LAN969x Watchdog

1. SoC Resources

LAN969x SoC supports one instance of Watchdog Timer from Synopsys DW.

2. Kernel configurations

Following kernel config options should be enabled to use LAN969x WDT:

CONFIG_DW_WATCHDOG - Synopsys Watchdog driver config option.

3. Devicetree Configuration

To enable the 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 36 IRQ_TYPE_LEVEL_HIGH>.

Peripheral	Shared Peripheral Interrupt	CPU INTR
watchdog	68	36

Peripheral

Shared Peripheral Interrupt

CPU INTR

watchdog

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 <&fabric_clk>.

3.1. References

4. 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 36 IRQ_TYPE_LEVEL_HIGH>;
	clocks = <&fabric_clk>;
};

4.1. UserSpace

4.1.1. Confirm instances are created

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

4.1.2. Direct activation of the watchdog

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 2023.04 (Nov 07 2023 - 14:41:53 +0100)

CPU:   ARM A53
Model: lan969x ev23x71a (pcb8398)
DRAM:  896 MiB (effective 897.9 MiB)
Core:  27 devices, 16 uclasses, devicetree: fit
MMC:   emmc@e0830000: 0
Loading Environment from MMC... OK
In:    serial
Out:   serial
Err:   serial
Net:   eth0: switch@0
Hit any key to stop autoboot:  0

4.1.3. Using the 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

4.1.4. Running the watchdog in the background

Add watchdog configurations to /etc/watchdog.conf file.
Run command watchdog -c /etc/watchdog.conf. By default, Busybox watchdog command runs in background.
Check for Hardware watchdog process ID.
Kill the watchdog process.
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
# watchdog -c /etc/watchdog.conf
# ps -ef | grep watchdog
   28 root     [watchdogd]
  477 root     watchdog -c /etc/watchdog.conf
  481 root     grep watchdog
# kill -9 477 ; uptime ; tail -f /var/log/messages
[ 2933.075931] watchdog: watchdog0: watchdog did not stop!
 00:48:53 up 48 min,  load average: 0.00, 0.00, 0.00
Jan  1 00:48:38 vcoreiii daemon.info watchdog[477]:  interface: no interface to check
Jan  1 00:48:38 vcoreiii daemon.info watchdog[477]:  temperature: no sensors to check
Jan  1 00:48:38 vcoreiii daemon.info watchdog[477]:  no test binary files
Jan  1 00:48:38 vcoreiii daemon.info watchdog[477]:  no repair binary files
Jan  1 00:48:38 vcoreiii daemon.info watchdog[477]:  error retry time-out = 60 seconds
Jan  1 00:48:38 vcoreiii daemon.info watchdog[477]:  repair attempts = 1
Jan  1 00:48:38 vcoreiii daemon.info watchdog[477]:  alive=/dev/watchdog heartbeat=[none] to=root no_act=no force=no
Jan  1 00:48:38 vcoreiii daemon.info watchdog[477]: watchdog now set to 20 seconds
Jan  1 00:48:38 vcoreiii daemon.info watchdog[477]: hardware watchdog identity: Synopsys DesignWare Watchdog
Jan  1 00:48:53 vcoreiii kern.crit kernel: [ 2933.075931] watchdog: watchdog0: watchdog did not stop!
NOTICE:  Booting Trusted Firmware

...More trace...

U-Boot 2023.04 (Nov 07 2023 - 14:41:53 +0100)

CPU:   ARM A53
Model: lan969x ev23x71a (pcb8398)
DRAM:  896 MiB (effective 897.9 MiB)
Core:  27 devices, 16 uclasses, devicetree: fit
MMC:   emmc@e0830000: 0
Loading Environment from MMC... OK
In:    serial
Out:   serial
Err:   serial
Net:   eth0: switch@0
Hit any key to stop autoboot:  0

4.1.5. Running the watchdog in the foreground

Add watchdog configurations to the /etc/watchdog.conf file.
Run the watchdog in foreground using the '-F' option.
Press CTRL + z to suspend the watchdog process.
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.

# watchdog -c /etc/watchdog.conf -F
watchdog: starting daemon (5.16):
watchdog:  int=1s realtime=yes sync=no load=0,0,0 soft=no
watchdog:  memory not checked
watchdog:  ping: no machine to check
watchdog:  file: /var/log/messages:1500
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
[1]+  Stopped                    watchdog -c /etc/watchdog.conf -F
# NOTICE:  Booting Trusted Firmware

...More traces...

NOTICE:  Direct boot of BL33 binary image


U-Boot 2023.04 (Nov 07 2023 - 14:41:53 +0100)

CPU:   ARM A53
Model: lan969x ev23x71a (pcb8398)
DRAM:  896 MiB (effective 897.9 MiB)
Core:  27 devices, 16 uclasses, devicetree: fit
MMC:   emmc@e0830000: 0
Loading Environment from MMC... OK
In:    serial
Out:   serial
Err:   serial
Net:   eth0: switch@0
Hit any key to stop autoboot:  0