On Sat, 6 May 2000, Bernd Harries wrote:
> Some thoughts on your ISA ideas:
>
> Geert Uytterhoeven wrote:
>
> > On most other machines (ARM, MIPS, PPC), ISA memory
> > space is located somewhere else in PCI memory space.
>
> - What qualifies a 16 MB region to be called ISA space?
The fact that memory accesses to this region are propagated on the ISA bus as
ISA memory accesses.
> - Can there only be 1 of these regions? 4 GB could hold 256 spaces a 16
> MB
If you have multiple host/PCI bridges, I think you can have multiple ISA
memory spaces. Cfr. what happens on the PowerMacs with two host/PCI bridges.
> > However, there are still some problems left:
> >
> > 1. How to allocate ISA memory space?
> >
> > Some drivers do
> >
> > request_mem_region(0xA0000, 65535, ...)
>
> If start is a long int it it could easyly be 0x7F0A0000 or 0xFE0A0000.
Sorry, I don't understand what you're trying to say here. My problem is that
drivers assume 0xA0000 (VGA memory) in ISA memory space is at 0xA0000 in CPU
memory space.
> What would it be like to access ISA IO space on archs which have mmapped
> IO?
On my CHRP LongTrail PPC box, ISA memory space is at 0xf7000000. on PReP PPC,
it's at 0xc0000000.
> Some even have ISA IO inside 64K of _each_ ISA MEM space.
Huh?
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- Linux/{m68k~Amiga,PPC~CHRP} -- geert@linux-m68k.org
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
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