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Date: Sat, 26 Mar 2005 16:37:29 +0000
From: Russell King <rmk+lkml@arm.linux.org.uk>
To: Phil Oester <kernel@linuxace.com>
Cc: Jan Engelhardt <jengelh@linux01.gwdg.de>, Luca <kronos@kronoz.cjb.net>,
       linux-kernel@vger.kernel.org
Subject: Re: Garbage on serial console after serial driver loads
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On Sat, Mar 26, 2005 at 07:55:49AM -0800, Phil Oester wrote:
> On Sat, Mar 26, 2005 at 03:10:05PM +0000, Russell King wrote:
> > Doesn't matter.  The problem is that dwmw2's NS16550A patch (from ages
> > ago) changes the prescaler setting for this device so we can use the
> > higher speed baud rates.  This means any programmed divisor (programmed
> > at early serial console initialisation time) suddenly becomes wrong as
> > soon as we fiddle with the prescaler during normal UART initialisation
> > time.
> 
> FWIW, I see the same thing here on some Dell Poweredge boxes:
> 
> serio: i8042 AUX port at 0x60,0x64 irq 12
> serio: i8042 KBD port at 0x60,0x64 irq 1
> Serial: 8250/16550 driver $Revision: 1.90 $ 8 ports, IRQ sharing disabled
> ttyS0 at I/O 0x3f8 (irq = 4) is a NS16550A
> ttyS1 at I/O 0x2f8 (irq = 3) is a 16550A
> <garbage>
> 
> But intererstingly, on identical boxes, the garbage only appears on
> those hooked up to a PortMaster device - those using a Cyclades never
> display this problem. (???)

Sorry, I don't understand your scenarios.  Can you explain the
circumstances under which you see corruption?

>From the kernel messages you've quoted above, I can only think that
you're not using ttyS0 as the serial console - if you were, my
understanding of this issue would indicate that you should get the
garbage immediately after the line starting "Serial:"

Either my understanding of the cause of this problem is wrong, or
I'm not understanding your setup.

-- 
Russell King
 Linux kernel    2.6 ARM Linux   - http://www.arm.linux.org.uk/
 maintainer of:  2.6 Serial core
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