From mboxrd@z Thu Jan  1 00:00:00 1970
From: "Rafael J. Wysocki" <rjw@sisk.pl>
Subject: Re: khibernation and ACPI
Date: Thu, 4 Oct 2007 17:32:20 +0200
Message-ID: <200710041732.21853.rjw@sisk.pl>
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To: Pavel Machek <pavel@ucw.cz>
Cc: Nigel Cunningham <nigel@nigel.suspend2.net>, Andrew Morton <akpm@linux-foundation.org>, linux-pm@lists.linux-foundation.org, Jeremy Maitin-Shepard <jbms@cmu.edu>
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On Thursday, 4 October 2007 12:12, Pavel Machek wrote:
> Hi!
> 
> > > > The root filesystem is initramfs, so that, the only devices needed by kernel
> > > > B is timer.
> > > > e. In kernel B, put needed devices back to normal state. 
> > > > f. Write memory image of kernel A out
> > > > g. Put all devices in quiescent and low power state
> > > > h. Execute acpi_enter_sleep_state(ACPI_STATE_S4)
> > > 
> > > Yes, apart from d. this looks doable.
> > > 
> > 
> > To deal with the issue of d, the following scheme can be used:
> > 
> > a. Boot kernel A with ACPI on
> > b. In kernel A, load the image of a new kernel B with sys_kexec_load
> > c. In kernel A, put all devices in quiescent and low power state
> > d. In kernel A, kexec kernel B with ACPI on (some devices may be put in
> > normal state during boot)
> > e. In kernel B, put all devices in quiescent and low power state
> > f. In kernel B, Jump back to kernel A
> > g. In kernel A, put all devices in normal state
> > h. In kernel A, put all devices in low power state
> > i. In kernel A, execute _PTS of ACPI
> > j. In kernel A, jump to kernel B again
> > k. In kernel B, put needed devices back to normal state.
> > l. In kernel B, write memory image of kernel A out
> > m. In kernel B, put all devices in quiescent and low power state
> > n. In kernel B, Execute acpi_enter_sleep_state(ACPI_STATE_S4)
> 
> That starts looking pretty complex.
> 
> Maybe we should solve the !ACPI case first (should be useful for live
> crashdumping, etc)?

Yeah, I'd suggest leaving ACPI alone, at least for now. ;-)

Greetings,
Rafael