soc/rtc_clk: split rtc_clk_init into separate object file

rtc_clk_init and related functions don’t need to be in IRAM/DRAM.

components/soc/esp32/rtc_clk_common.h

@@ -0,0 +1,38 @@
+// Copyright 2015-2018 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
+
+#define MHZ (1000000)
+
+void rtc_clk_cpu_freq_to_xtal(int freq, int div);
+
+/* Values of RTC_XTAL_FREQ_REG and RTC_APB_FREQ_REG are stored as two copies in
+ * lower and upper 16-bit halves. These are the routines to work with such a
+ * representation.
+ */
+static inline bool clk_val_is_valid(uint32_t val) {
+    return (val & 0xffff) == ((val >> 16) & 0xffff) &&
+            val != 0 &&
+            val != UINT32_MAX;
+}
+
+static inline uint32_t reg_val_to_clk_val(uint32_t val) {
+    return val & UINT16_MAX;
+}
+
+static inline uint32_t clk_val_to_reg_val(uint32_t val) {
+    return (val & UINT16_MAX) | ((val & UINT16_MAX) << 16);
+}
+