Re: [PATCH v2 6/7] PCI/PM: warn about incomplete actions in ->runtime_suspend()callback

[Konstantin Khlebnikov]

Rafael J. Wysocki wrote:
> On Monday, February 04, 2013 03:56:12 PM Konstantin Khlebnikov wrote:
> > Documentation/power/pci.txt says:
> > | It is expected that the device driver's pm->runtime_suspend() callback will
> > | not attempt to prepare the device for signaling wakeup or to put it into a
> > | low-power state.  The driver ought to leave these tasks to the PCI subsystem
> > | that has all of the information necessary to perform them.
> >
> > After commit 42eca2302146fed51335b95128e949ee6f54478f
> > ("PCI: Don't touch card regs after runtime suspend D3")
> > | If the driver takes care of state saving, don't touch any registers on it.
> > pci_pm_runtime_suspend() thinks if state has been saved by ->runtime_suspend()
> > that means device alredy prepared for wakeup and probably no longer accessible.
> >
> > Thus driver must either do all actions or leave all these tasks to PCI subsystem.
>
> I don't like this one, because it will generate noise for drivers that
> legitimately use pci_save_state() in their runtime suspend callbacks
> and know what they are doing.

Ok, you're right. Both these warnings can be false-positive.
For example some of wifi cards easily might be weird enough for this.

> Thanks,
> Rafael
>
>
> > Signed-off-by: Konstantin Khlebnikov<khlebnikov@xxxxxxxxxx>
> > Cc: Rafael J. Wysocki<rafael.j.wysocki@xxxxxxxxx>
> > Cc: Bjorn Helgaas<bhelgaas@xxxxxxxxxx>
> > Cc: linux-pci@xxxxxxxxxxxxxxx
> > ---
> >   drivers/pci/pci-driver.c |   15 +++++++++++----
> >   1 file changed, 11 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c
> > index f9aa311..2b0ff9a 100644
> > --- a/drivers/pci/pci-driver.c
> > +++ b/drivers/pci/pci-driver.c
> > @@ -1009,12 +1009,19 @@ static int pci_pm_runtime_suspend(struct device *dev)
> >   		return 0;
> >   	}
> >
> > -	if (!pci_dev->state_saved) {
> > -		pci_save_state(pci_dev);
> > -		pci_finish_runtime_suspend(pci_dev);
> > +	if (pci_dev->state_saved) {
> > +		WARN_ONCE(pci_dev->current_state == prev,
> > +			"PCI PM: Power state of device not changed by %pF\n",
> > +			pm->runtime_suspend);
> > +		WARN_ONCE(pci_dev_run_wake(pci_dev)&&
> > +				!pci_dev->wakeup_prepared,
> > +			"PCI PM: Waking of device not configured by %pF\n",
> > +			pm->runtime_suspend);
> > +		return 0;
> >   	}
> >
> > -	return 0;
> > +	pci_save_state(pci_dev);
> > +	return pci_finish_runtime_suspend(pci_dev);
> >   }
> >
> >   static int pci_pm_runtime_resume(struct device *dev)
> >
> > --
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