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, we borrow it from our children. - S.M.A.R.T Person
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