[U-Boot-Users] watchdog support

[U-Boot-Users] watchdog support

[Josef Baumgartner]

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

[U-Boot-Users] watchdog support

[Wolfgang Denk]

In message <200401091148.40211.josef.baumgartner@telex.de> you wrote:
> 
> 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?

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).

> 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?

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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