Messages in this thread | | | Subject | Re: Reworking suspend-resume sequence (was: Re: PCI PM: Restore standard config registers of all devices early) | From | Benjamin Herrenschmidt <> | Date | Wed, 04 Feb 2009 10:05:27 +1100 |
| |
> (Newer) ACPI says that devices should be put into low power states (presumably > with the help of appropriate ACPI AML routines) before the _PTS method is > called. In turn, we're supposed to disable nonboot CPUs after calling _PTS. > There is analogous requirement for the _WAK method during resume. > > Currently, the suspend code ordering follows these rules, but if we move > the putting of devices into low power states into the suspend_late part, they > will have to be done after _PTS and that is likely to break things (we've > already had this problem once and I have really bad memories related to it).
Wait wait wait ... the -whole- point of the exercise, wether using local_irq_save or disable_irq, -is- to put the ACPI bit -after- setting the device in low power state and before the restore on wakeup...
So basically, that isn't changing.
The -one- thing that indeed conflicts here is that we disable nonboot CPUs earlier. Right ?
Now, I doubt that would be a big issue, ie, we are supposedly capable of dynamically disabling/enabling CPUs anyway, but if it is, then indeed I see how the using of higher level PIC irq disabling would allow to move the whole suspend_late() over to before disabling non-boot CPUs.
That does introduce a significant change in semantics for drivers in the sense that now, suspend_late will be called with timers running, things scheduling, requests coming in, etc... One of the big reasons for doing suspend_late with IRQs off was precisely that drivers wouldn't have to synchronize with all these things. They now do.
Thus I tend to think that keeping the disabling of nonboot CPUs earlier than the suspending of devices is the least of two evils. _BUT_ As I said, I'm no ACPI expert and not -that- familiar with x86 land, it might indeed be a can of worms.
Cheers, Ben.
| |