Ticker: add fire interrupt now function

fire_interrupt function should be used for events in the past. As we have now
64bit timestamp, we can figure out what is in the past, and ask a target to invoke
an interrupt immediately. The previous attemps in the target HAL tickers were not ideal, as it can wrap around easily (16 or 32 bit counters). This new
functionality should solve this problem.

set_interrupt for tickers in HAL code should not handle anything but the next match interrupt. If it was in the past is handled by the upper layer.

It is possible that we are setting next event to the close future, so once it is set it is already in the past. Therefore we add a check after set interrupt to verify it is in future.
If it is not, we fire interrupt immediately. This results in
two events - first one immediate, correct one. The second one might be scheduled in far future (almost entire ticker range),
that should be discarded.

The specification for the fire_interrupts are:
- should set pending bit for the ticker interrupt (as soon as possible),
the event we are scheduling is already in the past, and we do not want to skip
any events
- no arguments are provided, neither return value, not needed
- ticker should be initialized prior calling this function (no need to check if it is already initialized)

All our targets provide this new functionality, removing old misleading if (timestamp is in the past) checks.

Author: 0xc0170

hal/lp_ticker_api.h

@@ -74,6 +74,12 @@ void lp_ticker_disable_interrupt(void);
  */
 void lp_ticker_clear_interrupt(void);
 
+/** Set pending interrupt that should be fired right away.
+ * 
+ * The ticker should be initialized prior calling this function.
+ */
+void lp_ticker_fire_interrupt(void);
+
 /**@}*/
 
 #ifdef __cplusplus

hal/mbed_lp_ticker_api.c

@@ -25,6 +25,7 @@ static const ticker_interface_t lp_interface = {
     .disable_interrupt = lp_ticker_disable_interrupt,
     .clear_interrupt = lp_ticker_clear_interrupt,
     .set_interrupt = lp_ticker_set_interrupt,
+    .fire_interrupt = lp_ticker_fire_interrupt,
 };
 
 static const ticker_data_t lp_data = {

hal/mbed_ticker_api.c

@@ -117,14 +117,23 @@ static void schedule_interrupt(const ticker_data_t *const ticker)
 
         // if the event at the head of the queue is in the past then schedule
         // it immediately.
-        if (next_event_timestamp < present) {
-            relative_timeout = 0;
+        if (next_event_timestamp <= present) {
+            ticker->interface->fire_interrupt();
+            return;
         } else if ((next_event_timestamp - present) < MBED_TICKER_INTERRUPT_TIMESTAMP_MAX_DELTA) {
             relative_timeout = next_event_timestamp - present;
         }
     } 
 
-    ticker->interface->set_interrupt(ticker->queue->present_time + relative_timeout);
+    us_timestamp_t new_match_time = ticker->queue->present_time + relative_timeout;
+    ticker->interface->set_interrupt(new_match_time);
+    // there could be a delay, reread the time, check if it was set in the past
+    // As result, if it is already in the past, we fire it immediately
+    update_present_time(ticker);
+    us_timestamp_t present = ticker->queue->present_time;
+    if (present >= new_match_time) {
+        ticker->interface->fire_interrupt();
+    }
 }
 
 void ticker_set_handler(const ticker_data_t *const ticker, ticker_event_handler handler)

hal/mbed_us_ticker_api.c

@@ -23,6 +23,7 @@ static const ticker_interface_t us_interface = {
     .disable_interrupt = us_ticker_disable_interrupt,
     .clear_interrupt = us_ticker_clear_interrupt,
     .set_interrupt = us_ticker_set_interrupt,
+    .fire_interrupt = us_ticker_fire_interrupt,
 };
 
 static const ticker_data_t us_data = {

hal/ticker_api.h

@@ -60,6 +60,7 @@ typedef struct {
     void (*disable_interrupt)(void);              /**< Disable interrupt function */
     void (*clear_interrupt)(void);                /**< Clear interrupt function */
     void (*set_interrupt)(timestamp_t timestamp); /**< Set interrupt function */
+    void (*fire_interrupt)(void);                 /**< Fire interrupt right-away */
 } ticker_interface_t;
 
 /** Ticker's event queue structure

hal/us_ticker_api.h

@@ -72,6 +72,12 @@ void us_ticker_disable_interrupt(void);
  */
 void us_ticker_clear_interrupt(void);
 
+/** Set pending interrupt that should be fired right away.
+ * 
+ * The ticker should be initialized prior calling this function.
+ */
+void us_ticker_fire_interrupt(void);
+
 /**@}*/
 
