Re: PCI PM: Restore standard config registers of all devices early

Linus Torvalds
2009-02-03T17:54:21Z

On Tue, 3 Feb 2009, Rafael J. Wysocki wrote:
>
> As I said, I tend to prefer the "loop of disable_irq()" approach, because it
> would allow us to preserve the current ordering of ACPI operations. Namely,
> if we do:
>
> suspend devices (normal suspend)
> loop of disable_irq()
> late suspend of devices
> _PTS
> disable nonboot CPUs
> local_irq_disable()
> sysdev suspend
> enter sleep state
> get control from the BIOS
> sysdev resume
> (*)
> local_irq_enable()
> enable nonboot CPUs
> _WAK
> early resume of devices
> loop of enable_irq()
> resume devices (normal resume)
>
> the ordering of _PTS with respect to putting devices into low power states and
> disabling the nonboot CPUs will be the same as it is now and the same applies
> to _WAK and putting devices into D0 etc. (I really _really_ wouldn't like to
> change this ordering, since this alone is likely to break things badly).

Yes.

Also, make the "loop of disable/enable_irq()" phase be a helper function
that also sets system_state to SYSTEM_SUSPENDING/SYSTEM_RUNNING
respectively, and it should all be pretty clean, and the changes really
should be pretty minimal.

> Now, there's one subtle problem with resume in this picture. Namely, before
> running the "early resume of devices" we have to make sure that the interrupts
> will be masked. However, masking MSI-X, for example, means writing into
> the memory space of the device, so we can't do it at this point.

I really don't think it matters. Why? We simply don't care.

All MSI-X things will still have to go through the regular irq layer, so
the disable/enable_irq part, so even though we've done the
"local_irq_enable()", we just don't care.

Linus