linux-kernel - Re: [PATCH v5 3/3] PM / devfreq: Add required OPPs support to passive governor

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Date:   Thu, 4 Feb 2021 15:07:21 +0800
From:   Hsin-Yi Wang <hsinyi@...omium.org>
To:     Viresh Kumar <viresh.kumar@...aro.org>
Cc:     Viresh Kumar <vireshk@...nel.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        Nishanth Menon <nm@...com>, Stephen Boyd <sboyd@...nel.org>,
        "Rafael J . Wysocki" <rjw@...ysocki.net>,
        lkml <linux-kernel@...r.kernel.org>,
        "MyungJoo Ham )" <myungjoo.ham@...sung.com>,
        Kyungmin Park <kyungmin.park@...sung.com>,
        Chanwoo Choi <cw00.choi@...sung.com>,
        Saravana Kannan <saravanak@...gle.com>
Subject: Re: [PATCH v5 3/3] PM / devfreq: Add required OPPs support to passive governor

On Thu, Feb 4, 2021 at 10:49 AM Viresh Kumar <viresh.kumar@...aro.org> wrote:
>
> On 03-02-21, 17:24, Hsin-Yi Wang wrote:
> > From: Saravana Kannan <saravanak@...gle.com>
> >
> > 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>
> > Signed-off-by: Hsin-Yi Wang <hsinyi@...omium.org>
> > ---
> >  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 63332e4a65ae8..8d92b1964f9c3 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;
>
> I would initialize p_opp to ERR_PTR(-ENODEV) to avoid using
> IS_ERR_OR_NULL. There is no need to initialize opp as well.
>
> >       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;
>
> Perhaps just return from here, the goto is useless here.
>
> >       }
> >
> > -     dev_pm_opp_put(opp);
> > +     if (devfreq->opp_table && parent_devfreq->opp_table)
> > +             opp = dev_pm_opp_xlate_required_opp(parent_devfreq->opp_table,
> > +                                                 devfreq->opp_table, p_opp);
> > +     if (opp) {
>
> This needs to be part of the above if block itself, else the opp will
> always be NULL, isn't it ?
>
> > +             *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))
>
> you should be checking for p_opp here, isn't it ? And perhaps we don't
> need this check as well as p_opp can't be invalid here.
>
> > +             dev_pm_opp_put(p_opp);
> > +
> >       return ret;
> >  }
> >
> > --
> > 2.30.0.365.g02bc693789-goog
>
Thanks for the review. I'll fix them and send next version

> --
> viresh