[U-Boot] U-Boot on ARM9

[Roman Mashak]

Hello.

I have a few questions on arm926 initialization code, located in
${U_BOOT}/cpu/arm926ejs/start.S:
1) what is the point of deliberately setting up SVC mode, as it's
already in this mode right upon the reset?
2) I can't quite understand what 'CONFIG_USE_IRQ' is used for. It is
defined on just a few targets.
3) The stack set up -- commonly startup code initializes stacks for
all modes, but it's not clear how it's done in 'start.S'. Seems like
somehow stacks are run-time configured, but I didn't perceive  how.

Thanks in advance for comments.

-- 
Roman Mashak