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

ollie ollie at lanl.gov
Tue Sep 5 19:22:28 CEST 2006

On Tue, 2006-09-05 at 12:46 +0200, jf simon wrote:
> Hi,
> I have read the excellent paper on FreeVGA
> http://www.linuxbios.org/data/vgabios/
> and I am thinking on using it on a powerpc design we have made based on 
> IBM 970fx ppc64 CPU (after it runs linuxbios of course, but I am trying 
> to plan ahead and see what is needed to have PCI graphic cards running 
> on it).
> I have looked at the x86emu code, and more precisely to the 
> X86EMU_pioFuncs  function which is in charge of I/O accesses whenever 
> the VGA BIOS makes  an x86 int/out instruction to some I/O port (for 
> example to the range of VGA control registers in the 0x3XX region). The 
> graphic I intend to use is an ATI Radeon RV100 PCI card. So it looks 
> like I will have to program the X86EMU_pioFuncs with  a function that 
> will redirect I/O accesses from the low 0x3XX addresses,  to the ATI PCI 
> I/O region that contains VGA registers. Here is an excerpt of an "lspci 
> -vv" on my graphic card (see below). I am planning to re-direct all 
> these  I/O accesses  to the region 1 (I/O ports at f4015000). The VGA 
> registers have to be in there...where else?
> So it shouldn't be too hard. Am I overlooking things? The FreeVGA paper 
> said he should be rather complicated to do on powerpc....so i may be to 
> optimistic

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.


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