/**
 * \file
 *
 * \brief SAM D20 System related functionality
 *
 * 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
 *
 */
#ifndef SYSTEM_H_INCLUDED
#define SYSTEM_H_INCLUDED

#include <compiler.h>
#include <clock.h>
#include <gclk.h>
#include <pinmux.h>

/**
 * \defgroup asfdoc_samd20_system_group SAM D20 System Driver (SYSTEM)
 *
 * This driver for SAM D20 devices provides an interface for the configuration
 * and management of the device's system relation functionality, necessary for
 * the basic device operation. This is not limited to a single peripheral, but
 * extends across multiple hardware peripherals,
 *
 * The following peripherals are used by this module:
 *
 * - SYSCTRL (System Control)
 * - PM (Power Manager)
 *
 * The outline of this documentation is as follows:
 *  - \ref asfdoc_samd20_system_prerequisites
 *  - \ref asfdoc_samd20_system_module_overview
 *  - \ref asfdoc_samd20_system_special_considerations
 *  - \ref asfdoc_samd20_system_extra_info
 *  - \ref asfdoc_samd20_system_examples
 *  - \ref asfdoc_samd20_system_api_overview
 *
 *
 * \section asfdoc_samd20_system_prerequisites Prerequisites
 *
 * There are no prerequisites for this module.
 *
 *
 * \section asfdoc_samd20_system_module_overview Module Overview
 *
 * The System driver provides a collection of interfaces between the user
 * application logic, and the core device functionality (such as clocks, reset
 * cause determination, etc.) that is required for all applications. It contains
 * a number of sub-modules that control one specific aspect of the device:
 *
 * - System Core (this module)
 * - \ref asfdoc_samd20_system_clock_group "System Clock Control" (sub-module)
 * - \ref asfdoc_samd20_system_interrupt_group "System Interrupt Control" (sub-module)
 * - \ref asfdoc_samd20_system_pinmux_group "System Pin Multiplexer Control" (sub-module)
 *
 *
 * \subsection asfdoc_samd20_system_module_overview_vref Voltage References
 * The various analog modules within the SAM D20 devices (such as AC, ADC and
 * DAC) require a voltage reference to be configured to act as a reference point
 * for comparisons and conversions.
 *
 * The SAM D20 devices contain multiple references, including an internal
 * temperature sensor, and a fixed band-gap voltage source. When enabled, the
 * associated voltage reference can be selected within the desired peripheral
 * where applicable.
 *
 * \subsection asfdoc_samd20_system_module_overview_reset_cause System Reset Cause
 * In some application there may be a need to execute a different program
 * flow based on how the device was reset. For example, if the cause of reset
 * was the Watchdog timer (WDT), this might indicate an error in the application
 * and a form of error handling or error logging might be needed.
 *
 * For this reason, an API is provided to retrieve the cause of the last system
 * reset, so that appropriate action can be taken.
