Re: [PATCH v2 3/4] PM: domains: Drop/restore performance state votes for devices at runtime PM

Dmitry Osipenko
2021-06-03T19:03:19Z

03.06.2021 12:34, Ulf Hansson пишет:
> A subsystem/driver that need to manage OPPs for its device, should
> typically drop its vote for the OPP when the device becomes runtime
> suspended. In this way, the corresponding aggregation of the performance
> state votes that is managed in genpd for the attached PM domain, may find
> that the aggregated vote can be decreased. Hence, it may allow genpd to set
> the lower performance state for the PM domain, thus avoiding to waste
> energy.
>
> To accomplish this, typically a subsystem/driver would need to call
> dev_pm_opp_set_rate|opp() for its device from its ->runtime_suspend()
> callback, to drop the vote for the OPP. Accordingly, it needs another call
> to dev_pm_opp_set_rate|opp() to restore the vote for the OPP from its
> ->runtime_resume() callback.
>
> To avoid boilerplate code in subsystems/driver to deal with these things,
> let's instead manage this internally in genpd.
>
> Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
> ---
>
> Changes in v2:
> - Rebased.
> - A few minor cosmetic changes.
> - Deal with the error path in genpd_runtime_resume().

I tested this on NVIDIA Tegra by removing the boilerplate code from
drivers' RPM and haven't noticed any problems, the performance state is
dropped/restored as expected. Thank you.