FreeRTOS/Demo/CORTEX_M0+_Atmel_SAMD20_XPlained/RTOSDemo/src/ASF/sam0/drivers/system/clock/clock.c

/**
 * \file
 *
 * \brief SAM D20 Clock Driver
 *
 * Copyright (C) 2012-2013 Atmel Corporation. All rights reserved.
 *
 * \asf_license_start
 *
 * \page License
 *
 * 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. The name of Atmel may not be used to endorse or promote products derived
 *    from this software without specific prior written permission.
 *
 * 4. This software may only be redistributed and used in connection with an
 *    Atmel microcontroller product.
 *
 * THIS SOFTWARE IS PROVIDED BY ATMEL "AS IS" AND ANY EXPRESS OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT ARE
 * EXPRESSLY AND SPECIFICALLY DISCLAIMED. IN NO EVENT SHALL ATMEL 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.
 *
 * \asf_license_stop
 *
 */
#include <clock.h>
#include <conf_clocks.h>

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

/**
 * \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_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,
		},
		.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 (!(SYSCTRL->PCLKSR.reg & SYSCTRL_PCLKSR_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 (!(SYSCTRL->PCLKSR.reg & SYSCTRL_PCLKSR_OSC32KRDY)) {
		/* Wait for OSC32K sync */
	}
}

static inline void _system_clock_source_dfll_set_config_errata_9905(void)
{

	/* Disable ONDEMAND mode while writing configurations */
	SYSCTRL->DFLLCTRL.reg = _system_clock_inst.dfll.control & ~SYSCTRL_DFLLCTRL_ONDEMAND;
	_system_dfll_wait_for_sync();

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

	/* Write full configuration to DFLL control register */
	SYSCTRL->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 to get the frequency of
 *
 * \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_OSC8M:
		return 8000000UL >> SYSCTRL->OSC8M.bit.PRESC;

	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 & SYSCTRL_DFLLCTRL_ENABLE))
			return 0;

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

		/* Check if operating in closed loop mode */
		if (_system_clock_inst.dfll.control & SYSCTRL_DFLLCTRL_MODE) {
			return system_gclk_chan_get_hz(SYSCTRL_GCLK_ID_DFLL48) *
					(_system_clock_inst.dfll.mul & 0xffff);
		}

		return 48000000UL;

	default:
		return 0;
	}
}

/**
 * \brief Configure the internal OSC8M oscillator clock source
 *
 * Configures the 8MHz (nominal) internal RC oscillator with the given
 * configuration settings.
 *
 * \param[in] config  OSC8M configuration structure containing the new config
 */
void system_clock_source_osc8m_set_config(
		struct system_clock_source_osc8m_config *const config)
{
	SYSCTRL_OSC8M_Type temp = SYSCTRL->OSC8M;

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

	SYSCTRL->OSC8M = 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)
{
	SYSCTRL_OSC32K_Type temp = SYSCTRL->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;

	SYSCTRL->OSC32K  = 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)
{
	SYSCTRL_XOSC_Type temp = SYSCTRL->XOSC;

	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 automatic gain control is not selected */
	if (!config->auto_gain_control) {
		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;

	SYSCTRL->XOSC = 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)
{
	SYSCTRL_XOSC32K_Type temp = SYSCTRL->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.AAMPEN = config->auto_gain_control;
	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;

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

	SYSCTRL->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 =
			SYSCTRL_DFLLVAL_COARSE(config->coarse_value) |
			SYSCTRL_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->run_in_standby << SYSCTRL_DFLLCTRL_RUNSTDBY_Pos |
			(uint32_t)config->on_demand << SYSCTRL_DFLLCTRL_ONDEMAND_Pos;

	if (config->loop_mode == SYSTEM_CLOCK_DFLL_LOOP_MODE_CLOSED) {
		_system_clock_inst.dfll.mul =
				SYSCTRL_DFLLMUL_CSTEP(config->coarse_max_step) |
				SYSCTRL_DFLLMUL_FSTEP(config->fine_max_step)   |
				SYSCTRL_DFLLMUL_MUL(config->multiply_factor);

