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    SubjectRe: 2.6.25-rc2 System no longer powers off after suspend-to-disk. Screen becomes green.


    On Thu, 21 Feb 2008, Rafael J. Wysocki wrote:
    >
    > In fact we have acpi_pci_choose_state() that tells the driver which power
    > state to put the device into in ->suspend(). If that is used, the device ends
    > up in the state expected by to BIOS for S4.

    First off, nobody should *ever* use that directly anyway.

    Secondly, the one that people should use ("pci_choose_state()") doesn't
    actually do what you claim it does. It does all kinds of wrong things, and
    doesn't even take the target state into account at all. So look again.

    > No. Again, if there are devices that wake us up from S4, but not from S5,
    > they need to be handled differently in the *enter S4* case (hibernation) and
    > in the *enter S5* case (powering off the system).

    And again, what does this have to do with (the example I used) the
    graphics hardware? Answer: nothing. The example I gave you we simply DO
    THE WRONG THING FOR.

    Same thing for things like USB devices - where pci_choose_state() doesn't
    work to begin with. Why do we call "suspend()" on such a thing when we
    don't want to suspend it? We shouldn't. We should call "freeze/unfreeze"
    (which are no-ops) and then finally perhaps "poweroff", and that final
    stage might want to spin things down or similar.

    But *none* of it has anything to do with suspend, and none of it has
    anything to do with pci_choose_state() (much less acpi_pci_choose_state)

    The fact is, we should let the driver decide, and we should make it clear
    to the driver writer what he is deciding about - rather than basically lie
    and say "suspend the device and put it into D3" even when that's the last
    thing it should ever do.

    Linus


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