Feed watchdog in Zephyr idle thread

[Pedro]

Hi all,

Is there any way to use the Zephyr idle thread to feed the watchdog? I do that with freeRTOS and is an elegant way to feed the watchdog.

The other way is to create a task with a very low priority (just one step above the idle thread priority) and periodically feed it.

Thanks and kind regards,

Pedro.

[Learner]

Hi Pedro,

Are you using the hardware watchdog ?

I am looking for examples on how to configure it and use it to prevent lock-ups.

All the examples I found were about task_watchdog.

zephyr\samples\drivers\watchdog

zephyr\samples\subsys\task_wdt

Thank you.

Kind regards

Mohamed

[Pedro]

Hi Mohamed,

Yes, I'm using hardware watchdog.

Use this for reference:

#include <drivers/watchdog.h>
#include <logging/log.h>

#define WDT_MAX_WINDOW  10000U

LOG_MODULE_REGISTER(wdt);

static const struct device *wdt = DEVICE_DT_GET(DT_NODELABEL(wdt0));
static int wdt_channel_id;

int wdt_wdtSetup() {
	int err;

	if (!device_is_ready(wdt) || wdt == NULL)
	{
		LOG_WRN("Watchdog not ready");
		return -EIO;
	}

	struct wdt_timeout_cfg wdt_config = {
	    /* Reset SoC when watchdog timer expires. */
	    .flags = WDT_FLAG_RESET_SOC,

	    /* Expire watchdog after max window */
	    .window.min = 0U,
	    .window.max = WDT_MAX_WINDOW};

	wdt_channel_id = wdt_install_timeout(wdt, &wdt_config);
	if (wdt_channel_id < 0)
	{
		LOG_ERR("Watchdog install error.");
		return wdt_channel_id;
	}

	err = wdt_setup(wdt, WDT_OPT_PAUSE_HALTED_BY_DBG);
	if (err)
	{
		LOG_ERR("Watchdog setup error");
		return err;
	}

	return 0;
}

void wdt_wdtFeed() {
	wdt_feed(wdt, wdt_channel_id);
}

Remember to enable wdt in prj.conf

CONFIG_WATCHDOG=y
CONFIG_WDT_LOG_LEVEL_DBG=y
CONFIG_WDT_DISABLE_AT_BOOT=n

Regards,

Pedro.

[Learner]

Thank you Pedro.

Much appreciated.

Am I right in assuming #define WDT_MAX_WINDOW  10000U is in [ms] i.e. the maximum timeout is 10 seconds? This is not the absolute maximum timeout period.

I believe the absolute maximum timeout period allowed is dictated by the size of the CRV register which is 0xFFFFFFFF * 32768 seconds.

Kind regards

Mohamed

[Pedro]

Hi Mohamed,

WDT_MAX_WINDOW defines the WDT window time, in ms, i.e. the maximum time WDT can be without feeding it. In my example, if WDT is more than 10000ms without feeding, it triggers a reset.

Kind regards,

Pedro.

[Learner]

Thank you Pedro for your response.

Understood.

My second comment was about the WDT CRV register size (32 bits). This will allow the absolute maximum WDT timeout to be set to 131071 seconds i.e. 36.4 hours.

Kind regards

Mohamed