/*
    FreeRTOS V7.3.0 - Copyright (C) 2012 Real Time Engineers Ltd.

    FEATURES AND PORTS ARE ADDED TO FREERTOS ALL THE TIME.  PLEASE VISIT 
    http://www.FreeRTOS.org TO ENSURE YOU ARE USING THE LATEST VERSION.

    ***************************************************************************
     *                                                                       *
     *    FreeRTOS tutorial books are available in pdf and paperback.        *
     *    Complete, revised, and edited pdf reference manuals are also       *
     *    available.                                                         *
     *                                                                       *
     *    Purchasing FreeRTOS documentation will not only help you, by       *
     *    ensuring you get running as quickly as possible and with an        *
     *    in-depth knowledge of how to use FreeRTOS, it will also help       *
     *    the FreeRTOS project to continue with its mission of providing     *
     *    professional grade, cross platform, de facto standard solutions    *
     *    for microcontrollers - completely free of charge!                  *
     *                                                                       *
     *    >>> See http://www.FreeRTOS.org/Documentation for details. <<<     *
     *                                                                       *
     *    Thank you for using FreeRTOS, and thank you for your support!      *
     *                                                                       *
    ***************************************************************************


    This file is part of the FreeRTOS distribution.

    FreeRTOS is free software; you can redistribute it and/or modify it under
    the terms of the GNU General Public License (version 2) as published by the
    Free Software Foundation AND MODIFIED BY the FreeRTOS exception.
    >>>NOTE<<< The modification to the GPL is included to allow you to
    distribute a combined work that includes FreeRTOS without being obliged to
    provide the source code for proprietary components outside of the FreeRTOS
    kernel.  FreeRTOS is distributed in the hope that it will be useful, but
    WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
    or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
    more details. You should have received a copy of the GNU General Public
    License and the FreeRTOS license exception along with FreeRTOS; if not it
    can be viewed here: http://www.freertos.org/a00114.html and also obtained
    by writing to Richard Barry, contact details for whom are available on the
    FreeRTOS WEB site.

    1 tab == 4 spaces!
    
    ***************************************************************************
     *                                                                       *
     *    Having a problem?  Start by reading the FAQ "My application does   *
     *    not run, what could be wrong?"                                     *
     *                                                                       *
     *    http://www.FreeRTOS.org/FAQHelp.html                               *
     *                                                                       *
    ***************************************************************************

    
    http://www.FreeRTOS.org - Documentation, training, latest versions, license 
    and contact details.  
    
    http://www.FreeRTOS.org/plus - A selection of FreeRTOS ecosystem products,
    including FreeRTOS+Trace - an indispensable productivity tool.

    Real Time Engineers ltd license FreeRTOS to High Integrity Systems, who sell 
    the code with commercial support, indemnification, and middleware, under 
    the OpenRTOS brand: http://www.OpenRTOS.com.  High Integrity Systems also
    provide a safety engineered and independently SIL3 certified version under 
    the SafeRTOS brand: http://www.SafeRTOS.com.
*/

/*-----------------------------------------------------------
 * Implementation of functions defined in portable.h for the ARM CM3 port.
 *----------------------------------------------------------*/

/* Scheduler includes. */
#include "FreeRTOS.h"
#include "task.h"

/* For backward compatibility, ensure configKERNEL_INTERRUPT_PRIORITY is
defined.  The value should also ensure backward compatibility.
FreeRTOS.org versions prior to V4.4.0 did not include this definition. */
#ifndef configKERNEL_INTERRUPT_PRIORITY
	#define configKERNEL_INTERRUPT_PRIORITY 255
#endif

#ifndef configSYSTICK_CLOCK_HZ
	#define configSYSTICK_CLOCK_HZ configCPU_CLOCK_HZ
	#if configUSE_TICKLESS_IDLE == 1
		static const unsigned long ulStoppedTimerCompensation = 45UL;
	#endif
#else /* configSYSTICK_CLOCK_HZ */
	#if configUSE_TICKLESS_IDLE == 1
		/* Assumes the SysTick clock is slower than the CPU clock. */
		static const unsigned long ulStoppedTimerCompensation = 45UL / ( configCPU_CLOCK_HZ / configSYSTICK_CLOCK_HZ );
	#endif
#endif	/* configSYSTICK_CLOCK_HZ */

