#include "sam.h"

#ifdef __cplusplus
extern "C" {
#endif

/**
 * Initial system clock frequency. The System RC Oscillator (RCSYS) provides
 *  the source for the main clock at chip startup.
 */
#define __SYSTEM_CLOCK    (1000000ul)
#define __CLOCK_48MHz     (48000000ul)
#define __CLOCK_32KHz     (32000ul)

uint32_t SystemCoreClock = __SYSTEM_CLOCK;/*!< System Clock Frequency (Core Clock)*/

/**
 * Initialize the system
 *
 * @brief  Setup the microcontroller system.
 *         Initialize the System and update the SystemCoreClock variable.
 * It configures the needed clocks and according Flash Read Wait States.
 * At reset:
 * - OSC8M clock source is enabled with a divider by 8 (1MHz).
 * - Generic Clock Generator 0 (GCLKMAIN) is using OSC8M as source.
 * We need to:
 * 1) Enable XOSC32K clock (External on-board 32.768Hz oscillator), will be used as DFLL48M reference.
 * 2) Put XOSC32K as source of Generic Clock Generator 1
 * 3) Put Generic Clock Generator 1 as source for Generic Clock Multiplexer 0 (DFLL48M reference)
 * 4) Enable DFLL48M clock
 * 5) Switch Generic Clock Generator 0 to DFLL48M. CPU will run at 48MHz.
 * 6) Modify PRESCaler value of OSCM to have 8MHz
 * 7) Put OSC8M as source for Generic Clock Generator 3
 */
// Constants for Clock generators
#define GENERIC_CLOCK_GENERATOR_MAIN      (0u)
#define GENERIC_CLOCK_GENERATOR_XOSC32K   (1u)
#define GENERIC_CLOCK_GENERATOR_OSCULP32K (2u) /* Initialized at reset for WDT */
#define GENERIC_CLOCK_GENERATOR_OSC8M     (3u)
#define GENERIC_CLOCK_GENERATOR_OSC1M     (4u)
// Constants for Clock multiplexers
#define GENERIC_CLOCK_MULTIPLEXER_DFLL48M (0u)

void SystemInit( void )
{
  /* Set 1 Flash Wait State for 48MHz, cf tables 20.9 and 35.27 in SAMD21 Datasheet */
  NVMCTRL->CTRLB.bit.RWS = NVMCTRL_CTRLB_RWS_HALF_Val ;

  /* Turn on the digital interface clock */
  PM->APBAMASK.reg |= PM_APBAMASK_GCLK ;

  /* ----------------------------------------------------------------------------------------------
   * 1) Enable XOSC32K clock (External on-board 32.768Hz oscillator)
   */
  SYSCTRL->XOSC32K.reg = SYSCTRL_XOSC32K_STARTUP( 0x6u ) | /* cf table 15.10 of product datasheet in chapter 15.8.6 */
                         SYSCTRL_XOSC32K_XTALEN | SYSCTRL_XOSC32K_EN32K ;
  SYSCTRL->XOSC32K.bit.ENABLE = 1 ; /* separate call, as described in chapter 15.6.3 */

  while ( (SYSCTRL->PCLKSR.reg & SYSCTRL_PCLKSR_XOSC32KRDY) == 0 )
  {
    /* Wait for oscillator stabilization */
  }

  /* Software reset the module to ensure it is re-initialized correctly */
  /* Note: Due to synchronization, there is a delay from writing CTRL.SWRST until the reset is complete.
   * CTRL.SWRST and STATUS.SYNCBUSY will both be cleared when the reset is complete, as described in chapter 13.8.1
   */
  GCLK->CTRL.reg = GCLK_CTRL_SWRST ;

  while ( (GCLK->CTRL.reg & GCLK_CTRL_SWRST) && (GCLK->STATUS.reg & GCLK_STATUS_SYNCBUSY) )
  {
    /* Wait for reset to complete */
  }

  /* ----------------------------------------------------------------------------------------------
   * 2) Put XOSC32K as source of Generic Clock Generator 1
   */
  GCLK->GENDIV.reg = GCLK_GENDIV_ID( GENERIC_CLOCK_GENERATOR_XOSC32K ) ; // Generic Clock Generator 1

  while ( GCLK->STATUS.reg & GCLK_STATUS_SYNCBUSY )
  {
    /* Wait for synchronization */
  }

