kernel boot stuck at udbg_putc_cpm()

Scott Wood scottwood at
Sat Jul 10 01:59:46 EST 2010

On Fri, 9 Jul 2010 00:35:43 -0700
Shawn Jin <shawnxjin at> wrote:

> I changed my toolchain and rebuilt the kernel image. This time all the
> messages below magically displayed on the serial port. :-D Are all
> these the early debugging messages?

Yes, it's an alternate output for the regular console (there are
sometimes more messages, if you hook up .progress in your ppc_md, but
that's mainly of interest if you don't get this far).

> Now the kernel stuck at the while loop that waits for transmitter fifo
> to be empty. It seems that the CPM UART stopped working in the middle
> of printing a message. I'm using minicom to connect to the serial
> port. I heard minicom is problematic. Will it be the cause here?

I doubt it...

You're probably getting to the point where udbg is disabled because the
real serial driver is trying to take over -- and something's going
wrong with the real serial port driver.  Check to make sure the brg
config is correct (both the input clock and the baud rate you're trying
to switch to).  Commenting out the call to cpm_set_brg can be
a quick way of determining if that's the problem.


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