Subject: Re: [PATCH 8/8] Cell IOMMU fixed mapping support

From: Michael Ellerman <[email-masked]>
Date: Wed, 30 Jan 2008 02:13:45 +1100

On Tue, 2008-01-29 at 09:15 -0600, Olof Johansson wrote:
> On Wed, Jan 30, 2008 at 01:14:03AM +1100, Michael Ellerman wrote:
> 
> > For example a machine with 4GB of memory would end up with the normal
> > IOMMU window from 0-2GB and the fixed mapping window from 2GB to 6GB. In
> > this case a 64-bit device wishing to DMA to 1GB would be told to DMA to
> > 3GB, plus any offset required by firmware. The firmware offset is encoded
> > in the "dma-ranges" property.
> 
> Shouldn't the fixed mapping be between 4G and 8G (and the offset for 1G
> is at 5G), to account for the MMIO range at 2-4G?

I don't think so, ie. it works setup like that, but I'm not entirely
sure why. Presumably the 2-4GB for MMIO is only for cycles heading out
of the CPU.

cheers

-- 
Michael Ellerman
OzLabs, IBM Australia Development Lab

wwweb: http://michael.ellerman.id.au
phone: +61 2 6212 1183 (tie line 70 21183)

We do not inherit the earth from our ancestors,
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