[coreboot] [RFC] CMOS options

Stefan Reinauer stepan at coresystems.de
Tue Dec 8 23:15:23 CET 2009

Rudolf Marek wrote:
> Hi all,
> Is there someone who is actively using most of the CMOS options? For
> example I
> just know that Luc is using at least the VRAM size. I think he
> mentioned that on
> M2V-MX SE memory init options are too dangerous and board won't boot
> anymore if
> set wrong - maybe even after cmos clear?

I am using all CMOS options on Kontron 986LCD-M. Actually, if options
are not supposed to be used, they should be dropped. Many boards have
options that make no sense because people love copy and paste for that
stuff. The only time CMOS options cause an error is when you use an
option in auto.c phase and it's not in cmos.layout. No error in stage 2
and no error when you leave unused options in.

CMOS clear does not happen at all, or correctly. It should write CMOS to
a defined state of default values. right now we don't even define
default values in the CMOS table but only in the code where the values
are actually used. This can lead to troublesome situations.
> I noticed that century byte is happily ignored - need to check if it
> really
> collides.
Is that good for anything? Does the BIOS need to care? I thought hwclock
--sys-to-hc does that ;-)

> Question is what to do with that. Maybe it would be useful if someone
> could do
> some payload aka "setup" screen to change those options.
Have a look at the nvramtool in util/ ... it provides a setup screen
with ssh and support and you can even choose to have X11 running with
animations next to it.

> Maybe it would make
> sense to get rid of most and have there only which are really used.
Yes. We should eliminate dead code.


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