[coreboot] Any intro available for adding cbmem support to an old platform?

[Paul Menzel]

Dear Keith,


Am Freitag, den 07.07.2017, 21:55 -0400 schrieb Keith Hui:
> Hi (again) coreboot:

Welcome back!

> My original question got lost in the list probably because of a bad
> subject, so I'm asking again with a better one.

Indeed, a good, descriptive subject line is useful.

> I read that after 4.7 we are going to drop older platforms without
> "cbmem support in romstage", and that includes one that I brought into
> coreboot. I am interested in bringing this platform up to standard.
> Where can I read up on adding this cbmem support?

I am probably not the best person to answer the question, but see
commit 3bf38548 (CBMEM: Tag chipsets with LATE_CBMEM_INIT) [1]:

> In preparation to remove the static CBMEM allocator, tag the chipsets
> that still do not implement get_top_of_ram() for romstage.

So you need to implement that function for your chipset, remove the
Kconfig selection, and if I remember correctly, everything else should
then start working nicely.

If I am not mistaken, Kyösti did a lot of the work during Google Summer
of Code some years back. Maybe you find some information in the
corresponding blog posts [2].

The next step is then to also add time-stamps to CBMEM, that you can
read out with `cbmem -t`.

> I just checked out the master from git in case they are part of the readings.

Did you also test the latest code with your board? Could you please
upload the *current* status to the board status repository [3]? Then it
will also automatically be correctly tagged on the Wiki page *Supported
Motherboards* [4].


Thanks,

Paul


[1] https://review.coreboot.org/7850
[2] https://blogs.coreboot.org/blog/author/kmalkki/
[3] https://review.coreboot.org/cgit/coreboot.git/tree/util/board_status/README
[4] https://www.coreboot.org/Supported_Motherboards
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