/**
 * \file
 *
 * \brief SAM R30 Clock Driver
 *
 * Copyright (c) 2016-2018 Microchip Technology Inc. and its subsidiaries.
 *
 * \asf_license_start
 *
 * \page License
 *
 * Subject to your compliance with these terms, you may use Microchip
 * software and any derivatives exclusively with Microchip products.
 * It is your responsibility to comply with third party license terms applicable
 * to your use of third party software (including open source software) that
 * may accompany Microchip software.
 *
 * THIS SOFTWARE IS SUPPLIED BY MICROCHIP "AS IS". NO WARRANTIES,
 * WHETHER EXPRESS, IMPLIED OR STATUTORY, APPLY TO THIS SOFTWARE,
 * INCLUDING ANY IMPLIED WARRANTIES OF NON-INFRINGEMENT, MERCHANTABILITY,
 * AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT WILL MICROCHIP BE
 * LIABLE FOR ANY INDIRECT, SPECIAL, PUNITIVE, INCIDENTAL OR CONSEQUENTIAL
 * LOSS, DAMAGE, COST OR EXPENSE OF ANY KIND WHATSOEVER RELATED TO THE
 * SOFTWARE, HOWEVER CAUSED, EVEN IF MICROCHIP HAS BEEN ADVISED OF THE
 * POSSIBILITY OR THE DAMAGES ARE FORESEEABLE.  TO THE FULLEST EXTENT
 * ALLOWED BY LAW, MICROCHIP'S TOTAL LIABILITY ON ALL CLAIMS IN ANY WAY
 * RELATED TO THIS SOFTWARE WILL NOT EXCEED THE AMOUNT OF FEES, IF ANY,
 * THAT YOU HAVE PAID DIRECTLY TO MICROCHIP FOR THIS SOFTWARE.
 *
 * \asf_license_stop
 *
 */
/*
 * Support and FAQ: visit <a href="https://www.microchip.com/support/">Microchip Support</a>
 */
#include <clock.h>
#include <conf_clocks.h>
#include <system.h>


/**
 * \internal
 * \brief DFLL-specific data container.
 */
struct _system_clock_dfll_config {
	uint32_t control;
	uint32_t val;
	uint32_t mul;
};

/**
 * \internal
 * \brief DPLL-specific data container.
 */
struct _system_clock_dpll_config {
	uint32_t frequency;
};


/**
 * \internal
 * \brief XOSC-specific data container.
 */
struct _system_clock_xosc_config {
	uint32_t frequency;
};

/**
 * \internal
 * \brief System clock module data container.
 */
struct _system_clock_module {
	volatile struct _system_clock_dfll_config dfll;
	volatile struct _system_clock_dpll_config dpll;

	volatile struct _system_clock_xosc_config xosc;
	volatile struct _system_clock_xosc_config xosc32k;
};

/**
 * \internal
 * \brief Internal module instance to cache configuration values.
 */
static struct _system_clock_module _system_clock_inst = {
		.dfll = {
			.control     = 0,
			.val     = 0,
			.mul     = 0,
		},
		.dpll = {
			.frequency   = 0,
		},
		.xosc = {
			.frequency   = 0,
		},
		.xosc32k = {
			.frequency   = 0,
		},
	};

/**
 * \internal
 * \brief Wait for sync to the DFLL control registers.
 */
static inline void _system_dfll_wait_for_sync(void)
{
	while (!(OSCCTRL->STATUS.reg & OSCCTRL_STATUS_DFLLRDY)) {
		/* Wait for DFLL sync */
	}
}

/**
 * \internal
 * \brief Wait for sync to the OSC32K control registers.
 */
static inline void _system_osc32k_wait_for_sync(void)
{
	while (!(OSC32KCTRL->STATUS.reg & OSC32KCTRL_STATUS_OSC32KRDY)) {
		/* Wait for OSC32K sync */
	}
}

/**
 * \internal
 * \brief OSC16M frequency selection.
 *  Frequency selection can be done only when OSC16M is disabled,thus,
 *  OSCULP32K is temporarily used as a new clocksource for mainclock .
 *
 */
static inline void _system_clock_source_osc16m_freq_sel(void)
{
	struct system_gclk_gen_config gclk_conf;
	struct system_clock_source_osc16m_config osc16m_conf;

	/* Select OSCULP32K as new clock source for mainclock temporarily */
	system_gclk_gen_get_config_defaults(&gclk_conf);
	gclk_conf.source_clock = SYSTEM_CLOCK_SOURCE_ULP32K;
	system_gclk_gen_set_config(GCLK_GENERATOR_0, &gclk_conf);

	/* GCLK0 is enabled after POR */

	/* Disable OSC16M clock*/
	system_clock_source_disable(SYSTEM_CLOCK_SOURCE_OSC16M);

	/* Switch to new frequency selection and enable OSC16M */
	system_clock_source_osc16m_get_config_defaults(&osc16m_conf);
	osc16m_conf.fsel      		= CONF_CLOCK_OSC16M_FREQ_SEL;
	osc16m_conf.on_demand       = 0;
	osc16m_conf.run_in_standby  = CONF_CLOCK_OSC16M_RUN_IN_STANDBY;
	system_clock_source_osc16m_set_config(&osc16m_conf);
	system_clock_source_enable(SYSTEM_CLOCK_SOURCE_OSC16M);
	while(!system_clock_source_is_ready(SYSTEM_CLOCK_SOURCE_OSC16M));

