MMU issue on mpc8270

[Lei Sun]

Hi all:
    While trying to bring up the kernel-2.4.30, my debugger failed to
show memory content after MMU is turned on. So I added some debug
serial_putc() function copied from u-boot. (since u-boot has
intialized the UART). The code did printed out the debug message
untill it reached "mapin_ram()" function.  To be precise, in
map_page() funcion, after pte_alloc() , serial_putc() doesn't work
anymore.

My questions are :

1. in mapin_ram() function, since it uses "bat_mapin_ram()" , why does
it still map in page?
2. why would pte_alloc() affect my serial debug output ?

Rigth now, my kernel does seems to be running, but i just couldn't see
anything on the serial console, I have examined the serial console
portion of the code for many times, couldn't seems any thing wrong.
The worst is that i can't set break point with MMU turned on.

Any suggestion?

Thanks
lei