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    SubjectRe: [linux-pm] Re: [RFC][PATCH 1/2 -mm] kexec based hibernation -v3: kexec jump
    On 9/21/07, Rafael J. Wysocki <rjw@sisk.pl> wrote:
    > On Friday, 21 September 2007 15:14, huang ying wrote:
    > > On 9/21/07, Rafael J. Wysocki <rjw@sisk.pl> wrote:
    > > > On Friday, 21 September 2007 05:33, Eric W. Biederman wrote:
    > > > > Nigel Cunningham <nigel@nigel.suspend2.net> writes:
    > [--snip--]
    > > > >
    > > > > No one has yet attacked the hard problem of coming up with separate
    > > > > hibernate methods for drivers.
    > > >
    > > > Well, I've been playing a bit with that for some time, but it's not easy by any
    > > > means.
    > > >
    > > > In short, I'm seeing some problems related to the handling of ACPI that seem to
    > > > shatter the entire idea of having separate hibernate methods, at least as far
    > > > as ACPI systems are concerned.
    > >
    > > So sadly to hear this. Can you details it a little? Or a link?
    >
    > Well, the problem is that apparently some systems (eg. my HP nx6325) expect us
    > to execute the _PTS ACPI global control method before creating the image _and_
    > to execute acpi_enter_sleep_state(ACPI_STATE_S4) in order to finally put the
    > system into the sleep state. In particular, on nx6325, if we don't do that,
    > then after the restore the status of the AC power will not be reported
    > correctly (and if you replace the battery while in the sleep state, the
    > battery status will not be updated correctly after the restore). Similar
    > issues have been reported for other machines.
    >
    > Now, the ACPI specification requires us to put devices into low power states
    > before executing _PTS and that's exactly what we're doing before a suspend to
    > RAM. Thus, it seems that in general we need to do the same for hibernation on
    > ACPI systems.

    Then, is it possible to separate device quiesce from device suspend.
    Perhaps not for swsusp, but for kexec based hibernation?

    Best Regards,
    Huang Ying
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