esp_clk.h: make public, add getters for RTC time, CPU/APB freq

components/esp32/esp_clk_internal.h

@@ -0,0 +1,39 @@
+// Copyright 2015-2017 Espressif Systems (Shanghai) PTE LTD
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#pragma once
+
+/**
+ * @file esp_clk_internal.h
+ *
+ * Private clock-related functions
+ */
+
+/**
+ * @brief Initialize clock-related settings
+ *
+ * Called from cpu_start.c, not intended to be called from other places.
+ * This function configures the CPU clock, RTC slow and fast clocks, and
+ * performs RTC slow clock calibration.
+ */
+void esp_clk_init(void);
+
+
+/**
+ * @brief Disables clock of some peripherals
+ *
+ * Called from cpu_start.c, not intended to be called from other places.
+ * This function disables clock of useless peripherals when cpu starts.
+ */
+void esp_perip_clk_init(void);