 *
 * \subsection asfdoc_samd20_system_module_overview_sleep_mode Sleep Modes
 * The SAM D20 devices have several sleep modes, where the sleep mode controls
 * which clock systems on the device will remain enabled or disabled when the
 * device enters a low power sleep mode.
 * \ref asfdoc_samd20_system_module_sleep_mode_table "The table below" lists the
 * clock settings of the different sleep modes.
 *
 * \anchor asfdoc_samd20_system_module_sleep_mode_table
 * <table>
 *  <caption>SAM D20 Device Sleep Modes</caption>
 * 	<tr>
 * 		<th>Sleep mode</th>
 * 		<th>CPU clock</th>
 * 		<th>AHB clock</th>
 * 		<th>APB clocks</th>
 * 		<th>Clock sources</th>
 * 		<th>System clock</th>
 * 		<th>32KHz</th>
 * 		<th>Reg mode</th>
 * 		<th>RAM mode</th>
 * 	</tr>
 * 	<tr>
 * 		<td>IDLE 0</td>
 * 		<td>Stop</td>
 * 		<td>Run</td>
 * 		<td>Run</td>
 * 		<td>Run</td>
 * 		<td>Run</td>
 * 		<td>Run</td>
 * 		<td>Normal</td>
 * 		<td>Normal</td>
 * 	</tr>
 * 	<tr>
 * 		<td>IDLE 1</td>
 * 		<td>Stop</td>
 * 		<td>Stop</td>
 * 		<td>Run</td>
 * 		<td>Run</td>
 * 		<td>Run</td>
 * 		<td>Run</td>
 * 		<td>Normal</td>
 * 		<td>Normal</td>
 *	</tr>
 * 	<tr>
 * 		<td>IDLE 2</td>
 * 		<td>Stop</td>
 * 		<td>Stop</td>
 * 		<td>Stop</td>
 * 		<td>Run</td>
 * 		<td>Run</td>
 * 		<td>Run</td>
 * 		<td>Normal</td>
 * 		<td>Normal</td>
 *	</tr>
 * 	<tr>
 * 		<td>STANDBY</td>
 * 		<td>Stop</td>
 * 		<td>Stop</td>
 * 		<td>Stop</td>
 * 		<td>Stop</td>
 * 		<td>Stop</td>
 * 		<td>Stop</td>
 * 		<td>Low Power</td>
 * 		<td>Source/Drain biasing</td>
 * 	</tr>
 * </table>
 *
 * To enter device sleep, one of the available sleep modes must be set, and the
 * function to enter sleep called. The device will automatically wake up in
 * response to an interrupt being generated or other device event.
 *
 * Some peripheral clocks will remain enabled during sleep, depending on their
 * configuration; if desired, modules can remain clocked during sleep to allow
 * them to continue to operate while other parts of the system are powered down
 * to save power.
 *
 *
 * \section asfdoc_samd20_system_special_considerations Special Considerations
 *
 * Most of the functions in this driver have device specific restrictions and
 * caveats; refer to your device datasheet.
 *
 *
 * \section asfdoc_samd20_system_extra_info Extra Information
 *
 * For extra information see \ref asfdoc_samd20_system_extra. This includes:
 *  - \ref asfdoc_samd20_system_extra_acronyms
 *  - \ref asfdoc_samd20_system_extra_dependencies
 *  - \ref asfdoc_samd20_system_extra_errata
 *  - \ref asfdoc_samd20_system_extra_history
 *
 *
 * \section asfdoc_samd20_system_examples Examples
 *
 * For SYSTEM module related examples, please refer to the sub-modules listed in
 * the \ref asfdoc_samd20_system_module_overview "system module overview".
 *
 *
 * \section asfdoc_samd20_system_api_overview API Overview
 * @{
 */

