I tried the sample application wd_test.c (as suggested in the docs for DigiESP 5.2 Linux) to test the watchdog with my ME 9210.
Everything seems to work, except for disabling the watchdog. The ioctl WDIOC_SETOPTIONS with WDIOS_DISABLECARD bit set simply does not have any effect, the watchdog keeps running and resets the system.
This would be correct behaviour only if CONFIG_WATCHDOG_NOWAYOUT was set to Y in the kernel config. However, this is not the case, so it should definitely be possible to disable the watchdog.
Any idea what could be wrong?