path: root/hw/bsp/stm32f4discovery/src/system_stm32f4xx.c

/**
  ******************************************************************************
  * @file    system_stm32f4xx.c
  * @author  MCD Application Team
  * @version V1.3.0
  * @date    01-July-2015
  * @brief   CMSIS Cortex-M4 Device Peripheral Access Layer System Source File.
  *
  *   This file provides two functions and one global variable to be called from 
  *   user application:
  *      - SystemInit(): This function is called at startup just after reset and 
  *                      before branch to main program. This call is made inside
  *                      the "startup_stm32f4xx.s" file.
  *
  *      - SystemCoreClock variable: Contains the core clock (HCLK), it can be used
  *                                  by the user application to setup the SysTick 
  *                                  timer or configure other parameters.
  *                                     
  *      - SystemCoreClockUpdate(): Updates the variable SystemCoreClock and must
  *                                 be called whenever the core clock is changed
  *                                 during program execution.
  *
  *
  ******************************************************************************
  * @attention
  *
  * <h2><center>&copy; COPYRIGHT 2015 STMicroelectronics</center></h2>
  *
  * Redistribution and use in source and binary forms, with or without modification,
  * are permitted provided that the following conditions are met:
  *   1. Redistributions of source code must retain the above copyright notice,
  *      this list of conditions and the following disclaimer.
  *   2. Redistributions in binary form must reproduce the above copyright notice,
  *      this list of conditions and the following disclaimer in the documentation
  *      and/or other materials provided with the distribution.
  *   3. Neither the name of STMicroelectronics nor the names of its contributors
  *      may be used to endorse or promote products derived from this software
  *      without specific prior written permission.
  *
  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
  * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
  * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
  * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  *
  ******************************************************************************
  */

/** @addtogroup CMSIS
  * @{
  */

/** @addtogroup stm32f4xx_system
  * @{
  */  
  
/** @addtogroup STM32F4xx_System_Private_Includes
  * @{
  */

#include "mcu/stm32f4xx.h"
#include "bsp/cmsis_nvic.h"

/**
  * @}
  */

/** @addtogroup STM32F4xx_System_Private_TypesDefinitions
  * @{
  */

/**
  * @}
  */

/** @addtogroup STM32F4xx_System_Private_Defines
  * @{
  */

/**
  * @}
  */

/** @addtogroup STM32F4xx_System_Private_Macros
  * @{
  */

/**
  * @}
  */

/** @addtogroup STM32F4xx_System_Private_Variables
  * @{
  */
  /* This variable is updated in three ways:
      1) by calling CMSIS function SystemCoreClockUpdate()
      2) by calling HAL API function HAL_RCC_GetHCLKFreq()
      3) each time HAL_RCC_ClockConfig() is called to configure the system clock frequency 
         Note: If you use this function to configure the system clock; then there
               is no need to call the 2 first functions listed above, since SystemCoreClock
               variable is updated automatically.
  */
uint32_t SystemCoreClock = 168000000;

const uint8_t AHBPrescTable[16] = {0, 0, 0, 0, 0, 0, 0, 0, 1, 2, 3, 4, 6, 7, 8, 9};

/**
  * @}
  */

/** @addtogroup STM32F4xx_System_Private_FunctionPrototypes
  * @{
  */

static void SystemClock_Config(void);

/**
  * @}
  */

/** @addtogroup STM32F4xx_System_Private_Functions
  * @{
  */

/**
  * @brief  Setup the microcontroller system
  *         Initialize the FPU setting, vector table location and External memory 
  *         configuration.
  * @param  None
  * @retval None
  */
void SystemInit(void)
{
  /* FPU settings ------------------------------------------------------------*/
  #if (__FPU_PRESENT == 1) && (__FPU_USED == 1)
    SCB->CPACR |= ((3UL << 10*2)|(3UL << 11*2));  /* set CP10 and CP11 Full Access */
  #endif
  /* Reset the RCC clock configuration to the default reset state ------------*/
  /* Set HSION bit */
  RCC->CR |= (uint32_t)0x00000001;

  /* Reset CFGR register */
  RCC->CFGR = 0x00000000;

