Revert explicit equeue_tick initialisation

equeue_tick_init raises several questions around reentrancy. Can
equeue_tick_init be called multiple times in the case we create multiple
equeues? What about equeue_tick_deinit? Should equeue_tick_init be
allowed to fail and return an error?

Also equeue_tick_init makes less sense when supporting other OSs. Mbed
seems unique in requiring a equeue_tick_init.

equeue.c

@@ -64,7 +64,6 @@ int equeue_create_inplace(equeue_t *q, size_t size, void *buffer) {
     q->slab.data = q->buffer;
 
     q->queue = 0;
-    equeue_tick_init();
     q->tick = equeue_tick();
     q->generation = 0;
     q->break_requested = false;

equeue_mbed.cpp

@@ -27,13 +27,21 @@ using namespace mbed;
 #include "rtos/Kernel.h"
 #include "platform/mbed_os_timer.h"
 
-void equeue_tick_init() {
+static bool equeue_tick_inited = false;
+
+static void equeue_tick_init() {
 #if defined MBED_TICKLESS || !MBED_CONF_RTOS_PRESENT
     mbed::internal::init_os_timer();
 #endif
+
+    equeue_tick_inited = true;
 }
 
 unsigned equeue_tick() {
+    if (!equeue_tick_inited) {
+        equeue_tick_init();
+    }
+
 #if defined MBED_TICKLESS || !MBED_CONF_RTOS_PRESENT
     // It is not safe to call get_ms_count from ISRs, both
     // because documentation says so, and because it will give
@@ -72,6 +80,7 @@ unsigned equeue_tick() {
 #define ALIAS_TIMEOUT    Timeout
 #endif
 
+static bool equeue_tick_inited = false;
 static volatile unsigned equeue_minutes = 0;
 static unsigned equeue_timer[
         (sizeof(ALIAS_TIMER)+sizeof(unsigned)-1)/sizeof(unsigned)];
@@ -83,7 +92,7 @@ static void equeue_tick_update() {
     reinterpret_cast<ALIAS_TIMER*>(equeue_timer)->reset();
 }
 
-void equeue_tick_init() {
+static void equeue_tick_init() {
     MBED_STATIC_ASSERT(sizeof(equeue_timer) >= sizeof(ALIAS_TIMER),
             "The equeue_timer buffer must fit the class Timer");
     MBED_STATIC_ASSERT(sizeof(equeue_ticker) >= sizeof(ALIAS_TICKER),
@@ -94,9 +103,15 @@ void equeue_tick_init() {
     equeue_minutes = 0;
     timer->start();
     ticker->attach_us(equeue_tick_update, 1000 << 16);
+
+    equeue_tick_inited = true;
 }
 
 unsigned equeue_tick() {
+    if (!equeue_tick_inited) {
+        equeue_tick_init();
+    }
+
     unsigned minutes;
     unsigned ms;
 

equeue_platform.h

@@ -60,7 +60,6 @@ extern "C" {
 // limited by the accuracy of this tick.
 //
 // Must intentionally overflow to 0 after 2^32-1
-void equeue_tick_init(void);
 unsigned equeue_tick(void);
 
 

equeue_posix.c

@@ -14,9 +14,6 @@
 
 
 // Tick operations
-void equeue_tick_init(void) {
-}
-
 unsigned equeue_tick(void) {
     struct timeval tv;
     gettimeofday(&tv, 0);