Diff: hal/mbed_ticker_api.c

Revision:

167:e84263d55307

Parent:

162:e13f6fdb2ac4

--- a/hal/mbed_ticker_api.c	Thu Jun 08 15:02:37 2017 +0100
+++ b/hal/mbed_ticker_api.c	Wed Jun 21 17:46:44 2017 +0100
@@ -13,50 +13,183 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+#include <stdio.h>
 #include <stddef.h>
 #include "hal/ticker_api.h"
 #include "platform/mbed_critical.h"
 
-void ticker_set_handler(const ticker_data_t *const data, ticker_event_handler handler) {
-    data->interface->init();
+static void schedule_interrupt(const ticker_data_t *const ticker);
+static void update_present_time(const ticker_data_t *const ticker);
+
+/*
+ * Initialize a ticker instance.  
+ */
+static void initialize(const ticker_data_t *ticker)
+{
+    // return if the queue has already been initialized, in that case the 
+    // interface used by the queue is already initialized.
+    if (ticker->queue->initialized) { 
+        return;
+    }
 
-    data->queue->event_handler = handler;
+    ticker->interface->init();
+    
+    ticker->queue->event_handler = NULL;
+    ticker->queue->head = NULL;
+    ticker->queue->present_time = 0;
+    ticker->queue->initialized = true;
+    
+    update_present_time(ticker);
+    schedule_interrupt(ticker);
+}
+
+/**
+ * Set the event handler function of a ticker instance. 
+ */
+static void set_handler(const ticker_data_t *const ticker, ticker_event_handler handler)
+{
+    ticker->queue->event_handler = handler;
 }
 
-void ticker_irq_handler(const ticker_data_t *const data) {
-    data->interface->clear_interrupt();
+/*
+ * Convert a 32 bit timestamp into a 64 bit timestamp.
+ *
+ * A 64 bit timestamp is used as the point of time of reference while the 
+ * timestamp to convert is relative to this point of time. 
+ *
+ * The lower 32 bits of the timestamp returned will be equal to the timestamp to 
+ * convert. 
+ * 
+ * If the timestamp to convert is less than the lower 32 bits of the time 
+ * reference then the timestamp to convert is seen as an overflowed value and 
+ * the upper 32 bit of the timestamp returned will be equal to the upper 32 bit 
+ * of the reference point + 1. 
+ * Otherwise, the upper 32 bit returned will be equal to the upper 32 bit of the 
+ * reference point. 
+ *
+ * @param ref: The 64 bit timestamp of reference.
+ * @param timestamp: The timestamp to convert.
+ */
+static us_timestamp_t convert_timestamp(us_timestamp_t ref, timestamp_t timestamp)
+{
+    bool overflow = timestamp < ((timestamp_t) ref) ? true : false;
+
+    us_timestamp_t result = (ref & ~((us_timestamp_t)UINT32_MAX)) | timestamp;
+    if (overflow) { 
+        result += (1ULL<<32);
+    }
+
+    return result;
+}
+
+/**
+ * Update the present timestamp value of a ticker.
+ */
+static void update_present_time(const ticker_data_t *const ticker)
+{ 
+    ticker->queue->present_time = convert_timestamp(
+        ticker->queue->present_time, 
+        ticker->interface->read()
+    );
+}
+
+/**
+ * Compute the time when the interrupt has to be triggered and schedule it.  
+ * 
+ * If there is no event in the queue or the next event to execute is in more 
+ * than MBED_TICKER_INTERRUPT_TIMESTAMP_MAX_DELTA us from now then the ticker 
+ * irq will be scheduled in MBED_TICKER_INTERRUPT_TIMESTAMP_MAX_DELTA us.
+ * Otherwise the irq will be scheduled to happen when the running counter reach 
+ * the timestamp of the first event in the queue.
+ * 
+ * @note If there is no event in the queue then the interrupt is scheduled to 
+ * in MBED_TICKER_INTERRUPT_TIMESTAMP_MAX_DELTA. This is necessary to keep track 
+ * of the timer overflow.
+ */
+static void schedule_interrupt(const ticker_data_t *const ticker)
+{
+    update_present_time(ticker);
+    uint32_t relative_timeout = MBED_TICKER_INTERRUPT_TIMESTAMP_MAX_DELTA;
+
+    if (ticker->queue->head) {
+        us_timestamp_t present = ticker->queue->present_time;
+        us_timestamp_t next_event_timestamp = ticker->queue->head->timestamp;
+
+        // 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;
+        } 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);
+}
+
+void ticker_set_handler(const ticker_data_t *const ticker, ticker_event_handler handler)
+{
+    initialize(ticker);
+    set_handler(ticker, handler);
+}
+
+void ticker_irq_handler(const ticker_data_t *const ticker)
+{
+    ticker->interface->clear_interrupt();
 
