cpu/stm32_common: added common clk interface

cpu/stm32_common/include/stmclk.h

@@ -0,0 +1,92 @@
+/*
+ * Copyright (C) 2017 Freie Universität Berlin
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser General
+ * Public License v2.1. See the file LICENSE in the top level directory for more
+ * details.
+ */
+
+/**
+ * @ingroup         cpu_stm32_common
+ * @{
+ *
+ * @file
+ * @brief           Interface for configuring the clock tree of STM32 CPUs
+ *
+ * @todo            This interface should probably be moved and implemented for
+ *                  every STM32 CPU
+ *
+ * @author          Hauke Petersen <hauke.pertersen@fu-berlin.de>
+*/
+
+#ifndef STMCLK_H
+#define STMCLK_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * @brief   Configure the  high speed clock domain (main system clock)
+ *
+ * This function initializes and configures the main systems clock(s). For this,
+ * the following actions are carried out:
+ * - enable the HSI
+ * - use the HSI as system clock (so now we are always in a defined state)
+ * - configure flash wait states and AHB/APB bus dividers
+ * - [opt] enable the HSE / MSI
+ * - configure the PLL
+ * - use PLL as system clock
+ * - turn off the HSI if unused
+ *
+ * All of these options are configurable through the board's periph_conf.h
+ */
+void stmclk_init_sysclk(void);
+
+/**
+ * @brief   Enable the internal high speed clock (HSI)
+ */
+void stmclk_enable_hsi(void);
+
+/**
+ * @brief   Disable the internal high speed clock (HSI)
+ *
+ * @note    The HSI is only disabled, if it is at that point not used to drive
+ *          the system clock or the PLL
+ */
+void stmclk_disable_hsi(void);
+
+/**
+ * @brief   Configure and enable the low speed clock domain
+ *
+ * The actual clock used as input for the low frequency clock can be either the
+ * external low speed clock (LSE) or the internal low speed clock (LSI). This
+ * is configured in the board's periph_conf.h file.
+ */
+void stmclk_enable_lfclk(void);
+
+/**
+ * @brief   Disable the low frequency clock domain
+ *
+ * @note    When calling this function, better know what you do: be sure that
+ *          the clock is not needed by any peripheral before calling this
+ *          function.
+ */
+void stmclk_disable_lfclk(void);
+
+/**
+ * @brief   Unlock write access to the backup domain control
+ */
+void stmclk_bdp_unlock(void);
+
+/**
+ * @brief   Lock write access to backup control domain
+ */
+void stmclk_bdp_lock(void);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* STMCLK_H */
+/** @} */