linux-kernel - Re: [PATCH] PCI / PM: Restore the original behavior of pci_set_power

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Message-Id: <201207052357.44494.rjw@sisk.pl>
Date:	Thu, 5 Jul 2012 23:57:44 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Bjorn Helgaas <bhelgaas@...gle.com>
Cc:	Jesse Barnes <jbarnes@...tuousgeek.org>,
	Linux PM mailing list <linux-pm@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Matthew Garrett <mjg59@...f.ucam.org>,
	"linux-pci" <linux-pci@...r.kernel.org>,
	Huang Ying <ying.huang@...el.com>
Subject: Re: [PATCH] PCI / PM: Restore the original behavior of pci_set_power_state()

On Thursday, July 05, 2012, Bjorn Helgaas wrote:
> On Thu, Jun 28, 2012 at 4:01 AM, Rafael J. Wysocki <rjw@...k.pl> wrote:
> > From: Rafael J. Wysocki <rjw@...k.pl>
> >
> > Commit cc2893b6 (PCI: Ensure we re-enable devices on resume)
> > addressed the problem with USB not being powered after resume on
> > recent Lenovo machines, but it did that in a suboptimal way.
> > Namely, it should have changed the relevant code paths only,
> > which are pci_pm_resume_noirq() and pci_pm_restore_noirq() supposed
> > to restore the device's power and standard configuration registers
> > after system resume from suspend or hibernation.  Instead, however,
> > it modified pci_set_power_state() which is executed in several
> > other situations too.  That resulted in some undesirable effects,
> > like attempting to change a device's power state in the same way
> > multiple times in a row (up to as many as 4 times in a row in the
> > snd_hda_intel driver).
> >
> > Fix the bug addressed by commit cc2893b6 in an alternative way,
> > by forcibly powering up all devices in pci_pm_default_resume_early(),
> > which is called by pci_pm_resume_noirq() and pci_pm_restore_noirq()
> > to restore the device's power and standard configuration registers,
> > and modifying pci_pm_runtime_resume() to avoid the forcible power-up
> > if not necessary.  Then, revert the changes made by commit cc2893b6
> > to make the confusion introduced by it go away.
> >
> > Signed-off-by: Rafael J. Wysocki <rjw@...k.pl>
> > ---
> >  drivers/pci/pci-driver.c |   14 ++++++++------
> >  drivers/pci/pci.c        |   19 ++++++++++++++++++-
> >  drivers/pci/pci.h        |    1 +
> >  3 files changed, 27 insertions(+), 7 deletions(-)
> >
> > Index: linux/drivers/pci/pci.c
> > ===================================================================
> > --- linux.orig/drivers/pci/pci.c
> > +++ linux/drivers/pci/pci.c
> > @@ -662,6 +662,19 @@ void pci_update_current_state(struct pci
> >  }
> >
> >  /**
> > + * pci_power_up - Put the given device into D0 forcibly
> > + * @dev: PCI device to power up
> > + */
> > +void pci_power_up(struct pci_dev *dev)
> > +{
> > +       if (platform_pci_power_manageable(dev))
> > +               platform_pci_set_power_state(dev, PCI_D0);
> > +
> > +       pci_raw_set_power_state(dev, PCI_D0);
> > +       pci_update_current_state(dev, PCI_D0);
> > +}
> > +
> > +/**
> >   * pci_platform_power_transition - Use platform to change device power state
> >   * @dev: PCI device to handle.
> >   * @state: State to put the device into.
> > @@ -707,7 +720,7 @@ static void __pci_start_power_transition
> >   */
> >  int __pci_complete_power_transition(struct pci_dev *dev, pci_power_t state)
> >  {
> > -       return state >= PCI_D0 ?
> > +       return state > PCI_D0 ?
> >                         pci_platform_power_transition(dev, state) : -EINVAL;
> 
> This hunk conflicted with Huang's D3_COLD patches.  I fixed it up; can
> you check and make sure I did it correctly?
> 
> I pushed the resolution to here:
> git://git.kernel.org/pub/scm/linux/kernel/git/helgaas/pci.git on the
> pci/rafael-pci_set_power_state-rebase branch.

Yes, it looks good.  The point is to make __pci_complete_power_transition()
return the error code for PCI_DO too.

Thanks,
Rafael
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