MPC83xx console : no output after handover

Matthew L. Creech mlcreech at
Wed Apr 1 09:22:24 EST 2009

On Tue, Mar 31, 2009 at 5:26 PM, Gary Thomas <gary at> wrote:
> The fact that you get the ttyS1 line printed is interesting.  At
> this point, the kernel is switching from raw console I/O (only
> suitable for bring-up messages) to the general serial driver
> (interrupt driven, etc).  I'm curious about what the ttyS1 driver
> is causing to break...
> A couple of things you could try:
>  * Disable ttyS1 (take it out of your device tree)

I tried taking ttyS1 out - the results are no different (other than
the fact that "console handover" is now the last line that prints).
My debug printk()s at the end of 8250_init() show up, which would seem
to imply that ttyS0 was initialized correctly, so I'm not sure what
else could be stomping on it.

>  * Look at the console log when this happens.  Look in your system
>    map for the symbol '__log_buf', e.g.
>       c031ca54 b __log_buf
>    This will get stored at physical location '0x31ca54' and will
>    often contain data that didn't get a chance to print, for example
>    if you have stuck interrupts that prevent the console from working.
>    I'd just run it to this point and then examine the memory - either
>    using a BDI if one is attached, or press RESET (I hope you have one!)
>    and then look using your boot loader (uBoot, RedBoot, ...)

I think I can get my hands on a BDI tomorrow, so I'll give this a try
then.  Thanks for the reply

Matthew L. Creech

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