Ulf Hansson =D0=BF=D0=B8=D1=88=D0=B5=D1=82:
> >> 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 performan=
ce
> >> state votes that is managed in genpd for the attached PM domain, may f=
ind
> >> that the aggregated vote can be decreased. Hence, it may allow genpd t=
o 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 thin=
gs,
> >> 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>

Thanks a lot, much appreciated!

Kind regards
Uffe