counter: add counter_ticks_to_ns()

Add new API to get nanosecond from counter ticks.

Signed-off-by: Jiafei Pan <[email protected]>

Author: JiafeiPan

include/zephyr/drivers/counter.h

@@ -338,6 +338,22 @@ static inline uint64_t z_impl_counter_ticks_to_us(const struct device *dev,
 	return ((uint64_t)ticks * USEC_PER_SEC) / z_impl_counter_get_frequency(dev);
 }
 
+/**
+ * @brief Function to convert ticks to nanoseconds.
+ *
+ * @param[in]  dev    Pointer to the device structure for the driver instance.
+ * @param[in]  ticks  Ticks.
+ *
+ * @return Converted nanoseconds.
+ */
+__syscall uint64_t counter_ticks_to_ns(const struct device *dev, uint32_t ticks);
+
+static inline uint64_t z_impl_counter_ticks_to_ns(const struct device *dev,
+					       uint32_t ticks)
+{
+	return ((uint64_t)ticks * NSEC_PER_SEC) / z_impl_counter_get_frequency(dev);
+}
+
 /**
  * @brief Function to retrieve maximum top value that can be set.
  *