 #ifdef __cplusplus

targets/TARGET_ARM_SSG/TARGET_BEETLE/lp_ticker.c

@@ -115,27 +115,24 @@ uint32_t lp_ticker_read(void)
  */
 void lp_ticker_set_interrupt(timestamp_t timestamp)
 {
-    int32_t delta = 0;
-
     /* Verify if lp_ticker has been not Initialized */
     if (lp_ticker_initialized == 0)
         lp_ticker_init();
 
     /* Calculate the delta */
-    delta = (int32_t)(timestamp - lp_ticker_read());
-    /* Check if the event was in the past */
-    if (delta <= 0) {
-        /* This event was in the past */
-        DualTimer_SetInterrupt_1(DUALTIMER0, 0,
-                DUALTIMER_COUNT_32 | DUALTIMER_ONESHOT);
-        return;
-    }
+    uint32_t delta = timestamp - lp_ticker_read();
 
     /* Enable interrupt on SingleTimer1 */
     DualTimer_SetInterrupt_1(DUALTIMER0, delta,
             DUALTIMER_COUNT_32 | DUALTIMER_ONESHOT);
 }
 
+void lp_ticker_fire_interrupt(void)
+{
+    uint32_t lp_ticker_irqn = DualTimer_GetIRQn(DUALTIMER0);
+    NVIC_SetPendingIRQ((IRQn_Type)lp_ticker_irqn);
+}
+
 /**
  * Disable low power ticker interrupt
  */

targets/TARGET_ARM_SSG/TARGET_BEETLE/us_ticker.c

@@ -91,22 +91,19 @@ uint32_t us_ticker_read() {
 }
 
 void us_ticker_set_interrupt(timestamp_t timestamp) {
-    int32_t delta = 0;
-
     if (!us_ticker_inited)
         us_ticker_init();
-    delta = (int32_t)(timestamp - us_ticker_read());
-    /* Check if the event was in the past */
-    if (delta <= 0) {
-        /* This event was in the past */
-        Timer_SetInterrupt(TIMER0, 0);
-        return;
-    }
 
-    /* If the event was not in the past enable interrupt */
+    uint32_t delta = timestamp - us_ticker_read();
     Timer_SetInterrupt(TIMER0, delta);
 }
 
+void us_ticker_fire_interrupt(void)
+{
+    uint32_t us_ticker_irqn1 = Timer_GetIRQn(TIMER1);
+    NVIC_SetPendingIRQ((IRQn_Type)us_ticker_irqn1);
+}
+
 void us_ticker_disable_interrupt(void) {
     Timer_DisableInterrupt(TIMER0);
 }

targets/TARGET_ARM_SSG/TARGET_CM3DS_MPS2/us_ticker.c

@@ -108,22 +108,23 @@ uint32_t us_ticker_read()
 
 void us_ticker_set_interrupt(timestamp_t timestamp)
 {
-    int32_t delta = 0;
+    uint32_t delta = 0;
 
     if (!us_ticker_drv_data.inited) {
         us_ticker_init();
     }
 
-    delta = (int32_t)(timestamp - us_ticker_read());
+    delta = timestamp - us_ticker_read();
 
-    /* Check if the event was in the past */
-    if (delta <= 0) {
-        /* This event was in the past */
-        Timer_SetInterrupt(TIMER0, 0);
-    } else {
-        /* If the event was not in the past enable interrupt */
-        Timer_SetInterrupt(TIMER0, delta);
-    }
+    /* If the event was not in the past enable interrupt */
+    Timer_SetInterrupt(TIMER0, delta);
+
+}
+
+void us_ticker_fire_interrupt(void)
+{
+    uint32_t us_ticker_irqn1 = Timer_GetIRQn(TIMER1);
+    NVIC_SetPendingIRQ((IRQn_Type)us_ticker_irqn1);
 }
 
 void us_ticker_disable_interrupt(void)

targets/TARGET_ARM_SSG/TARGET_IOTSS/us_ticker.c

@@ -69,6 +69,11 @@ void us_ticker_set_interrupt(timestamp_t timestamp) {
     US_TICKER_TIMER1->TimerControl |= 0x80; //enable timer
 }
 
+void us_ticker_fire_interrupt(void)
+{
+    NVIC_SetPendingIRQ(US_TICKER_TIMER_IRQn);
+}
+
 void us_ticker_disable_interrupt(void) {
 
     US_TICKER_TIMER1->TimerControl &= 0xDF;