On 10/23/19 6:22 PM, Oleksij Rempel wrote: > Signed-off-by: Oleksij Rempel <o.rempel@xxxxxxxxxxxxxx> > --- > Documentation/user/user-manual.rst | 1 + > Documentation/user/watchdog.rst | 85 ++++++++++++++++++++++++++++++ > 2 files changed, 86 insertions(+) > create mode 100644 Documentation/user/watchdog.rst > > diff --git a/Documentation/user/user-manual.rst b/Documentation/user/user-manual.rst > index f04981c3f0..41fdb8805c 100644 > --- a/Documentation/user/user-manual.rst > +++ b/Documentation/user/user-manual.rst > @@ -34,6 +34,7 @@ Contents: > state > random > debugging > + watchdog > > * :ref:`search` > * :ref:`genindex` > diff --git a/Documentation/user/watchdog.rst b/Documentation/user/watchdog.rst > new file mode 100644 > index 0000000000..7373b81a8d > --- /dev/null > +++ b/Documentation/user/watchdog.rst > @@ -0,0 +1,85 @@ > +Watchdog Support > +================ > + > +Barebox Watchdog Functionality > +------------------------------ > + > +Nevertheless, in some cases we are not able to influence the hardware design The Nevertheless is out of place here. I assume it's a left over from when there was a prior paragraph, > +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 enabled: > + > +Polling > +~~~~~~~ > + > +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 > +your needs ``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: > + > +.. code-block:: console > + > + wdog0.autoping=1 > + > +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: > + > +.. code-block:: console > + > + wdog0.timeout_cur=7 > + > +To read the current watchdog's configuration, run: > + > +.. code-block:: console > + > + devinfo wdog0 > + > +The output may look as follows where ``timeout_cur`` and ``timeout_max`` are > +measured in seconds: > + > +.. code-block:: console > + > + barebox@DPTechnics DPT-Module:/ devinfo wdog0 > + Parameters: > + autoping: 1 (type: bool) > + timeout_cur: 7 (type: uint32) > + timeout_max: 10 (type: uint32) > + > +Use barebox' environment to persist these changes between reboots: > + > +.. code-block:: console > + > + nv dev.wdog0.autoping=1 > + nv dev.wdog0.timeout_cur=7 > + > +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 > + > +.. code-block:: console > + > + global boot.watchdog_timeout=10 > + > +or persistently by > + > +.. code-block:: console > + > + nv boot.watchdog_timeout=10 > + > +where the used value again is measured in seconds. > + > +On a system with multiple watchdogs, only the first one (wdog0) is affected by > +the ``boot.watchdog_timeout`` parameter. This is not correct. barebox maintains a list of watchdogs ordered by probe order and then searches for the highest priority watchdog and uses that as default. If there are multiple watchdogs, it will take the _last_ one in the list. You could rephrase this as: On a system with multiple watchdogs, the highest priority watchdog is the one affected by the ``boot.watchdog_timeout`` parameter. If multipel watchdogs share the same priority, the order is indeterminate. > + > -- Pengutronix e.K. | | Industrial Linux Solutions | http://www.pengutronix.de/ | Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 | _______________________________________________ barebox mailing list barebox@xxxxxxxxxxxxxxxxxxx http://lists.infradead.org/mailman/listinfo/barebox
