[coreboot] PCI IO Address space over 0xffff

Carl-Daniel Hailfinger c-d.hailfinger.devel.2006 at gmx.net
Sat May 22 22:25:21 CEST 2010

On 22.05.2010 20:54, Joe Korty wrote:
> On Sat, May 22, 2010 at 12:54:08PM -0400, ron minnich wrote:
>> pci bridges have always rounded to 4k multiples ... it's in the very
>> earliest spec.
> Thanks.  It does seem that PCI-e uses more bridges than the older PCIs;
> if so that would explain the excessive spreading-out of IO port addresses
> under PCI-e.

I think someone mentioned that some PCIe bridges can map IO port space
to memory space to give non-x86 systems access to IO port space (many
architectures do not have a separate IO port space).

If you manage to find such a PCIe bridge chip with mem<->IOport mapping
capability and if you can hack up Linux to use the memory accessor
functions for the devices behind such a bridge, you can work around
IOport resource space constraints. It would definitely be interesting to
see if that is possible in paractice without breaking lots of stuff.



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