serial port problems

Ian Pallfreeman ip at
Wed May 22 16:36:52 BST 2002

Can anyone help with this, please? I'm about to start punching things.

The serial ports on my desktop have stopped working with kernels less than
a few weeks old, including 4.6-RC. A "boot -v" tells me:

sio0: irq maps: 0xa61 0x871 0x861 0xa61
sio0: probe failed test(s): 4
sio0 at port 0x3f8-0x3ff irq 4 flags 0x10 on isa0
sio0: type 16550A
sio1: irq maps: 0xa61 0xa69 0xa61 0xa61
sio1: probe failed test(s): 4
sio1 failed to probe at port 0x2f8-0x2ff irq 3 on isa0

I've been playing with the BIOS settings, assuming it was something that I'd
done. Sometimes neither port is probed OK, sometimes the first port _seems_
OK but doesn't want to talk sense to the modem attached to it -- echo lags
input and often doesn't happen at all. 

The ports are OK with a kernel from mid-February, a 3.5 kernel, and when
tested by "PC Doctor".

Can anyone tell me exactly what "failed test 4" means, and why failing this
test means sio0 probes OK, but sio1 fails? I've peeked into sio.c, of course, 
but although I've hacked on the 6850, the 8250 is a mystery to me. I feel a
bug report coming on...


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