Re: [PATCH v2] PM / Sleep: Add pm_generic functions to re-use runtime PM callbacks

[Ulf Hansson <ulf.hansson@linaro.org>]

>>
>> There are already a generic callbacks that does this. Normally the
>> generic callbacks is used from buses and power domains.
>>
>> My new callbacks are intended to be used from the driver, so those are
>> kind of different from the others in that sense.
>
> Hmm.  I see.
>
> For that to work, the subsystem's .suspend() and .resume() callbacks will
> have to be implemented in a special way, because of the unknown runtime PM
> status of devices while those callbacks are being executed.

Not sure I understand why you think the runtime PM status is unknown?

In .suspend the runtime status can still be changed. Since the PM core
disables runtime PM before invoking .suspend_late and since the PM
core will keep runtime PM disabled until after the .resume_early has
been invoked, it will be safe to operate on the runtime PM callbacks
during this period - if the driver/bus are adopted for it. While the
.resume callback gets invoked, the runtime status are restored to it's
previous state, which the bus/driver would expect.

Do you want me to send a patch for a driver that uses these callbacks?
I suppose it would clarify how I am thinking...

>
> Presumably you think about subsystems that don't implement those callbacks
> at all?

If you mean that "drivers" is not a part of the term "subsystem" here,
then I somewhat agree.

My view is that it will be mostly drivers that make use of these callbacks.

Though, I don't think we need to prevent subsystems or power domains
from using them, they will only have to know what the consequences
are. :-)

Maybe there could even be some cases were it actually makes good sense
of using them for subsystems, even if I yet not have come a cross such
a case.

Kind regards
Ulf Hansson

>
> Rafael
>