[U-Boot-Users] AT91 u-boot lowlevel init Dataflash

[Peter Menzebach <pm@mw-itcon.de>]

Marco Cavallini wrote:
> 
> BTW I wonder if could be useful (and appreciated) if I should merge 
> RomBoot settings into u-boot allowing u-boot to be the one and only 
> loader for Dataflash too.
> 
> Ciao
Hi,
this is *not* possible, if you want to use only dataflash. *No* code can 
be executed directly out of the dataflash, since the access is serial 
and therefore it is not directly adressable by the CPU.

So the boot sequence (slightly simplified) is as follows:

- The internal boot code in ROM within the CPU copies up to 12K of code 
from dataflash to internal SRAM (this is romboot) and starts it.
- romboot initializes CPU frequencies and sets up SDRAM (normally the 
CPU runs after this at 180 MHZ on the DK board, unless you got a buggy 
version of precompiled romboot.
- romboot now copies u-boot to SDRAM and starts it.

It use the romboot version from teest.com, which Andreas mentioned and 
this sequence works fine with the recent u-boot releases.

You will find more information about this in various documents related 
to the processor and the dk board on the atmel home page..

Best regards
Peter

-- 
Peter Menzebach
Menzebach und Wolff IT-Consulting GbR
Phone +49 751 355 387 1