[coreboot] [PATCH] fix normal vs. fallback

[Myles Watson]

> 0. Maybe we should hard code the Normal / Fallback ("BOOT_BYTE") into
> the cmos.layout parser tool so anyone who tries to use that byte gets a
> decent error.
It seems more flexible to use the value from cmos.layout unless there isn't
one, then hard code it.  But I agree we don't want it to be part of the
checksum.

> 1. Should Fallback always ignore CMOS? I think it would make more sense
> if Normal and Fallback were the same and both would write a decent set
> of CMOS defaults in the case of a bad checksum.
Agreed.  The way we build each image separately now, you could have a
different set of defaults for Normal and Fallback.

> 2. Ok, so what should happen when bad settings are detected?
> 2.1 Go back to fallback (the same path like when the normal rom image is
> corrupted)?
> 2.1.1 leave BOOT_BYTE alone ...?
> 2.1.2 dump a set of cmos default values
> 2.2 Stay in Normal
> 2.2.1 leave BOOT_BYTE alone ...?
> 2.2.2 dump a set of cmos default values

Stay in Normal, set boot count to maximum, set CMOS to default.

Then if it fails, fallback is tried next.  I guess it would be nice to have
fallback set CMOS to its default values if it gets selected because the boot
count was too high.  Booting fallback with normal's defaults doesn't seem
wise.
 
> 3. Do we want an extra "checksum" for BOOT_BYTE?
Might be good.  One byte seems cheap.

Thanks,
Myles