[PATCH 8/8] Cell IOMMU fixed mapping support
michael at ellerman.id.au
Wed Jan 30 02:13:45 EST 2008
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.
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