[U-Boot] Question about mpc85xx startup using Nor Flash

[郭佳]

I'm porting u-boot to P2040 based board these days.

As u-boot/arch/powerpc/mpc85xx/start.s commented:
*The processor starts at 0xffff_fffc and the code is first executed in the
last 4K page in flash/rom.*

The E500MCRM Chapter 6.6 mentioned:

*This default TLB entry translates the first instruction fetch out of
reset(at effective address 0xffff_fffc).*
*This instruction should be a branch to the beginning of this page.*

So, if I configure the HCW to let powerpc boot from Nor Flash, why should I
suppose that the Nor Flash's
last 4K is mapped to 0xffff_f000~0xffff_ffff. Since there're no LAW setup
yet and the default BR0/OR0 of Local Bus
does not match that range. And what is the instruction at 0xffff_fffc and
where is it from?

Best Regards,
Hook Guo