[PATCH v8 01/34] opp: Add dev_pm_opp_sync() helper

[Dmitry Osipenko]

23.08.2021 13:46, Ulf Hansson пишет:
>>> ...
>>> dev_pm_opp_set_rate(rate)
>>> pm_runtime_get_noresume()
>>> pm_runtime_set_active()
>>> pm_runtime_enable()
>>> ...
>>> pm_runtime_put()
>>> ...
>>>
>>> We need to call genpd_set_performance_state() independently of whether
>>> the device is runtime suspended or not.
>>
>> I don't see where is the problem in yours example.
>>
>> pm_runtime_suspended() = false while RPM is disabled. When device is
>> resumed, the rpm_pstate=0, so it won't change the pstate on resume.
> 
> Yes, you are certainly correct, my bad! I mixed it up with
> pm_runtime_status_suspended(), which only cares about the status.
> 
> So, after a second thought, your suggestion sounds very much
> reasonable to me! I have also tried to consider all different
> scenarios, including the system suspend/resume path, but I think it
> should be fine.

It could be improved slightly to cover more cases.

> I also think that a patch like the above should be considered as a
> fix, because it actually fixes a problem, according to what I said in
> my earlier reply, below.
> 
> Fixes : 5937c3ce2122 ("PM: domains: Drop/restore performance state
> votes for devices at runtime PM").
> 
>>
>>> Although, it actually seems like good idea to update
>>> dev_gpd_data(dev)->rpm_pstate = state here, as to make sure
>>> genpd_runtime_resume() doesn't restore an old/invalid value that was
>>> saved while dropping the performance state vote for the device in
>>> genpd_runtime_suspend() earlier.
>>>
>>> Let me send a patch for this shortly, to close this window of a possible error.
>>
>> It will also remove the need to resume device just to change the clock
>> rate, like I needed to do it in the PWM patch of this series.
> 
> Do you want to send the patch formally? Or do you prefer it if I do it?

I'll send the patch.