Re: [PATCH v5 1/2] PM / Domains: Add support for 'required-opps' to set default perf state

[Rajendra Nayak]

On 8/2/2021 6:29 PM, Ulf Hansson wrote:
> On Tue, 20 Jul 2021 at 09:12, Rajendra Nayak <rnayak@xxxxxxxxxxxxxx> wrote:
> > Some devices within power domains with performance states do not
> > support DVFS, but still need to vote on a default/static state
> > while they are active. They can express this using the 'required-opps'
> > property in device tree, which points to the phandle of the OPP
> > supported by the corresponding power-domains.
> >
> > Add support to parse this information from DT and then set the
> > specified performance state during attach and drop it on detach.
> > runtime suspend/resume callbacks already have logic to drop/set
> > the vote as needed and should take care of dropping the default
> > perf state vote on runtime suspend and restore it back on runtime
> > resume.
> >
> > Signed-off-by: Rajendra Nayak <rnayak@xxxxxxxxxxxxxx>
> > ---
> >   drivers/base/power/domain.c | 28 +++++++++++++++++++++++++---
> >   include/linux/pm_domain.h   |  1 +
> >   2 files changed, 26 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
> > index a934c67..f454031 100644
> > --- a/drivers/base/power/domain.c
> > +++ b/drivers/base/power/domain.c
> > @@ -2598,6 +2598,12 @@ static void genpd_dev_pm_detach(struct device *dev, bool power_off)
> >
> >          dev_dbg(dev, "removing from PM domain %s\n", pd->name);
> >
> > +       /* Drop the default performance state */
> > +       if (dev_gpd_data(dev)->default_pstate) {
> > +               dev_pm_genpd_set_performance_state(dev, 0);
> > +               dev_gpd_data(dev)->default_pstate = 0;
> > +       }
> > +
> >          for (i = 1; i < GENPD_RETRY_MAX_MS; i <<= 1) {
> >                  ret = genpd_remove_device(pd, dev);
> >                  if (ret != -EAGAIN)
> > @@ -2635,9 +2641,10 @@ static void genpd_dev_pm_sync(struct device *dev)
> >   static int __genpd_dev_pm_attach(struct device *dev, struct device *base_dev,
> >                                   unsigned int index, bool power_on)
> >   {
> > +       struct device_node *np;
> >          struct of_phandle_args pd_args;
> >          struct generic_pm_domain *pd;
> > -       int ret;
> > +       int ret, pstate;
> >
> >          ret = of_parse_phandle_with_args(dev->of_node, "power-domains",
> >                                  "#power-domain-cells", index, &pd_args);
> > @@ -2675,10 +2682,25 @@ static int __genpd_dev_pm_attach(struct device *dev, struct device *base_dev,
> >                  genpd_unlock(pd);
> >          }
> >
> > -       if (ret)
> > +       if (ret) {
> >                  genpd_remove_device(pd, dev);
> > +               return -EPROBE_DEFER;
> > +       }
> > +
> > +       /* Set the default performance state */
> > +       np = base_dev->of_node;
>
> Please use dev->of_node instead (it is set to the same of_node as
> base_dev by the callers of __genpd_dev_pm_attach) as it's more
> consistent with existing code.
>
> > +       if (of_parse_phandle(np, "required-opps", index)) {
> > +               pstate = of_get_required_opp_performance_state(np, index);
> > +               if (pstate < 0) {
> > +                       ret = pstate;
> > +                       dev_err(dev, "failed to set required performance state for power-domain %s: %d\n",
> > +                               pd->name, ret);
> > +               }
> > +               dev_pm_genpd_set_performance_state(dev, pstate);
> > +               dev_gpd_data(dev)->default_pstate = pstate;
>
> This doesn't look entirely correct to me. If we fail to translate a
> required opp to a performance state, we shouldn't try to set it.

yeah, that does not seem right at all :(

> Perhaps it's also easier to call
> of_get_required_opp_performance_state() unconditionally of whether a
> "required-opps" specifier exists. If it fails with the translation,
> then we just skip setting a default state and continue with returning
> 1.
>
> Would that work?

I think it should, I'll redo the error handling, hopefully right this time,
and re-post. Thanks for the review.

> > +       }
> >
> > -       return ret ? -EPROBE_DEFER : 1;
> > +       return ret ? ret : 1;
> >   }
> >
> >   /**
> > diff --git a/include/linux/pm_domain.h b/include/linux/pm_domain.h
> > index 21a0577..67017c9 100644
> > --- a/include/linux/pm_domain.h
> > +++ b/include/linux/pm_domain.h
> > @@ -198,6 +198,7 @@ struct generic_pm_domain_data {
> >          struct notifier_block *power_nb;
> >          int cpu;
> >          unsigned int performance_state;
> > +       unsigned int default_pstate;
> >          unsigned int rpm_pstate;
> >          ktime_t next_wakeup;
> >          void *data;
> > --
> > QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member
> > of Code Aurora Forum, hosted by The Linux Foundation
>
> Kind regards
> Uffe

--
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of Code Aurora Forum, hosted by The Linux Foundation