/**
 * \brief Voltage references within the device.
 *
 * List of available voltage references (VREF) that may be used within the
 * device.
 */
enum system_voltage_reference {
	/** Temperature sensor voltage reference. */
	SYSTEM_VOLTAGE_REFERENCE_TEMPSENSE,
	/** Bandgap voltage reference. */
	SYSTEM_VOLTAGE_REFERENCE_BANDGAP,
};

/**
 * \brief Device sleep modes.
 *
 * List of available sleep modes in the device. A table of clocks available in
 * different sleep modes can be found in \ref asfdoc_samd20_system_module_overview_sleep_mode.
 */
enum system_sleepmode {
	/** IDLE 0 sleep mode. */
	SYSTEM_SLEEPMODE_IDLE_0,
	/** IDLE 1 sleep mode. */
	SYSTEM_SLEEPMODE_IDLE_1,
	/** IDLE 2 sleep mode. */
	SYSTEM_SLEEPMODE_IDLE_2,
	/** Standby sleep mode. */
	SYSTEM_SLEEPMODE_STANDBY,
};

/**
 * \brief Reset causes of the system.
 *
 * List of possible reset causes of the system.
 */
enum system_reset_cause {
	/** The system was last reset by a software reset. */
	SYSTEM_RESET_CAUSE_SOFTWARE       = PM_RCAUSE_SYST,
	/** The system was last reset by the watchdog timer. */
	SYSTEM_RESET_CAUSE_WDT            = PM_RCAUSE_WDT,
	/** The system was last reset because the external reset line was pulled low. */
	SYSTEM_RESET_CAUSE_EXTERNAL_RESET = PM_RCAUSE_EXT,
	/** The system was last reset by the BOD33. */
	SYSTEM_RESET_CAUSE_BOD33          = PM_RCAUSE_BOD33,
	/** The system was last reset by the BOD12. */
	SYSTEM_RESET_CAUSE_BOD12          = PM_RCAUSE_BOD12,
	/** The system was last reset by the POR (Power on reset). */
	SYSTEM_RESET_CAUSE_POR            = PM_RCAUSE_POR,
};

/**
 * \name System identification
 * @{
 */

/**
 * \brief Retrieve the device identification signature
 *
 * Retrieves the signature of the current device.
 *
 * \return Device ID signature as a 32-bit integer.
 */
static inline uint32_t system_get_device_id(void)
{
	return DSU->DID.reg;
}

/**
 * @}
 */


/**
 * \name Voltage references
 * @{
 */

/**
 * \brief Enable the selected voltage reference
 *
 * Enables the selected voltage reference source, making the voltage reference
 * available on a pin as well as an input source to the analog peripherals.
 *
 * \param[in] vref  Voltage reference to enable
 */
static inline void system_voltage_reference_enable(
		const enum system_voltage_reference vref)
{
	switch (vref) {
		case SYSTEM_VOLTAGE_REFERENCE_TEMPSENSE:
			SYSCTRL->VREF.reg |= SYSCTRL_VREF_TSEN;
			break;

		case SYSTEM_VOLTAGE_REFERENCE_BANDGAP:
			SYSCTRL->VREF.reg |= SYSCTRL_VREF_BGOUTEN;
			break;

		default:
			Assert(false);
			return;
	}
}

/**
 * \brief Disable the selected voltage reference
 *
 * Disables the selected voltage reference source.
 *
 * \param[in] vref  Voltage reference to disable
 */
static inline void system_voltage_reference_disable(
		const enum system_voltage_reference vref)
{
	switch (vref) {
		case SYSTEM_VOLTAGE_REFERENCE_TEMPSENSE:
			SYSCTRL->VREF.reg &= ~SYSCTRL_VREF_TSEN;
			break;

		case SYSTEM_VOLTAGE_REFERENCE_BANDGAP:
			SYSCTRL->VREF.reg &= ~SYSCTRL_VREF_BGOUTEN;
			break;

		default:
			Assert(false);
			return;
	}
}

/**
 * @}
 */


/**
 * \name Device sleep
 * @{
 */

/**
 * \brief Set the sleep mode of the device
 *
 * Sets the sleep mode of the device; the configured sleep mode will be entered
 * upon the next call of the \ref system_sleep() function.
 *
 * For an overview of which systems are disabled in sleep for the different
 * sleep modes, see \ref asfdoc_samd20_system_module_overview_sleep_mode.
 *
 * \param[in] sleep_mode  Sleep mode to configure for the next sleep operation
 *
 * \retval STATUS_OK               Operation completed successfully
 * \retval STATUS_ERR_INVALID_ARG  The requested sleep mode was invalid or not
 *                                 available
 */
static inline enum status_code system_set_sleepmode(
	const enum system_sleepmode sleep_mode)
{
	switch (sleep_mode) {
		case SYSTEM_SLEEPMODE_IDLE_0:
		case SYSTEM_SLEEPMODE_IDLE_1:
		case SYSTEM_SLEEPMODE_IDLE_2:
			SCB->SCR &= ~SCB_SCR_SLEEPDEEP_Msk;
			PM->SLEEP.reg = sleep_mode;
			break;

