linux-kernel - Re: iommu breaks usb after resume

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Message-ID: <20080327133451.GH29105@one.firstfloor.org>
Date:	Thu, 27 Mar 2008 14:34:51 +0100
From:	Andi Kleen <andi@...stfloor.org>
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>, "Rafael J. Wysocki" <rjw@...k.pl>
Subject: Re: iommu breaks usb after resume

On Thu, Mar 27, 2008 at 02:29:23PM +0100, Pavel Machek wrote:
> Hi!
> 
> > > ...this sounds like it needs to be done during resume, too, no?
> > 
> > This is only a workaround for BIOS that don't set up an aperture,
> > but yes if they don't do that it is likely needed on resume too.
> > 
> > You would need to add a resume handler to aperture.c
> 
> Probably this needs to be redone during resume, right?

Yes, but using the standard pci access functions to avoid races which
the early boot code can ignore.

> 
> 	/* Fix up the north bridges */
> 	for (num = 24; num < 32; num++) {
> 		if (!early_is_k8_nb(read_pci_config(0, num, 3, 0x00)))
> 			continue;
> 
> 		/*
> 		 * Don't enable translation yet. That is done later.
> 		 * Assume this BIOS didn't initialise the GART so
> 		 * just overwrite all previous bits
> 		 */
> 		write_pci_config(0, num, 3, 0x90, aper_order<<1);
> 		write_pci_config(0, num, 3, 0x94, aper_alloc>>25);
> 	}
> 
> ....plus the "enable translation" part... but where is that hiding?

Both pci-gart and the AGP driver have code for this.

-Andi

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