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

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Message-Id: <201209212130.50085.rjw@sisk.pl>
Date:	Fri, 21 Sep 2012 21:30:49 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Huang Ying <ying.huang@...el.com>
Cc:	Bjorn Helgaas <bhelgaas@...gle.com>, linux-kernel@...r.kernel.org,
	linux-pci@...r.kernel.org, linux-pm@...r.kernel.org,
	Eric Biederman <ebiederm@...ssion.com>,
	kexec@...ts.infradead.org
Subject: Re: [RFC 1/3] PCI/PM: Fix kexec for D3cold and bridge suspending

On Friday, September 21, 2012, Huang Ying wrote:
> 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@...el.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?

I'd say every device for starters.

Thanks,
Rafael


> > 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@...el.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);
> > > 
> > > 
> > 
> 
> 
> 
> 

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