[U-Boot-Users] clarifications u-boot for arm

[Wolfgang Denk]

In message <8bf247760607140029l62f6c124idee300237361518f at mail.gmail.com> you wrote:
>
>     I am trying to understand the flow of u-boot - what really happens
> when the board is powered on till i get the u-boot prompt which
> accepts commands from the user.

You've posted the same question before.

>    I started with the file u-boot-1.1.4/cpu/arm926ejs/start.S
>    Is this the place where u-boot actually starts?.

Yes.

>    It tries switch the cpu mode to SVC32 mode and relocates u-boot to
> RAM, disables MMU
>    and does so many things which i dont really understand.

I recommend toi follow the flow step by  step.  Most  functions  have
pretty descriptive names.

>    Could anyone explain it to me what really is happening out there and why?.

We initialize the system step by step as  needed  to  get  a  running
system capable of booting Linux.

>    Then i figured out that a function start_armboot() is called.  This
> function is present in
>     lib_arm/board.c is this function called by start.S?
> 
>     Where exactly it is called from?.

Use grep to find the call.

>    There is a reference to start_armboot in start.S not sure if it is the one?.

Why not?

>     ldr pc, _start_armboot
> _start_armboot:
>     .word start_armboot
> 
>   Does this actually invoke start_armboot?.

Guess what happens when you load a new address into the rpgram counter?

>   I have got so far. could  you please tell me am i right in my understarting?.

Yes.

>   I understand that start_armboot initialises the the cpu, board, dram....
>   Once this is done - we can say that the board has been initialised.

More or less.

>   Any other information and pointers u provide will be helpful

Read the README, the manual, and the sources.

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
"The lesser of two evils -- is evil."             - Seymour (Sy) Leon