Re: [PATCH 2/2] thermal: rcar_thermal: use pm_runtime_put_sync()

From: Ulf Hansson
Date: Wed Nov 11 2015 - 06:04:00 EST

On 11 November 2015 at 00:57, Rafael J. Wysocki <rjw@xxxxxxxxxxxxx> wrote:
> On Tuesday, November 10, 2015 02:00:38 PM Ulf Hansson wrote:
>> +Rafael, Alan
>> On 10 November 2015 at 11:10, Geert Uytterhoeven <geert@xxxxxxxxxxxxxx> wrote:
>> > Hi Ulf,
>> >
> [cut]
>> >>
>> >> The problem is that the runtime PM status of the device isn't
>> >> correctly updated at ->remove(). The effect is that the the
>> >> pm_runtime_get_sync() in ->probe() at re-bind will *not* trigger the
>> >> ->runtime_resume() callbacks to be invoked, as the runtime PM core
>> >> believes the device is already runtime resumed.
>> >
>> > So that's where it should be fixed?
>> That would be a more generic approach, although I am not sure how the
>> driver/PM core should be able to take the correct decision in this
>> phase. Devices may be runtime PM managed also without a driver bound.
>> Perhaps when __device_release_driver() finds a bounded driver for the
>> device, it could after all actions been performed to unbind the
>> driver, check if runtime PM is enabled. If it isn't, it could set the
>> runtime PM status to suspended!?
>> I have no idea if that would introduce other issues as it would kind
>> of force the runtime PM status of the device to suspend, without
>> actually knowing if it's the correct thing to do.
> IMO, that needs to depend on the bus type. If the bus type has a way
> to manage PM for devices without drivers, it should be allowed to do so.

By following my suggestion above, we would allow the bus/driver's
->remove() to manage whether runtime PM should be enabled/disabled for
the device, before __device_release_driver() checks that.
Don't you think that the driver core could rely on that information?

I realize that it would be a kind of policy decision for runtime PM,
but it's quite similar as when register/unregister devices when we set
the runtime PM status to suspended.

If you don't think this is a good idea, I guess we need to deal with
this from subsystem level code somehow instead.

> Of course, the platform bus type is somewhat special in that respect,
> but it looks like we simply need some sort of a convention in there too
> (the expectations should be the same for everybody).
> Thanks,
> Rafael

Kind regards
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