/* Constants required to manipulate the core.  Registers first... */
#define portNVIC_SYSTICK_CTRL_REG			( * ( ( volatile unsigned long * ) 0xe000e010 ) )
#define portNVIC_SYSTICK_LOAD_REG			( * ( ( volatile unsigned long * ) 0xe000e014 ) )
#define portNVIC_SYSTICK_CURRENT_VALUE_REG	( * ( ( volatile unsigned long * ) 0xe000e018 ) )
#define portNVIC_INT_CTRL_REG				( * ( ( volatile unsigned long * ) 0xe000ed04 ) )
#define portNVIC_SYSPRI2_REG				( * ( ( volatile unsigned long * ) 0xe000ed20 ) )
/* ...then bits in the registers. */
#define portNVIC_SYSTICK_CLK_BIT			( 1UL << 2UL )
#define portNVIC_SYSTICK_INT_BIT			( 1UL << 1UL )
#define portNVIC_SYSTICK_ENABLE_BIT			( 1UL << 0UL )
#define portNVIC_SYSTICK_COUNT_FLAG_BIT		( 1UL << 16UL )
#define portNVIC_PENDSVSET_BIT				( 1UL << 28UL )
#define portNVIC_PENDSVCLEAR_BIT 			( 1UL << 27UL )
#define portNVIC_PEND_SYSTICK_CLEAR_BIT		( 1UL << 25UL )

#define portNVIC_PENDSV_PRI				( ( ( unsigned long ) configKERNEL_INTERRUPT_PRIORITY ) << 16UL )
#define portNVIC_SYSTICK_PRI			( ( ( unsigned long ) configKERNEL_INTERRUPT_PRIORITY ) << 24UL )

/* Constants required to set up the initial stack. */
#define portINITIAL_XPSR			( 0x01000000 )

/* The priority used by the kernel is assigned to a variable to make access
from inline assembler easier. */
const unsigned long ulKernelPriority = configKERNEL_INTERRUPT_PRIORITY;

/* Each task maintains its own interrupt status in the critical nesting
variable. */
static unsigned portBASE_TYPE uxCriticalNesting = 0xaaaaaaaa;

/*
 * Setup the timer to generate the tick interrupts.
 */
static void prvSetupTimerInterrupt( void );

/*
 * Exception handlers.
 */
void xPortPendSVHandler( void ) __attribute__ (( naked ));
void xPortSysTickHandler( void );
void vPortSVCHandler( void ) __attribute__ (( naked ));

/*
 * Start first task is a separate function so it can be tested in isolation.
 */
static void prvPortStartFirstTask( void ) __attribute__ (( naked ));

/*-----------------------------------------------------------*/

/*
 * The number of SysTick increments that make up one tick period.
 */
static unsigned long ulTimerReloadValueForOneTick = 0;

/*
 * The maximum number of tick periods that can be suppressed is limited by the
 * 24 bit resolution of the SysTick timer.
 */
#if configUSE_TICKLESS_IDLE == 1
	static unsigned long xMaximumPossibleSuppressedTicks = 0;
#endif /* configUSE_TICKLESS_IDLE */


/*-----------------------------------------------------------*/

/*
 * See header file for description.
 */
portSTACK_TYPE *pxPortInitialiseStack( portSTACK_TYPE *pxTopOfStack, pdTASK_CODE pxCode, void *pvParameters )
{
	/* Simulate the stack frame as it would be created by a context switch
	interrupt. */
	pxTopOfStack--; /* Offset added to account for the way the MCU uses the stack on entry/exit of interrupts. */
	*pxTopOfStack = portINITIAL_XPSR;	/* xPSR */
	pxTopOfStack--;
	*pxTopOfStack = ( portSTACK_TYPE ) pxCode;	/* PC */
	pxTopOfStack--;
	*pxTopOfStack = 0;	/* LR */
	pxTopOfStack -= 5;	/* R12, R3, R2 and R1. */
	*pxTopOfStack = ( portSTACK_TYPE ) pvParameters;	/* R0 */
	pxTopOfStack -= 8;	/* R11, R10, R9, R8, R7, R6, R5 and R4. */

	return pxTopOfStack;
}
/*-----------------------------------------------------------*/

