[U-Boot] Avoiding Relocation on ARM When Earlier Bootloader Inits RAM?

[Wolfgang Denk]

Dear Tim Kryger,

In message <loom.20110214T175951-507 at post.gmane.org> you wrote:
> 
> After looking at code, searching the mailing list archive, and reviewing the git
> commit log, I now understand that for ARM relocation is performed unless U-Boot
> is already running at its final destination as computed within board_init_f. 
> Since this computation attempts to back off from the end of RAM the resulting
> address varies when U-Boot changes size.  On my board I have an earlier

It varies not only then. It may also vary when you are for example
using features like protected RAm or frame buffers with adjustable
resolution / color depth.  Then the location in RAM may even depend on
settings of environment variables, i. e. it can change dynamically
from boot to boot.

> bootloader that initializes RAM.  Presently, it copies U-Boot near the start of
> RAM and lets U-Boot relocate itself to the end.  This is inefficient and I would

This is only the case when booting from NAND; it does not apply for
example when booting from NOR flash.

> like to eliminate the extra copy.  I suspect that my situation is not unique and
> would be grateful to anyone willing to share their thoughts or experiences on
> how best to deal with this.

There are situation where the memory map is fixed and doesn;t change -
then you can U-Boot load to it's final location, and no second copy is
needed.

Best regards,

Wolfgang Denk

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