	/* Select OSC16M for mainclock again */
	system_gclk_gen_get_config_defaults(&gclk_conf);
	gclk_conf.source_clock = SYSTEM_CLOCK_SOURCE_OSC16M;
	system_gclk_gen_set_config(GCLK_GENERATOR_0, &gclk_conf);
	if (CONF_CLOCK_OSC16M_ON_DEMAND){
		OSCCTRL->OSC16MCTRL.reg |= OSCCTRL_OSC16MCTRL_ONDEMAND;
	}
}

static inline void _system_clock_source_dfll_set_config_errata_9905(void)
{

	/* Disable ONDEMAND mode while writing configurations */
	OSCCTRL->DFLLCTRL.reg = OSCCTRL_DFLLCTRL_ENABLE;
	_system_dfll_wait_for_sync();

	OSCCTRL->DFLLMUL.reg = _system_clock_inst.dfll.mul;
	OSCCTRL->DFLLVAL.reg = _system_clock_inst.dfll.val;

	/* Write full configuration to DFLL control register */
	OSCCTRL->DFLLCTRL.reg = 0;
	_system_dfll_wait_for_sync();
	OSCCTRL->DFLLCTRL.reg = _system_clock_inst.dfll.control;
}

/**
 * \brief Retrieve the frequency of a clock source.
 *
 * Determines the current operating frequency of a given clock source.
 *
 * \param[in] clock_source  Clock source
 *
 * \returns Frequency of the given clock source, in Hz.
 */
uint32_t system_clock_source_get_hz(
		const enum system_clock_source clock_source)
{
	switch (clock_source) {
	case SYSTEM_CLOCK_SOURCE_XOSC:
		return _system_clock_inst.xosc.frequency;

	case SYSTEM_CLOCK_SOURCE_OSC16M:
		return (OSCCTRL->OSC16MCTRL.bit.FSEL+1)*4000000UL;

	case SYSTEM_CLOCK_SOURCE_OSC32K:
		return 32768UL;

	case SYSTEM_CLOCK_SOURCE_ULP32K:
		return 32768UL;

	case SYSTEM_CLOCK_SOURCE_XOSC32K:
		return _system_clock_inst.xosc32k.frequency;

	case SYSTEM_CLOCK_SOURCE_DFLL:

		/* Check if the DFLL has been configured */
		if (!(_system_clock_inst.dfll.control & OSCCTRL_DFLLCTRL_ENABLE))
			return 0;

		/* Make sure that the DFLL module is ready */
		_system_dfll_wait_for_sync();

		/* Check if operating in closed loop (USB) mode */
		switch(_system_clock_inst.dfll.control &
				(OSCCTRL_DFLLCTRL_MODE | OSCCTRL_DFLLCTRL_USBCRM)) {
		case OSCCTRL_DFLLCTRL_MODE:
			return system_gclk_chan_get_hz(OSCCTRL_GCLK_ID_DFLL48) *
					(_system_clock_inst.dfll.mul & 0xffff);
		default:
			return 48000000UL;
		}

	case SYSTEM_CLOCK_SOURCE_DPLL:
		if (!(OSCCTRL->DPLLCTRLA.reg & OSCCTRL_DPLLCTRLA_ENABLE)) {
			return 0;
		}

		return _system_clock_inst.dpll.frequency;

	default:
		return 0;
	}
}

/**
 * \brief Configure the internal OSC16M oscillator clock source.
 *
 * Configures the 16MHz (nominal) internal RC oscillator with the given
 * configuration settings.
 *
 * \note Frequency selection can be done only when OSC16M is disabled.
 *
 * \param[in] config  OSC16M configuration structure containing the new config
 */
void system_clock_source_osc16m_set_config(
		struct system_clock_source_osc16m_config *const config)
{
	OSCCTRL_OSC16MCTRL_Type temp = OSCCTRL->OSC16MCTRL;

	/* Use temporary struct to reduce register access */
	temp.bit.FSEL    = config->fsel;
	temp.bit.ONDEMAND = config->on_demand;
	temp.bit.RUNSTDBY = config->run_in_standby;

	OSCCTRL->OSC16MCTRL = temp;
}

/**
 * \brief Configure the internal OSC32K oscillator clock source.
 *
 * Configures the 32KHz (nominal) internal RC oscillator with the given
 * configuration settings.
 *
 * \param[in] config  OSC32K configuration structure containing the new config
 */
void system_clock_source_osc32k_set_config(
		struct system_clock_source_osc32k_config *const config)
{
	OSC32KCTRL_OSC32K_Type temp = OSC32KCTRL->OSC32K;


	/* Update settings via a temporary struct to reduce register access */
	temp.bit.EN1K     = config->enable_1khz_output;
	temp.bit.EN32K    = config->enable_32khz_output;
	temp.bit.STARTUP  = config->startup_time;
	temp.bit.ONDEMAND = config->on_demand;
	temp.bit.RUNSTDBY = config->run_in_standby;
	temp.bit.WRTLOCK  = config->write_once;

	OSC32KCTRL->OSC32K  = temp;
}

/**
 * \brief Configure the internal OSCULP32K oscillator clock source.
 *
 * Configures the Ultra Low Power 32KHz internal RC oscillator with the given
 * configuration settings.
 *
 * \note The OSCULP32K is enabled by default after a Power On Reset (POR) and
 *       will always run except during POR.
 *
 * \param[in] config  OSCULP32K configuration structure containing the new config
 */
void system_clock_source_osculp32k_set_config(
		struct system_clock_source_osculp32k_config *const config)
{
	OSC32KCTRL_OSCULP32K_Type temp = OSC32KCTRL->OSCULP32K;
	/* Update settings via a temporary struct to reduce register access */
	temp.bit.WRTLOCK  = config->write_once;
	OSC32KCTRL->OSCULP32K  = temp;
}

