[U-Boot] Loading and Running u-boot from context RAM

[Wolfgang Denk]

Dear Ronny D,

In message <875745.66478.qm at web46116.mail.sp1.yahoo.com> you wrote:
>
> I am working on PPC440 based customized board having 4MB context ram.
> 
> what are all changes need to perform to skip relocation of u-boot in DDR
> and relocated it to context ram and run from the same location.

first: why would you want to do that? Which advantages do you expect
compared to running from DDR?

It might be sufficient to change the initialization of "addr" in
board_init_f() in "lib_ppc/board.c"; instead of basing it on
"CONFIG_SYS_SDRAM_BASE + get_effective_memsize()" set it to the end
address of your contaxt RAM (+1). Be careful about the relocation of
the exception vectors, though. These probably still need to be
relocated to 0. I don't know which other obstacles might be on that
way - U-Boot's memory map on Power silently assumes that it has
contiguous memory from 0 through the current image address. Also, 4 MB
might not be sufficient for example to hold the malloc arena if you
want to uncompress bigger bz2 compressed images, and so on.

All in all I expect some effort especially for debugging, and little
or no benefit.

Best regards,

Wolfgang Denk

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