[RFC 1/3] PCI/PM: Fix kexec for D3cold and bridge suspending

[Huang Ying]

On Thu, 2012-09-20 at 21:20 +0200, Rafael J. Wysocki wrote:
> On Monday, September 17, 2012, Bjorn Helgaas wrote:
> > +cc Eric and kexec list
> > 
> > On Mon, Sep 17, 2012 at 2:54 AM, Huang Ying <ying.huang at intel.com> wrote:
> > > If PCI devices are put into D3cold before kexec, because the
> > > configuration registers of PCI devices in D3cold are not accessible.
> > >
> > > And if PCI bridges are put into low power state before kexec,
> > > configuration registers of PCI devices underneath the PCI bridges are
> > > not accessible too.
> > >
> > > These will make some PCI devices can not be scanned after kexec, so
> > > resume the PCI devices in D3cold or PCI bridges in low power state
> > > before kexec.
> > 
> > Don't we need to resume the device even without the kexec issue?  And
> > even if it's in D1 or D2?
> > 
> > It looks to me like pci_msi_shutdown() (and probably drv->shutdown())
> > depend on the device being in D0.
> 
> We should in theory, but we didn't do any power management of PCI bridges
> before, so this is the first time we have a problem with it.
> 
> So I'd say, yeah, let's resume if current_state is between D1 and D3cold
> inclusive and the kexec comment is not very helpful (the problem is not
> kexec-specific in general).

Resume from D1 to D3cold for any device or just bridges?

Best Regards,
Huang Ying

> Speaking of kexec, it might consider using the hibernation device freeze
> instead of device shutdown (which the kexec jump feature does).  I've seen
> reports of problems that would be solved this way most likely.
> 
> Thanks,
> Rafael
> 
> 
> > > Signed-off-by: Huang Ying <ying.huang at intel.com>
> > > ---
> > >  drivers/pci/pci-driver.c |    4 ++++
> > >  1 file changed, 4 insertions(+)
> > >
> > > --- a/drivers/pci/pci-driver.c
> > > +++ b/drivers/pci/pci-driver.c
> > > @@ -421,6 +421,10 @@ static void pci_device_shutdown(struct d
> > >         struct pci_dev *pci_dev = to_pci_dev(dev);
> > >         struct pci_driver *drv = pci_dev->driver;
> > >
> > > +       /* Resume bridges and devices in D3cold for kexec to work properly */
> > > +       if (pci_dev->current_state == PCI_D3cold || pci_dev->subordinate)
> > > +               pm_runtime_resume(dev);
> > > +
> > >         if (drv && drv->shutdown)
> > >                 drv->shutdown(pci_dev);
> > >         pci_msi_shutdown(pci_dev);
> > 
> > 
>