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

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

[Kraitschy, Tobias]

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.

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?

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

Best regards,

Tobias Kraitschy

[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

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

[alfred steele]

> 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?
>
> I already tried to remove the corresponding code in the start.S and searched the README for switches, but without success.
Did you try the "CONFIG_SKIP_RELOCATE_UBOOT" ? I am not sure if it
serves your purpose here. It depends upon whether or not your
"start.S" uses it at all.

-Alfred

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

[Jerry Van Baren]

alfred steele wrote:
>> 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?
>>
>> I already tried to remove the corresponding code in the start.S and searched the README for switches, but without success.
> Did you try the "CONFIG_SKIP_RELOCATE_UBOOT" ? I am not sure if it
> serves your purpose here. It depends upon whether or not your
> "start.S" uses it at all.
> 
> -Alfred

Tobias can try CONFIG_SKIP_RELOCATE_UBOOT, but it isn't likely to work 
as is.  That flag is to configure u-boot to be loaded directly into RAM 
and run out of RAM (i.e. no relocation from flash to RAM).  U-Boot was 
not designed to run from flash (aka. XIP - eXecute In Place) and nobody 
has done that as far as I know.

That doesn't mean u-boot cannot run XIP, it means that it will take an 
unknown amount of effort to make it happen.

gvb