/dev/ttyS0 on nc6000 not working

[thor2]

Hi, I have a HP compaq nc6000 laptop and I want to use the serial port
to connect to other computers and use kermit or minicom. Unfortunately,
it doesn't work. The seems to be blocked or broken in some way. It
works fine under WinXP. It also works on my desktop under FC6 but not on
the nc6000. And it also works under Solaris (Belenix) on the nc6000.
I also tried FC5 in rescue mode and tested the port with a python script (and
a loop back connector) and it seemed to work.
But not under FC6. This implies a problem with linux.

The laptop is running Fedora Core 6 (and will also boot WinXP). The
kernel version is:

Linux version 2.6.19-1.2895.fc6 (brewbuilder@hs20-bc2-2.build.redhat.com) (gcc version 4.1.1 20070105 (Red Hat 4.1.1-51)) #1 SMP Wed Jan 10 19:28:18 EST 2007

The serial port is detected during boot-up as indicated by:

# grep tty dmesg
serial8250: ttyS0 at I/O 0x3f8 (irq = 4) is a 16550A
serial8250: ttyS2 at I/O 0x3e8 (irq = 3) is a 16550A
00:02: ttyS0 at I/O 0x3f8 (irq = 4) is a 16550A

If I look in /sys/devices/pnp0/00:02 I see:
# ls
bus driver id options power resources subsystem tty:ttyS0 uevent

...and...

# cat resources
state = active
io 0x3f8-0x3ff
irq 4

This info is identical to what WinXP's hardware manager gives.

Also, /proc/tty/driver/serial gives:

# cat /proc/tty/driver/serial
serinfo:1.0 driver revision:
0: uart:16550A port:000003F8 irq:4 tx:0 rx:0 CTS|DSR|CD|RI
1: uart:unknown port:000002F8 irq:3
2: uart:16550A port:000003E8 irq:3 tx:0 rx:0 CTS|DSR|CD|RI
3: uart:unknown port:000002E8 irq:3

and setserial gives:
# setserial -a /dev/ttyS0
/dev/ttyS0, Line 0, UART: 16550A, Port: 0x03f8, IRQ: 4
Baud_base: 115200, close_delay: 50, divisor: 0
closing_wait: 3000
Flags: spd_normal skip_test

If I run lsmod I see the "serio_raw" module only and no module called
"serial" or "8250" (although 8250 is listed in /sys/modules).

It looks like its there but if I run kermit and do "set line" it says that
/dev/ttyS0 is not a terminal device ala:

# kermit
C-Kermit 8.0.211, 10 Apr 2004, for Red Hat Linux 9.0
Copyright (C) 1985, 2004,
Trustees of Columbia University in the City of New York.
Type ? or HELP for help.
(/root/) C-Kermit>set line /dev/ttyS0
/dev/ttyS0 is not a terminal device
Connection to /dev/ttyS0 failed:
(/root/) C-Kermit>set line

After this I get a line in /var/log/messages:

Feb 9 11:50:33 localhost kernel: ttyS0: LSR safety check engaged!

as if it can't see the registers on the serial device.

I posted this on LinuxQuestions as well, but got no usefull responses.

Question: Is there a fix? Any ideas?

[thor2]

It seems the serial port works with version 2.6.16 of the kernel but not 2.6.17. So some
patch broke it on hp nc6000's. I'm still investigating.

[thor2]

The problem seems to be in the acpi code. Setting acpi=off or acpi=ht in the kernel
parameters in grub.conf causes the serial port to work.

[thor2]

I set pnpacpi=off in the kernel boot parameters in grub.conf. That allowed the serial port
to work and I had all the other acpi features.