I'm using an IBM TP 600 loaded with RH 8.0 (2.4.20) and am currently trying to get the internal modem to work. Yep, I'm aware that it can be a pain, but I think I am very close....

1. I compiled the kernel with the mwave support (not as a module).
2. I ran `setserial /dev/ttyS1 autoconfig` as suggested on the IBM developer's site where the mwave drivers are available. Following that, /dev/ttyS1 is set to:

/dev/ttyS1, UART: 16550A, Port: 0x02f8, IRQ: 3

3. I soft-linked /dev/modem to /dev/ttyS1 for ease.
4. I ran kppp and get "modem busy". Same results for running a test against the modem with any modem based connection program (kermit, minicom, etc).
5. syslogs show no anomalies whatsoever.

Any ideas? Here is the output of /proc interrupts:
CPU0
0: 182850 XT-PIC timer
1: 2277 XT-PIC keyboard
2: 0 XT-PIC cascade
3: 0 XT-PIC mwave_3780i
9: 3501 XT-PIC 3c589_cs
11: 0 XT-PIC Texas Instruments PCI1250, Texas Instruments PCI1250 (#2)
12: 21102 XT-PIC PS/2 Mouse
14: 13233 XT-PIC ide0
NMI: 0
LOC: 0
ERR: 0
MIS: 0

# ll /dev/modem
lrwxrwxrwx 1 root root 10 May 27 15:32 /dev/modem -> /dev/ttyS1

# ll /dev/ttyS1
crw-rw---- 1 root uucp 4, 65 Aug 30 2002 /dev/ttyS1

# cat /proc/mwave
3780i_IRQ 3
3780i_DMA 6
3780i_IO 0x0130
UART_IRQ 3
UART_IO 0x02f8