[powerstation-owners] questions about boot debugging

[Tejun Heo]

Hello,

I'm messing with early boot code in Linux and the kernel dies after
prom access goes away but before printk comes online.  early_setup()
finishes fine but gets stuck after rfid enables RI/DI.  The machine
simply hangs and I have no way of finding out where the problem
occurred (my last resort on x86 is combination of infinite loop and
reset by doublefault but dunno how to do something like that on
powerpc).

The udbg stuff looks like the equivalent of early_printk() on x86 and
RTAS_PANEL/CONSOLE seems to be the right one but the machine hangs if
I enable it.  I ordered rj45 to db9 gender hoping that I could get
more information from the debug port, so my questions are...

1. The rj45 gender needs to be wired.  There seems to be several
   different rj45 to db9 mappings.  How should I wire it?

2. Is the debug port gonna help at all?

3. Any ideas on how to get early debug output?  At this point, I'll be
   _VERY_ happy if I can just get the a double word value written in
   some nv storage and then retrieve it after hard reset.

Thanks.

-- 
tejun