linux-kernel - Re: [PATCH 3/3 -mm] kexec based hibernation -v6: kexec hibernate/resume

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Date:	Tue, 20 Nov 2007 10:50:33 +0800
From:	"Huang, Ying" <ying.huang@...el.com>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Pavel Machek <pavel@....cz>, nigel@...el.suspend2.net,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jeremy Maitin-Shepard <jbms@....edu>,
	linux-kernel@...r.kernel.org, linux-pm@...ts.linux-foundation.org,
	Kexec Mailing List <kexec@...ts.infradead.org>
Subject: Re: [PATCH 3/3 -mm] kexec based hibernation -v6: kexec
	hibernate/resume

On Tue, 2007-11-20 at 03:24 +0100, Rafael J. Wysocki wrote:
> On Tuesday, 20 of November 2007, Huang, Ying wrote:
> > On Mon, 2007-11-19 at 19:22 +0100, Rafael J. Wysocki wrote:
> > > > +#ifdef CONFIG_KEXEC
> > > > +static void kexec_hibernate_power_down(void)
> > > > +{
> > > > +	switch (hibernation_mode) {
> > > > +	case HIBERNATION_TEST:
> > > > +	case HIBERNATION_TESTPROC:
> > > > +		break;
> > > > +	case HIBERNATION_REBOOT:
> > > > +		machine_restart(NULL);
> > > > +		break;
> > > > +	case HIBERNATION_PLATFORM:
> > > > +		if (!hibernation_ops)
> > > > +			break;
> > > > +		hibernation_ops->enter();
> > > 
> > > hibernation_platform_enter() should be used here (as of the current mainline).
> > 
> > The power_down will be called with interrupt disabled, device suspended,
> > non-boot CPU disabled. But the latest hibernate_platform_enter calls the
> > device_suspend, disable_nonboot_cpus etc function. So, I use
> > hibernation_ops->enter() directly instead of
> > hibernation_platform_enter().
> 
> Hm, you need to call device_power_down(PMSG_SUSPEND) before
> hibernation_ops->enter().
> 
> Also, all of the ACPI global calls need to be carried out before that and the
> devices should be suspended rather than shut down in that case.
> 
> That's why hibernation_platform_enter() has been introduced, BTW.

Situation is a little different between u/swsusp and khiberantion.

u/swsusp:

platform_start();
suspend console();
device_suspend(PMSG_FREEZE);
platform_pre_snapshot();
disable_nonboot_cpus();
local_irq_disable();
device_power_down(PMSG_FREEZE);
/* create snapshot */
device_power_up();
local_irq_enable();
enable_nonboot_cpus();
platform_finish();
device_resume();
resume_console();
/* write the image out */
hibernation_ops->start();
suspend_console();
device_suspend(PMSG_SUSPEND);
hibernation_ops->prepare();
disable_nonboot_cpus();
local_irq_disable();
device_power_down(PMSG_SUSPEND);
hibernation_ops->enter();

khibernation:

suspend_console();
platform_start();
device_suspend(PMSG_FREEZE);
platform_pre_snapshot();
disable_nonboot_cpus();
local_irq_disable();
device_power_down(PMSG_FREEZE);
/* jump to kexeced (hibernating) kernel */
/* in kexeced kernel */
device_power_up();
local_irq_eanble();
enable_nonboot_cpus();
device_resume();
resume_console();
/* write the image */
suspend_console();
device_suspend(PMSG_FREEZE);
disable_nonboot_cpus();
local_irq_disable();
device_power_down(PMSG_FREEZE);
/* jump to original (hibernated) kernel */
/* in original kernel */
hibernation_ops->enter();

The difference is:

- In u/swsusp, ACPI methods are executed twice, before writing out the
image and after writing out the image.
- After writing out the image, the PMSG_SUSPEND is used instead of
PMSG_FREEZE.

Some questions:

- What is the difference between PMSG_SUSPEND and PMSG_FREEZE?
- The ACPI methods should be executed once or twice? According to ACPI
specification?

Best Regards,
Huang Ying
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