[coreboot] Native init for AMD cards

[Rudolf Marek]

Hi David,

 > I read the kernel sources today, looking for a way of doing native init for 
AMD boards like the F2A85-M.
 > Comments welcome on the insanity of this proposal :)

In fact I did the same some time ago, but there is a problem with the AtomBIOS 
and the graphical data paths.

> 2. Do coreboot developers have contact with the radeon driver developers? A
> little nudge from time to time could keep a project like this on track.

I was speaking with Alex (I put him on CC) My Q was:

 > My plan (which may sound bit naiive), is/was to Initialize the GPU with
 > AsicInit (so simple run of AtomBIOS interpreter) and then switch it to legacy VGA
 > mode and handle this with SeaBIOS VGA BIOS. Maybe there is a gap between -
 > setting up a legacy VGA and AsicInit, I don't know, possibly I need to detect 
what kind of output is used, but all I need is simple text mode
 >
 > Please can you throw some light on this topic?

Alex told me:

The AsicInit table just performs low level setup on the asic, it doesn't mess 
with the displays at all.  The radeon vbios has real mode x86 code that gets 
executed at post or via vbe calls to read in the information in the atombios 
tables, figure out the display topology and detect and light up whatever 
displays are attached.  You would need to implement that functionality in your 
vbios replacement.  If you want a bios console, you'll have to use the open 
source radeon driver as a guide to how to write a vbios replacement that 
enumerates and lights up the displays.

END

Also it turned out that the bytecode is there for the OEM so the changed 
topology does not need the new VBIOS assembly but just the AtomBIOS bytecode.
Which is quite bad, because the VBIOS  is depending on how it is routed and may 
only work with similar boards even when chipset is same. We would have to find 
out a way how to include the AtomBIOS in some form in the coreboot or re-write 
it somehow, because the bytecode is not even "property" of AMD but OEM and 
radeon driver needs that to be present in a rom. Maybe it would be possible to 
write some commmon init and handle just small changes in the bytecode.

For now, I would say kind of "reply" init might work, it depends if your goals 
are similar like we have with intel, so just graphic framebuffer for grub2 or 
something like I had in my mind.

Thanks
Rudolf