Add HwWatchdog

- mbed_watchdog_mgr has interface name mbed_wdog_manager_start(),mbed_wdog_manager_stop(),mbed_wdog_manager_kick()
    - HwWatchdog is going to attach with LowPowerTIcker for periodic callback functionality
    - mbed_wdog_manager_start() will either get start either by BL/RTOS Aps,it reads the timeout value specified via macro and macro gets defined in target.json file.
    - mbed_wdog_manager_start() internally configure below HAL hw watchdog with timeout specified via target.json
    - mbed_wdog_manager_start() internally divide the timeout(specified in target.json) by the 2 and attach LowPowerTicker with periodic callback of hw_kick()
    - mbed_wdog_manager_start() internally create one instance of sw watchdog class,to access the static list data structure of sw watchdog class
    - mbed_wdog_manager_kick() function periodically get called and refresh the hw watchdog to avoid watchdog reset
    - converted C++ code into C based APIs
    - added boolean to control watchdog start and stop
    - Added detach from ticker on stop API

mbed.h

@@ -77,7 +77,7 @@
 
 // mbed Internal components
 #include "drivers/ResetReason.h"
-#include "drivers/Watchdog.h"
+#include "platform/mbed_watchdog_mgr.h"
 #include "drivers/Timer.h"
 #include "drivers/Ticker.h"
 #include "drivers/Timeout.h"

platform/mbed_watchdog_mgr.cpp

@@ -0,0 +1,109 @@
+
+/* mbed Microcontroller Library
+ * Copyright (c) 2018 ARM Limited
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+#ifdef DEVICE_WATCHDOG
+
+#include "mbed_watchdog_mgr.h"
+
+static bool is_watchdog_started = false; //boolean to control watchdog start and stop
+#define MS_TO_US(x) ((x) * 1000) //macro to convert millisecond to microsecond
+
+MBED_STATIC_ASSERT((HW_WATCHDOG_TIMEOUT >= 0),"Timeout must be greater than zero");
+
+
+/** Create singleton instance of LowPowerTicker for watchdog periodic call back of kick.
+ */
+static LowPowerTicker *get_ticker()
+{
+    static LowPowerTicker ticker;
+    return &ticker;
+}
+
+/** Refreshes the watchdog timer.
+ *
+ * This function should be called periodically before the watchdog times out.
+ * Otherwise, the system is reset.
+ *
+ * If the watchdog timer is not currently running this function does nothing
+ */
+static void mbed_wdog_manager_kick()
+{
+    core_util_critical_section_enter();
+    hal_watchdog_kick();
+    core_util_critical_section_exit();
+}
+
+uint32_t mbed_wdog_manager_get_max_timeout()
+{
+    const watchdog_features_t features = hal_watchdog_get_platform_features();
+    return features.max_timeout;
+}
+
+bool mbed_wdog_manager_start()
+{
+
+    watchdog_status_t sts;
+    bool msts = true;
+    MBED_ASSERT(HW_WATCHDOG_TIMEOUT < mbed_wdog_manager_get_max_timeout());
+    core_util_critical_section_enter();
+    if(is_watchdog_started) {
+    	core_util_critical_section_exit();
+        return false;
+    }
+    watchdog_config_t config;
+    config.timeout_ms = HW_WATCHDOG_TIMEOUT;
+    sts = hal_watchdog_init(&config);
+    if(sts != WATCHDOG_STATUS_OK) {
+        msts = false;
+    } else {
+        us_timestamp_t timeout = (MS_TO_US(HW_WATCHDOG_TIMEOUT)/2);
+        get_ticker()->attach_us(callback(&mbed_wdog_manager_kick),timeout);
+        is_watchdog_started = true;
+    }
+    core_util_critical_section_exit();
+    return msts;
+}
+
+bool mbed_wdog_manager_stop()
+{
+    watchdog_status_t sts;
+    bool msts = true;
+    core_util_critical_section_enter();
+    if(is_watchdog_started) {
+        sts = hal_watchdog_stop();
+        if(sts != WATCHDOG_STATUS_OK) {
+            msts = false;
+        } else {
+            get_ticker()->detach();
+            is_watchdog_started = false;
+        }
+
+    } else {
+         msts = false;
+    }
+    core_util_critical_section_exit();
+    return msts;
+}
+
+
+uint32_t mbed_wdog_manager_get_reload_value()
+{
+    return hal_watchdog_get_reload_value();
+}
+
+
+#endif // DEVICE_WATCHDOG

platform/mbed_watchdog_mgr.h

@@ -0,0 +1,92 @@
+/* mbed Microcontroller Library
+ * Copyright (c) 2018 ARM Limited
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef MBED_WATCHDOG_H
+#define MBED_WATCHDOG_H
+
+#ifdef DEVICE_WATCHDOG
+
+#include "watchdog_api.h"
+#include "mbed_error.h"
+#include "mbed.h"
+#include "platform/mbed_critical.h"
+#include "LowPowerTicker.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/** \addtogroup drivers */
+/** A system timer that will reset the system in the case of system failures or
+ *  malfunctions.
+ *
+ * Example:
+ * @code
+ *
+ * mbed_wdog_manager_start();
+ *
+ * while (true) {
+ *    wait(0.3);
+ *
+ * }
+ * @endcode
+ * @ingroup drivers
+ */
+
+/** Start an independent watchdog timer
+ *
+ *
+ *  @return status true if the watchdog timer was started
+ *                 successfully. assert if one of the input parameters is out of range for the current platform.
+ *                 false if watchdog timer was not started
+ */
+bool mbed_wdog_manager_start();
+
+/** Stops the watchdog timer
+ *
+ * Calling this function will attempt to disable any currently running
+ * watchdog timers if supported by the current platform.
+ *
+ * @return Returns true if the watchdog timer was succesfully
+ *         stopped, or if the timer was never started. Returns
+ *         false if the watchdog cannot be disabled
+ *         on the current platform.
+ */
+bool mbed_wdog_manager_stop();
+
+
+/** Get the watchdog timer refresh value
+ *
+ * This function returns the refresh timeout of the watchdog timer.
+ *
+ * @return Reload value for the watchdog timer in milliseconds.
+ */
+uint32_t mbed_wdog_manager_get_reload_value();
+
+
+/** Get the maximum refresh value for the current platform in milliseconds
+ *
+ * @return Maximum refresh value supported by the watchdog for the current
+ *         platform in milliseconds
+ */
+uint32_t mbed_wdog_manager_get_max_timeout();
+
+#ifdef __cplusplus
+}
+#endif
+#endif // DEVICE_WATCHDOG
+#endif // MBED_WATCHDOG_H

targets/targets.json

@@ -51,6 +51,11 @@
             "init-us-ticker-at-boot": {
                 "help": "Initialize the microsecond ticker at boot rather than on first use, and leave it initialized. This speeds up wait_us in particular.",
                 "value": false
+            },
+            "hw-watchdog_timeout": {
+                "help": "Define the timeout in ms value LowPowerTicker to do HW kick",
+                "value": "800",
+                "macro_name": "HW_WATCHDOG_TIMEOUT"
             }
         }
     },