[U-Boot] [PATCH] ARM: Add support for edb93xx boards

[Wolfgang Denk <wd@denx.de>]

Dear Matthias Kaehlcke,

In message <20091208151358.GD31886@darwin> you wrote:
> 
> i am starting to look at this issue and it seems i need some more guidance:
> 
> before relocating U-Boot to RAM for ARM920T processors a jump to the
> label *lowlevel_init* is performed, where RAM timings are supposed to
> be set up. in the patch i sent these operations are performed in
> assembly and you asked me to rewrite them in C.
> 
> i'm relativly new to low-level setup, so i apologize if the following
> question sounds plain stupid to you: is C really available at this
> point? if my interpretation of the code in cpu/arm920t/start.S is
> correct, C code starts at start_armboot, after relocation of
> U-Boot. and after that point i'd think it's to late to change RAM
> timings as U-Boot is running from RAM.

After relocation we have a full-blown, "normal" C runtime environment.
Before that, you can use C as well, if you mind the restrictions (like
data and bss not being available/writable yet, no real stack, etc.).

> could you please give some advice to clear my confusion and maybe
> provide a pointer to a board/cpu which handles low-level setup in
> the intended way?

If you check theinit code in cpu/arm920t/start.S you will notice that
one of the really early things it does is calling coloured_LED_init()
and red_LED_on(). Note that these functions are implemented in C.

What can be done here, should also be possible in your case.

Best regards,

Wolfgang Denk

-- 
DENX Software Engineering GmbH,     MD: Wolfgang Denk & Detlev Zundel
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de
Commitment, n.:      Commitment can be illustrated by a breakfast
of ham and eggs. The chicken was involved, the pig was committed.