[coreboot] [PATCH]tinybootblock

Patrick Georgi patrick at georgi-clan.de
Wed Dec 23 13:55:07 CET 2009

Am 22.12.2009 23:17, schrieb Myles Watson:
> On Tue, Dec 22, 2009 at 2:27 PM, Patrick Georgi
> <patrick at georgi-clan.de <mailto:patrick at georgi-clan.de>> wrote:
>     - Provide a framework to build image selection logic
>     In newconfig, most boards have their own code to select the image. The
>     goal in this layout is to have generic decision routines to take
>     care of
>     that, and encourage their use.
> Is it possible to have it be generic?  Won't we have to unify CMOS
> layouts for that to happen?
In a way, it's just the do_normal_boot() code in
We already have everything in the tree to make it all generic, but we
didn't properly use it. Maybe because the generic code came after the
copied versions and no-one dared to refactor things.

It's not simply a port because of the intrusive change of moving CAR out
of the bootblock, and this time, the generic code will be around from
the start, so it has a chance to be used.
> I think it would be a mistake to bring romcc to targets that don't
> need it now.
The alternative at that point is to do that code in assembly, or to move
CAR to the bootblock again.
romcc works quite fine for small code, and the code in the bootblock is
supposed to be small.

>     - Look up fallback/romstage in CBFS (this can be extended with
>     selection
>     logic if desired) ("selection logic" is C, compiled with romcc, lookup
>     is assembly)
> It's more important to me to avoid assembly than to have the absolute
> minimum size bootblock.  Especially for K8 & Fam10, there's plenty of
> space to not have to do this.
Among the reasons: The way it is done now, it's always exactly one copy
of the tree walker. If it's written in C and compiled with romcc, it
could end up several times in the bootblock, if there are various calls
(fallback, normal, ...), probably giving the register allocator a harder

> Picky detail:
> Since CONFIG_TINY_BOOTBLOCK is referenced in a Makefile that isn't
> board specific, the Kconfig entry for it should go there too (with a
> default n).  There should just be a "select" in qemu-x86/Kconfig
Fixed, thanks for the reminder. I wanted to keep things minimal and
forgot about it. It's not a big issue, as in Makefiles, missing
variables simply expand to the empty string, but it's cleaner the way
you proposed.

> Acked-by: Myles Watson <mylesgw at gmail.com <mailto:mylesgw at gmail.com>>
Thanks, r4989
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