Hi Peter,
I've figured out most of the boot process by following through the code, but I have a few questions about start.S:
- Calls to RVECENT and XVEVENT: what exactly do these do? RVECENT just
branches to the first parameter f, and does nothing with the second parameter.
These macros are used to setup up "reserved vector entries" - and "exception vector entries".
Yet the first argument passed is romReserved which is defined:
This is not quite correct. "romReserved" is only used for the, well, reserved entries. There are other parameters passed, these two are pretty important for example:
_start: RVECENT(reset,0) /* U-boot entry point */ RVECENT(reset,1) /* software reboot */
And they will yield calls to "reset".
romReserved: b romReserved
Isn't that just an infinite loop?
Yep - but the vectors are reserved, so they should never be jumped to.
- What are these for?:
#ifdef CONFIG_PURPLE /* 0xbfc00400 */ .word 0xdc870000 .word 0xfca70000 .word 0x20840008....etc..
Absolutely no idea :)
Maybe some magic stuff needed by some other hardware? I advise to ignore this unless you find something comparable in the boot code you have for your CPU.
Cheers Detlev