Virtex4FX12LC hangs in calibrating delay loop

[Thomas Glanzmann]

Hello,
I used the HEAD secretlabs kernel and used ml403 defconfig. I still see
no serial output from the _kernel_ on the serial console. But I do see
output from the in kernel embedded boot loader "load_kernel". I typed in
stop in xmd and got an instruction pointer which points to:

        c00045a0 <__delay>:
        c00045a0:       2c 03 00 00     cmpwi   r3,0
        c00045a4:       7c 69 03 a6     mtctr   r3
        c00045a8:       4d 82 00 20     beqlr
        c00045ac:       42 00 00 00     bdnz-   c00045ac <__delay+0xc>       <<<<<<<<
        c00045b0:       4e 80 00 20     blr

So I guess it is the calibrating delay loop and I am not sure. I can reproduce
this. It is always in this function. Now I wonder is my board missing
timer interrupts? What could be the reason for this. And of course one
much more important question:

        - Is the serial console initialized before or after the
          calibrating delay loop?

Is there a way to get a backtrace out of this? If that is the case what
do I have to do? Recompile the Kernel with frame pointers and attach
gdb?

        Thomas