/**
 * \brief Configure the external oscillator clock source.
 *
 * Configures the external oscillator clock source with the given configuration
 * settings.
 *
 * \param[in] config  External oscillator configuration structure containing
 *                    the new config
 */
void system_clock_source_xosc_set_config(
		struct system_clock_source_xosc_config *const config)
{
	OSCCTRL_XOSCCTRL_Type temp = OSCCTRL->XOSCCTRL;

	temp.bit.STARTUP = config->startup_time;

	if (config->external_clock == SYSTEM_CLOCK_EXTERNAL_CRYSTAL) {
		temp.bit.XTALEN = 1;
	} else {
		temp.bit.XTALEN = 0;
	}

	temp.bit.AMPGC = config->auto_gain_control;

	/* Set gain */
	if (config->frequency <= 2000000) {
		temp.bit.GAIN = 0;
	} else if (config->frequency <= 4000000) {
		temp.bit.GAIN = 1;
	} else if (config->frequency <= 8000000) {
		temp.bit.GAIN = 2;
	} else if (config->frequency <= 16000000) {
		temp.bit.GAIN = 3;
	} else if (config->frequency <= 30000000) {
		temp.bit.GAIN = 4;
	}

	temp.bit.ONDEMAND = config->on_demand;
	temp.bit.RUNSTDBY = config->run_in_standby;

	/* Store XOSC frequency for internal use */
	_system_clock_inst.xosc.frequency = config->frequency;

	OSCCTRL->XOSCCTRL = temp;
}

/**
 * \brief Configure the XOSC32K external 32KHz oscillator clock source.
 *
 * Configures the external 32KHz oscillator clock source with the given
 * configuration settings.
 *
 * \param[in] config  XOSC32K configuration structure containing the new config
 */
void system_clock_source_xosc32k_set_config(
		struct system_clock_source_xosc32k_config *const config)
{
	OSC32KCTRL_XOSC32K_Type temp = OSC32KCTRL->XOSC32K;

	temp.bit.STARTUP = config->startup_time;

	if (config->external_clock == SYSTEM_CLOCK_EXTERNAL_CRYSTAL) {
		temp.bit.XTALEN = 1;
	} else {
		temp.bit.XTALEN = 0;
	}

	temp.bit.EN1K = config->enable_1khz_output;
	temp.bit.EN32K = config->enable_32khz_output;

	temp.bit.ONDEMAND = config->on_demand;
	temp.bit.RUNSTDBY = config->run_in_standby;
	temp.bit.WRTLOCK  = config->write_once;

	/* Cache the new frequency in case the user needs to check the current
	 * operating frequency later */
	_system_clock_inst.xosc32k.frequency = config->frequency;

	OSC32KCTRL->XOSC32K = temp;
}

/**
 * \brief Configure the DFLL clock source.
 *
 * Configures the Digital Frequency Locked Loop clock source with the given
 * configuration settings.
 *
 * \note The DFLL will be running when this function returns, as the DFLL module
 *       needs to be enabled in order to perform the module configuration.
 *
 * \param[in] config  DFLL configuration structure containing the new config
 */
void system_clock_source_dfll_set_config(
		struct system_clock_source_dfll_config *const config)
{
	_system_clock_inst.dfll.val =
			OSCCTRL_DFLLVAL_COARSE(config->coarse_value) |
			OSCCTRL_DFLLVAL_FINE(config->fine_value);

	_system_clock_inst.dfll.control =
			(uint32_t)config->wakeup_lock     |
			(uint32_t)config->stable_tracking |
			(uint32_t)config->quick_lock      |
			(uint32_t)config->chill_cycle     |
			((uint32_t)config->on_demand << OSCCTRL_DFLLCTRL_ONDEMAND_Pos) |
			((uint32_t)config->run_in_stanby << OSCCTRL_DFLLCTRL_RUNSTDBY_Pos);

	if (config->loop_mode == SYSTEM_CLOCK_DFLL_LOOP_MODE_CLOSED) {

		_system_clock_inst.dfll.mul =
				OSCCTRL_DFLLMUL_CSTEP(config->coarse_max_step) |
				OSCCTRL_DFLLMUL_FSTEP(config->fine_max_step)   |
				OSCCTRL_DFLLMUL_MUL(config->multiply_factor);

		/* Enable the closed loop mode */
		_system_clock_inst.dfll.control |= config->loop_mode;
	}
	if (config->loop_mode == SYSTEM_CLOCK_DFLL_LOOP_MODE_USB_RECOVERY) {

		_system_clock_inst.dfll.mul =
				OSCCTRL_DFLLMUL_CSTEP(config->coarse_max_step) |
				OSCCTRL_DFLLMUL_FSTEP(config->fine_max_step)   |
				OSCCTRL_DFLLMUL_MUL(config->multiply_factor);

		/* Enable the USB recovery mode */
		_system_clock_inst.dfll.control |= config->loop_mode |
				OSCCTRL_DFLLCTRL_MODE | OSCCTRL_DFLLCTRL_BPLCKC;
	}
}

/**
 * \brief Configure the DPLL clock source.
 *
 * Configures the Digital Phase-Locked Loop clock source with the given
 * configuration settings.
 *
 * \note The DPLL will be running when this function returns, as the DPLL module
 *       needs to be enabled in order to perform the module configuration.
 *
 * \param[in] config  DPLL configuration structure containing the new config
 */
void system_clock_source_dpll_set_config(
		struct system_clock_source_dpll_config *const config)
{

	uint32_t tmpldr;
	uint8_t  tmpldrfrac;
	uint32_t refclk;

	refclk = config->reference_frequency;

	/* Only reference clock REF1 can be divided */
	if (config->reference_clock == SYSTEM_CLOCK_SOURCE_DPLL_REFERENCE_CLOCK_XOSC) {
		refclk = refclk / (2 * (config->reference_divider + 1));
	}

	/* Calculate LDRFRAC and LDR */
	tmpldr = (config->output_frequency << 4) / refclk;
	tmpldrfrac = tmpldr & 0x0f;
	tmpldr = (tmpldr >> 4) - 1;