  /* Reset HSEON, CSSON and PLLON bits */
  RCC->CR &= (uint32_t)0xFEF6FFFF;

  /* Reset PLLCFGR register */
  RCC->PLLCFGR = 0x24003010;

  /* Reset HSEBYP bit */
  RCC->CR &= (uint32_t)0xFFFBFFFF;

  /* Disable all interrupts */
  RCC->CIR = 0x00000000;

  /* Configure System Clock */
  SystemClock_Config();

  /* Relocate the vector table */
  NVIC_Relocate();
}

/**
   * @brief  Update SystemCoreClock variable according to Clock Register Values.
  *         The SystemCoreClock variable contains the core clock (HCLK), it can
  *         be used by the user application to setup the SysTick timer or configure
  *         other parameters.
  *           
  * @note   Each time the core clock (HCLK) changes, this function must be called
  *         to update SystemCoreClock variable value. Otherwise, any configuration
  *         based on this variable will be incorrect.         
  *     
  * @note   - The system frequency computed by this function is not the real 
  *           frequency in the chip. It is calculated based on the predefined 
  *           constant and the selected clock source:
  *             
  *           - If SYSCLK source is HSI, SystemCoreClock will contain the HSI_VALUE(*)
  *                                              
  *           - If SYSCLK source is HSE, SystemCoreClock will contain the HSE_VALUE(**)
  *                          
  *           - If SYSCLK source is PLL, SystemCoreClock will contain the HSE_VALUE(**) 
  *             or HSI_VALUE(*) multiplied/divided by the PLL factors.
  *         
  *         (*) HSI_VALUE is a constant defined in stm32f4xx_hal_conf.h file (default value
  *             16 MHz) but the real value may vary depending on the variations
  *             in voltage and temperature.   
  *    
  *         (**) HSE_VALUE is a constant defined in stm32f4xx_hal_conf.h file (its value
  *              depends on the application requirements), user has to ensure that HSE_VALUE
  *              is same as the real frequency of the crystal used. Otherwise, this function
  *              may have wrong result.
  *                
  *         - The result of this function could be not correct when using fractional
  *           value for HSE crystal.
  *     
  * @param  None
  * @retval None
  */
void SystemCoreClockUpdate(void)
{
  uint32_t tmp = 0, pllvco = 0, pllp = 2, pllsource = 0, pllm = 2;
  
  /* Get SYSCLK source -------------------------------------------------------*/
  tmp = RCC->CFGR & RCC_CFGR_SWS;

  switch (tmp)
  {
    case 0x00:  /* HSI used as system clock source */
      SystemCoreClock = HSI_VALUE;
      break;
    case 0x04:  /* HSE used as system clock source */
      SystemCoreClock = HSE_VALUE;
      break;
    case 0x08:  /* PLL used as system clock source */

      /* PLL_VCO = (HSE_VALUE or HSI_VALUE / PLL_M) * PLL_N
         SYSCLK = PLL_VCO / PLL_P
         */    
      pllsource = (RCC->PLLCFGR & RCC_PLLCFGR_PLLSRC) >> 22;
      pllm = RCC->PLLCFGR & RCC_PLLCFGR_PLLM;
      
      if (pllsource != 0)
      {
        /* HSE used as PLL clock source */
        pllvco = (HSE_VALUE / pllm) * ((RCC->PLLCFGR & RCC_PLLCFGR_PLLN) >> 6);
      }
      else
      {
        /* HSI used as PLL clock source */
        pllvco = (HSI_VALUE / pllm) * ((RCC->PLLCFGR & RCC_PLLCFGR_PLLN) >> 6);
      }

      pllp = (((RCC->PLLCFGR & RCC_PLLCFGR_PLLP) >>16) + 1 ) *2;
      SystemCoreClock = pllvco/pllp;
      break;
    default:
      SystemCoreClock = HSI_VALUE;
      break;
  }
  /* Compute HCLK frequency --------------------------------------------------*/
  /* Get HCLK prescaler */
  tmp = AHBPrescTable[((RCC->CFGR & RCC_CFGR_HPRE) >> 4)];
  /* HCLK frequency */
  SystemCoreClock >>= tmp;
}

