Comment 38 for bug 74034

Thinkpad T61 running 8.04 with the serial+parallel adapter for the ultrabay-slim (pass through connectors to the mainboard's 8250 serial adapter).

After boot, the serial port works. However, after a suspend resume it disappears and the kernel emits "ttyS0: LSR safety check engaged!".

workaround: boot with the kernel option: pnpacpi=off

misc notes, hints, and guesswork:
- Looking at my udev log, I saw that the 8250 serial port is detected and activated. And right after that, the pnp code detected and activated the serial port again. Hmmnn...

'''
UEVENT[1227045158.127887] add /bus/platform/drivers/serial8250 (drivers)
ACTION=add
DEVPATH=/bus/platform/drivers/serial8250
SUBSYSTEM=drivers
SEQNUM=1893

UEVENT[1227045158.127898] add /bus/pnp (bus)
ACTION=add
DEVPATH=/bus/pnp
SUBSYSTEM=bus
SEQNUM=1894

UEVENT[1227045158.127904] add /bus/pnp/drivers/serial (drivers)
ACTION=add
DEVPATH=/bus/pnp/drivers/serial
SUBSYSTEM=drivers
SEQNUM=1895
'''

- After disabling pnpacpi the "/sys/bus/pnp/devices/" node is empty, but "/sys/bus/platform/devices/serial8250/tty/" is populated.

- Also, my lspci shows an LPC bus via ISA bridge as someone else noted above:
00:1f.0 ISA bridge: Intel Corporation 82801HBM (ICH8M-E) LPC Interface Controller (rev 03)