/**
 * @defgroup        cpu_stm32_common STM32 common
 * @ingroup         cpu
 * @brief           STM32 common code and definitions
 *
 * This module contains all common code and definition to all STM32 cpu
 * families supported by RIOT: @ref cpu_stm32f0, @ref cpu_stm32l0,
 * @ref cpu_stm32f1, @ref cpu_stm32f2, @ref cpu_stm32f3, @ref cpu_stm32f4,
 * @ref cpu_stm32l4, @ref cpu_stm32f7.
 *
 * STM32Fx Clock configuration
 * =================================
 *
 * stm32fx cpus share clock configuration code and macro.
 * It can be configured as described here.
 *
 * The following macro must be defined in the board's periph_conf.h:
 *  - CLOCK_HSE: 0 if HSI must be used as PLL source, frequency in Hz otherwise,
 *  - CLOCK_LSE: 0 if LSI must be used as low speed clock, 1 otherwise
 * (the LSE is a 32.768kHz crytal)
 *  - CLOCK_CORECLOCK: desired main clock frequency
 *  - CLOCK_AHB_DIV, CLOCK_AHB: AHB prescaler in register value and AHB frequecny in Hz
 *  - CLOCK_APB1_DIV, CLOCK_APB1: APB1 prescaler in register value and APB1 frequecny in Hz
 *  - CLOCK_APB2_DIV, CLOCK_APB2: APB2 prescaler in register value and APB2 frequecny in Hz
 * (CLOCK_APB2_DIV is not needed for stm32f0)
 *
 * The following macro must be defined for stm32f[2|4|7]:
 *  - CLOCK_PLL_M, CLOCK_PLL_N, CLOCK_PLL_P, CLOCK_PLL_Q, (CLOCK_PLL_R, optional):
 * Main PLL factors
 *
 * The following macro must be defined for stm32f[0|1|3]:
 *  - PLL_MUL, PLL_PREDIV: PLL factors. These values are used as is. A PREDIV of 2
 * can be assumed when HSI is selected as PLL input. Some model support any value
 * as PREDIV even with HSI though. The `clk_conf` tool will assume PREDIV must be
 * to with HSI and will set it accordingly.
 *
 * The following macro are optional and can be defined depending on board config
 * and application needs:
 *  - CLOCK_ENABLE_PLL_I2S: if a second PLL (PLL I2S) is available on the cpu, it
 * can be activated with this macro, then CLOCK_PLL_I2S_M, CLOCK_PLL_I2S_N,
 * CLOCK_PLL_I2S_P and CLOCK_PLL_I2S_Q need to be defined, CLOCK_PLL_I2S_R is optional.
 *  - CLOCK_ENABLE_PLL_SAI: if a second PLL (PLL SAI) is available on the cpu, it
 * can be activated with this macro, then CLOCK_PLL_SAI_M, CLOCK_PLL_SAI_N,
 * CLOCK_PLL_SAI_P and CLOCK_PLL_SAI_Q need to be defined, CLOCK_PLL_SAI_R is optional.
 *  - CLOCK_USE_ALT_48MHZ: if the 48MHz clock should be generated by the alternate
 * source (PLL I2S or PLL SAI, depending on cpu)
 *
 * All the previous constants can be generated using the tool in
 * `cpu/stm32_common/dist/clk_conf`.
 *
 * Clock outputs can also be setup with macro:
 *  - CLOCK_MCOx_SRC, CLOCK_MCOx_PRE, with x=1,2: MCO1 and MCO2 output configuration
 * macros. CLOCK_MCOx_SRC defines the MCOx source, as a register value (see vendor header),
 * CLOCK_MCOx_PRE defines the MCOx prescaler, as a register value.
 */