[PATCH V4] workaround for mpc52xx erratum #364 (serial may not be reset in break state)

[René Bürgel]

This patch is a workaround for bug #364 found in the MPC52xx processor.
The errata document can be found under 
http://www.freescale.com/files/32bit/doc/errata/MPC5200E.pdf?fpsp=1&WT_TYPE=Errata&WT_VENDOR=FREESCALE&WT_FILE_FORMAT=pdf&WT_ASSET=Documentation 


When a device with a low baudrate is connected to the serial port, but 
the processor "listens" on a higher baudrate, it might falsely receive 
breaks from the controller. During a break, the serial controller may 
not be reset. The appended patch provides a workaround for that 
situation by lowering the baudrate without resetting the controller and 
waiting until no break is received anymore.

This is v4 if the patch, just reformatted to fit the linux kernel coding 
style without functional changes.

Wolfram Sang schrieb:
> Hi René,
>
> On Tue, Nov 04, 2008 at 08:40:09PM +0100, René Bürgel wrote
>> But there's still one thing, that bothers me a bit - if there is REALLY  
>> a break on the line, closing the driver may take until it's gone. I  
>> don't know whether this is really satisfying, but i think it's better  
>> than the alternative: no serial connection until the next reboot.
>>     
>
> I think we should CC linux-serial to get some opinions about this. At
> least, if it stays like this, it should be mentioned in the source.

What's the opinion from the linux-serial folks about this issue?

-- 
René Bürgel
Software Engineer
Unicontrol Systemtechnik GmbH
OT Dittersbach
Sachsenburger Weg 34
09669 Frankenberg
 
Tel.: 03 72 06/ 88 73 - 19
Fax: 03 72 06/ 88 73 - 60
E-Mail: r.buergel at unicontrol.de
Internet: www.unicontrol.de
 
Unicontrol Systemtechnik GmbH
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Sitz der Gesellschaft: Frankenberg
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