		/* Enable the closed loop mode */
		_system_clock_inst.dfll.control |= config->loop_mode;
	}
}

/**
 * \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 OSC8MHZ:
 *  - 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_ERR_INVALID_ARG  The selected clock source is not available
 */
enum status_code system_clock_source_write_calibration(
		const enum system_clock_source clock_source,
		const uint16_t calibration_value,
		const uint8_t freq_range)
{
	switch (clock_source) {
	case SYSTEM_CLOCK_SOURCE_OSC8M:

		if (calibration_value > 0xfff || freq_range > 4) {
			return STATUS_ERR_INVALID_ARG;
		}

		SYSCTRL->OSC8M.bit.CALIB  = calibration_value;
		SYSCTRL->OSC8M.bit.FRANGE = freq_range;
		break;

	case SYSTEM_CLOCK_SOURCE_OSC32K:

		if (calibration_value > 128) {
			return STATUS_ERR_INVALID_ARG;
		}

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

	case SYSTEM_CLOCK_SOURCE_ULP32K:

		if (calibration_value > 32) {
			return STATUS_ERR_INVALID_ARG;
		}

		SYSCTRL->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
 *
 * \retval STATUS_ERR_NOT_INITIALIZED DFLL configuration is not initialized
 */
enum status_code system_clock_source_enable(
		const enum system_clock_source clock_source)
{
	switch (clock_source) {
	case SYSTEM_CLOCK_SOURCE_OSC8M:
		SYSCTRL->OSC8M.reg |= SYSCTRL_OSC8M_ENABLE;
		return STATUS_OK;

	case SYSTEM_CLOCK_SOURCE_OSC32K:
		SYSCTRL->OSC32K.reg |= SYSCTRL_OSC32K_ENABLE;
		break;

	case SYSTEM_CLOCK_SOURCE_XOSC:
		SYSCTRL->XOSC.reg |= SYSCTRL_XOSC_ENABLE;
		break;

	case SYSTEM_CLOCK_SOURCE_XOSC32K:
		SYSCTRL->XOSC32K.reg |= SYSCTRL_XOSC32K_ENABLE;
		break;

	case SYSTEM_CLOCK_SOURCE_DFLL:
		_system_clock_inst.dfll.control |= SYSCTRL_DFLLCTRL_ENABLE;
		_system_clock_source_dfll_set_config_errata_9905();
		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_OSC8M:
		SYSCTRL->OSC8M.reg &= ~SYSCTRL_OSC8M_ENABLE;
		break;

	case SYSTEM_CLOCK_SOURCE_OSC32K:
		SYSCTRL->OSC32K.reg &= ~SYSCTRL_OSC32K_ENABLE;
		break;

	case SYSTEM_CLOCK_SOURCE_XOSC:
		SYSCTRL->XOSC.reg &= ~SYSCTRL_XOSC_ENABLE;
		break;

	case SYSTEM_CLOCK_SOURCE_XOSC32K:
		SYSCTRL->XOSC32K.reg &= ~SYSCTRL_XOSC32K_ENABLE;
		break;

	case SYSTEM_CLOCK_SOURCE_DFLL:
		_system_clock_inst.dfll.control &= ~SYSCTRL_DFLLCTRL_ENABLE;
		SYSCTRL->DFLLCTRL.reg = _system_clock_inst.dfll.control;
		break;

	case SYSTEM_CLOCK_SOURCE_ULP32K:
		/* Not possible to disable */
		return STATUS_ERR_INVALID_ARG;

	default:
		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;

	switch (clock_source) {
	case SYSTEM_CLOCK_SOURCE_OSC8M:
		mask = SYSCTRL_PCLKSR_OSC8MRDY;
		break;

	case SYSTEM_CLOCK_SOURCE_OSC32K:
		mask = SYSCTRL_PCLKSR_OSC32KRDY;
		break;

	case SYSTEM_CLOCK_SOURCE_XOSC:
		mask = SYSCTRL_PCLKSR_XOSCRDY;
		break;

	case SYSTEM_CLOCK_SOURCE_XOSC32K:
		mask = SYSCTRL_PCLKSR_XOSC32KRDY;
		break;

