The internal watchdog is enabled by default in the kernel configuration.
To verify that the i.MX watchdog driver (CONFIG_IMX2_WDT) is enabled in your kernel configuration:
- In menuconfig: Device Drivers -> Watchdog Timer Support -> <*> IMX2+ Watchdog
Using a command line
Watchdog will be activated as soon as /dev/watchdog is opened and will reboot unless the watchdog is pinged within timeout (128 is the preconfigured value).
# echo "1" > /dev/watchdog0
Within 128 seconds the board will reset.
Compile a watchdog test application
There's a watchdog testing utility C code example in the kernel source tree: tools/testing/selftests/watchdog-test.c (in older kernels: Documentation/watchdog/src/watchdog-test.c).
To cross compile it:
Install the toolchain and source the environment setup script, by following the guide, then run:
$ $CC ./tools/testing/selftests/watchdog-test.c -o ./watchdog-test