/**
  * @brief  System Clock Configuration
  *         The system Clock is configured as follow : 
  *            System Clock source            = PLL (HSE)
  *            SYSCLK(Hz)                     = 168000000
  *            HCLK(Hz)                       = 168000000
  *            AHB Prescaler                  = 1
  *            APB1 Prescaler                 = 4
  *            APB2 Prescaler                 = 2
  *            HSE Frequency(Hz)              = 12000000
  *            PLL_M                          = 12
  *            PLL_N                          = 336
  *            PLL_P                          = 2
  *            PLL_Q                          = 7
  *            VDD(V)                         = 3.3
  *            Main regulator output voltage  = Scale1 mode
  *            Flash Latency(WS)              = 5
  * @param  None
  * @retval None
  */
static void SystemClock_Config(void)
{
  /* Configure Flash prefetch, Instruction cache, Data cache */ 
#if (INSTRUCTION_CACHE_ENABLE != 0)
    __HAL_FLASH_INSTRUCTION_CACHE_ENABLE();
#endif /* INSTRUCTION_CACHE_ENABLE */

#if (DATA_CACHE_ENABLE != 0)
    __HAL_FLASH_DATA_CACHE_ENABLE();
#endif /* DATA_CACHE_ENABLE */

#if (PREFETCH_ENABLE != 0)
    __HAL_FLASH_PREFETCH_BUFFER_ENABLE();
#endif /* PREFETCH_ENABLE */

    /* Enable Power Control clock */
    __HAL_RCC_PWR_CLK_ENABLE();
  
    /* The voltage scaling allows optimizing the power consumption when the device is 
     clocked below the maximum system frequency, to update the voltage scaling value 
     regarding system frequency refer to product datasheet.  */
    __HAL_PWR_VOLTAGESCALING_CONFIG(PWR_REGULATOR_VOLTAGE_SCALE1);

    /* Enable HSE and wait till HSE is ready */  
    RCC->CR |= ((uint32_t)RCC_CR_HSEON);
    while(__HAL_RCC_GET_FLAG(RCC_FLAG_HSERDY) == RESET) {
        /* XXX: some error should occur here */
    }

    /* HCLK Configuration */
    MODIFY_REG(RCC->CFGR, RCC_CFGR_HPRE, RCC_SYSCLK_DIV1);

    /* PCLK1 Configuration */ 
    MODIFY_REG(RCC->CFGR, RCC_CFGR_PPRE1, RCC_HCLK_DIV4);

    /* PCLK2 Configuration */ 
    MODIFY_REG(RCC->CFGR, RCC_CFGR_PPRE2, (RCC_HCLK_DIV2 << 3));

    /* Configure the main PLL clock source, multiplication and division factors. */
    WRITE_REG(RCC->PLLCFGR, (RCC_PLLSOURCE_HSE  | \
                             12                 | \
                             (336 << POSITION_VAL(RCC_PLLCFGR_PLLN))  | \
                             (((RCC_PLLP_DIV2 >> 1) -1) << POSITION_VAL(RCC_PLLCFGR_PLLP)) | \
                             (7 << POSITION_VAL(RCC_PLLCFGR_PLLQ))));

    /* Enable the main PLL. */
    __HAL_RCC_PLL_ENABLE();

    /* Wait till PLL is ready */  
    while(__HAL_RCC_GET_FLAG(RCC_FLAG_PLLRDY) == RESET) {
        /* XXX: handle this */
    }

    /* Enable the Flash prefetch */
    __HAL_FLASH_PREFETCH_BUFFER_ENABLE();

    /* Set flash wait states */
    __HAL_FLASH_SET_LATENCY(FLASH_LATENCY_5);
  
    /* Start PLL */  
    __HAL_RCC_SYSCLK_CONFIG(RCC_SYSCLKSOURCE_PLLCLK);

    while (__HAL_RCC_GET_SYSCLK_SOURCE() != RCC_SYSCLKSOURCE_STATUS_PLLCLK) {
        /* XXX: deal with this*/
    }
}

/**
  * @}
  */

/**
  * @}
  */
  
/**
  * @}
  */    
/************************ (C) COPYRIGHT STMicroelectronics *****END OF FILE****/