[LinuxBIOS] RE : Re: VGA bios and i/o access for powerpc

ollie ollie at lanl.gov
Tue Sep 5 22:53:16 CEST 2006

On Tue, 2006-09-05 at 20:02 +0200, jean-francois simon wrote:
>         Those legacy IO ports are NOT necessary mapped to the PCI IO
>         address.
>         Some VGA card does and some others come with some kind of
>         remapping
>         or offset. Your system chipset should have a way to map legacy
>         VGA IO
>         ports to memory address. You have to read the doc to the PPC
>         chipset 
>         carefully to find it out.
> I have read the chipset doc and there is no such VGA support.
> But could you plse explain more on the different ways for VGA cards to
> map the VGA registers? Since the registers are located on a PCI agent
> (the graphic card), there must be a way to access them by generating
> PCI cycles?
> Thanks

I don't know how exactly those legacy IO address is implemented by the
HW and/or the bus protocol. But the Appendix G of PCI sepc says it is
possible for PCI device to decode those legacy ports independent of
the base address register.



More information about the coreboot mailing list