netdev - Re: [PATCH 1/3] tg3: Avoid setting power.can_wakeup for devices that cannot wake up

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Message-Id: <201102102208.42410.rjw@sisk.pl>
Date:	Thu, 10 Feb 2011 22:08:42 +0100
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	"Matt Carlson" <mcarlson@...adcom.com>
Cc:	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"David Miller" <davem@...emloft.net>,
	"Michael Chan" <mchan@...adcom.com>,
	"Linux PM mailing list" <linux-pm@...ts.linux-foundation.org>,
	"Thomas Fjellstrom" <thomas@...llstrom.ca>,
	"Jay Cliburn" <jcliburn@...il.com>,
	"Chris Snook" <chris.snook@...il.com>,
	"Jie Yang" <jie.yang@...eros.com>
Subject: Re: [PATCH 1/3] tg3: Avoid setting power.can_wakeup for devices that cannot wake up

On Thursday, February 10, 2011, Matt Carlson wrote:
> On Thu, Feb 10, 2011 at 08:53:09AM -0800, Rafael J. Wysocki wrote:
> > From: Rafael J. Wysocki <rjw@...k.pl>
> > 
> > The tg3 driver uses device_init_wakeup() in such a way that the
> > device's power.can_wakeup flag may be set even though the PCI
> > subsystem cleared it before, in which case the device cannot wake
> > up the system from sleep states.  Modify the driver to only change
> > the power.can_wakeup flag if the device is not capable of generating
> > wakeup signals.
> > 
> > Signed-off-by: Rafael J. Wysocki <rjw@...k.pl>
> > ---
> >  drivers/net/tg3.c |    6 ++++--
> >  1 file changed, 4 insertions(+), 2 deletions(-)
> > 
> > Index: linux-2.6/drivers/net/tg3.c
> > ===================================================================
> > --- linux-2.6.orig/drivers/net/tg3.c
> > +++ linux-2.6/drivers/net/tg3.c
> > @@ -12403,9 +12403,11 @@ static void __devinit tg3_get_eeprom_hw_
> >  			tp->tg3_flags3 |= TG3_FLG3_RGMII_EXT_IBND_TX_EN;
> >  	}
> >  done:
> > -	device_init_wakeup(&tp->pdev->dev, tp->tg3_flags & TG3_FLAG_WOL_CAP);
> > -	device_set_wakeup_enable(&tp->pdev->dev,
> > +	if (tp->tg3_flags & TG3_FLAG_WOL_CAP)
> > +		device_set_wakeup_enable(&tp->pdev->dev,
> >  				 tp->tg3_flags & TG3_FLAG_WOL_ENABLE);
> > +	else
> > +		device_set_wakeup_capable(&tp->pdev->dev, false);
> 
> I did this because I couldn't see where 'can_wakeup' gets set.  I don't
> see a call to device_init_wakeup() that would be relevant to tg3
> devices.  I do see a couple calls to device_set_wakeup_capable() in
> acpi/glue.c and acpi/scan.c.  Is that the place?

No, it's pci_pm_init() or platform_pci_wakeup_init() and they both use
device_set_wakeup_capable() rather tha device_init_wakeup(), which is just a
combination of device_set_wakeup_capable() and device_set_wakeup_enable()
anyway.

And there's no why reason PCI drivers should use device_pm_init() at all.

> >  }
> >  
> >  static int __devinit tg3_issue_otp_command(struct tg3 *tp, u32 cmd)
> 
> This is something I was always curious about too.  The TG3_FLAG_WOL_CAP
> tracks whether or not the device can handle WOL.  Is it safe to do away
> with this flag and lean on the 'can_wakeup' flag instead?

I don't think so.  power.can_wakeup only tracks the capability to generate
wakeup signals from the PCI perspective and it is set by PCI if the device
appears to be able to generate wakeup signals.

So, I think the driver should work as in the $subject patch - reset the
power.can_wakeup flag if TG3_FLAG_WOL_CAP is unset and don't touch it
otherwise.

Thanks,
Rafael
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