  /* Write Generic Clock Generator 1 configuration */
  GCLK->GENCTRL.reg = GCLK_GENCTRL_ID( GENERIC_CLOCK_GENERATOR_XOSC32K ) | // Generic Clock Generator 1
                      GCLK_GENCTRL_SRC_XOSC32K | // Selected source is External 32KHz Oscillator
//                      GCLK_GENCTRL_OE | // Output clock to a pin for tests
                      GCLK_GENCTRL_GENEN ;

  while ( GCLK->STATUS.reg & GCLK_STATUS_SYNCBUSY )
  {
    /* Wait for synchronization */
  }

  /* ----------------------------------------------------------------------------------------------
   * 3) Put Generic Clock Generator 1 as source for Generic Clock Multiplexer 0 (DFLL48M reference)
   */
  GCLK->CLKCTRL.reg = GCLK_CLKCTRL_ID( GENERIC_CLOCK_MULTIPLEXER_DFLL48M ) | // Generic Clock Multiplexer 0
                      GCLK_CLKCTRL_GEN_GCLK1 | // Generic Clock Generator 1 is source
                      GCLK_CLKCTRL_CLKEN ;

  while ( GCLK->STATUS.reg & GCLK_STATUS_SYNCBUSY )
  {
    /* Wait for synchronization */
  }

  /* ----------------------------------------------------------------------------------------------
   * 4) Enable DFLL48M clock
   */

  /* DFLL Configuration in Closed Loop mode, cf product datasheet chapter 15.6.7.1 - Closed-Loop Operation */

  /* Remove the OnDemand mode, Bug http://avr32.icgroup.norway.atmel.com/bugzilla/show_bug.cgi?id=9905 */
  SYSCTRL->DFLLCTRL.bit.ONDEMAND = 0 ;

  while ( (SYSCTRL->PCLKSR.reg & SYSCTRL_PCLKSR_DFLLRDY) == 0 )
  {
    /* Wait for synchronization */
  }

  SYSCTRL->DFLLMUL.reg = SYSCTRL_DFLLMUL_CSTEP( 31 ) | // Coarse step is 31, half of the max value
                         SYSCTRL_DFLLMUL_FSTEP( 511 ) | // Fine step is 511, half of the max value
                         SYSCTRL_DFLLMUL_MUL( (__CLOCK_48MHz/__CLOCK_32KHz) ) ; // External 32KHz is the reference

  while ( (SYSCTRL->PCLKSR.reg & SYSCTRL_PCLKSR_DFLLRDY) == 0 )
  {
    /* Wait for synchronization */
  }

  /* Write full configuration to DFLL control register */
  SYSCTRL->DFLLCTRL.reg |= SYSCTRL_DFLLCTRL_MODE | /* Enable the closed loop mode */
                           SYSCTRL_DFLLCTRL_WAITLOCK |
                           SYSCTRL_DFLLCTRL_QLDIS ; /* Disable Quick lock */

  while ( (SYSCTRL->PCLKSR.reg & SYSCTRL_PCLKSR_DFLLRDY) == 0 )
  {
    /* Wait for synchronization */
  }

  /* Enable the DFLL */
  SYSCTRL->DFLLCTRL.reg |= SYSCTRL_DFLLCTRL_ENABLE ;

  while ( (SYSCTRL->PCLKSR.reg & SYSCTRL_PCLKSR_DFLLLCKC) == 0 ||
          (SYSCTRL->PCLKSR.reg & SYSCTRL_PCLKSR_DFLLLCKF) == 0 )
  {
    /* Wait for locks flags */
  }

  while ( (SYSCTRL->PCLKSR.reg & SYSCTRL_PCLKSR_DFLLRDY) == 0 )
  {
    /* Wait for synchronization */
  }