	OSCCTRL->DPLLCTRLA.reg =
			((uint32_t)config->on_demand << OSCCTRL_DPLLCTRLA_ONDEMAND_Pos) |
			((uint32_t)config->run_in_standby << OSCCTRL_DPLLCTRLA_RUNSTDBY_Pos);

	OSCCTRL->DPLLRATIO.reg =
			OSCCTRL_DPLLRATIO_LDRFRAC(tmpldrfrac) |
			OSCCTRL_DPLLRATIO_LDR(tmpldr);

	while(OSCCTRL->DPLLSYNCBUSY.reg & OSCCTRL_DPLLSYNCBUSY_DPLLRATIO){
		}

	OSCCTRL->DPLLCTRLB.reg =
			OSCCTRL_DPLLCTRLB_DIV(config->reference_divider) |
			((uint32_t)config->lock_bypass << OSCCTRL_DPLLCTRLB_LBYPASS_Pos) |
			OSCCTRL_DPLLCTRLB_LTIME(config->lock_time) |
			OSCCTRL_DPLLCTRLB_REFCLK(config->reference_clock) |
			((uint32_t)config->wake_up_fast << OSCCTRL_DPLLCTRLB_WUF_Pos) |
			((uint32_t)config->low_power_enable << OSCCTRL_DPLLCTRLB_LPEN_Pos) |
			OSCCTRL_DPLLCTRLB_FILTER(config->filter);

	OSCCTRL->DPLLPRESC.reg  = OSCCTRL_DPLLPRESC_PRESC(config->prescaler);
	while(OSCCTRL->DPLLSYNCBUSY.reg & OSCCTRL_DPLLSYNCBUSY_DPLLPRESC){
		}
	/*
	 * Fck = Fckrx * (LDR + 1 + LDRFRAC / 16) / (2^PRESC)
	 */
	_system_clock_inst.dpll.frequency =
			(refclk * (((tmpldr + 1) << 4) + tmpldrfrac)) >> (4 + config->prescaler);
}

/**
 * \brief Writes the calibration values for a given oscillator clock source.
 *
 * Writes an oscillator calibration value to the given oscillator control
 * registers. The acceptable ranges are:
 *
 * For OSC32K:
 *  - 7 bits (max. value 128)
 * For OSC16MHZ:
 *  - 8 bits (max. value 255)
 * For OSCULP:
 *  - 5 bits (max. value 32)
 *
 * \note The frequency range parameter applies only when configuring the 8MHz
 *       oscillator and will be ignored for the other oscillators.
 *
 * \param[in] clock_source       Clock source to calibrate
 * \param[in] calibration_value  Calibration value to write
 * \param[in] freq_range         Frequency range (8MHz oscillator only)
 *
 * \retval STATUS_OK               The calibration value was written
 *                                 successfully
 * \retval STATUS_ERR_INVALID_ARG  The setting is not valid for selected clock
 *                                 source
 */
enum status_code system_clock_source_write_calibration(
		const enum system_clock_source clock_source,
		const uint16_t calibration_value,
		const uint8_t freq_select)
{
	switch (clock_source) {
	case SYSTEM_CLOCK_SOURCE_OSC16M:
		//to enable DSU test mode and add calibration value
		return STATUS_OK;

	case SYSTEM_CLOCK_SOURCE_OSC32K:

		if (calibration_value > 128) {
			return STATUS_ERR_INVALID_ARG;
		}

		_system_osc32k_wait_for_sync();
		OSC32KCTRL->OSC32K.bit.CALIB = calibration_value;
		break;

	case SYSTEM_CLOCK_SOURCE_ULP32K:

		if (calibration_value > 32) {
			return STATUS_ERR_INVALID_ARG;
		}

		OSC32KCTRL->OSCULP32K.bit.CALIB = calibration_value;
		break;

	default:
		Assert(false);
		return STATUS_ERR_INVALID_ARG;
		break;
	}

	return STATUS_OK;
}

/**
 * \brief Enables a clock source.
 *
 * Enables a clock source which has been previously configured.
 *
 * \param[in] clock_source       Clock source to enable
 *
 * \retval STATUS_OK               Clock source was enabled successfully and
 *                                 is ready
 * \retval STATUS_ERR_INVALID_ARG  The clock source is not available on this
 *                                 device
 */
enum status_code system_clock_source_enable(
		const enum system_clock_source clock_source)
{
	switch (clock_source) {
	case SYSTEM_CLOCK_SOURCE_OSC16M:
		OSCCTRL->OSC16MCTRL.reg |= OSCCTRL_OSC16MCTRL_ENABLE;
		return STATUS_OK;

	case SYSTEM_CLOCK_SOURCE_OSC32K:
		OSC32KCTRL->OSC32K.reg |= OSC32KCTRL_OSC32K_ENABLE;
		break;

	case SYSTEM_CLOCK_SOURCE_XOSC:
		OSCCTRL->XOSCCTRL.reg |= OSCCTRL_XOSCCTRL_ENABLE;
		break;

	case SYSTEM_CLOCK_SOURCE_XOSC32K:
		OSC32KCTRL->XOSC32K.reg |= OSC32KCTRL_XOSC32K_ENABLE;
		break;

	case SYSTEM_CLOCK_SOURCE_DFLL:
		_system_clock_inst.dfll.control |= OSCCTRL_DFLLCTRL_ENABLE;
		_system_clock_source_dfll_set_config_errata_9905();
		break;

	case SYSTEM_CLOCK_SOURCE_DPLL:
		OSCCTRL->DPLLCTRLA.reg |= OSCCTRL_DPLLCTRLA_ENABLE;
		while(OSCCTRL->DPLLSYNCBUSY.reg & OSCCTRL_DPLLSYNCBUSY_ENABLE){
		}
		break;

