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Diffstat (limited to 'Documentation/user/watchdog.rst')
| -rw-r--r-- | Documentation/user/watchdog.rst | 47 |
1 files changed, 43 insertions, 4 deletions
diff --git a/Documentation/user/watchdog.rst b/Documentation/user/watchdog.rst index 02bd576a89..0220965598 100644 --- a/Documentation/user/watchdog.rst +++ b/Documentation/user/watchdog.rst @@ -10,6 +10,15 @@ the bootloader. For these scenarios barebox provides the watchdog framework with the following functionality and at least ``CONFIG_WATCHDOG`` should be enabled. +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 :ref:`boot-watchdog-timeout` for how to use the watchdog in the field. + Polling ~~~~~~~ @@ -57,6 +66,9 @@ 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) @@ -67,6 +79,36 @@ Use barebox' environment to persist these changes between reboots: nv dev.wdog0.autoping=1 nv dev.wdog0.timeout_cur=7 +Watchdog State +~~~~~~~~~~~~~~ + +To check whether a watchdog is currently running, the ``running`` device +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 ``unknown``. + +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, :ref:`command_wd` can be used. + +Default Watchdog +~~~~~~~~~~~~~~~~ + +barebox supports multiple concurrent watchdogs. The default watchdog used +with :ref:`command_wd`, ``boot.watchdog_timeout`` and :ref:`command_boot`'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). + +.. _boot-watchdog-timeout: + Boot Watchdog Timeout ~~~~~~~~~~~~~~~~~~~~~ @@ -85,7 +127,4 @@ or persistently by nv boot.watchdog_timeout=10 where the used value again is measured in seconds. - -On a system with multiple watchdogs, the watchdog with the highest positive -priority is the one affected by the ``boot.watchdog_timeout`` parameter. If -multiple watchdogs share the same priority, only one will be started. +Only the default watchdog will be started. |