Define a cutstom tick_t type which can be set to uint32_t

In many embedded devices, a 32 bit tick is sufficent for any
applications. it's also more performant than the 64 bit tick. This patch
adds support for switching to 32 bit ticks where it makes sense to do
so.

Signed-off-by: Siddharth Chandrasekaran <sidcha.dev@gmail.com>

Author: sidcha

include/utils/utils.h

@@ -166,6 +166,23 @@ extern "C" {
 #define PATH_SEPARATOR          '/'
 #endif
 
+#if defined(__BARE_METAL__) && defined(USE_32BIT_TICK_T)
+/*
+ * Bare-metal timing note:
+ *
+ * When __BARE_METAL__ and USE_32BIT_TICK_T are both enabled, tick_t uses
+ * 32-bit storage. The selected tick source and tick width together define the
+ * maximum delay interval that can be measured safely in the project.
+ *
+ * Example: with a 1 kHz tick source, uint32_t spans about 49.7 days.
+ * Make sure your largest required delay/timeout remains safe for your chosen
+ * tick source and counter width.
+ */
+typedef uint32_t tick_t;
+#else
+typedef uint64_t tick_t;
+#endif
+
 /**
  * @brief Return random number between 0 and `limit` both inclusive.
  *
@@ -199,18 +216,18 @@ void hexdump(const void *data, size_t len, const char *fmt, ...);
 /**
  * @brief Get the time in micro seconds.
  */
-int64_t usec_now();
+tick_t usec_now();
 
 /**
  * @brief Get time elapsed in micro seconds since `last`. Used along with
  * usec_now().
  */
-int64_t usec_since(int64_t last);
+tick_t usec_since(tick_t last);
 
 /**
  * @brief Get the time in milli seconds.
  */
-int64_t millis_now();
+tick_t millis_now();
 
 /**
  * @brief Get time in seconds and micro_seconds
@@ -228,7 +245,7 @@ int add_iso8601_utc_datetime(char *buf, size_t size);
  * @brief Get time elapsed in milli seconds since `last`. Used along with
  * millis_now().
  */
-int64_t millis_since(int64_t last);
+tick_t millis_since(tick_t last);
 
 /**
  * @brief Print the stack trace

include/utils/workqueue.h

@@ -31,7 +31,7 @@ enum work_status {
 
 typedef struct {
 	queue_node_t node;
-	int64_t slice;
+	tick_t slice;
 	enum work_status status;
 	uint32_t requests;
 
@@ -117,4 +117,4 @@ bool workqueue_work_is_complete(workqueue_t *wq, work_t *work);
 }
 #endif
 
-#endif /* _UTILS_WORKQUEUE_H_ */
+#endif /* _UTILS_WORKQUEUE_H_ */

src/utils.c

@@ -218,15 +218,15 @@ int add_iso8601_utc_datetime(char* buf, size_t size) {
 
 #endif
 
-int64_t usec_now()
+tick_t usec_now()
 {
-	int64_t usec;
+	uint64_t usec;
 	struct timeval tv;
 
 	gettimeofday(&tv, NULL);
 	usec = tv.tv_sec * 1000LL * 1000LL + tv.tv_usec;
 
-	return usec;
+	return (tick_t)usec;
 }
 
 void get_time(uint32_t *seconds, uint32_t *micro_seconds)
@@ -238,17 +238,17 @@ void get_time(uint32_t *seconds, uint32_t *micro_seconds)
 	*micro_seconds = tv.tv_usec;
 }
 
-int64_t usec_since(int64_t last)
+tick_t usec_since(tick_t last)
 {
 	return usec_now() - last;
 }
 
-int64_t millis_now()
+tick_t millis_now()
 {
-	return (int64_t)(usec_now() / 1000LL);
+	return (tick_t)(usec_now() / 1000U);
 }
 
-int64_t millis_since(int64_t last)
+tick_t millis_since(tick_t last)
 {
 	return millis_now() - last;
 }

src/workqueue.c

@@ -41,7 +41,7 @@ static void complete_work(work_t *work)
 static int do_work(work_t *work)
 {
 	int rc;
-	int64_t slice;
+	tick_t slice;
 
 	slice = usec_now();
 	rc = work->work_fn(work->arg);