	case SYSTEM_CLOCK_SOURCE_ULP32K:
		/* Always enabled */
		return STATUS_OK;

	default:
		Assert(false);
		return STATUS_ERR_INVALID_ARG;
	}

	return STATUS_OK;
}

/**
 * \brief Disables a clock source.
 *
 * Disables a clock source that was previously enabled.
 *
 * \param[in] clock_source  Clock source to disable
 *
 * \retval STATUS_OK               Clock source was disabled successfully
 * \retval STATUS_ERR_INVALID_ARG  An invalid or unavailable clock source was
 *                                 given
 */
enum status_code system_clock_source_disable(
		const enum system_clock_source clock_source)
{
	switch (clock_source) {
	case SYSTEM_CLOCK_SOURCE_OSC16M:
		OSCCTRL->OSC16MCTRL.reg &= ~OSCCTRL_OSC16MCTRL_ENABLE;
		break;

	case SYSTEM_CLOCK_SOURCE_OSC32K:
		OSC32KCTRL->OSC32K.reg &= ~OSC32KCTRL_OSC32K_ENABLE;
		break;

	case SYSTEM_CLOCK_SOURCE_XOSC:
		OSCCTRL->XOSCCTRL.reg &= ~OSCCTRL_XOSCCTRL_ENABLE;
		break;

	case SYSTEM_CLOCK_SOURCE_XOSC32K:
		OSC32KCTRL->XOSC32K.reg &= ~OSC32KCTRL_XOSC32K_ENABLE;
		break;

	case SYSTEM_CLOCK_SOURCE_DFLL:
		_system_clock_inst.dfll.control &= ~OSCCTRL_DFLLCTRL_ENABLE;
		OSCCTRL->DFLLCTRL.reg = _system_clock_inst.dfll.control;
		break;
	case SYSTEM_CLOCK_SOURCE_DPLL:
		OSCCTRL->DPLLCTRLA.reg &= ~OSCCTRL_DPLLCTRLA_ENABLE;
		break;
	case SYSTEM_CLOCK_SOURCE_ULP32K:
		/* Not possible to disable */

	default:
		Assert(false);
		return STATUS_ERR_INVALID_ARG;

	}

	return STATUS_OK;
}

/**
 * \brief Checks if a clock source is ready.
 *
 * Checks if a given clock source is ready to be used.
 *
 * \param[in] clock_source  Clock source to check if ready
 *
 * \returns Ready state of the given clock source.
 *
 * \retval true   Clock source is enabled and ready
 * \retval false  Clock source is disabled or not yet ready
 */
bool system_clock_source_is_ready(
		const enum system_clock_source clock_source)
{
	uint32_t mask = 0;

	switch (clock_source) {
	case SYSTEM_CLOCK_SOURCE_OSC16M:
		mask = OSCCTRL_STATUS_OSC16MRDY;
		return ((OSCCTRL->STATUS.reg & mask) == mask);

	case SYSTEM_CLOCK_SOURCE_OSC32K:
		mask = OSC32KCTRL_STATUS_OSC32KRDY;
		return ((OSC32KCTRL->STATUS.reg & mask) == mask);

	case SYSTEM_CLOCK_SOURCE_XOSC:
		mask = OSCCTRL_STATUS_XOSCRDY;
		return ((OSCCTRL->STATUS.reg & mask) == mask);

	case SYSTEM_CLOCK_SOURCE_XOSC32K:
		mask = OSC32KCTRL_STATUS_XOSC32KRDY;
		return ((OSC32KCTRL->STATUS.reg & mask) == mask);

	case SYSTEM_CLOCK_SOURCE_DFLL:
		if (CONF_CLOCK_DFLL_LOOP_MODE == SYSTEM_CLOCK_DFLL_LOOP_MODE_CLOSED) {
			mask = (OSCCTRL_STATUS_DFLLRDY |
			        OSCCTRL_STATUS_DFLLLCKF | OSCCTRL_STATUS_DFLLLCKC);
		} else {
			mask = OSCCTRL_STATUS_DFLLRDY;
		}
		return ((OSCCTRL->STATUS.reg & mask) == mask);

	case SYSTEM_CLOCK_SOURCE_DPLL:
		return ((OSCCTRL->DPLLSTATUS.reg &
				(OSCCTRL_DPLLSTATUS_CLKRDY | OSCCTRL_DPLLSTATUS_LOCK)) ==
				(OSCCTRL_DPLLSTATUS_CLKRDY | OSCCTRL_DPLLSTATUS_LOCK));
	case SYSTEM_CLOCK_SOURCE_ULP32K:
		/* Not possible to disable */
		return true;

	default:
		return false;
	}
}

/* Include some checks for conf_clocks.h validation */
#include "clock_config_check.h"

#if !defined(__DOXYGEN__)
/** \internal
 *
 * Configures a Generic Clock Generator with the configuration from \c conf_clocks.h.
 */
#  define _CONF_CLOCK_GCLK_CONFIG(n, unused) \
	if (CONF_CLOCK_GCLK_##n##_ENABLE == true) { \
		struct system_gclk_gen_config gclk_conf;                          \
		system_gclk_gen_get_config_defaults(&gclk_conf);                  \
		gclk_conf.source_clock    = CONF_CLOCK_GCLK_##n##_CLOCK_SOURCE;   \
		gclk_conf.division_factor = CONF_CLOCK_GCLK_##n##_PRESCALER;      \
		gclk_conf.run_in_standby  = CONF_CLOCK_GCLK_##n##_RUN_IN_STANDBY; \
		gclk_conf.output_enable   = CONF_CLOCK_GCLK_##n##_OUTPUT_ENABLE;  \
		system_gclk_gen_set_config(GCLK_GENERATOR_##n, &gclk_conf);       \
		system_gclk_gen_enable(GCLK_GENERATOR_##n);                       \
	}

