[coreboot] SeaBIOS and the Geode LX framebuffer

[Jordan Crouse]

On 06/10/08 16:55 +0100, Stephen Crocker wrote:
> Jordan Crouse wrote:
> > On 06/10/08 16:24 +0100, Stephen Crocker wrote:
> >> Jordan Crouse wrote:
> >>> On 06/10/08 15:31 +0100, Stephen Crocker wrote:
> >>>> Carl-Daniel Hailfinger wrote:
> >>>>> On 03.10.2008 12:29, Stephen Crocker wrote:
> >>>>>> Is there a way of getting VGA support with SeaBIOS on the AMD Geode LX
> >>>>>> framebuffer?  I have successfully built and tested a BIOS image that
> >>>>>> appears to boot into DOS but the lack of display means that it is of
> >>>>>> little use.  Is there a VGA ROM image that I can include?
> >>>>> You'd need a VGA emulation VSA and AFAIK that piece of software is not
> >>>>> available as open source due to an interesting rights situation.
> >>>> How much of this is handled in AMD's binary VSA module?  I have been 
> >>>> looking through both the AMD and OpenVSA source and it looks as if the 
> >>>> lxvg module is supposed to handle VGA SMIs but I cannot find where this 
> >>>> is actually done.
> >>> None of it - the VGA is actually a seperate component under difference
> >>> licensing.  Thats why you don't see it in the VSA code.
> >> This is quite an important point, as a lot of programs access the I/O 
> >> ports and framebuffer directly.  A VGA BIOS would be able to handle the 
> >> functions provided by INT 10 but in my experience, that would not be 
> >> enough.
> > 
> > Not sure what you are trying to say here - beyond the PCI emulation, the
> > VSA neither grants nor restricts access to the graphics hardware.  This
> > is why we have been able to get away without VGA up to this point - both
> > the libpayload driver and the kernel framebuffer drivers are perfectly
> > good replacements for standard int 10 behavior.
> 
> I was under the impression that the Geode display hardware does not 
> provide the standard I/O ports and memory areas exposed by standard VGA 
> hardware (eg. ports 3d4/3d5 and segment A000) and that this was all 
> emulated in the VSA using SMIs.  Am I incorrect about this?

Oh, I see what you mean - I thought you meant you have no access to
the GPU outside of VSA/VGA.  Yes, I believe that is correct for VGA
users.

Jordan

-- 
Jordan Crouse
Systems Software Development Engineer 
Advanced Micro Devices, Inc.