LAN966x Watchdog

SoC Resources

LAN966x SoC supports one instance of Watchdog Timer from Synopsys DW.

Kernel configurations

Following kernel config options should be enabled to use LAN966x WDT:

  • CONFIG_DW_WATCHDOG - Synopsys Watchdog driver config option.

Devicetree Configuration

To enable Watchdog timer, following configurations are required in device tree:

  • compatible string must be set to snps,dw-wdt.

  • reg property must be set to <0xe0090000 0x1000>.

  • interrupts property must be set with interrupt details as <GIC_SPI 38 IRQ_TYPE_LEVEL_HIGH>.

Peripheral Shared Peripheral Interrupt CPU INTR

watchdog

70

38
Note

Shared peripheral interrupt lines start at index ID32. So, CPU INTR must be calculated as [Shared peripheral interrupt number - 32].

  • clocks property must be set to <&nic_clk>.

References

Example

Following example shows how a Watchdog timer should be defined in DT:

dtsi file:

watchdog: watchdog@e0090000 {
	compatible = "snps,dw-wdt";
	reg = <0xe0090000 0x1000>;
	interrupts = <GIC_SPI 38 IRQ_TYPE_LEVEL_HIGH>;
	clocks = <&nic_clk>;
	status = "disabled";
};

dts file changes:

&watchdog {
        status = "okay";
};

UserSpace

Confirm instances are created

  • Check for /dev/watchdog. If this file is present, that means the watchdog kernel device driver is loaded.

Example on how to use

Run cat /dev/watchdog0 and you see linux reboots in 30-40secs.

# cat /dev/watchdog0
[ 7879.765752] watchdog: watchdog0: watchdog did not stop!
#
#
#
U-Boot 2019.04-linux4sam_6.2-icp (Sep 24 2021 - 09:49:43 +0200)

CPU: SAMA7
Crystal frequency:        0 MHz
CPU clock        :        0 MHz
Master clock     :        0 MHz
DRAM:  1 GiB
MMC:   sdhci-host@e0830000: 0, emmc@e0830000: 1
Loading Environment from SPI Flash... SF: Detected sst26vf016b with page size 256 Bytes, erase size 4 KiB, total 2 MiB
OK
In:    serial
Out:   serial
Err:   serial
Net:   eth0: switch@0
Hit any key to stop autoboot:  0
m =>

Example using Busybox watchdog utility:

  • Configure buildroot and install Watchdog utility provided by Busybox.

  • The main watchdog configuration file is /etc/watchdog.conf.

# busybox | grep watchdog
        vconfig, vi, vlock, w, watch, watchdog, wc, wget, which, who, whoami,
#
# watchdog --help
watchdog: unrecognized option `--help'
watchdog version 5.16, usage:
watchdog [options]
options:
  -c | --config-file <file>  specify location of config file
  -f | --force               don't sanity-check config or use PID file
  -F | --foreground          run in foreground
  -X | --loop-exit <number>  run a fixed number of loops then exit
  -q | --no-action           do not reboot or halt
  -b | --softboot            soft-boot on error
  -s | --sync                sync filesystem
  -v | --verbose             verbose messages

# ls -l /etc/watchdog.conf
-rw-r--r--    1 root     root          6102 May 18  2022 /etc/watchdog.conf

Verify system reboot by running watchdog in background:

