Implement nanostack eventloop tick timer

Nanostack eventloop tick timer can be used in case high resolution
platform timer is not needed. One usecase for that is Pelion
Cloud client when using for example cellular connectivity. This enables
PDMC application to enter deep sleep state.

features/nanostack/nanostack-hal-mbed-cmsis-rtos/arm_hal_timer.cpp

@@ -24,6 +24,7 @@
 #include "platform/mbed_assert.h"
 #include "Timeout.h"
 #include "Timer.h"
+#include "Ticker.h"
 #include "events/Event.h"
 #include "events/mbed_shared_queues.h"
 
@@ -45,6 +46,61 @@ static EventQueue *equeue;
 static uint32_t due;
 static void (*arm_hal_callback)(void);
 
+#if defined(NS_EVENTLOOP_USE_TICK_TIMER)
+
+#if MBED_CONF_NANOSTACK_HAL_CRITICAL_SECTION_USABLE_FROM_INTERRUPT
+static SingletonPtr<Ticker> tick_ticker;
+#endif
+
+static int tick_timer_id;
+static void (*tick_timer_cb)(void);
+
+int8_t platform_tick_timer_register(void (*tick_timer_cb_handler)(void))
+{
+#if !MBED_CONF_NANOSTACK_HAL_CRITICAL_SECTION_USABLE_FROM_INTERRUPT
+    equeue = mbed_highprio_event_queue();
+    MBED_ASSERT(equeue != NULL);
+#endif
+
+    tick_timer_cb = tick_timer_cb_handler;
+    return 0;
+}
+
+int8_t platform_tick_timer_start(uint32_t period_ms)
+{
+    int8_t retval = -1;
+    if (tick_timer_cb && tick_timer_id == 0) {
+#if !MBED_CONF_NANOSTACK_HAL_CRITICAL_SECTION_USABLE_FROM_INTERRUPT
+        tick_timer_id = equeue->call_every(period_ms, tick_timer_cb);
+        if (tick_timer_id != 0) {
+            retval = 0;
+        }
+#else
+        tick_ticker->attach_us(tick_timer_cb, period_ms * 1000);
+        tick_timer_id = 1;
+        retval = 0;
+#endif
+    }
+    return retval;
+}
+
+int8_t platform_tick_timer_stop(void)
+{
+    int8_t retval = -1;
+    if (tick_timer_id != 0) {
+#if !MBED_CONF_NANOSTACK_HAL_CRITICAL_SECTION_USABLE_FROM_INTERRUPT
+        equeue->cancel(tick_timer_id);
+#else
+        tick_ticker->detach();
+#endif
+        tick_timer_id = 0;
+        retval = 0;
+    }
+    return retval;
+}
+#endif // NS_EVENTLOOP_USE_TICK_TIMER
+
+
 // Called once at boot
 void platform_timer_enable(void)
 {

features/nanostack/nanostack-hal-mbed-cmsis-rtos/ns_hal_init.c

@@ -43,7 +43,9 @@ void ns_hal_init(void *heap, size_t h_size, void (*passed_fptr)(heap_fail_t), me
     }
     platform_critical_init();
     ns_dyn_mem_init(heap, h_size, passed_fptr, info_ptr);
+#ifndef NS_EXCLUDE_HIGHRES_TIMER
     platform_timer_enable();
+#endif
     eventOS_scheduler_init();
 
     // We do not initialise randlib, as it should be done after