A good first pass is to enable YABEL instead of native execution and watch what it does. That's how I've had to debug graphics before.

Also, if you can do a serial console only setup, you can run the VBIOS once linux is booted and try to debug it that way. 

It's very hard to debug a VBIOS issue as you are doing it now, however. It will take years off of your life :-)

ron

On Sun, Mar 22, 2015 at 9:07 AM Martin Roth <gaumless@gmail.com> wrote:
My experience is that the aspeed chip based graphics card that comes with Mohon Peak has a bug in the vbios causing it to hang when run.  If you need to use this specific card, you'll need to debug it, probably with a jtag debugger, going through the assembly, and see what's causing the issue.  My initial guess is that they're looking for some value in the bda or ebda that isn't present, but I'm not sure what this might be.

Martin

On Sun, Mar 22, 2015 at 8:45 AM, Kevin O'Connor <kevin@koconnor.net> wrote:
On Fri, Mar 20, 2015 at 12:30:38PM +0300, Kuzmichev Viktor wrote:
> I tried not to include any VBIOS file in coreboot ROM much earlier, in my
> first tests. With 'Run VGA Option ROMs' option checked the board just hung.
>
> And as I mentioned in my previous email VGA works fine with vendor's BIOS.
> So the card itself should be fine.
>
> Sadly, I don't have another card to try. Even if I had, I still would need
> to make this one work somehow as Mohon Peak is just a reference board and
> the target board will have a similar VGA controller.
>
> So please, let me know if there are some other things I could try or if I am
> mistaken somewhere.

Hi Viktor,

It seems you've tried a bunch of different configurations.  However,
this is making your trouble report hard to understand as it becomes
unclear which config had which results.

If you have an external VGA card, then please build coreboot with
CONFIG_VGA_ROM_RUN, CONFIG_ON_DEVICE_ROM_RUN, CONFIG_VGA_BIOS, and
CONFIG_PXE_ROM all disabled.  Please use either the SeaBIOS provided
by coreboot, or build SeaBIOS with a default config (only
CONFIG_COREBOOT and if needed CONFIG_DEBUG_SERIAL changed from the
seabios defaults).  This is described at:
http://www.coreboot.org/SeaBIOS

In particular, there should be no "pciXXXX,YYYY.rom" or "vgaroms/XXX"
files in your cbfs rom.

If the above does not work, please use the above config and recompile
SeaBIOS at debug level 8, and post the full debug log along with the
output of "cbfstool print".

Cheers,
-Kevin

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