change(esp_hw_support): add interface to calculate slow clock period by clock frequency

components/esp_hw_support/port/esp32/include/soc/rtc.h

@@ -481,6 +481,14 @@ bool rtc_dig_8m_enabled(void);
  */
 uint32_t rtc_clk_freq_cal(uint32_t cal_val);
 
+/**
+ * @brief Calculate the slow clock period value by slow clock frequency
+ *
+ * @param freq_hz Frequency of the slow clock in Hz
+ * @return Fixed point value of slow clock period in microseconds
+ */
+uint32_t rtc_clk_freq_to_period(uint32_t freq_hz);
+
 /**
  * @brief sleep configuration for rtc_sleep_init function
  */

components/esp_hw_support/port/esp32/rtc_time.c

@@ -191,6 +191,8 @@ uint32_t rtc_clk_freq_cal(uint32_t cal_val)
     return 1000000ULL * (1 << RTC_CLK_CAL_FRACT) / cal_val;
 }
 
+uint32_t rtc_clk_freq_to_period(uint32_t) __attribute__((alias("rtc_clk_freq_cal")));
+
 /// @brief if the calibration is used, we need to enable the timer group0 first
 __attribute__((constructor))
 static void enable_timer_group0_for_calibration(void)