system/ppp watchdog

[Brandon Pedersen]

I am wondering if there is any sort of watchdog available that will reset the system automatically if it freezes?

I am also wondering if there is some way of detecting if the ppp link goes down and resetting the device as well (or possibly retrying the connection until the link comes back up).

[Jesse Gilles]

Regarding watchdog, there is a hardware watchdog in the processor, but it is disabled by default. Enabling it requires a minor modification to the at91bootstrap code and passing the proper parameters to the linux watchdog driver (at91sam9_wdt). There is currently no support in the U-Boot version we are using the for the watchdog, however. This means anything done in U-Boot has to be done quickly before the watchdog resets (16 seconds by default).

If you are interested in this, I can provide more detailed information. The U-Boot lack of support is the biggest limitation currently. Hopefully this can be resolved in a future update.

Regarding ppp, you have two options that come to mind:

1. You can use ppp with the ‘persist’ option. This makes pppd try to keep the connection up even if it goes down periodically.

2. You can use ppp without the persist option and write your own script to act as a ppp watchdog. When the connection goes down, pppd will no longer be running. You could check for the existence of pppd and if it is down, reset the modem (if desired) and then start pppd again.

[Samuel Chen]

Hi Jesse,

I am interested in learning more about how to enable the watchdog. How can I contact you to get more information ?

Thanks,
Samuel

[Jesse Gilles]

If you want to enable the hardware watchdog, you can edit the following bbappend file and uncomment the line that brings in the watchdog patch. Then build the new bootstrap and flash it in.

http://git.multitech.net/cgi-bin/cgit.cgi/corecdp.git/tree/multitech/recipes/at91bootstrap/at91bootstrap_2.13.bbappend

# uncomment to enable watchdog in bootstrap
#SRC_URI += ” file://at91bootstrap-2.13-enable-watchdog.patch”

[Herraiz Stéphane]

Hi,
Is it possible to increase the watchdog reset timeout (12s by default) and how?
Thanks

[Herraiz Stéphane]

I check this Watchdog U-Boot driver on github:
https://github.com/lentinj/u-boot/blob/master/drivers/watchdog/at91sam9_wdt.c

Any idea how implement this?

• This reply was modified 10 years ago by Herraiz Stéphane.

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