MPC83xx console : no output after handover

Gary Thomas gary at
Wed Apr 1 07:45:20 EST 2009

Matthew L. Creech wrote:
> (Sorry if this is a dupe, but I think my first attempt was filtered out)

Nope, it made it.

> Hi,
> I'm trying to get Linux booting on a custom board based on the MPC8313
> ERDB, but there's no output after the console is transferred.  I get
> the following:
> Using MPC831x RDB machine description
> Linux version 2.6.29 (mlcreech at lap) (gcc version 4.3.2 (Sourcery G++ Lite 4.3-50
> ) ) #2 PREEMPT Tue Mar 31 14:54:27 EDT 2009
> console [udbg0] enabled
> ... (normal boot output) ...
> Serial: 8250/16550 driver, 4 ports, IRQ sharing disabled
> serial8250.0: ttyS0 at MMIO 0xe0004500 (irq = 16) is a 16550A
> console handover: boot [udbg0] -> real [ttyS0]
> serial8250.0: ttyS1 at MMIO 0xe0004600 (irq = 17) is a 16550A
> If I boot with "console=udbg0,115200", then it gets much further along
> before printing "turn off boot console udbg0".  So presumably the
> kernel is booting beyond this point, but my console isn't printing any
> output.  I traced from that last line back up the call stack to the
> end of drivers/serial/8250.c:serial8250_init(), and everything seems
> okay (it returns 0, and pritnk() still works fine at that point).  I'm
> not sure where to go from there to figure out where the problem lies.
> Could someone point me in the right direction, or suggest what might
> cause a console problem like this?

What does your command line (boot args) when it fails?  It should
probably have something like "console=ttyS0,115200" in it.

Gary Thomas                 |  Consulting for the
MLB Associates              |    Embedded world

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