Re: [PATCH 3/3] PM: domains: Add a ->dev_get_performance_state() callback to genpd

[Ulf Hansson <ulf.hansson@linaro.org>]

On Thu, 9 Sept 2021 at 15:48, Dmitry Osipenko <digetx@gmail.com> wrote:
>
> 07.09.2021 12:57, Ulf Hansson пишет:
> > I don't mind extending the genpd API, but it needs to serve a good purpose.
> >
> > As I said earlier, genpd doesn't know nor can control how the consumer
> > driver deploys runtime PM. Unfortunately, that also includes genpd
> > providers, as the behavior isn't a platform or PM domain specific
> > thing. This means genpd needs to be generic enough so it works for all
> > cases.
> >
> > In the $subject patch, we rely on the pm_runtime_suspended() check in
> > dev_pm_genpd_set_performance_state(), which should work for all cases,
> > even if it may be sub-optimal for some scenarios.
> >
> > Note that, in the approach your suggested [1],
> > pm_runtime_status_suspended() is used instead. This doesn't work when
> > a consumer driver doesn't enable runtime PM - or calls
> > pm_runtime_set_active() during ->probe(), because
> > genpd_runtime_resume() won't be invoked to restore the gpd->rpm_state.
> >
> > That said, I wouldn't mind to simply skip adding the
> > ->dev_get_performance_state() all together, if that is what you
> > prefer? In this way, it becomes the responsibility for the consumer
> > driver to do right thing, with the cost of some boilerplate code added
> > in its ->probe() routine.
>
> Until a day ago, it wasn't clear to me that consumer drivers now can set
> up rpm_pstate during probe(), which is a cleaner solution that works
> well. So let's skip adding the questionable ->dev_get_performance_state().
>
> The boilerplate code in the probe() is minimal in comparison to a
> previous variant with the state-syncing done by rpm-resume callbacks of
> consumer drivers, it's good enough.

Alright, that sounds good to me as well.

I am happy to help with review of the consumer driver changes, just
keep me posted.

Thanks and kind regards
Uffe