[gentoo-sparc] Ultra 80: serial ports problem

[Etaoin Shrdlu]

I'm trying to use a modem connected on the serial port of an Ultra 80, 
but with no luck until now. 

# dmesg | grep tty

ttyS0 at MMIO 0x1fff1400000 (irq = 8800672) is a SAB82532 V3.2
ttyS1 at MMIO 0x1fff1400040 (irq = 8800672) is a SAB82532 V3.2

If using minicom (configured to use /dev/ttyS0) to access the modem, the 
screen remains black and the only thing I can do is exit the program.
A simple 

# echo "AA" > /dev/ttyS0    # this does nothing on a PC

hangs, and if I hit ctrl-C to exit I get 

-bash: /dev/ttyS0: Interrupted system call

Trying to send anything to the ports from outside (eg, attaching a serial 
mouse and moving it, expecting to see some garbage - don't know it this 
is a right way to test the port though) produces a kernel panic:

Unable to handle kernel NULL pointer dereference
tsk->{mm,active_mm}->context = 00000000000000a0
tsk->{mm,active_mm}->pgd = fffff80002d6e000
Kernel panic - not syncing: Aiee, killing interrupt handler!

I see the same behaviour if I use /dev/ttyS1 (the system has 2 serial 
ports).

I'm using vanilla-sources-2.6.16_rc1, which has otherwise worked 
flawlessy until now.

In my kernel config, i have

# CONFIG_MOUSE_SERIAL is not set
# CONFIG_SERIAL_NONSTANDARD is not set
# Serial drivers
# Non-8250 serial port support
CONFIG_SERIAL_SUNCORE=y
# CONFIG_SERIAL_SUNZILOG is not set
# CONFIG_SERIAL_SUNSU is not set
CONFIG_SERIAL_SUNSAB=y
# CONFIG_SERIAL_SUNSAB_CONSOLE is not set
CONFIG_SERIAL_CORE=y
CONFIG_SERIAL_CORE_CONSOLE=y

Is the serial port on this box a RS232?

I'm not a sparc guru, so I'm probably missing something here.
Thanks for any help.
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