/** \internal
 *
 * Configures a Generic Clock Generator with the configuration from \c conf_clocks.h,
 * provided that it is not the main Generic Clock Generator channel.
 */
#  define _CONF_CLOCK_GCLK_CONFIG_NONMAIN(n, unused) \
		if (n > 0) { _CONF_CLOCK_GCLK_CONFIG(n, unused); }
#endif

/**
 * \brief Initialize clock system based on the configuration in conf_clocks.h.
 *
 * This function will apply the settings in conf_clocks.h when run from the user
 * application. All clock sources and GCLK generators are running when this function
 * returns.
 *
 * \note OSC16M is always enabled and if user selects other clocks for GCLK generators,
 * the OSC16M default enable can be disabled after system_clock_init. Make sure the
 * clock switches successfully before disabling OSC8M.
 */
void system_clock_init(void)
{
	/* Various bits in the INTFLAG register can be set to one at startup.
	   This will ensure that these bits are cleared */
	OSCCTRL->INTFLAG.reg = OSCCTRL_INTFLAG_DFLLRDY;
	SUPC->INTFLAG.reg = SUPC_INTFLAG_BOD33RDY | SUPC_INTFLAG_BOD33DET;

	system_flash_set_waitstates(CONF_CLOCK_FLASH_WAIT_STATES);

	/*  Switch to PL2 to be sure configuration of GCLK0 is safe */
	system_switch_performance_level(SYSTEM_PERFORMANCE_LEVEL_2);

	/* XOSC */
#if CONF_CLOCK_XOSC_ENABLE == true
	struct system_clock_source_xosc_config xosc_conf;
	system_clock_source_xosc_get_config_defaults(&xosc_conf);

	xosc_conf.external_clock    = CONF_CLOCK_XOSC_EXTERNAL_CRYSTAL;
	xosc_conf.startup_time      = CONF_CLOCK_XOSC_STARTUP_TIME;
	xosc_conf.frequency         = CONF_CLOCK_XOSC_EXTERNAL_FREQUENCY;
	xosc_conf.run_in_standby    = CONF_CLOCK_XOSC_RUN_IN_STANDBY;

	system_clock_source_xosc_set_config(&xosc_conf);
	system_clock_source_enable(SYSTEM_CLOCK_SOURCE_XOSC);
	while(!system_clock_source_is_ready(SYSTEM_CLOCK_SOURCE_XOSC));
	if (CONF_CLOCK_XOSC_ON_DEMAND || CONF_CLOCK_XOSC_AUTO_GAIN_CONTROL) {
		OSCCTRL->XOSCCTRL.reg |=
			(CONF_CLOCK_XOSC_ON_DEMAND << OSCCTRL_XOSCCTRL_ONDEMAND_Pos) |
			(CONF_CLOCK_XOSC_AUTO_GAIN_CONTROL << OSCCTRL_XOSCCTRL_AMPGC_Pos);
	}
#endif

	/* XOSC32K */
#if CONF_CLOCK_XOSC32K_ENABLE == true
	struct system_clock_source_xosc32k_config xosc32k_conf;
	system_clock_source_xosc32k_get_config_defaults(&xosc32k_conf);

	xosc32k_conf.frequency           = 32768UL;
	xosc32k_conf.external_clock      = CONF_CLOCK_XOSC32K_EXTERNAL_CRYSTAL;
	xosc32k_conf.startup_time        = CONF_CLOCK_XOSC32K_STARTUP_TIME;
	xosc32k_conf.enable_1khz_output  = CONF_CLOCK_XOSC32K_ENABLE_1KHZ_OUPUT;
	xosc32k_conf.enable_32khz_output = CONF_CLOCK_XOSC32K_ENABLE_32KHZ_OUTPUT;
	xosc32k_conf.on_demand           = false;
	xosc32k_conf.run_in_standby      = CONF_CLOCK_XOSC32K_RUN_IN_STANDBY;

	system_clock_source_xosc32k_set_config(&xosc32k_conf);
	system_clock_source_enable(SYSTEM_CLOCK_SOURCE_XOSC32K);
	while(!system_clock_source_is_ready(SYSTEM_CLOCK_SOURCE_XOSC32K));
	if (CONF_CLOCK_XOSC32K_ON_DEMAND) {
		OSC32KCTRL->XOSC32K.bit.ONDEMAND = 1;
	}
#endif

	/* OSCK32K */
#if CONF_CLOCK_OSC32K_ENABLE == true

	struct system_clock_source_osc32k_config osc32k_conf;
	system_clock_source_osc32k_get_config_defaults(&osc32k_conf);

	osc32k_conf.startup_time        = CONF_CLOCK_OSC32K_STARTUP_TIME;
	osc32k_conf.enable_1khz_output  = CONF_CLOCK_OSC32K_ENABLE_1KHZ_OUTPUT;
	osc32k_conf.enable_32khz_output = CONF_CLOCK_OSC32K_ENABLE_32KHZ_OUTPUT;
	osc32k_conf.on_demand           = CONF_CLOCK_OSC32K_ON_DEMAND;
	osc32k_conf.run_in_standby      = CONF_CLOCK_OSC32K_RUN_IN_STANDBY;

	system_clock_source_osc32k_set_config(&osc32k_conf);
	system_clock_source_enable(SYSTEM_CLOCK_SOURCE_OSC32K);
#endif

	/* OSC16M */
	if (CONF_CLOCK_OSC16M_FREQ_SEL == SYSTEM_OSC16M_4M){
		OSCCTRL->OSC16MCTRL.bit.ONDEMAND = CONF_CLOCK_OSC16M_ON_DEMAND ;
		OSCCTRL->OSC16MCTRL.bit.RUNSTDBY = CONF_CLOCK_OSC16M_RUN_IN_STANDBY;
	} else {
		_system_clock_source_osc16m_freq_sel();
	}

