[U-Boot] U-Boot on ARM9

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.