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

[Matthias Kaehlcke]

hi wolfgang,

El Tue, Dec 08, 2009 at 09:33:18PM +0100 Wolfgang Denk ha dit:

> In message <20091208151358.GD31886 at 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.

thanks a lot for your explications and for providing an example

best regards

-- 
Matthias Kaehlcke
Embedded Linux Developer
Barcelona

              Insanity: doing the same thing over and over
                again and expecting different results
                            (Albert Einstein)
                                                                 .''`.
    using free software / Debian GNU/Linux | http://debian.org  : :'  :
                                                                `. `'`
gpg --keyserver pgp.mit.edu --recv-keys 47D8E5D4                  `-