MA-E3xx シリーズでは、Hardware Watchdog Timer driver を組み込んでいます。
watchdog パッケージにより、簡単な設定で Watchdog Timer を利用することができます。

root@plum:~# dpkg -l watchdog|cat
Desired=Unknown/Install/Remove/Purge/Hold
| Status=Not/Inst/Conf-files/Unpacked/halF-conf/Half-inst/trig-aWait/Trig-pend
|/ Err?=(none)/Reinst-required (Status,Err: uppercase=bad)
||/ Name                                  Version                          Architecture Description
+++-=====================================-================================-============-=============================================================
ii  watchdog                              5.13-1                           armhf        system health checker and software/hardware watchdog handler

有効化するために、/etc/default/watchdog ファイルを編集します。

root@plum:~# nano -w /etc/default/watchdog

watchdog

# Start watchdog at boot time? 0 or 1
run_watchdog=1
# Load module before starting watchdog
watchdog_module="none"
# Specify additional watchdog options here (see manpage).

run_watchdog を 1 にします。

/etc/watchdog.conf を編集します。

#ping			= 172.31.14.1
#ping			= 172.26.1.255
#interface		= eth0
#file			= /var/log/messages
#change			= 1407
 
# Uncomment to enable test. Setting one of these values to '0' disables it.
# These values will hopefully never reboot your machine during normal use
# (if your machine is really hung, the loadavg will go much higher than 25)
#max-load-1		= 24
#max-load-5		= 18
#max-load-15		= 12
 
# Note that this is the number of pages!
# To get the real size, check how large the pagesize is on your machine.
#min-memory		= 1
 
#repair-binary		= /usr/sbin/repair
#repair-timeout		= 
#test-binary		= 
#test-timeout		= 
 
watchdog-device	= /dev/watchdog
 
# Defaults compiled into the binary
#temperature-device	=
#max-temperature	= 120
 
# Defaults compiled into the binary
#admin			= root
#interval		= 1
#logtick                = 1
#log-dir		= /var/log/watchdog
 
# This greatly decreases the chance that watchdog won't be scheduled before
# your machine is really loaded
realtime		= yes
priority		= 1
 
# Check if rsyslogd is still running by enabling the following line
#pidfile		= /var/run/rsyslogd.pid  

変更点

root@plum:~# diff -u /ro/etc/watchdog.conf /etc/watchdog.conf 
--- /ro/etc/watchdog.conf	2013-02-01 20:15:44.000000000 +0900
+++ /etc/watchdog.conf	2017-07-12 16:48:04.731702357 +0900
@@ -20,7 +20,7 @@
 #test-binary		= 
 #test-timeout		= 
 
-#watchdog-device	= /dev/watchdog
+watchdog-device	= /dev/watchdog
 
 # Defaults compiled into the binary
 #temperature-device	=

MA-E3xx の起動時に自動で実行するように設定します。

root@plum:~# update-rc.d watchdog enable
update-rc.d: warning:  start runlevel arguments (none) do not match watchdog Default-Start values (2 3 4 5)
update-rc.d: warning:  stop runlevel arguments (none) do not match watchdog Default-Stop values (0 1 6)
 Enabling system startup links for /etc/init.d/watchdog ...
 Removing any system startup links for /etc/init.d/watchdog ...
   /etc/rc0.d/K11watchdog
   /etc/rc1.d/K11watchdog
   /etc/rc2.d/S89watchdog
   /etc/rc3.d/S89watchdog
   /etc/rc4.d/S89watchdog
   /etc/rc5.d/S89watchdog
   /etc/rc6.d/K11watchdog
 Adding system startup for /etc/init.d/watchdog ...
   /etc/rc0.d/K11watchdog -> ../init.d/watchdog
   /etc/rc1.d/K11watchdog -> ../init.d/watchdog
   /etc/rc6.d/K11watchdog -> ../init.d/watchdog
   /etc/rc2.d/S89watchdog -> ../init.d/watchdog
   /etc/rc3.d/S89watchdog -> ../init.d/watchdog
   /etc/rc4.d/S89watchdog -> ../init.d/watchdog
   /etc/rc5.d/S89watchdog -> ../init.d/watchdog
root@plum:~# 

root@plum:~# ls /etc/rc2.d/
K59apcupsd  S09wd_keepalive  S20ddclient   S20redis-server  S70dns-clean  S89watchdog
K80hostapd  S15dnsmasq       S20firewalld  S20smstools      S70pppd-dns   S99rc.local
README      S19cpufrequtils  S20nginx      S23ntp           S75sudo
root@plum:~# 

S89watchdog の symbolic link が作られていることが確認できます。

起動させてみます。

root@plum:~# /etc/init.d/watchdog start
 * Stopping watchdog keepalive daemon...                                                               [ OK ] 
 * Starting watchdog daemon...                                                                         [ OK ] 
root@plum:~# 

syslog に下記のように出力され、watchdog daemon が起動したことが確認できます。

Jul 20 11:26:57 plum watchdog[11594]: stopping daemon (5.13)
Jul 20 11:27:02 plum wd_keepalive[11750]: starting watchdog keepalive daemon (5.13):
Jul 20 11:27:02 plum wd_keepalive[11750]:  int=10 alive=/dev/watchdog realtime=yes
Jul 20 11:27:02 plum wd_keepalive[11750]: hardware watchdog identity: OMAP Watchdog