feat: WDT: added WDT demo application

* Modified SoC init function configures COP WDT to time out after 8192ms
if CONFIG_WATCHDOG is set.
* A demo application shows how the WDT must be reloaded in order not to
time out.
* Closes zephyrproject-rtos#15

Author: Alexander Preißner

arch/arm/soc/nxp_kinetis/kwx/soc_kw4xz.c

@@ -112,8 +112,13 @@ static int kwx_init(struct device *arg)
 	/* disable interrupts */
 	oldLevel = irq_lock();
 
-	/* Disable the watchdog */
+	/* Configure or disable the watchdog */
+#if defined(CONFIG_WATCHDOG)
+	/* 1kHz LPC clock, 2^13 cycles = 8192ms */
+	SIM->COPC = SIM_COPC_COPCLKSEL(00) | SIM_COPC_COPCLKS(1) | SIM_COPC_COPT(01);
+#else
 	SIM->COPC = 0;
+#endif
 
 	/* Initialize system clock to 40 MHz */
 	clkInit();

samples/watchdog/CMakeLists.txt

@@ -0,0 +1,6 @@
+
+include($ENV{ZEPHYR_BASE}/cmake/app/boilerplate.cmake NO_POLICY_SCOPE)
+project(NONE)
+
+target_sources(app PRIVATE src/main.c)
+target_sources(app PRIVATE $ENV{ZEPHYR_BASE}/ext/hal/nxp/mcux/drivers/fsl_vref.c)

samples/watchdog/prj.conf

@@ -0,0 +1,2 @@
+CONFIG_STDOUT_CONSOLE=y
+CONFIG_WATCHDOG=y

samples/watchdog/sample.yaml

@@ -0,0 +1,18 @@
+sample:
+  description: Hello World sample, the simplest Zephyr
+    application
+  name: hello world
+  platforms: all
+common:
+    tags: samples
+    harness: console
+    harness_config:
+      type: one_line
+      regex:
+        - "Hello World! (.*)"
+tests:
+  singlethread:
+    extra_args: CONF_FILE=prj_single.conf
+    filter: not CONFIG_BT and not CONFIG_GPIO_SCH and ASSERT == 0
+  test:
+    tags: samples

samples/watchdog/src/main.c

@@ -0,0 +1,72 @@
+/*
+ * Copyright (c) 2018 blik GmbH
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/**
+ * @file main.c
+ *
+ * @copyright 2018 blik GmbH
+ *
+ * @author Alexander Preißner <[email protected]>
+ *
+ * This is a sample application that demonstrates how to use the KW41Z
+ * Watchdog Timer.
+ */
+
+/*----------------------------------------------------------------------------*/
+/*                                HEADERS                                     */
+/*----------------------------------------------------------------------------*/
+
+#include <zephyr.h>
+
+#include <misc/printk.h>
+
+#include <fsl_common.h>
+#include <misc/util.h>
+
+
+/*----------------------------------------------------------------------------*/
+/*                                MACROS                                      */
+/*----------------------------------------------------------------------------*/
+
+/**
+ * @brief Watchdog Timer reload sequence
+ *
+ * The exact sequence 0x55 and 0xAA MUST be written to the SRVCOP register
+ * in order to reload the Watchdog Timer.
+ */
+#if defined(CONFIG_WATCHDOG)
+#define WDT_RELOAD()        SIM->SRVCOP = SIM_SRVCOP_SRVCOP(0x55); \
+                            SIM->SRVCOP = SIM_SRVCOP_SRVCOP(0xAA)
+#else
+#define WDT_RELOAD()
+#endif
+
+/**
+ * @brief Switch defining whether watchdog timer is reloaded or not in this
+ * sample.
+ *
+ * If this variable is '0' "Hello blik!" should be printed to STDOUT every
+ * 8.192 seconds.
+ */
+#define RELOAD_WATCHDOG     0
+
+
+/**
+ * @brief Function for Main thread
+ */
+void main(void) {
+    // Print what this sample is about
+    printk("Hello blik!\n");
+
+    while(RELOAD_WATCHDOG)
+    {
+        WDT_RELOAD();
+
+        k_sleep(1000);
+    }
+
+    return;
+}