  /* ----------------------------------------------------------------------------------------------
   * 5) Switch Generic Clock Generator 0 to DFLL48M. CPU will run at 48MHz.
   */
  GCLK->GENDIV.reg = GCLK_GENDIV_ID( GENERIC_CLOCK_GENERATOR_MAIN ) ; // Generic Clock Generator 0

  while ( GCLK->STATUS.reg & GCLK_STATUS_SYNCBUSY )
  {
    /* Wait for synchronization */
  }

  /* Write Generic Clock Generator 0 configuration */
  GCLK->GENCTRL.reg = GCLK_GENCTRL_ID( GENERIC_CLOCK_GENERATOR_MAIN ) | // Generic Clock Generator 0
                      GCLK_GENCTRL_SRC_DFLL48M | // Selected source is DFLL 48MHz
//                      GCLK_GENCTRL_OE | // Output clock to a pin for tests
                      GCLK_GENCTRL_IDC | // Set 50/50 duty cycle
                      GCLK_GENCTRL_GENEN ;

  while ( GCLK->STATUS.reg & GCLK_STATUS_SYNCBUSY )
  {
    /* Wait for synchronization */
  }

  /* ----------------------------------------------------------------------------------------------
   * 6) Modify PRESCaler value of OSC8M to have 8MHz
   */
  SYSCTRL->OSC8M.bit.PRESC = SYSCTRL_OSC8M_PRESC_0_Val ;
  SYSCTRL->OSC8M.bit.ONDEMAND = 0 ;

  /* ----------------------------------------------------------------------------------------------
   * 7) Put OSC8M as source for Generic Clock Generator 3
   */
  GCLK->GENDIV.reg = GCLK_GENDIV_ID( GENERIC_CLOCK_GENERATOR_OSC8M ) ; // Generic Clock Generator 3

  /* Write Generic Clock Generator 3 configuration */
  GCLK->GENCTRL.reg = GCLK_GENCTRL_ID( GENERIC_CLOCK_GENERATOR_OSC8M ) | // Generic Clock Generator 3
                      GCLK_GENCTRL_SRC_OSC8M | // Selected source is RC OSC 8MHz (already enabled at reset)
//                      GCLK_GENCTRL_OE | // Output clock to a pin for tests
                      GCLK_GENCTRL_GENEN ;

  while ( GCLK->STATUS.reg & GCLK_STATUS_SYNCBUSY )
  {
    /* Wait for synchronization */
  }

  /* ----------------------------------------------------------------------------------------------
   * 8) Put OSC8M as source for Generic Clock Generator 2, with freq/8
   */
  GCLK->GENDIV.reg = GCLK_GENDIV_ID( GENERIC_CLOCK_GENERATOR_OSC1M ) | 8 << 8; // Generic Clock Generator 4

  /* Write Generic Clock Generator 3 configuration */
  GCLK->GENCTRL.reg = GCLK_GENCTRL_ID( GENERIC_CLOCK_GENERATOR_OSC1M ) | // Generic Clock Generator 4
                      GCLK_GENCTRL_SRC_OSC8M | // Selected source is RC OSC 8MHz (already enabled at reset)
//                      GCLK_GENCTRL_OE | // Output clock to a pin for tests
                      GCLK_GENCTRL_GENEN ;

  while ( GCLK->STATUS.reg & GCLK_STATUS_SYNCBUSY )
  {
    /* Wait for synchronization */
  }

  /*
   * Now that all system clocks are configured, we can set CPU and APBx BUS clocks.
   * There values are normally the one present after Reset.
   */
  PM->CPUSEL.reg  = PM_CPUSEL_CPUDIV_DIV1 ;
  PM->APBASEL.reg = PM_APBASEL_APBADIV_DIV1_Val ;
  PM->APBBSEL.reg = PM_APBBSEL_APBBDIV_DIV1_Val ;
  PM->APBCSEL.reg = PM_APBCSEL_APBCDIV_DIV1_Val ;

  SystemCoreClock=__CLOCK_48MHz ;

	return;
}

/**
 * Update SystemCoreClock variable
 *
 * @brief  Updates the SystemCoreClock with current core Clock
 *         retrieved from cpu registers.
 */
void SystemCoreClockUpdate(void)
{
	// Not implemented

	return;
}

#ifdef __cplusplus
}
#endif