driver/rtc: add rtc_gpio_isolate helper function to disconnect RTC IO

Author: igrr

components/driver/include/driver/rtc_io.h

@@ -224,6 +224,24 @@ esp_err_t rtc_gpio_hold_en(gpio_num_t gpio_num);
  */
 esp_err_t rtc_gpio_hold_dis(gpio_num_t gpio_num);
 
+/**
+ * @brief Helper function to disconnect internal circuits from an RTC IO
+ * This function disables input, output, pullup, pulldown, and enables
+ * hold feature for an RTC IO.
+ * Use this function if an RTC IO needs to be disconnected from internal
+ * circuits in deep sleep, to minimize leakage current.
+ *
+ * In particular, for ESP32-WROVER module, call
+ * rtc_gpio_isolate(GPIO_NUM_12) before entering deep sleep, to reduce
+ * deep sleep current.
+ *
+ * @param gpio_num GPIO number (e.g. GPIO_NUM_12).
+ * @return
+ *      - ESP_OK on success
+ *      - ESP_ERR_INVALID_ARG if GPIO is not an RTC IO
+ */
+esp_err_t rtc_gpio_isolate(gpio_num_t gpio_num);
+
 /**
  * @brief Disable force hold signal for all RTC IOs
  *

components/driver/rtc_module.c

@@ -381,6 +381,19 @@ esp_err_t rtc_gpio_hold_dis(gpio_num_t gpio_num)
     return ESP_OK;
 }
 
+esp_err_t rtc_gpio_isolate(gpio_num_t gpio_num)
+{
+    if (rtc_gpio_desc[gpio_num].reg == 0) {
+        return ESP_ERR_INVALID_ARG;
+    }
+
+    rtc_gpio_pullup_dis(gpio_num);
+    rtc_gpio_pulldown_dis(gpio_num);
+    rtc_gpio_set_direction(gpio_num, RTC_GPIO_MODE_DISABLED);
+    rtc_gpio_hold_en(gpio_num);
+
+    return ESP_OK;
+}
 
 void rtc_gpio_force_hold_dis_all()
 {