Re: [PATCH 1/2] OPP: Use _set_opp_level() for single genpd case

Viresh Kumar
2023-10-25T06:55:08Z

On 19-10-23, 13:16, Ulf Hansson wrote:
> On Thu, 19 Oct 2023 at 12:22, Viresh Kumar <viresh.kumar@linaro.org> wrote:
> > +static int _link_required_opps(struct dev_pm_opp *opp, struct opp_table *opp_table,
> > struct opp_table *required_table, int index)
> > {
> > struct device_node *np;
> > @@ -314,6 +314,25 @@ static int _link_required_opps(struct dev_pm_opp *opp,
> > return -ENODEV;
> > }
> >
> > + /*
> > + * There are two genpd (as required-opp) cases that we need to handle,
> > + * devices with a single genpd and ones with multiple genpds.
> > + *
> > + * The single genpd case requires special handling as we need to use the
> > + * same `dev` structure (instead of a virtual one provided by genpd
> > + * core) for setting the performance state. Lets treat this as a case
> > + * where the OPP's level is directly available without required genpd
> > + * link in the DT.
> > + *
> > + * Just update the `level` with the right value, which
> > + * dev_pm_opp_set_opp() will take care of in the normal path itself.
> > + */
> > + if (required_table->is_genpd && opp_table->required_opp_count == 1 &&
> > + !opp_table->genpd_virt_devs) {
> > + if (!WARN_ON(opp->level))
>
> Hmm. Doesn't this introduce an unnecessary limitation?
>
> An opp node that has a required-opps phande, may have "opp-hz",
> "opp-microvolt", etc. Why would we not allow the "opp-level" to be
> used too?

Coming back to this, why would we ever want a device to have "opp-level" and
"required-opp" (set to genpd's table) ? That would mean we will call:

dev_pm_domain_set_performance_state() twice to set different level values.

And so it should be safe to force that if required-opp table is set to a genpd,
then opp-level shouldn't be set. Maybe we should fail in that case, which isn't
happening currently.

--
viresh