1.28. Watchdog Support¶
1.28.1. Barebox Watchdog Functionality¶
In some cases we are not able to influence the hardware design anymore or while
developing one needs to be able to feed the watchdog to disable it from within
the bootloader. For these scenarios barebox provides the watchdog framework
with the following functionality and at least
CONFIG_WATCHDOG should be
18.104.22.168. Disabling for development¶
The shorthand command
wd -x will disable all watchdogs.
If hardware (or driver) doesn’t support turning off the watchdog,
an autpoller will be registered to periodically feed watchdogs.
This should only be needed for development.
See Boot Watchdog Timeout for how to use the watchdog in the field.
Watchdog polling/feeding allows to feed the watchdog and keep it running on one
side and to not reset the system on the other side. It is needed on hardware
with short-time watchdogs. For example the Atheros ar9331 watchdog has a
maximal timeout of 7 seconds, so it may reset even on netboot.
Or it can be used on systems where the watchdog is already running and can’t be
disabled, an example for that is the watchdog of the i.MX2 series.
This functionally can be seen as a threat, since in error cases barebox will
continue to feed the watchdog even if that is not desired. So, depending on
CONFIG_WATCHDOG_POLLER can be enabled or disabled at compile
time. Even if barebox was built with watchdog polling support, it is not
enabled by default. To start polling from command line run:
NOTE Using this feature might have the effect that the watchdog is effectively disabled. In case barebox is stuck in a loop that includes feeding the watchdog, then the watchdog will never trigger. Only use this feature during development or when a bad watchdog design (Short watchdog timeout enabled as boot default) doesn’t give you another choice.
The poller interval is not configurable, but fixed at 500ms and the watchdog timeout is configured by default to the maximum of the supported values by hardware. To change the timeout used by the poller, run:
To read the current watchdog’s configuration, run:
The output may look as follows where
measured in seconds:
barebox@DPTechnics DPT-Module:/ devinfo wdog0 Parameters: autoping: 1 (type: bool) priority: 100 (type: uint32) running: 1 (type: enum) (values: "unknown", "1", "0") seconds_to_expire: 7 (type: uint32) timeout_cur: 7 (type: uint32) timeout_max: 10 (type: uint32)
Use barebox’ environment to persist these changes between reboots:
nv dev.wdog0.autoping=1 nv dev.wdog0.timeout_cur=7
22.214.171.124. Watchdog State¶
To check whether a watchdog is currently running, the
parameter can be consulted. Not all watchdog devices (or their drivers)
provide the information whether a watchdog was running prior to barebox.
In that case, the parameter will contain the value
Watchdogs started by barebox can be monitored using the
seconds_to_expire parameter. A well-behaving system of watchdog
device, watchdog driver and clocksource should reset as soon as the
count down reaches zero.
To manually start a watchdog, wd - enable/disable/trigger the watchdog can be used.
126.96.36.199. Default Watchdog¶
barebox supports multiple concurrent watchdogs. The default watchdog used
with wd - enable/disable/trigger the watchdog,
boot.watchdog_timeout and boot - boot from script, device, …’s
-w option is the one with the highest positive priority.
If multiple watchdogs share the same priority, only one will be affected.
The priority is initially set by drivers and can be overridden in the
device tree or via the
priority device parameter. Normally, watchdogs
that have a wider effect should be given the higher priority (e.g.
PMIC watchdog resetting the board vs. SoC’s watchdog resetting only itself).
188.8.131.52. Boot Watchdog Timeout¶
With this functionality barebox may start a watchdog or update the timeout of an already-running one, just before kicking the boot image. It can be configured temporarily via
or persistently by
where the used value again is measured in seconds. Only the default watchdog will be started.