linux-kernel - Re: iommu breaks usb after resume

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Date:	Fri, 28 Mar 2008 00:52:00 +0100
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Pavel Machek <pavel@....cz>
Cc:	Andi Kleen <andi@...stfloor.org>, Ingo Molnar <mingo@...e.hu>,
	kernel list <linux-kernel@...r.kernel.org>,
	Greg KH <greg@...ah.com>
Subject: Re: iommu breaks usb after resume

On Friday, 28 of March 2008, Pavel Machek wrote:
> On Thu 2008-03-27 21:30:37, Rafael J. Wysocki wrote:
> > On Wednesday, 26 of March 2008, Pavel Machek wrote:
> > > Hi!
> > > 
> > > > > CONFIG_AGP=y
> > > > > CONFIG_AGP_AMD64=y
> > > > > CONFIG_AGP_INTEL=y
> > > > > # CONFIG_AGP_SIS is not set
> > > > > CONFIG_AGP_VIA=y
> > > > > CONFIG_DRM=y
> > > > > # CONFIG_DRM_TDFX is not set
> > > > > 
> > > > > ...do I need to enable something more?
> > > > 
> > > > Should have worked then. Ok modulo bugs. Maybe the ordering
> > > > is wrong now (AGP resume would need to run before anything
> > > > using the IOMMU)
> > > 
> > > So agp_amd64_resume() is responsible for reiniting iommu on new amd64
> > > boxes?
> > > 
> > > It is registered as normal pci driver:
> > > 
> > > static struct pci_driver agp_amd64_pci_driver = {
> > > 	.name		= "agpgart-amd64",
> > > 	.id_table	= agp_amd64_pci_table,
> > > 	.probe		= agp_amd64_probe,
> > > 	.remove		= agp_amd64_remove,
> > > #ifdef CONFIG_PM
> > > 	.suspend	= agp_amd64_suspend,
> > > 	.resume		= agp_amd64_resume,
> > > #endif
> > > };
> > > 
> > > ...should it be modified to run early, as other pci devices (USB
> > > controllers) may rely on this?
> > > 
> > > I did this... I'll verify it in 10 hours or so. If someone has amd64
> > > system with >=4G ram, there should be hibernation problems. This
> > > should fix it:
> > > 
> > > diff --git a/drivers/char/agp/amd64-agp.c b/drivers/char/agp/amd64-agp.c
> > > index d8200ac..4e85178 100644
> > > --- a/drivers/char/agp/amd64-agp.c
> > > +++ b/drivers/char/agp/amd64-agp.c
> > > @@ -594,12 +594,14 @@ static int agp_amd64_suspend(struct pci_
> > >  
> > >  static int agp_amd64_resume(struct pci_dev *pdev)
> > >  {
> > > +	printk("agp_amd64: resume\n");
> > >  	pci_set_power_state(pdev, PCI_D0);
> > >  	pci_restore_state(pdev);
> > >  
> > >  	if (pdev->vendor == PCI_VENDOR_ID_NVIDIA)
> > >  		nforce3_agp_init(pdev);
> > >  
> > > +	printk("agp_amd64: 8151 configure\n");
> > >  	return amd_8151_configure();
> > >  }
> > >  
> > > @@ -733,8 +735,8 @@ static struct pci_driver agp_amd64_pci_d
> > >  	.probe		= agp_amd64_probe,
> > >  	.remove		= agp_amd64_remove,
> > >  #ifdef CONFIG_PM
> > > -	.suspend	= agp_amd64_suspend,
> > > -	.resume		= agp_amd64_resume,
> > > +	.suspend_late	= agp_amd64_suspend,
> > > +	.resume_early	= agp_amd64_resume,
> > >  #endif
> > >  };
> > 
> > Okay, a couple of questions:
> > 
> > (1) Are you sure that the .suspend() and .resume() callbacks will just work
> >     with interrupts disabled?
> 
> I have not really checked -- it turned out this is not "my" problem
> after all. My machine (called leet) uses different setup. If they will
> not, I guess lockdep will tell us ;-).

Lockdep need not tell us about it, I think.  OTOH, I don't really see a
scenario in which having interrupts disabled while executing ->suspend() and
->resume() might hurt.

> > (2) Even if they work, is it sufficient to just move them to the "late" and
> >     "early" parts?  That is, isn't there anything using the iommu in the
> >     "early" and "late" callbacks of the other devices?
> 
> We definitely have iommu users in "normal" callbacks: USB.

Oh, there may be more.  You never know what appears in future systems. :-)

> I do not think we have iommu users in early/late callbacks...

Perhaps not at the moment, but what's the guarantee there won't be any in the
future?

Rafael
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