samples: subsys: task_wdt: add sample application

The sample demonstrates how to use the task watchdog in different
threads.

Signed-off-by: Martin Jäger <martin@libre.solar>

samples/subsys/task_wdt/CMakeLists.txt

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+# SPDX-License-Identifier: Apache-2.0
+
+cmake_minimum_required(VERSION 3.13.1)
+find_package(Zephyr REQUIRED HINTS $ENV{ZEPHYR_BASE})
+project(task_wdt)
+
+target_sources(app PRIVATE src/main.c)

samples/subsys/task_wdt/README.rst

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+.. _task_wdt_sample:
+
+Task Watchdog Sample
+####################
+
+Overview
+********
+
+This sample allows to test the task watchdog subsystem.
+
+Building and Running
+********************
+
+It should be possible to build and run the task watchdog sample on almost any
+board. If a hardware watchdog is defined in the devicetree, it is used as a
+fallback. Otherwise the task watchdog will run independently.
+
+Building and Running for ST Nucleo L073RZ
+=========================================
+The sample can be built and executed for the
+:ref:`nucleo_l073rz_board` as follows:
+
+.. zephyr-app-commands::
+   :zephyr-app: samples/subsys/task_wdt
+   :board: nucleo_l073rz
+   :goals: build flash
+   :compact:
+
+For other boards just replace the board name.
+
+Sample output
+=============
+
+The following output is printed and continuously repeated (after each
+reset):
+
+.. code-block:: console
+
+Task watchdog sample application.
+Main thread still alive...
+Control thread started.
+Main thread still alive...
+Main thread still alive...
+Main thread still alive...
+Control thread getting stuck...
+Main thread still alive...
+Task watchdog channel 1 callback, thread: control
+Resetting device...

samples/subsys/task_wdt/prj.conf

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+CONFIG_LOG=y
+
+CONFIG_WATCHDOG=y
+CONFIG_WDT_LOG_LEVEL_DBG=y
+CONFIG_WDT_DISABLE_AT_BOOT=y
+
+CONFIG_TASK_WDT=y
+CONFIG_TASK_WDT_MIN_TIMEOUT=50
+
+CONFIG_THREAD_NAME=y

samples/subsys/task_wdt/sample.yaml

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+sample:
+  name: Task Watchdog Subsytem Sample
+tests:
+  sample.subsys.task_wdt:
+    tags: subsys
+    harness: console
+    harness_config:
+      type: multi_line
+      ordered: true
+      regex:
+        - "Task watchdog sample application."
+        - "Control thread started."
+        - "Main thread still alive..."
+        - "Control thread getting stuck..."
+        - "Task watchdog channel 1 callback, thread: control"
+        - "Resetting device...(.*)"
+        - "Task watchdog sample application."
+    depends_on: watchdog
+    integration_platforms:
+      - nucleo_g474re

samples/subsys/task_wdt/src/main.c

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+/*
+ * Copyright (c) 2020 Libre Solar Technologies GmbH
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <zephyr.h>
+#include <device.h>
+#include <drivers/watchdog.h>
+#include <power/reboot.h>
+#include <task_wdt/task_wdt.h>
+#include <sys/printk.h>
+#include <stdbool.h>
+
+/*
+ * To use this sample, either the devicetree's /aliases must have a
+ * 'watchdog0' property, or one of the following watchdog compatibles
+ * must have an enabled node.
+ */
+#if DT_NODE_HAS_STATUS(DT_ALIAS(watchdog0), okay)
+#define WDT_NODE DT_ALIAS(watchdog0)
+#elif DT_HAS_COMPAT_STATUS_OKAY(st_stm32_window_watchdog)
+#define WDT_NODE DT_INST(0, st_stm32_window_watchdog)
+#elif DT_HAS_COMPAT_STATUS_OKAY(st_stm32_watchdog)
+#define WDT_NODE DT_INST(0, st_stm32_watchdog)
+#elif DT_HAS_COMPAT_STATUS_OKAY(nordic_nrf_watchdog)
+#define WDT_NODE DT_INST(0, nordic_nrf_watchdog)
+#elif DT_HAS_COMPAT_STATUS_OKAY(espressif_esp32_watchdog)
+#define WDT_NODE DT_INST(0, espressif_esp32_watchdog)
+#elif DT_HAS_COMPAT_STATUS_OKAY(silabs_gecko_wdog)
+#define WDT_NODE DT_INST(0, silabs_gecko_wdog)
+#elif DT_HAS_COMPAT_STATUS_OKAY(nxp_kinetis_wdog32)
+#define WDT_NODE DT_INST(0, nxp_kinetis_wdog32)
+#elif DT_HAS_COMPAT_STATUS_OKAY(microchip_xec_watchdog)
+#define WDT_NODE DT_INST(0, microchip_xec_watchdog)
+#endif
+
+/*
+ * If the devicetree has a watchdog node, get its label property. Otherwise
+ * the task watchdog will be used without a hardware watchdog fallback.
+ */
+#ifdef WDT_NODE
+#define WDT_DEV_NAME DT_LABEL(WDT_NODE)
+#endif
+
+static void task_wdt_callback(int channel_id, void *user_data)
+{
+	printk("Task watchdog channel %d callback, thread: %s\n",
+		channel_id, k_thread_name_get((k_tid_t)user_data));
+
+	/*
+	 * If the issue could be resolved, call task_wdt_feed(channel_id) here
+	 * to continue operation.
+	 *
+	 * Otherwise we can perform some cleanup and reset the device.
+	 */
+
+	printk("Resetting device...\n");
+
+	sys_reboot(SYS_REBOOT_COLD);
+}
+
+void main(void)
+{
+#ifdef WDT_DEV_NAME
+	const struct device *hw_wdt_dev = device_get_binding(WDT_DEV_NAME);
+#else
+	const struct device *hw_wdt_dev = NULL;
+#endif
+
+	printk("Task watchdog sample application.\n");
+
+	task_wdt_init(hw_wdt_dev);
+
+	/* passing NULL instead of callback to trigger system reset */
+	int task_wdt_id = task_wdt_add(1100U, NULL, NULL);
+
+	while (true) {
+		printk("Main thread still alive...\n");
+		task_wdt_feed(task_wdt_id);
+		k_sleep(K_MSEC(1000));
+	}
+}
+
+/*
+ * This high-priority thread needs a tight timing
+ */
+void control_thread(void)
+{
+	int task_wdt_id;
+	int count = 0;
+
+	printk("Control thread started.\n");
+
+	/*
+	 * Add a new task watchdog channel with custom callback function and
+	 * the current thread ID as user data.
+	 */
+	task_wdt_id = task_wdt_add(100U, task_wdt_callback,
+		(void *)k_current_get());
+
+	while (true) {
+		if (count == 50) {
+			printk("Control thread getting stuck...\n");
+			k_sleep(K_FOREVER);
+		}
+
+		task_wdt_feed(task_wdt_id);
+		k_sleep(K_MSEC(50));
+		count++;
+	}
+}
+
+K_THREAD_DEFINE(control, 1024, control_thread, NULL, NULL, NULL, -1, 0, 1000);