linux-kernel - Re: [PATCH v3 2/5] OPP: Add function to look up required OPP's for a given OPP

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Date:   Thu, 25 Jul 2019 08:28:49 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Saravana Kannan <saravanak@...gle.com>
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 2/5] OPP: Add function to look up required OPP's for a
 given OPP

On 23-07-19, 17:23, Saravana Kannan wrote:
> On Tue, Jul 23, 2019 at 2:53 AM Viresh Kumar <viresh.kumar@...aro.org> wrote:
> >
> > On 17-07-19, 15:23, Saravana Kannan wrote:
> > > Add a function that allows looking up required OPPs given a source OPP
> > > table, destination OPP table and the source OPP.
> > >
> > > Signed-off-by: Saravana Kannan <saravanak@...gle.com>
> > > ---
> > >  drivers/opp/core.c     | 54 ++++++++++++++++++++++++++++++++++++++++++
> > >  include/linux/pm_opp.h | 11 +++++++++
> > >  2 files changed, 65 insertions(+)
> > >
> > > diff --git a/drivers/opp/core.c b/drivers/opp/core.c
> > > index 438fcd134d93..72c055a3f6b7 100644
> > > --- a/drivers/opp/core.c
> > > +++ b/drivers/opp/core.c
> > > @@ -1883,6 +1883,60 @@ void dev_pm_opp_detach_genpd(struct opp_table *opp_table)
> > >  }
> > >  EXPORT_SYMBOL_GPL(dev_pm_opp_detach_genpd);
> > >
> > > +/**
> > > + * dev_pm_opp_xlate_opp() - Find required OPP for src_table OPP.
> > > + * @src_table: OPP table which has dst_table as one of its required OPP table.
> > > + * @dst_table: Required OPP table of the src_table.
> > > + * @pstate: OPP of the src_table.
> >
> > You should use @ before parameters in the comments as well ? Just like
> > you did that below.
> 
> And I should probably be deleting the @pstate phantom parameter :)
> 
> > > + *
> > > + * This function returns the OPP (present in @dst_table) pointed out by the
> > > + * "required-opps" property of the OPP (present in @src_table).
> > > + *
> > > + * The callers are required to call dev_pm_opp_put() for the returned OPP after
> > > + * use.
> > > + *
> > > + * Return: destination table OPP on success, otherwise NULL on errors.
> > > + */
> > > +struct dev_pm_opp *dev_pm_opp_xlate_opp(struct opp_table *src_table,
> >
> > Please name it dev_pm_opp_xlate_required_opp().
> 
> Ok
> 
> >
> > > +                                     struct opp_table *dst_table,
> > > +                                     struct dev_pm_opp *src_opp)
> > > +{
> > > +     struct dev_pm_opp *opp, *dest_opp = NULL;
> > > +     int i;
> > > +
> > > +     if (!src_table || !dst_table || !src_opp)
> > > +             return NULL;
> > > +
> > > +     for (i = 0; i < src_table->required_opp_count; i++) {
> > > +             if (src_table->required_opp_tables[i]->np == dst_table->np)
> >
> > Why can't we just compare the table pointers instead ? Yeah, I know
> > that's how I wrote that in the other xlate function, but I am confused
> > now :)
> 
> I almost said "not sure. Let me just compare pointers".
> I think (not sure) it has to do with the same OPP table being used to
> create multiple OPP table copies if the "shared OPP table" flag isn't
> set?
> Can you confirm if this makes sense? If so, I can add a comment patch
> that adds comments to the existing code and then copies it into this
> function in this patch.

Right, that was the reason but we also need to fix ...

> > > +                     break;
> > > +     }
> > > +
> > > +     if (unlikely(i == src_table->required_opp_count)) {
> > > +             pr_err("%s: Couldn't find matching OPP table (%p: %p)\n",
> > > +                    __func__, src_table, dst_table);
> > > +             return NULL;
> > > +     }
> > > +
> > > +     mutex_lock(&src_table->lock);
> > > +
> > > +     list_for_each_entry(opp, &src_table->opp_list, node) {
> > > +             if (opp == src_opp) {

... this as well. We must be comparing node pointers here as well.

> > > +                     dest_opp = opp->required_opps[i];
> > > +                     dev_pm_opp_get(dest_opp);
> > > +                     goto unlock;
> > > +             }
> > > +     }
> > > +
> > > +     pr_err("%s: Couldn't find matching OPP (%p: %p)\n", __func__, src_table,
> > > +            dst_table);
> > > +
> > > +unlock:
> > > +     mutex_unlock(&src_table->lock);
> > > +
> > > +     return dest_opp;
> > > +}
> > > +
> > >  /**
> > >   * dev_pm_opp_xlate_performance_state() - Find required OPP's pstate for src_table.
> > >   * @src_table: OPP table which has dst_table as one of its required OPP table.
> > > diff --git a/include/linux/pm_opp.h b/include/linux/pm_opp.h
> > > index af5021f27cb7..36f52b9cf24a 100644
> > > --- a/include/linux/pm_opp.h
> > > +++ b/include/linux/pm_opp.h
> > > @@ -131,6 +131,9 @@ void dev_pm_opp_unregister_set_opp_helper(struct opp_table *opp_table);
> > >  struct opp_table *dev_pm_opp_attach_genpd(struct device *dev, const char **names);
> > >  void dev_pm_opp_detach_genpd(struct opp_table *opp_table);
> > >  int dev_pm_opp_xlate_performance_state(struct opp_table *src_table, struct opp_table *dst_table, unsigned int pstate);
> > > +struct dev_pm_opp *dev_pm_opp_xlate_opp(struct opp_table *src_table,
> > > +                                     struct opp_table *dst_table,
> > > +                                     struct dev_pm_opp *src_opp);
> > >  int dev_pm_opp_set_rate(struct device *dev, unsigned long target_freq);
> > >  int dev_pm_opp_set_sharing_cpus(struct device *cpu_dev, const struct cpumask *cpumask);
> > >  int dev_pm_opp_get_sharing_cpus(struct device *cpu_dev, struct cpumask *cpumask);
> > > @@ -304,6 +307,14 @@ static inline int dev_pm_opp_xlate_performance_state(struct opp_table *src_table
> > >       return -ENOTSUPP;
> > >  }
> > >
> > > +static inline struct dev_pm_opp *dev_pm_opp_xlate_opp(
> > > +                                             struct opp_table *src_table,
> > > +                                             struct opp_table *dst_table,
> > > +                                             struct dev_pm_opp *src_opp)
> > > +{
> > > +     return NULL;
> > > +}
> > > +
> >
> > Keep the order of declaring routines same, so this goes before the
> > other xlate routine.
> 
> Will do.
> 
> -Saravana
> 
> > >  static inline int dev_pm_opp_set_rate(struct device *dev, unsigned long target_freq)
> > >  {
> > >       return -ENOTSUPP;
> > > --
> > > 2.22.0.510.g264f2c817a-goog
> >
> > --
> > viresh

-- 
viresh