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Re: How can I use DBAu1550 UART3 instead of UART0?

To: "Charles C.K.Lai" <>
Subject: Re: How can I use DBAu1550 UART3 instead of UART0?
From: Freddy Spierenburg <>
Date: Wed, 3 May 2006 10:15:37 +0200
In-reply-to: <017c01c66e86$811e56c0$8873608c@11088002601>
Original-recipient: rfc822;
References: <00fa01c66e5f$eb0af470$8873608c@11088002601> <> <017c01c66e86$811e56c0$8873608c@11088002601>
User-agent: Mutt/1.5.11+cvs20060403
Hi Charles,

I'm not sure what you try to accomplish, so I'll try to answer
your question in two ways.

On Wed, May 03, 2006 at 03:52:08PM +0800, Charles C.K.Lai wrote:
> If I'd like to build my kernel starting with UART port 3, 
> not starting with UART port 0, 
Do you want UART port 3 to become /dev/ttyS0 and completely
ignore the fact that your CPU has a UART port 0 and 1 too? So you
just only want to use 1 UART namely port 3 of you CPU?
If this is the case you can start fiddling around with
drivers/serial/8250_au1x00.c and also have a loog at

If you just want to have your serial console on UART port 3
instead of port 0 you have to do a little bit more. First you
need to tell yamon (the bootloader I expect you to use) to use
UART port 3 instead of port 0 and then you just boot the kernel
with the console= option. See Documentation/kernel-parameters.txt
for more information.

Hope this will help. Otherwist try to explain a little bit more
thoroughly what you try to accomplish. Good luck!

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Freddy Spierenburg <>
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