Re: [PATCH] [2/2] POWERPC: Lower threshold for DART enablement to 1GB, V2

[Muli Ben-Yehuda <mulix@mulix.org>]

On Fri, Apr 14, 2006 at 06:52:44AM +1000, Benjamin Herrenschmidt wrote:
> On Thu, 2006-04-13 at 20:31 +0300, Muli Ben-Yehuda wrote:
> > On Thu, Apr 13, 2006 at 11:07:12AM -0500, Olof Johansson wrote:
> > 
> > > Walking the DT means we need to hardcode it on PCI IDs, since the Apple
> > > OF doesn't give the Airport device a logical name. It's probably easier
> > > to implement than walking PCI, but we'd need to maintain a table. My
> > > vote is for PCI walking, I'll give that a shot over the weekend.
> > 
> > Cool! bonus points if you do it in drivers/pci and we can steal it
> > easily for Calgary on x8-64 :-)
> 
> How so ? Anything remotely related to the iommu is totally different...
> Besides, on x86-64, laptops _are_ more common, and thus the problem of
> cardbus cards is much more significant.

What I had in mind is an interface that given a PCI bridge will tell
you what's the most restrictive DMA mask for a device on that bridge,
so that you'll know whether you need to enable the IOMMU for that
bridge. I'll even settle for a function that tells you what's the most
restrictive DMA mask in the system, preiod. There's nothing inherently
arch specific about this.

(and as a side note, the IOMMU we are working on on x86-64 is Calgary,
which is actually roughly the same chipset used in some PPC
machines...)

Cheers,
Muli
-- 
Muli Ben-Yehuda
http://www.mulix.org | http://mulix.livejournal.com/

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