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

From: Dmitry Osipenko
Date: Thu Jun 03 2021 - 15:08:49 EST

03.06.2021 22:02, Dmitry Osipenko пишет:
> 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@xxxxxxxxxx>
>> ---
>> 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.

Tested-by: Dmitry Osipenko <digetx@xxxxxxxxx>