linux-kernel - Re: [PATCH] Make e100 suspend handler support PCI cards lacking PM capability

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Message-Id: <200906140045.25264.rjw@sisk.pl>
Date:	Sun, 14 Jun 2009 00:45:24 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	andi@...as.de
Cc:	akpm@...ux-foundation.org, e1000-devel@...ts.sourceforge.net,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Make e100 suspend handler support PCI cards lacking PM capability

On Sunday 14 June 2009, Rafael J. Wysocki wrote:
> On Saturday 13 June 2009, Andreas Mohr wrote:
> > Hi all,
> > 
> > after having added non-MII PHY card support to e100, I noticed that
> > the suspend handler rejects power-management non-capable PCI cards,
> 
> Well, that means we have a bug somewhere in the PCI PM core.
> 
> > causing a S2R request to immediately get back up to the desktop,
> > losing network access in the process (rtnl mutex deadlock).
> 
> That's bad.
> 
> > 
> > ChangeLog:
> > Support PCI cards which are lacking power management capability
> > in the e100 suspend handler.
> > 
> > 
> > Frankly I was unsure how to best add this to the driver in a clean way.
> > Usually drivers use pci_set_power_state(..., pci_choose_state(...))
> > in order to avoid the rejection of an open-coded
> > pci_set_power_state(..., PCI_D3hot) in case of a non-PM card,
> > however pci_choose_state() depends on the _pm-internal_ pm_message_t type,
> > which was doable in .suspend directly but not at the other e100
> > driver locations where it was used.
> > 
> > Next attempt was to extend __e100_power_off() with a pci_power_t parameter,
> > however since __e100_power_off() is called by two locations,
> > that meant that I'd have to use pci_choose_state() at _both_ call sites.
> > 
> > Thus I simply resorted to do a brute-force yet most simple
> > pci_find_capability() check in the __e100_power_off() function.
> > 
> > 
> > Tested on 2.6.30-rc8 and suspending/resuming fine, checkpatch.pl:ed.
> > Patch against 2.6.30-rc8 with my original non-MII support patch applied.
> > (should apply fine in any case, I'd think).
> > Intended for testing in -mmotm or so.
> > 
> > Thanks!
> > 
> > Signed-off-by: Andreas Mohr <andi@...as.de>
> > 
> > 
> > --- linux-2.6.30-rc8.e100/drivers/net/e100.c.my_patch_orig	2009-06-13 18:47:53.000000000 +0200
> > +++ linux-2.6.30-rc8.e100/drivers/net/e100.c	2009-06-13 20:27:46.000000000 +0200
> > @@ -2897,6 +2897,13 @@ static void __e100_shutdown(struct pci_d
> >  
> >  static int __e100_power_off(struct pci_dev *pdev, bool wake)
> >  {
> > +	/* some older devices don't support PCI PM
> > +	 * (e.g. mac_82557_D100_B combo card with 80c24 PHY)
> > +	 * - skip those! (they most likely won't support WoL either)
> > +	 */
> > +	if (!pci_find_capability(pdev, PCI_CAP_ID_PM))
> > +		return 0;
> 
> Devices without PCI_CAP_ID_PM may still be power-manageable by ACPI, so
> returning 0 at this point is not a general solution.
> 
> > +
> >  	if (wake) {
> >  		return pci_prepare_to_sleep(pdev);
> 
> pci_prepare_to_sleep() is supposed to return 0 for your device.  I'll have a
> look at it.

Please check if the appended patch helps.

Best,
Rafael

---
 drivers/pci/pci.c |    5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

Index: linux-2.6/drivers/pci/pci.c
===================================================================
--- linux-2.6.orig/drivers/pci/pci.c
+++ linux-2.6/drivers/pci/pci.c
@@ -1284,15 +1284,14 @@ pci_power_t pci_target_state(struct pci_
 		default:
 			target_state = state;
 		}
+	} else if (!dev->pm_cap) {
+		target_state = PCI_D0;
 	} else if (device_may_wakeup(&dev->dev)) {
 		/*
 		 * Find the deepest state from which the device can generate
 		 * wake-up events, make it the target state and enable device
 		 * to generate PME#.
 		 */
-		if (!dev->pm_cap)
-			return PCI_POWER_ERROR;
-
 		if (dev->pme_support) {
 			while (target_state
 			      && !(dev->pme_support & (1 << target_state)))
--
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