[coreboot] SeaBIOS, serial output, and grub

Kevin O'Connor kevin at koconnor.net
Fri May 1 03:00:59 CEST 2009

On Wed, Apr 29, 2009 at 11:04:32PM -0400, Ward Vandewege wrote:
> I tried exactly that today (gmta ;), but that didn't seem to work for me -
> and SeaBIOS complained about an option rom checksum mismatch on the
> sgabios.bin option rom.

That's odd - it works fine for me.  Can you confirm the sgabios build
and then forward me the SeaBIOS log with it in CBFS?

> Since every other component in the boot process already does serial - how
> hard would it be to make SeaBIOS do serial too?

Well, SeaBIOS does support serial.  What you're looking for is the
ability to forward vgabios requests over serial.  SeaBIOS doesn't have
any vgabios capabilities today, so it would be a bit of work.  Since
sgabios is already designed to do this, I'm not sure what the value
would be in duplicating it in SeaBIOS.

> > >   serial --unit=0 --speed=115200 --word=8 --parity=no --stop=1
> > >   terminal --timeout=5 serial console
> > 
> > The only thing I can think of is that SeaBIOS may be setting the
> > serial port settings to something that grub doesn't like.  You can try
> > disabling the code in debug_serial_setup() in src/output.c.  However,
> > if you've already tried disabling CONFIG_DEBUG_SERIAL, then I don't
> > think this will do much.  It could be a conflict with coreboot serial
> > setup and grub I suppose.
> Hmm. Suggestions for debugging?

You could try disabling serial in both coreboot and seabios.  It seems
like a "long shot" though.

You could change grub to dump the serial registers and then run it
from both the proprietary bios and from coreboot/seabios - just to see
if there is a serial port difference.

Maybe there is a debugging mode of grub that you could activate?


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