Non-console UART issues with 8xx

Scott Wood scottwood at
Sat Apr 16 06:41:10 EST 2011

On Fri, 15 Apr 2011 02:52:22 +0300
Eran Duchan <pavius at> wrote:

> Hey list
> I have a custom MPC875 board running 2.6.37. SMC1 is the console, SCC4 is a
> general purpose UART (DTS is set up accordingly). No hardware or software
> flow control for either.
> The issue is simple: the non-console UART transmits garbled characters at
> the end of the transmission.

Hmm, there's a wait_closing field in uart_cpm_port that doesn't seem to be
initialized anywhere.

The driver should also be sending the STOP_TX/GRA_STOP_TX command *before*
clearing the transmit enable bits, rather than after.

>  For example, set up SMC1 to console (works
> perfect) and SCC4 as non-console, run stty -F /dev/ttyCPM1 19200 raw and
> then echo -n 1234567890 > /dev/ttyCPM1 - transmission may be something like
> "1234567ø". Set the SCC4 as console (same baud rates) and the problem is
> reversed (SCC4 works perfect, SMC1 transmit garbled).
> Rx direction seems fine, after some rudementary testing.
> I dived into the code and see that the console UART has a completely
> different initialization sequence than the non-console UART. Short of diving
> into this ancient CPM architecture - does anyone have an idea?

The console is a bit different because it has a user that isn't tied to an
open file-handle -- which doesn't interact well with the driver's
(possibly misguided) desire to actually deconfigure the hardware when not


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