  1. Add watchdog configurations to /etc/watchdog.conf file.

  2. Run command watchdog -c /etc/watchdog.conf. By default, Busybox watchdog command runs in background.

  3. Check for Hardware watchdog process ID.

  4. Kill the watchdog process.

  5. Verify that system is rebooted after watchdog-timeout value.

# cat /etc/watchdog.conf
watchdog-device         = /dev/watchdog
watchdog-timeout        = 20
log-dir         = /var/log/watchdog
file            = /var/log/messages
change          = 1500
realtime                = yes
priority                = 1
#
# ps -ef | grep watchdog
   22 root     [watchdogd]
  131 root     grep watchdog
#
#
# watchdog -c /etc/watchdog.conf
#
#
# ps -ef | grep watchdog
   22 root     [watchdogd]
  135 root     watchdog -c /etc/watchdog.conf
  140 root     grep watchdog
#
#
# uptime
 00:09:09 up 9 min,  load average: 0.00, 0.03, 0.03
#
#
# kill -9 135 ; uptime; tail -f /var/log/messages
[  580.280482] watchdog: watchdog0: watchdog did not stop!
 00:09:40 up 9 min,  load average: 0.00, 0.02, 0.03
Jan  1 00:08:36 buildroot daemon.info watchdog[135]:  interface: no interface to check
Jan  1 00:08:36 buildroot daemon.info watchdog[135]:  temperature: no sensors to check
Jan  1 00:08:36 buildroot daemon.info watchdog[135]:  no test binary files
Jan  1 00:08:36 buildroot daemon.info watchdog[135]:  no repair binary files
Jan  1 00:08:36 buildroot daemon.info watchdog[135]:  error retry time-out = 60 seconds
Jan  1 00:08:36 buildroot daemon.info watchdog[135]:  repair attempts = 1
Jan  1 00:08:36 buildroot daemon.info watchdog[135]:  alive=/dev/watchdog heartbeat=[none] to=root no_act=no force=no
Jan  1 00:08:36 buildroot daemon.info watchdog[135]: watchdog now set to 20 seconds
Jan  1 00:08:36 buildroot daemon.info watchdog[135]: hardware watchdog identity: Synopsys DesignWare Watchdog
Jan  1 00:09:40 buildroot kern.crit kernel: [  580.280482] watchdog: watchdog0: watchdog did not stop!


U-Boot 2019.04-linux4sam_6.2-icp (Sep 24 2021 - 09:49:43 +0200)

CPU: SAMA7
Crystal frequency:        0 MHz
CPU clock        :        0 MHz
Master clock     :        0 MHz
DRAM:  1 GiB
MMC:   sdhci-host@e0830000: 0, emmc@e0830000: 1
Loading Environment from SPI Flash... SF: Detected sst26vf016b with page size 256 Bytes, erase size 4 KiB, total 2 MiB
OK
In:    serial
Out:   serial
Err:   serial
Net:   eth0: switch@0
Hit any key to stop autoboot:  0
m =>

Verify system reboot by running watchdog in foreground:

  1. Add watchdog configurations to /etc/watchdog.conf file.

  2. Run watchdog in foregroung using '-F' option in Busybox watchdog command as watchdog -c /etc/watchdog.conf -F.

  3. Press CTRL + z to suspend system.

  4. In this case, the Watchdog device is enabled but is no longer fed. After watchdog-timeout seconds, the system is reset by the Watchdog device.

# ls -l /dev/watchdog
crw-------    1 root     root       10, 130 Jan  1 00:00 /dev/watchdog
#
# uptime
 00:04:29 up 4 min,  load average: 0.02, 0.11, 0.06
#
#
# ps -ef | grep watchdog
   22 root     [watchdogd]
  132 root     grep watchdog
#
# cat /etc/watchdog.conf
watchdog-device         = /dev/watchdog
watchdog-timeout        = 20
log-dir         = /var/log/watchdog
file            = /var/log/messages
change          = 10
realtime                = yes
priority                = 1

#
# watchdog -c /etc/watchdog.conf -F
watchdog: starting daemon (5.16):
watchdog:  int=1s realtime=no sync=no load=0,0,0 soft=no
watchdog:  memory not checked
watchdog:  ping: no machine to check
watchdog:  file: /var/log/messages:10
watchdog:  pidfile: no server process to check
watchdog:  interface: no interface to check
watchdog:  temperature: no sensors to check
watchdog:  no test binary files
watchdog:  no repair binary files
watchdog:  error retry time-out = 60 seconds
watchdog:  repair attempts = 1
watchdog:  alive=/dev/watchdog heartbeat=[none] to=root no_act=no force=no
watchdog: watchdog now set to 20 seconds
watchdog: hardware watchdog identity: Synopsys DesignWare Watchdog
watchdog: file /var/log/messages was not changed in 11 seconds (more than 10)
watchdog: file /var/log/messages was not changed in 11 seconds (more than 10)
watchdog: file /var/log/messages was not changed in 11 seconds (more than 10)
^Z[1]+  Stopped                    watchdog -c /etc/watchdog.conf -F
#


U-Boot 2019.04-linux4sam_6.2-icp (Sep 24 2021 - 09:49:43 +0200)

CPU: SAMA7
Crystal frequency:        0 MHz
CPU clock        :        0 MHz
Master clock     :        0 MHz
DRAM:  1 GiB
MMC:   sdhci-host@e0830000: 0, emmc@e0830000: 1
Loading Environment from SPI Flash... SF: Detected sst26vf016b with page size 256 Bytes, erase size 4 KiB, total 2 MiB
OK
In:    serial
Out:   serial
Err:   serial
Net:   eth0: switch@0
Hit any key to stop autoboot:  0
m =>