		case SYSTEM_SLEEPMODE_STANDBY:
			SCB->SCR |=  SCB_SCR_SLEEPDEEP_Msk;
			break;

		default:
			return STATUS_ERR_INVALID_ARG;
	}

	return STATUS_OK;
}

/**
 * \brief Put the system to sleep waiting for interrupt
 *
 * Executes a device DSB (Data Synchronization Barrier) instruction to ensure
 * all ongoing memory accesses have completed, then a WFI (Wait For Interrupt)
 * instruction to place the device into the sleep mode specified by
 * \ref system_set_sleepmode until woken by an interrupt.
 */
static inline void system_sleep(void)
{
	__DSB();
	__WFI();
}

/**
 * @}
 */

/**
 * \name Reset control
 * @{
 */

/**
 * \brief Reset the MCU
 *
 * Resets the MCU and all associated peripherals and registers, except RTC, all 32kHz sources,
 * WDT (if ALWAYSON is set) and GCLK (if WRTLOCK is set).
 *
 */
static inline void system_reset(void)
{
	NVIC_SystemReset();
}

/**
 * \brief Return the reset cause
 *
 * Retrieves the cause of the last system reset.
 *
 * \return An enum value indicating the cause of the last system reset.
 */
static inline enum system_reset_cause system_get_reset_cause(void)
{
	return (enum system_reset_cause)PM->RCAUSE.reg;
}

/**
 * @}
 */


/**
 * \name System initialization
 * @{
 */

void system_init(void);

/**
 * @}
 */


/**
 * @}
 */

/**
 * \page asfdoc_samd20_system_extra Extra Information for SYSTEM Driver
 *
 * \section asfdoc_samd20_system_extra_acronyms Acronyms
 * Below is a table listing the acronyms used in this module, along with their
 * intended meanings.
 *
 * <table>
 *  <tr>
 *      <th>Acronym</th>
 *      <th>Definition</th>
 *  </tr>
 *  <tr>
 *		<td>PM</td>
 *		<td>Power Manager</td>
 *  </tr>
 *  <tr>
 *		<td>SYSCTRL</td>
 *		<td>System control interface</td>
 *  </tr>
 * </table>
 *
 *
 * \section asfdoc_samd20_system_extra_dependencies Dependencies
 * This driver has the following dependencies:
 *
 *  - None
 *
 *
 * \section asfdoc_samd20_system_extra_errata Errata
 * There are no errata related to this driver.
 *
 *
 * \section asfdoc_samd20_system_extra_history Module History
 * An overview of the module history is presented in the table below, with
 * details on the enhancements and fixes made to the module since its first
 * release. The current version of this corresponds to the newest version in
 * the table.
 *
 * <table>
 *	<tr>
 *		<th>Changelog</th>
 *	</tr>
 *	<tr>
 *		<td>Added new \c system_reset() to reset the complete MCU with some exceptions</td>
 *	</tr>
 *	<tr>
 *		<td>Added new \c system_get_device_id() function to retrieved the device
 *          ID.</td>
 *	</tr>
 *	<tr>
 *		<td>Initial Release</td>
 *	</tr>
 * </table>
 *
 * \page asfdoc_samd20_system_document_revision_history Document Revision History
 *
 * <table>
 *	<tr>
 *		<th>Doc. Rev.</td>
 *		<th>Date</td>
 *		<th>Comments</td>
 *	</tr>
 *	<tr>
 *		<td>B</td>
 *		<td>06/2013</td>
 *		<td>Corrected documentation typos.</td>
 *	</tr>
 *	<tr>
 *		<td>A</td>
 *		<td>06/2013</td>
 *		<td>Initial release</td>
 *	</tr>
 * </table>
 */

#endif /* SYSTEM_H_INCLUDED */