[U-Boot] Running u-boot without relocation to RAM?

[Jerry Van Baren]

Hi Tobias,

Kraitschy, Tobias wrote:
> Hi,
> 
> I´m working on running U-Boot from a Leon3-System on an evaluation
> board from Actel. Some GPIO and "Hello World" programs are already
> running.
> 
> Now I created the necessary files for my board/sytem and compiling of
> U-Boot goes well, but starting this application nothing is happening
> on the serial terminal. After checking my U-Boot and system
> configuration again, I think that my very small RAM area of only 16
> kB might be the problem while U-Boot relocates itself to RAM at
> startup.

Yes.  Major problem.

> So is it possible to completly disable the relocation process at
> startup and run U-Boot with having opcode in PROM and data in RAM? If
> yes, how could I achieve this?

You would be the first to achieve this.

One of the fundamental assumptions of u-boot is that it copies itself 
into RAM and runs out of RAM.  There are many good reasons for this: RAM 
tends to be faster, it allows u-boot to reprogram flash without jumping 
extra hoops, u-boot is a boot *loader* to load a "real" OS (into RAM), 
"real" OSes require gobs of RAM, etc.

While it isn't impossible, it appears to be a pretty daunting task.  On 
the other hand, everything looks daunting when you start.  Y'know, "a 
trip of a thousand miles starts with the first step" sort of stuff.

> I already tried to remove the corresponding code in the start.S and
> searched the README for switches, but without success.

Nobody has had success yet, but maybe they just haven't tried hard 
enough. ;-)

> Best regards,
> 
> Tobias Kraitschy

Best regards,
gvb