[U-Boot-Users] Questions about the U-Boot README, esp. CFG_IMMR

[U-Boot-Users] Questions about the U-Boot README, esp. CFG_IMMR

[Peter Asemann]

I got another question

About CFG_IMMR the README says: DO NOT CHANGE! (MPC8xx systems only)

This confuses me. As the IMMR is a SPR (special purpose register) in the 
MPC8xx, assigning it an address seems to make no sense.

Nevertheless CFG_IMMR is used everywhere in the U-Boot code, so there 
must be a preset for it, which I can't find in the source. Also, almost 
any config in include/configs sets this to 0xFF000000.
So what is it good for and what should I choose?

Peter Asemann

[U-Boot-Users] Questions about the U-Boot README, esp. CFG_IMMR

[Wolfgang Denk]

In message <41B6EC48.8050909@web.de> you wrote:
> 
> About CFG_IMMR the README says: DO NOT CHANGE! (MPC8xx systems only)

This is a bit  of  strong  language  to  scare  off  thos  who  don't
unterstand what they are doing.

> This confuses me. As the IMMR is a SPR (special purpose register) in the 
> MPC8xx, assigning it an address seems to make no sense.

Read this as:  special  register  which  holds  the  address  of  the
Internem Memory.

> Nevertheless CFG_IMMR is used everywhere in the U-Boot code, so there 
> must be a preset for it, which I can't find in the source. Also, almost 

RTFM - the 'M' is the MPC8xx User's Manual here.

> any config in include/configs sets this to 0xFF000000.
> So what is it good for and what should I choose?

This depends on the memory map you chose for  your  board.  Remember:
it's _you_ who defines the memory map.

Best regards,

Wolfgang Denk

-- 
Software Engineering:  Embedded and Realtime Systems,  Embedded Linux
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de
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