8543 console baud rate change problem

Dan Wilson dwilson at fulcrummicro.com
Sun Mar 30 13:13:47 EST 2008

We are using ELDK 4.1, linux kernel 2.6.22 on an 8543 board with a Layer 
2 switch on it (i.e., the actual packet switching is done in an external 
chip, not by the 8543 itself).  One of our customers has encountered a 
strange issue with system console baud rate changes.  The system console 
is connected to a UART port on the 8543.

Here is the sequence of events:

+ powercycle unit at 115200

+ have ping session going
+ establish telnet session
+ have L2 traffic traversing the switch

+ switch baud rate to any other baud rate beside 38400
+ hit a few returns
+ switch baud rate back to 115200 and no problem

+ switch baud rate to 38400
+ type a few char
+ switch baud rate back to 115200
+ console is not responsive

+ existing ping session is still going
+ L2 traffic is still OK
+ telnet session disconnected and can not reconnect;
   telnet session is being served by linux ip stack

+ Had to power cycle to get everything back



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