Enable watchdog in early boot

RE: Enable watchdog in early boot

Jonathan-WDTL — Thu, 27 Feb 2025 19:30:59 GMT

Got an email indicating there is a lot of interest in answer to this.

Can do without modifying mcuboot, by modifying zephyr's board files instead. The board file is built into both the zephyr app and mcuboot.

Copied board to our apps folder (so we're not modifying zephyr's repo) then add a new source file to zephyr board's CMakeLists.txt.
Add a function to init watchdog in the source file.
Use zephyr's sys init to call it where you want during OS startup.
i.e. SYS_INIT(your_fn, POST_KERNEL, 41);

The board file is built by both application and bootloader, we only wanted in bootloader, so wrapped the sys_init call in #ifdef CONFIG_MCUBOOT.

Wrt feeding from application after doing this, zephyr's wdt_feed call works fine with this setup.

RE: Enable watchdog in early boot

Jonathan-WDTL — Wed, 01 Jun 2022 21:01:26 GMT

I had a meeting with some people from nordic. They were also suggesting the same thing, but they weren't sure of whether it was possible to pass an additional source file to the mcuboot build via application cmakelists or additional args to west build. They said they were going to check with colleagues who knew a bit more about how the multi-image build system works. Probably if there isn't any way to do that, then as you say, modifying mcuboot would be the only way.

RE: Enable watchdog in early boot

Priyanka — Wed, 01 Jun 2022 13:08:11 GMT

Hi Jonathan,

I don't think it is possible to enable a function before MCUBoot which is implemented in your application and hence modifying the MCUBoot should be the solution.

Best Regards,

Priyanka