watchdog support

Hi u-boot users,

I'm currently experimenting with u-boot and watchdog support.

I'd like to have the possibility to configure u-boot for watchdog support but disable the watchdog if there's no autoboot and I want to use the booter. I looked at the code but I found no such feature at the moment, am I right?

If the watchdog is needed, it should be enabled very early. But at this point the environment is eventually not yet available. A possible way would be to enable the watchdog early in the boot stage and disable it short before the main loop if an environment variable was set (e.g. setenv watchdog off).

Another possibility would be a command to disable the watchdog instead of an environment variable.

All solutions assume that an enabled watchdog could be disabled again which is not true for all watchdog implementations. I plan to use it on the Motorola MCF5272, there it is no problem.

What is your opinion and experience to this topic?

Regards,

Josef

This is correct, because IMHO it makes no sense. With any decent watchdog there is no way by software to disable it once you started it. I know that some devices allw that, but there is no general

solution.  For  example,  on  the  MPC8xx  family  of  processors the
relevant control register is  write-once,  i.  e.  once  written  you

cannot overwrite the value so there is no way to stop a running watchdog. On some external watchdogs the behaviour is the same: once started, there is no way to stop them by software (only by reset).

You can do it, if you like. I don't consider such a feature useful. A watchdog, if present, is made for running, not for being stopped ;-)

Best regards,

Wolfgang Denk

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