On Wed, Jan 30, 2008 at 02:13:45AM +1100, Michael Ellerman wrote: > 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.
Ben denied that being so yesterday. :-) If that's the case, then you can stick the dynamic range there for >32GB configs, since it's still addressable with 32 bits. -Olof _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@ozlabs.org https://ozlabs.org/mailman/listinfo/linuxppc-dev
