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

["Rafael J. Wysocki" <rjw@sisk.pl>]

On Wednesday, 15 November 2006 08:03, Len Brown wrote:
> 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 */
> device_resume()

Which is a problem, because thaw_processes() is not SMP-safe.

Greetings,
Rafael


-- 
You never change things by fighting the existing reality.
		R. Buckminster Fuller