[linux-pm] Re: [RFC][PATCH 1/2 -mm] kexec based hibernation -v3: kexec jump

huang ying huang.ying.caritas at gmail.com
Fri Sep 21 11:02:01 EDT 2007

On 9/21/07, Rafael J. Wysocki <rjw at sisk.pl> wrote:
> On Friday, 21 September 2007 15:14, huang ying wrote:
> > On 9/21/07, Rafael J. Wysocki <rjw at sisk.pl> wrote:
> > > On Friday, 21 September 2007 05:33, Eric W. Biederman wrote:
> > > > Nigel Cunningham <nigel at 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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