     /* Go through all the pending TimerEvents */
     while (1) {
-        if (data->queue->head == NULL) {
-            // There are no more TimerEvents left, so disable matches.
-            data->interface->disable_interrupt();
-            return;
+        if (ticker->queue->head == NULL) {
+            break;
         }
 
-        if ((int)(data->queue->head->timestamp - data->interface->read()) <= 0) {
+        // update the current timestamp used by the queue 
+        update_present_time(ticker);
+
+        if (ticker->queue->head->timestamp <= ticker->queue->present_time) { 
             // This event was in the past:
             //      point to the following one and execute its handler
-            ticker_event_t *p = data->queue->head;
-            data->queue->head = data->queue->head->next;
-            if (data->queue->event_handler != NULL) {
-                (*data->queue->event_handler)(p->id); // NOTE: the handler can set new events
+            ticker_event_t *p = ticker->queue->head;
+            ticker->queue->head = ticker->queue->head->next;
+            if (ticker->queue->event_handler != NULL) {
+                (*ticker->queue->event_handler)(p->id); // NOTE: the handler can set new events
             }
             /* Note: We continue back to examining the head because calling the
              * event handler may have altered the chain of pending events. */
         } else {
-            // This event and the following ones in the list are in the future:
-            //      set it as next interrupt and return
-            data->interface->set_interrupt(data->queue->head->timestamp);
-            return;
-        }
+            break;
+        } 
     }
+
+    schedule_interrupt(ticker);
 }
 
-void ticker_insert_event(const ticker_data_t *const data, ticker_event_t *obj, timestamp_t timestamp, uint32_t id) {
-    /* disable interrupts for the duration of the function */
+void ticker_insert_event(const ticker_data_t *const ticker, ticker_event_t *obj, timestamp_t timestamp, uint32_t id)
+{
     core_util_critical_section_enter();
 
+    // update the current timestamp
+    update_present_time(ticker);
+    us_timestamp_t absolute_timestamp = convert_timestamp(
+        ticker->queue->present_time, 
+        timestamp
+    );
+    core_util_critical_section_exit();
+
+    // defer to ticker_insert_event_us
+    ticker_insert_event_us(
+        ticker, 
+        obj, absolute_timestamp, id
+    );
+}
+
+void ticker_insert_event_us(const ticker_data_t *const ticker, ticker_event_t *obj, us_timestamp_t timestamp, uint32_t id)
+{
+    core_util_critical_section_enter();
+
+    // update the current timestamp
+    update_present_time(ticker);
+
     // initialise our data
     obj->timestamp = timestamp;
     obj->id = id;
@@ -64,10 +197,10 @@
     /* Go through the list until we either reach the end, or find
        an element this should come before (which is possibly the
        head). */
-    ticker_event_t *prev = NULL, *p = data->queue->head;
+    ticker_event_t *prev = NULL, *p = ticker->queue->head;
     while (p != NULL) {
         /* check if we come before p */
-        if ((int)(timestamp - p->timestamp) < 0) {
+        if (timestamp < p->timestamp) {
             break;
         }
         /* go to the next element */
@@ -80,30 +213,28 @@
 
     /* if prev is NULL we're at the head */
     if (prev == NULL) {
-        data->queue->head = obj;
-        data->interface->set_interrupt(timestamp);
+        ticker->queue->head = obj;
     } else {
         prev->next = obj;
     }
 
+    schedule_interrupt(ticker);
+
     core_util_critical_section_exit();
 }
 
-void ticker_remove_event(const ticker_data_t *const data, ticker_event_t *obj) {
+void ticker_remove_event(const ticker_data_t *const ticker, ticker_event_t *obj)
+{
     core_util_critical_section_enter();
 
     // remove this object from the list
-    if (data->queue->head == obj) {
+    if (ticker->queue->head == obj) {
         // first in the list, so just drop me
-        data->queue->head = obj->next;
-        if (data->queue->head == NULL) {
-            data->interface->disable_interrupt();
-        } else {
-            data->interface->set_interrupt(data->queue->head->timestamp);
-        }
+        ticker->queue->head = obj->next;
+        schedule_interrupt(ticker);
     } else {
         // find the object before me, then drop me
-        ticker_event_t* p = data->queue->head;
+        ticker_event_t* p = ticker->queue->head;
         while (p != NULL) {
             if (p->next == obj) {
                 p->next = obj->next;
@@ -116,9 +247,15 @@
     core_util_critical_section_exit();
 }
 
-timestamp_t ticker_read(const ticker_data_t *const data)
+timestamp_t ticker_read(const ticker_data_t *const ticker)
 {
-    return data->interface->read();
+    return ticker_read_us(ticker);
+}
+
+us_timestamp_t ticker_read_us(const ticker_data_t *const ticker)
+{
+    update_present_time(ticker);
+    return ticker->queue->present_time;
 }
 
 int ticker_get_next_timestamp(const ticker_data_t *const data, timestamp_t *timestamp)