	/* DFLL Config (Open and Closed Loop) */
#if CONF_CLOCK_DFLL_ENABLE == true
	struct system_clock_source_dfll_config dfll_conf;
	system_clock_source_dfll_get_config_defaults(&dfll_conf);

	dfll_conf.loop_mode      = CONF_CLOCK_DFLL_LOOP_MODE;
	dfll_conf.on_demand      = false;
	dfll_conf.run_in_stanby  = CONF_CLOCK_DFLL_RUN_IN_STANDBY;

	/* Using DFLL48M COARSE CAL value from NVM Software Calibration Area Mapping
	   in DFLL.COARSE helps to output a frequency close to 48 MHz.*/
#define NVM_DFLL_COARSE_POS    26 /* DFLL48M Coarse calibration value bit position.*/
#define NVM_DFLL_COARSE_SIZE   6  /* DFLL48M Coarse calibration value bit size.*/

	uint32_t coarse =( *((uint32_t *)(NVMCTRL_OTP5)
			+ (NVM_DFLL_COARSE_POS / 32))
		>> (NVM_DFLL_COARSE_POS % 32))
		& ((1 << NVM_DFLL_COARSE_SIZE) - 1);
	/* In some revision chip, the Calibration value is not correct */
	if (coarse == 0x3f) {
		coarse = 0x1f;
	}

	dfll_conf.coarse_value = coarse;

	if (CONF_CLOCK_DFLL_LOOP_MODE == SYSTEM_CLOCK_DFLL_LOOP_MODE_OPEN) {
		dfll_conf.fine_value   = CONF_CLOCK_DFLL_FINE_VALUE;
	}

#  if CONF_CLOCK_DFLL_QUICK_LOCK == true
	dfll_conf.quick_lock = SYSTEM_CLOCK_DFLL_QUICK_LOCK_ENABLE;
#  else
	dfll_conf.quick_lock = SYSTEM_CLOCK_DFLL_QUICK_LOCK_DISABLE;
#  endif

#  if CONF_CLOCK_DFLL_TRACK_AFTER_FINE_LOCK == true
	dfll_conf.stable_tracking = SYSTEM_CLOCK_DFLL_STABLE_TRACKING_TRACK_AFTER_LOCK;
#  else
	dfll_conf.stable_tracking = SYSTEM_CLOCK_DFLL_STABLE_TRACKING_FIX_AFTER_LOCK;
#  endif

#  if CONF_CLOCK_DFLL_KEEP_LOCK_ON_WAKEUP == true
	dfll_conf.wakeup_lock = SYSTEM_CLOCK_DFLL_WAKEUP_LOCK_KEEP;
#  else
	dfll_conf.wakeup_lock = SYSTEM_CLOCK_DFLL_WAKEUP_LOCK_LOSE;
#  endif

#  if CONF_CLOCK_DFLL_ENABLE_CHILL_CYCLE == true
	dfll_conf.chill_cycle = SYSTEM_CLOCK_DFLL_CHILL_CYCLE_ENABLE;
#  else
	dfll_conf.chill_cycle = SYSTEM_CLOCK_DFLL_CHILL_CYCLE_DISABLE;
#  endif

	if (CONF_CLOCK_DFLL_LOOP_MODE == SYSTEM_CLOCK_DFLL_LOOP_MODE_CLOSED) {
		dfll_conf.multiply_factor = CONF_CLOCK_DFLL_MULTIPLY_FACTOR;
	}

	dfll_conf.coarse_max_step = CONF_CLOCK_DFLL_MAX_COARSE_STEP_SIZE;
	dfll_conf.fine_max_step   = CONF_CLOCK_DFLL_MAX_FINE_STEP_SIZE;

	if (CONF_CLOCK_DFLL_LOOP_MODE == SYSTEM_CLOCK_DFLL_LOOP_MODE_USB_RECOVERY) {
		dfll_conf.fine_max_step   = 10;
		dfll_conf.fine_value   = 0x1ff;
		dfll_conf.quick_lock = SYSTEM_CLOCK_DFLL_QUICK_LOCK_ENABLE;
		dfll_conf.stable_tracking = SYSTEM_CLOCK_DFLL_STABLE_TRACKING_TRACK_AFTER_LOCK;
		dfll_conf.wakeup_lock = SYSTEM_CLOCK_DFLL_WAKEUP_LOCK_KEEP;
		dfll_conf.chill_cycle = SYSTEM_CLOCK_DFLL_CHILL_CYCLE_DISABLE;

		dfll_conf.multiply_factor = 48000;
	}

	system_clock_source_dfll_set_config(&dfll_conf);
#endif

	/* GCLK */
#if CONF_CLOCK_CONFIGURE_GCLK == true
	system_gclk_init();

	/* Configure all GCLK generators except for the main generator, which
	 * is configured later after all other clock systems are set up */
	MREPEAT(GCLK_GEN_NUM, _CONF_CLOCK_GCLK_CONFIG_NONMAIN, ~);
#  if CONF_CLOCK_DFLL_ENABLE == true
	/* Enable DFLL reference clock if in closed loop mode */
	if (CONF_CLOCK_DFLL_LOOP_MODE == SYSTEM_CLOCK_DFLL_LOOP_MODE_CLOSED) {
		struct system_gclk_chan_config dfll_gclk_chan_conf;

		system_gclk_chan_get_config_defaults(&dfll_gclk_chan_conf);
		dfll_gclk_chan_conf.source_generator = CONF_CLOCK_DFLL_SOURCE_GCLK_GENERATOR;
		system_gclk_chan_set_config(OSCCTRL_GCLK_ID_DFLL48, &dfll_gclk_chan_conf);
		system_gclk_chan_enable(OSCCTRL_GCLK_ID_DFLL48);
	}
#  endif

