linux-kernel - Re: [PATCH v3 5/5] PM / devfreq: Add required OPPs support to passive governor

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Message-ID: <CAGETcx89X0Xra+3HK+jbuCHXMgRL7QCwSShyMy7DY2Bg1eVjDQ@mail.gmail.com>
Date:   Tue, 23 Jul 2019 17:26:30 -0700
From:   Saravana Kannan <saravanak@...gle.com>
To:     Viresh Kumar <viresh.kumar@...aro.org>
Cc:     MyungJoo Ham <myungjoo.ham@...sung.com>,
        Kyungmin Park <kyungmin.park@...sung.com>,
        Chanwoo Choi <cw00.choi@...sung.com>,
        Viresh Kumar <vireshk@...nel.org>, Nishanth Menon <nm@...com>,
        Stephen Boyd <sboyd@...nel.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Sibi Sankar <sibis@...eaurora.org>,
        Android Kernel Team <kernel-team@...roid.com>,
        Linux PM <linux-pm@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 5/5] PM / devfreq: Add required OPPs support to passive governor

On Tue, Jul 23, 2019 at 3:04 AM Viresh Kumar <viresh.kumar@...aro.org> wrote:
>
> On 17-07-19, 15:23, Saravana Kannan wrote:
> > Look at the required OPPs of the "parent" device to determine the OPP that
> > is required from the slave device managed by the passive governor. This
> > allows having mappings between a parent device and a slave device even when
> > they don't have the same number of OPPs.
> >
> > Signed-off-by: Saravana Kannan <saravanak@...gle.com>
> > Acked-by: MyungJoo Ham <myungjoo.ham@...sung.com>
> > Acked-by: Chanwoo Choi <cw00.choi@...sung.com>
> > ---
> >  drivers/devfreq/governor_passive.c | 20 +++++++++++++++-----
> >  1 file changed, 15 insertions(+), 5 deletions(-)
> >
> > diff --git a/drivers/devfreq/governor_passive.c b/drivers/devfreq/governor_passive.c
> > index 58308948b863..24ce94c80f06 100644
> > --- a/drivers/devfreq/governor_passive.c
> > +++ b/drivers/devfreq/governor_passive.c
> > @@ -19,7 +19,7 @@ static int devfreq_passive_get_target_freq(struct devfreq *devfreq,
> >                       = (struct devfreq_passive_data *)devfreq->data;
> >       struct devfreq *parent_devfreq = (struct devfreq *)p_data->parent;
> >       unsigned long child_freq = ULONG_MAX;
> > -     struct dev_pm_opp *opp;
> > +     struct dev_pm_opp *opp = NULL, *p_opp = NULL;
>
> This won't be required if ...
>
> >       int i, count, ret = 0;
> >
> >       /*
> > @@ -56,13 +56,20 @@ static int devfreq_passive_get_target_freq(struct devfreq *devfreq,
> >        * list of parent device. Because in this case, *freq is temporary
> >        * value which is decided by ondemand governor.
> >        */
> > -     opp = devfreq_recommended_opp(parent_devfreq->dev.parent, freq, 0);
> > -     if (IS_ERR(opp)) {
> > -             ret = PTR_ERR(opp);
> > +     p_opp = devfreq_recommended_opp(parent_devfreq->dev.parent, freq, 0);
> > +     if (IS_ERR(p_opp)) {
> > +             ret = PTR_ERR(p_opp);
> >               goto out;
> >       }
> >
> > -     dev_pm_opp_put(opp);
> > +     if (devfreq->opp_table && parent_devfreq->opp_table)
> > +             opp = dev_pm_opp_xlate_opp(parent_devfreq->opp_table,
> > +                                        devfreq->opp_table, p_opp);
>
> you put p_opp right here.
>
> Also shouldn't you try to get p_opp under the above if block only? As
> that is the only user of it ?

No, p_opp (used to be called opp) was used even before my changes. If
there's no required-opps mapping this falls back to assuming the slave
device OPP to pick should be the same index as the master device's
opp.

So I believe this patch is correct as-is.

-Saravana

>
> > +     if (opp) {
> > +             *freq = dev_pm_opp_get_freq(opp);
> > +             dev_pm_opp_put(opp);
> > +             goto out;
> > +     }
> >
> >       /*
> >        * Get the OPP table's index of decided freqeuncy by governor
> > @@ -89,6 +96,9 @@ static int devfreq_passive_get_target_freq(struct devfreq *devfreq,
> >       *freq = child_freq;
> >
> >  out:
> > +     if (!IS_ERR_OR_NULL(opp))
> > +             dev_pm_opp_put(p_opp);
> > +
> >       return ret;
> >  }
> >
> > --
> > 2.22.0.510.g264f2c817a-goog
>
> --
> viresh