Re: [PATCH 0/2] cpufreq/opp: rework regulator initialization

Rafael J. Wysocki
2019-02-08T10:52:38Z

On Fri, Feb 8, 2019 at 11:42 AM Rafael J. Wysocki <rafael@kernel.org> wrote:
>
> On Fri, Feb 8, 2019 at 11:31 AM Viresh Kumar <viresh.kumar@linaro.org> wrote:
> >
> > On 08-02-19, 11:22, Rafael J. Wysocki wrote:
> > > There are cpufreq driver suspend and resume callbacks, maybe use them?
> > >
> > > The driver could do the I2C transactions in its suspend/resume
> > > callbacks and do nothing in online/offline if those are part of
> > > system-wide suspend/resume.
> >
> > These are per-policy things that we need to do, not sure if driver
> > suspend/resume is a good place for that. It is more for a case where
> > CPU 0-3 are in one policy and 4-7 in another. Now 1-7 are
> > hot-unplugged during system suspend and hotplugged later on. This is
> > more like complete removal/addition of devices instead of
> > suspend/resume.
>
> No, it isn't. We don't remove devices on offline. We migrate stuff
> away from them and (opportunistically) power them down.
>
> If this is system suspend, the driver kind of knows that offline will
> take place, so it can prepare for it. Likewise, when online takes
> place during system-wide resume, it generally is known that this is
> system-wide resume (there is a flag to indicate that in CPU hotplug),
> it can be "smart" and avoid accessing suspended devices. Deferring
> the frequency set up until the driver resume time should do the trick
> I suppose.

BTW, do transitions to idle states involve I2C transactions on the
systems in question?