[coreboot] vm86 for gigabyte m57sli

Ronald Hoogenboom ronald at zonnet.nl
Mon Mar 10 23:52:35 CET 2008


Hi,

In my quest to get some life in my nvidia 8600GT board, I've been trying
to get the VGA rom executed by vm86 instead of x86emu.
There are a few other mainboards that do this too. The source file
implementing this turns out to be called 'vgabios.c', of which some
variants exist. I also figured out that the _RAMBASE must be set to
0x4000 for this to be linkable (otherwise truncated 16 bit relocations).

The one for via epia-m needs some support in the northbridge (vt8623) to
call the do_vgabios. The vgabios file is in the mainboard/via/epia-m
directory.

The one for artecgroup dbe61 seems to be the most stand-alone/versatile,
but it needs some modification of the device tree in Config.lb. The
vgabios.c is in mainboard/artecgroup/dbe61/realmode and it looks like
the intention is that this directory should be copied under drivers/pci
and some section

chip drivers/pci/realmode
   device pci 1.1 on end                   # VGA
   register "rom_address" = "0xf4100000"   # at the beginning of 256k
end

should be added to the Config.lb of the mainboard. But I cannot figure
out where it should be exactly. Putting it just after the 'end # PCI
domain' will just make the boot stops in 'Reading resources' without any
clue. Putting it just before the 'end # PCI domain' produces 'PCI: Left
over static devices....' in 'Enumerating busses'.
Also setting the rom address in there like this looks awkward to me, as
it will most probably be different for a different VGA card.

What is the way to go forward? Would I be better off using the epia-m
vm86 and change the northbridge for the m57sli (amdk8)?

Ronald.





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