On Thu, May 10, 2001 at 11:11:53AM -0700, Jun Sun wrote: > I would not normally assign IO space above 0xffff either. But recently I > found multiple PCI buses, especially dual PCI buses, are getting popular, as > examplified by two Gallelio chips and the new NEC Vrc5477 chips. > > Since all drivers share the same mips_io_port_base, - even though the devices > may be on different PCI buses - we need to assign the PCI IO windows > contiguously so that drivers can share the same base address. In most such > setups, you will get more than 0xffff IO ranges. After some discussion with some of the Linux PCI guys I think we should try to avoid extend the per-bus I/O address space beyond 64k ports. This is not a very strong ``should avoid'', though. The primary concern is a number of broken peripheral chips which apparently are floating around out there in good numbers. Another reason to not extend the PCI-bus address range to 4g ports is the size of the available physical address space in the main processor's address space itself. Limited by the 32-bit address space we can only address a limited number via in/out anyway, so we better shouldn't fake what we ain't got (cited freely after Seymoure Cray), so 4g ports is silly anyway. Ralf
