Drivers: locking sleep fix for attach/detach

As attach provides API to change a callback, lock/unlock should
only happen if we are doing the first/last callback (start-stop).

drivers/CAN.cpp

@@ -116,7 +116,10 @@ int CAN::filter(unsigned int id, unsigned int mask, CANFormat format, int handle
 void CAN::attach(Callback<void()> func, IrqType type) {
     lock();
     if (func) {
-        sleep_manager_lock_deep_sleep();
+        // lock deep sleep only the first time
+        if (_irq[(CanIrqType)type] == callback(donothing)) {
+            sleep_manager_lock_deep_sleep();
+        }
         _irq[(CanIrqType)type] = func;
         can_irq_set(&_can, (CanIrqType)type, 1);
     } else {

drivers/SerialBase.cpp

@@ -77,7 +77,10 @@ void SerialBase::attach(Callback<void()> func, IrqType type) {
     // Disable interrupts when attaching interrupt handler
     core_util_critical_section_enter();
     if (func) {
-        sleep_manager_lock_deep_sleep();
+        // lock deep sleep only the first time
+        if (_irq[type] == donothing) {
+            sleep_manager_lock_deep_sleep();
+        } 
         _irq[type] = func;
         serial_irq_set(&_serial, (SerialIrq)type, 1);
     } else {

drivers/Ticker.cpp

@@ -25,8 +25,11 @@ namespace mbed {
 void Ticker::detach() {
     core_util_critical_section_enter();
     remove();
+    // unlocked only if we were attached (we locked it)
+    if (_function) {
+        sleep_manager_unlock_deep_sleep();
+    }
     _function = 0;
-    sleep_manager_unlock_deep_sleep();
     core_util_critical_section_exit();
 }
 

drivers/Ticker.h

@@ -64,10 +64,10 @@ namespace mbed {
 class Ticker : public TimerEvent, private NonCopyable<Ticker> {
 
 public:
-    Ticker() : TimerEvent() {
+    Ticker() : TimerEvent(), _function(0) {
     }
 
-    Ticker(const ticker_data_t *data) : TimerEvent(data) {
+    Ticker(const ticker_data_t *data) : TimerEvent(data), _function(0) {
         data->interface->init();
     }
 
@@ -103,8 +103,11 @@ public:
      *  @param t the time between calls in micro-seconds
      */
     void attach_us(Callback<void()> func, us_timestamp_t t) {
+        // lock only for the initial callback setup
+        if (!_function) {
+            sleep_manager_lock_deep_sleep();
+        }
         _function = func;
-        sleep_manager_lock_deep_sleep();
         setup(t);
     }
 

drivers/Timer.cpp

@@ -41,8 +41,10 @@ void Timer::start() {
 void Timer::stop() {
     core_util_critical_section_enter();
     _time += slicetime();
+    if (_running) {
+        sleep_manager_unlock_deep_sleep();
+    }
     _running = 0;
-    sleep_manager_unlock_deep_sleep();
     core_util_critical_section_exit();
 }