Re: [PATCH v5 2/3] OPP: Add support for bandwidth OPP tables

[Saravana Kannan <saravanak@google.com>]

On Mon, Aug 19, 2019 at 11:13 PM Viresh Kumar <viresh.kumar@linaro.org> wrote:
>
> On 07-08-19, 15:31, Saravana Kannan wrote:
> > Not all devices quantify their performance points in terms of frequency.
> > Devices like interconnects quantify their performance points in terms of
> > bandwidth. We need a way to represent these bandwidth levels in OPP. So,
> > add support for parsing bandwidth OPPs from DT.
> >
> > Signed-off-by: Saravana Kannan <saravanak@google.com>
> > ---
> >  drivers/opp/of.c  | 41 ++++++++++++++++++++++++++++++++---------
> >  drivers/opp/opp.h |  4 +++-
> >  2 files changed, 35 insertions(+), 10 deletions(-)
> >
> > diff --git a/drivers/opp/of.c b/drivers/opp/of.c
> > index 1813f5ad5fa2..e1750033fef9 100644
> > --- a/drivers/opp/of.c
> > +++ b/drivers/opp/of.c
> > @@ -523,6 +523,35 @@ void dev_pm_opp_of_remove_table(struct device *dev)
> >  }
> >  EXPORT_SYMBOL_GPL(dev_pm_opp_of_remove_table);
> >
> > +static int _read_opp_key(struct dev_pm_opp *new_opp, struct device_node *np)
> > +{
> > +     int ret;
> > +     u64 rate;
> > +     u32 bw;
> > +
> > +     ret = of_property_read_u64(np, "opp-hz", &rate);
> > +     if (!ret) {
> > +             /*
> > +              * Rate is defined as an unsigned long in clk API, and so
> > +              * casting explicitly to its type. Must be fixed once rate is 64
> > +              * bit guaranteed in clk API.
> > +              */
> > +             new_opp->rate = (unsigned long)rate;
> > +             return 0;
> > +     }
> > +
>
> Please read opp-level also here and do error handling.

Can you please explain what's the reasoning? opp-level doesn't seem to
be a "key" based on looking at the code.

>
> > +     ret = of_property_read_u32(np, "opp-peak-kBps", &bw);
> > +     if (ret)
> > +             return ret;
> > +     new_opp->rate = (unsigned long) bw;
> > +
> > +     ret = of_property_read_u32(np, "opp-avg-kBps", &bw);
> > +     if (!ret)
> > +             new_opp->avg_bw = (unsigned long) bw;
>
> If none of opp-hz/level/peak-kBps are available, print error message here
> itself..

But you don't print any error for opp-level today. Seems like it's optional?

>
> > +
> > +     return 0;
>
> You are returning 0 on failure as well here.

Thanks.

> > +}
> > +
> >  /**
> >   * _opp_add_static_v2() - Allocate static OPPs (As per 'v2' DT bindings)
> >   * @opp_table:       OPP table
> > @@ -560,22 +589,16 @@ static struct dev_pm_opp *_opp_add_static_v2(struct opp_table *opp_table,
> >       if (!new_opp)
> >               return ERR_PTR(-ENOMEM);
> >
> > -     ret = of_property_read_u64(np, "opp-hz", &rate);
> > +     ret = _read_opp_key(new_opp, np);
> >       if (ret < 0) {
> >               /* "opp-hz" is optional for devices like power domains. */
> >               if (!opp_table->is_genpd) {
> > -                     dev_err(dev, "%s: opp-hz not found\n", __func__);
> > +                     dev_err(dev, "%s: opp-hz or opp-peak-kBps not found\n",
> > +                             __func__);
> >                       goto free_opp;
> >               }
> >
> >               rate_not_available = true;
>
> Move all above as well to read_opp_key().

Ok. I didn't want to print an error at the API level and instead print
at the caller level. But if that's what you want, that's fine by me.

>
> > -     } else {
> > -             /*
> > -              * Rate is defined as an unsigned long in clk API, and so
> > -              * casting explicitly to its type. Must be fixed once rate is 64
> > -              * bit guaranteed in clk API.
> > -              */
> > -             new_opp->rate = (unsigned long)rate;
> >       }
> >
> >       of_property_read_u32(np, "opp-level", &new_opp->level);
> > diff --git a/drivers/opp/opp.h b/drivers/opp/opp.h
> > index 01a500e2c40a..6bb238af9cac 100644
> > --- a/drivers/opp/opp.h
> > +++ b/drivers/opp/opp.h
> > @@ -56,7 +56,8 @@ extern struct list_head opp_tables;
> >   * @turbo:   true if turbo (boost) OPP
> >   * @suspend: true if suspend OPP
> >   * @pstate: Device's power domain's performance state.
> > - * @rate:    Frequency in hertz
> > + * @rate:    Frequency in hertz OR Peak bandwidth in kilobytes per second
> > + * @avg_bw:  Average bandwidth in kilobytes per second
>
> Please add separate entry for peak_bw here.
>
> I know you reused rate because you don't want to reimplement the helpers we
> have. Maybe we can just update them to return peak_bw when opp-hz isn't present.

How about I just rename this to "key"? That makes a lot more sense
than trying to save 3 different keys and going through them one at a
time.

> >   * @level:   Performance level
> >   * @supplies:        Power supplies voltage/current values
> >   * @clock_latency_ns: Latency (in nanoseconds) of switching to this OPP's
> > @@ -78,6 +79,7 @@ struct dev_pm_opp {
> >       bool suspend;
> >       unsigned int pstate;
> >       unsigned long rate;
> > +     unsigned long avg_bw;
> >       unsigned int level;
> >
> >       struct dev_pm_opp_supply *supplies;
> > --
> > 2.23.0.rc1.153.gdeed80330f-goog

-Saravana