[coreboot] PCI IO Address space over 0xffff

Joe Korty joe.korty at ccur.com
Sat May 22 17:49:40 CEST 2010

On Fri, May 21, 2010 at 05:04:26PM -0400, Carl-Daniel Hailfinger wrote:
> > On Fri, May 21, 2010 at 12:10:51PM -0400, Myles Watson wrote:
> >> On Fri, May 14, 2010 at 1:49 PM, Joe Korty <joe.korty at ccur.com> wrote:
> > I've solved this one, kind of.  It is PCI IO Space
> > overflow, we are going over 0xffff which apparently is
> > a hard limit.  I image this is there so that inb, outw,
> > etc instructions can be used to reference these devices.
> >
> > But if one doesn't use such instructions (instead using
> > memory mapped PCI IO space), I see no reason why Linux
> > and coreboot couldn't work with PCI IO Space addresses
> >> 0xffff.
> I'm interested in how you want to map port IO space to memory.
> Please explain.
> AFAIK PCI register space is totally independent of port IO space which
> is totally independent of memory space. You can access PCI register
> space via CF8/CFC port IO and via MMCONFIG memory, but I'm unaware of
> any mechanisms to map IO ports to memory or the other way round.

Well, all I know at this point is that the Linux kernel
sources have code that maps inb etc either to the
instructions or to a memory dereference, and the .config
for that chooses memory dereference for x86.

It's gonna be fun seeing if high-IO-address space can be
made to work..


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