	case SYSTEM_CLOCK_SOURCE_DFLL:
		mask = SYSCTRL_PCLKSR_DFLLRDY;
		break;

	case SYSTEM_CLOCK_SOURCE_ULP32K:
		/* Not possible to disable */
		return true;

	default:
		return false;
	}

	return ((SYSCTRL->PCLKSR.reg & mask) != 0);
}

/* 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.
 */
void system_clock_init(void)
{
        /* Workaround for errata 10558 */
        SYSCTRL->INTFLAG.reg = SYSCTRL_INTFLAG_BOD12RDY | SYSCTRL_INTFLAG_BOD33RDY |
                        SYSCTRL_INTFLAG_BOD12DET | SYSCTRL_INTFLAG_BOD33DET |
                        SYSCTRL_INTFLAG_DFLLRDY;

	system_flash_set_waitstates(CONF_CLOCK_FLASH_WAIT_STATES);

	/* 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.auto_gain_control = CONF_CLOCK_XOSC_AUTO_GAIN_CONTROL;
	xosc_conf.frequency         = CONF_CLOCK_XOSC_EXTERNAL_FREQUENCY;
	xosc_conf.on_demand         = CONF_CLOCK_XOSC_ON_DEMAND;
	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);
#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.auto_gain_control   = CONF_CLOCK_XOSC32K_AUTO_AMPLITUDE_CONTROL;
	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           = CONF_CLOCK_XOSC32K_ON_DEMAND;
	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);
#endif


	/* OSCK32K */
#if CONF_CLOCK_OSC32K_ENABLE == true
	SYSCTRL->OSC32K.bit.CALIB =
			(*(uint32_t *)SYSCTRL_FUSES_OSC32KCAL_ADDR >> SYSCTRL_FUSES_OSC32KCAL_Pos);

	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


	/* DFLL (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      = CONF_CLOCK_DFLL_ON_DEMAND;
	dfll_conf.run_in_standby = CONF_CLOCK_DFLL_RUN_IN_STANDBY;

	if (CONF_CLOCK_DFLL_LOOP_MODE == SYSTEM_CLOCK_DFLL_LOOP_MODE_OPEN) {
		dfll_conf.coarse_value = CONF_CLOCK_DFLL_COARSE_VALUE;
		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;

	system_clock_source_dfll_set_config(&dfll_conf);
	system_clock_source_enable(SYSTEM_CLOCK_SOURCE_DFLL);
#endif


	/* OSC8M */
	struct system_clock_source_osc8m_config osc8m_conf;
	system_clock_source_osc8m_get_config_defaults(&osc8m_conf);

	osc8m_conf.prescaler      = CONF_CLOCK_OSC8M_PRESCALER;
	osc8m_conf.on_demand      = CONF_CLOCK_OSC8M_ON_DEMAND;
	osc8m_conf.run_in_standby = CONF_CLOCK_OSC8M_RUN_IN_STANDBY;

	system_clock_source_osc8m_set_config(&osc8m_conf);
	system_clock_source_enable(SYSTEM_CLOCK_SOURCE_OSC8M);


	/* 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_MSB, _CONF_CLOCK_GCLK_CONFIG_NONMAIN, ~);

#  if (CONF_CLOCK_DFLL_ENABLE)
	/* 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(SYSCTRL_GCLK_ID_DFLL48, &dfll_gclk_chan_conf);
		system_gclk_chan_enable(SYSCTRL_GCLK_ID_DFLL48);
	}
#  endif

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


	/* CPU and BUS clocks */
	system_cpu_clock_set_divider(CONF_CLOCK_CPU_DIVIDER);
	system_main_clock_set_failure_detect(CONF_CLOCK_CPU_CLOCK_FAILURE_DETECT);
	system_apb_clock_set_divider(SYSTEM_CLOCK_APB_APBA, CONF_CLOCK_APBA_DIVIDER);
	system_apb_clock_set_divider(SYSTEM_CLOCK_APB_APBB, CONF_CLOCK_APBB_DIVIDER);
}