[linux-pm] [RFC] ACPI vs device ordering on resume

Len Brown len.brown at intel.com
Tue Nov 14 23:03:30 PST 2006

On Tuesday 14 November 2006 18:30, Stephen Hemminger wrote:
> If I do a suspend-to-ram then resume on a Sony Vaio laptop with sky2 driver,
> the first interrupt gets misrouted to the original shared IRQ, rather than
> to the MSI irq expected.
> During the pci_restore process, the MSI information and the PCI command register 
> are restored properly. But later during resume, inside the ACPI evaluation of
> the WAK method, the PCI_COMMAND  INTX_DISABLE (0x400) flag is being cleared.
> My guess is that the BIOS ends up doing some resetting of devices.
> I may be able to workaround the problem for this one device, but it brings up
> a more general issue about what the ordering should be during resume. If ACPI
> evaluation (which I assume talks to the BIOS), might change device state, it
> seems that ACPI code should execute before resuming devices not after. But changing
> the order here seems drastic.
> An alternate solution would be to have two pm_ops, one for early_resume
> and another for late, and split the ACPI work.
> --- 2.6.19-rc5.orig/kernel/power/main.c	2006-11-14 14:24:37.000000000 -0800
> +++ 2.6.19-rc5/kernel/power/main.c	2006-11-14 14:25:23.000000000 -0800
> @@ -132,12 +132,12 @@
>  static void suspend_finish(suspend_state_t state)
>  {
> +	if (pm_ops && pm_ops->finish)
> +		pm_ops->finish(state);
>  	device_resume();
>  	resume_console();
>  	thaw_processes();
>  	enable_nonboot_cpus();
> -	if (pm_ops && pm_ops->finish)
> -		pm_ops->finish(state);
>  	pm_restore_console();
>  }

Yes, I agree that _WAK needs to come before device_resume().
Need to let any BIOS nasties happen and get over with before we restore device drivers.
This is consistent with the wording in ACPI 3.0b (section 7.4) that says
11. _WAK is run
12. OSPM notifies all native device drivefrs of the return from the sleep state transition

However, commit 1a38416cea8ac801ae8f261074721f35317613dc says that
_WAK must follow INIT -- ie finish() must come after enable_nonboot_cpus(),
and this patch as it stands would violate that.

So it looks like we need this sequence:

enable_nonboot_cpus() /* INIT */
finish()	/* _WAK */


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