linux-kernel - Re: [PATCH] USB: Fix suspend-resume of PCI USB controllers

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Date:	Tue, 20 Jan 2009 22:03:42 +0100
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Len Brown <lenb@...nel.org>
Cc:	Alan Stern <stern@...land.harvard.edu>, Greg KH <gregkh@...e.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Andrey Borzenkov <arvidjaar@...l.ru>,
	LKML <linux-kernel@...r.kernel.org>,
	USB list <linux-usb@...r.kernel.org>,
	pm list <linux-pm@...ts.linux-foundation.org>,
	Christian Borntraeger <borntraeger@...ibm.com>,
	Zdenek Kabelac <zdenek.kabelac@...il.com>,
	Ingo Molnar <mingo@...e.hu>,
	Jeff Chua <jeff.chua.linux@...il.com>
Subject: Re: [PATCH] USB: Fix suspend-resume of PCI USB controllers

On Tuesday 20 January 2009, Len Brown wrote:
> 
> > > Alan, does this look ok for you?
> > 
> > There are a few things I don't like about it:
> > 
> > 	In usb_hcd_pci_suspend, the failure path for 
> > 	pci_set_power_state doesn't undo all the changes
> > 	that have already been made.  In fact, the easiest
> > 	way to do the rest of the recovery probably is to
> > 	call usb_hcd_pci_resume directly.
> > 
> > 	In the !has_pci_pm path we don't call pci_set_power_state.
> > 	This means controllers with legacy power management won't
> > 	get suspended.  Maybe pci_set_power_state should be
> > 	called always, and has_pci_pm be used only for
> > 	interpreting the return code and printing debug messages.
> > 
> > 	In usb_hcd_pci_resume, the pci_wake_from_d3 call
> > 	should be moved up right next to the pci_enable_wake
> > 	call.  It makes no sense for them to be separated by
> > 	pci_enable_device and pci_set_master.  After all,
> > 	even if you can't re-enable the device you probably
> > 	don't want it to continue being a wakeup source.
> > 
> > 	It's a little annoying that several debug messages
> > 	in usb_hcd_pci_resume have been removed.  Can't we
> > 	display the power state upon entry, before trying to
> > 	change it?
> > 
> > 	It stands out that the resume method contains no call
> > 	to match pci_set_power_state() in the suspend method.
> > 	There should at least be a comment about it.
> > 
> > Some of these problems predate Rafael's patch.  Given that it has 
> > already helped a number of people, we might want to merge the patch 
> > and then make additional changes to address these issues.
> 
> Rafael's patch is required for upstream to resume on my T61.
> 
> Tested-by: Len Brown <len.brown@...el.com>
> 
> Perhaps Greg can apply Rafael's patch now to fix upstream ASAP,
> while Alan prepares a 2nd patch to address his observations above?

I'd very much appreciate doing that.  My intention was only to fix the urgent
issue at hand.

Thanks,
Rafael
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