Re: [PATCH v4] pm_ops: add system quiesce/activate hooks

[Pavel Machek <pavel@ucw.cz>]

Hi!

> Ok, PowerPC Decrementer 101

(Thanks for explanation).

> Now, in addition to that, we have some weird motherboard stuff we need
> to turn off/on, which has to be done after drivers (because it renders
> various busses inaccessible in some cases, and might cause DMA snooping
> to stop working, I'm not 100% sure, but I know for sure it has to be
> done late) but can't be done as a sysdev because we need some
> infrastructure like the i2c stuff (and others) that requires semaphores
> and timers. It's based on something remotely akin to AML in that we have
> to execute "scripts" provided by the firmware and the code to do so need
> to run in an environment where scheduler & timers are operating.

Does the "weird motherboard" stuff need to be suspended/resumed for
swsusp memory snapshot?

> For all those reasons, I do think that the proper, clean and incremental
> approach to get our stuff working is to have that pair of hooks allowing
> us to "replace" the local_irq_disable/enable calls...
> 
> Now it does not need to be pm_ops. I'm fine with arch_pm_irq_quiesce()
> kind of thing (or find a better name if you can, maybe

Well, I guess arch_pm_irq_quiesce_for_s2ram() would be
acceptable... but that would be only called for s2ram... which should
be enough for decrementer AFAICT.

> It's basically about quiescing the scheduler/timers, which on powerpc
> (bcs of the way the DEC operates) requires a little bit more than just a
> call to local_irq_disable. And once the hook is there, use it for some
> other arch specific bits that we can't quite fit anywhere else at the
> moment.

As decrementer is special for s2ram, we can add the hook. (It is
single hook). If we need to do something for snapshots, too... well,
we can still add arch_pm_irq_quiesce_for_snapshot() and
arch_pm_irq_quiesce_for_powerdown() etc, but it would get ugly fast.

								Pavel
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