#  if CONF_CLOCK_DPLL_ENABLE == true
	/* Enable DPLL internal lock timer and reference clock */
	struct system_gclk_chan_config dpll_gclk_chan_conf;
	system_gclk_chan_get_config_defaults(&dpll_gclk_chan_conf);
	if (CONF_CLOCK_DPLL_LOCK_TIME != SYSTEM_CLOCK_SOURCE_DPLL_LOCK_TIME_DEFAULT) {
		dpll_gclk_chan_conf.source_generator = CONF_CLOCK_DPLL_LOCK_GCLK_GENERATOR;
		system_gclk_chan_set_config(OSCCTRL_GCLK_ID_FDPLL32K, &dpll_gclk_chan_conf);
		system_gclk_chan_enable(OSCCTRL_GCLK_ID_FDPLL32K);
	}

	if (CONF_CLOCK_DPLL_REFERENCE_CLOCK == SYSTEM_CLOCK_SOURCE_DPLL_REFERENCE_CLOCK_GCLK) {
		dpll_gclk_chan_conf.source_generator = CONF_CLOCK_DPLL_REFERENCE_GCLK_GENERATOR;
		system_gclk_chan_set_config(OSCCTRL_GCLK_ID_FDPLL, &dpll_gclk_chan_conf);
		system_gclk_chan_enable(OSCCTRL_GCLK_ID_FDPLL);
	}
#  endif
#endif

	/* DFLL Enable (Open and Closed Loop) */
#if CONF_CLOCK_DFLL_ENABLE == true
	system_clock_source_enable(SYSTEM_CLOCK_SOURCE_DFLL);
	while(!system_clock_source_is_ready(SYSTEM_CLOCK_SOURCE_DFLL));
	if (CONF_CLOCK_DFLL_ON_DEMAND) {
		OSCCTRL->DFLLCTRL.bit.ONDEMAND = 1;
	}
#endif

	/* DPLL */
#  if (CONF_CLOCK_DPLL_ENABLE == true)

	/* Enable DPLL reference clock */
	if (CONF_CLOCK_DPLL_REFERENCE_CLOCK == SYSTEM_CLOCK_SOURCE_DPLL_REFERENCE_CLOCK_XOSC32K) {
		/* XOSC32K should have been enabled for GCLK_XOSC32 */
		Assert(CONF_CLOCK_XOSC32K_ENABLE);
	} else if (CONF_CLOCK_DPLL_REFERENCE_CLOCK == SYSTEM_CLOCK_SOURCE_DPLL_REFERENCE_CLOCK_XOSC) {
		/* XOSC should have been enabled for GCLK_XOSC */
		Assert(CONF_CLOCK_XOSC_ENABLE);
	}
	else if (CONF_CLOCK_DPLL_REFERENCE_CLOCK == SYSTEM_CLOCK_SOURCE_DPLL_REFERENCE_CLOCK_GCLK) {
		/* GCLK should have been enabled */
		Assert(CONF_CLOCK_CONFIGURE_GCLK);
	}
	else {
		Assert(false);
	}

	struct system_clock_source_dpll_config dpll_config;
	system_clock_source_dpll_get_config_defaults(&dpll_config);

	dpll_config.on_demand        = false;
	dpll_config.run_in_standby   = CONF_CLOCK_DPLL_RUN_IN_STANDBY;
	dpll_config.lock_bypass      = CONF_CLOCK_DPLL_LOCK_BYPASS;
	dpll_config.wake_up_fast     = CONF_CLOCK_DPLL_WAKE_UP_FAST;
	dpll_config.low_power_enable = CONF_CLOCK_DPLL_LOW_POWER_ENABLE;

	dpll_config.filter           = CONF_CLOCK_DPLL_FILTER;
	dpll_config.lock_time        = CONF_CLOCK_DPLL_LOCK_TIME;

	dpll_config.reference_clock     = CONF_CLOCK_DPLL_REFERENCE_CLOCK;
	dpll_config.reference_frequency = CONF_CLOCK_DPLL_REFERENCE_FREQUENCY;
	dpll_config.reference_divider   = CONF_CLOCK_DPLL_REFERENCE_DIVIDER;
	dpll_config.output_frequency    = CONF_CLOCK_DPLL_OUTPUT_FREQUENCY;
	dpll_config.prescaler           = CONF_CLOCK_DPLL_PRESCALER;

	system_clock_source_dpll_set_config(&dpll_config);
	system_clock_source_enable(SYSTEM_CLOCK_SOURCE_DPLL);
	while(!system_clock_source_is_ready(SYSTEM_CLOCK_SOURCE_DPLL));
	if (CONF_CLOCK_DPLL_ON_DEMAND) {
		OSCCTRL->DPLLCTRLA.bit.ONDEMAND = 1;
	}

#  endif

	/* CPU and BUS clocks */
	system_backup_clock_set_divider(CONF_CLOCK_BACKUP_DIVIDER);
	system_low_power_clock_set_divider(CONF_CLOCK_LOW_POWER_DIVIDER);
	system_cpu_clock_set_divider(CONF_CLOCK_CPU_DIVIDER);
	system_main_clock_set_failure_detect(CONF_CLOCK_CPU_CLOCK_FAILURE_DETECT);

	/* GCLK 0 */
#if CONF_CLOCK_CONFIGURE_GCLK == true
	/* Configure the main GCLK last as it might depend on other generators */
	_CONF_CLOCK_GCLK_CONFIG(0, ~);
#endif

	/* If CPU frequency is less than 12MHz, scale down performance level to PL0 */
	uint32_t cpu_freq = system_cpu_clock_get_hz();
	if (cpu_freq <= 12000000) {
		system_switch_performance_level(SYSTEM_PERFORMANCE_LEVEL_0);
	}
}