The sp5100_tco module works out-of-the-box with newer kernels.

• Check if the kernel recognizes the watchdog device.

  dmesg |grep 5100
  sp5100_tco: SP5100/SB800 TCO WatchDog Timer Driver v0.05
  sp5100_tco: PCI Revision ID: 0x42
  sp5100_tco: Using 0xfed80b00 for watchdog MMIO address
  sp5100_tco: Last reboot was not triggered by watchdog.
  sp5100_tco: initialized (0xffffc9000074cb00). heartbeat=60 sec (nowayout=0)

• Load ELRepo repository.
• Install kernel-ml.

  yum --enablerepo=elrepo-kernel install kernel-ml

• Boot kernel 3.x (if you want, change default boot in /etc/grub.conf)
• Install watchdog program.

  yum install watchdog

• Edit /etc/watchdog.conf for example to ping the gateway every 10 seconds

  ping = 1.2.3.4

• Auto-start at boot.

  chkconfig watchdog on

• Start watchdog.

  service watchdog start

• Check pings with tcpdump.
• Disconnect network and the device should auto restart.

  May 16 22:22:12 sms watchdog[1342]: no response from ping (target: 1.2.3.4)
  May 16 22:22:52 sms watchdog[1342]: shutting down the system because of error 101

• Temporary:

  # modprobe sp5100_tco heartbeat=300
  # dmesg | grep sp5100_tco
  [    3.995335] sp5100_tco: SP5100/SB800 TCO WatchDog Timer Driver v0.05
  [    3.995571] sp5100_tco: PCI Revision ID: 0x42
  [    3.995680] sp5100_tco: Using 0xfed80b00 for watchdog MMIO address
  [    3.995696] sp5100_tco: Last reboot was not triggered by watchdog.
  [    3.995880] sp5100_tco: initialized (0xffffc90000746b00). heartbeat=60 sec (nowayout=0)
  [  208.726037] sp5100_tco: SP5100/SB800 TCO Watchdog Module Unloaded
  [  218.427251] sp5100_tco: SP5100/SB800 TCO WatchDog Timer Driver v0.05
  [  218.427436] sp5100_tco: PCI Revision ID: 0x42
  [  218.427547] sp5100_tco: Using 0xfed80b00 for watchdog MMIO address
  [  218.427564] sp5100_tco: Last reboot was not triggered by watchdog.
  [  218.431145] sp5100_tco: initialized (0xffffc9000074eb00). heartbeat=300 sec (nowayout=0)

• Permanent:

  # vi /etc/modprobe.d/watchdog.conf
  options sp5100_tco heartbeat=300