void vPortSVCHandler( void )
{
	__asm volatile (
					"	ldr	r3, pxCurrentTCBConst2		\n" /* Restore the context. */
					"	ldr r1, [r3]					\n" /* Use pxCurrentTCBConst to get the pxCurrentTCB address. */
					"	ldr r0, [r1]					\n" /* The first item in pxCurrentTCB is the task top of stack. */
					"	ldmia r0!, {r4-r11}				\n" /* Pop the registers that are not automatically saved on exception entry and the critical nesting count. */
					"	msr psp, r0						\n" /* Restore the task stack pointer. */
					"	mov r0, #0 						\n"
					"	msr	basepri, r0					\n"
					"	orr r14, #0xd					\n"
					"	bx r14							\n"
					"									\n"
					"	.align 2						\n"
					"pxCurrentTCBConst2: .word pxCurrentTCB				\n"
				);
}
/*-----------------------------------------------------------*/

static void prvPortStartFirstTask( void )
{
	__asm volatile(
					" ldr r0, =0xE000ED08 	\n" /* Use the NVIC offset register to locate the stack. */
					" ldr r0, [r0] 			\n"
					" ldr r0, [r0] 			\n"
					" msr msp, r0			\n" /* Set the msp back to the start of the stack. */
					" cpsie i				\n" /* Globally enable interrupts. */
					" svc 0					\n" /* System call to start first task. */
					" nop					\n"
				);
}
/*-----------------------------------------------------------*/

/*
 * See header file for description.
 */
portBASE_TYPE xPortStartScheduler( void )
{
	/* configMAX_SYSCALL_INTERRUPT_PRIORITY must not be set to 0.
	See http://www.FreeRTOS.org/RTOS-Cortex-M3-M4.html */
	configASSERT( configMAX_SYSCALL_INTERRUPT_PRIORITY );

	/* Make PendSV, CallSV and SysTick the same priroity as the kernel. */
	portNVIC_SYSPRI2_REG |= portNVIC_PENDSV_PRI;
	portNVIC_SYSPRI2_REG |= portNVIC_SYSTICK_PRI;

	/* Start the timer that generates the tick ISR.  Interrupts are disabled
	here already. */
	prvSetupTimerInterrupt();

	/* Initialise the critical nesting count ready for the first task. */
	uxCriticalNesting = 0;

	/* Start the first task. */
	prvPortStartFirstTask();

	/* Should not get here! */
	return 0;
}
/*-----------------------------------------------------------*/

void vPortEndScheduler( void )
{
	/* It is unlikely that the CM3 port will require this function as there
	is nothing to return to.  */
}
/*-----------------------------------------------------------*/

void vPortYieldFromISR( void )
{
	/* Set a PendSV to request a context switch. */
	portNVIC_INT_CTRL_REG = portNVIC_PENDSVSET_BIT;
}
/*-----------------------------------------------------------*/

void vPortEnterCritical( void )
{
	portDISABLE_INTERRUPTS();
	uxCriticalNesting++;
}
/*-----------------------------------------------------------*/

void vPortExitCritical( void )
{
	uxCriticalNesting--;
	if( uxCriticalNesting == 0 )
	{
		portENABLE_INTERRUPTS();
	}
}
/*-----------------------------------------------------------*/

__attribute__(( naked )) unsigned long ulPortSetInterruptMask( void )
{
	__asm volatile														\
	(																	\
		"	mrs r0, basepri											\n" \
		"	mov r1, %0												\n"	\
		"	msr basepri, r1											\n" \
		"	bx lr													\n" \
		:: "i" ( configMAX_SYSCALL_INTERRUPT_PRIORITY ) : "r0", "r1"	\
	);

	/* This return will not be reached but is necessary to prevent compiler
	warnings. */
	return 0;
}
/*-----------------------------------------------------------*/

__attribute__(( naked )) void vPortClearInterruptMask( unsigned long ulNewMaskValue )
{
	__asm volatile													\
	(																\
		"	msr basepri, r0										\n"	\
		"	bx lr												\n" \
		:::"r0"														\
	);
}
/*-----------------------------------------------------------*/

void xPortPendSVHandler( void )
{
	/* This is a naked function. */

	__asm volatile
	(
	"	mrs r0, psp							\n"
	"										\n"
	"	ldr	r3, pxCurrentTCBConst			\n" /* Get the location of the current TCB. */
	"	ldr	r2, [r3]						\n"
	"										\n"
	"	stmdb r0!, {r4-r11}					\n" /* Save the remaining registers. */
	"	str r0, [r2]						\n" /* Save the new top of stack into the first member of the TCB. */
	"										\n"
	"	stmdb sp!, {r3, r14}				\n"
	"	mov r0, %0							\n"
	"	msr basepri, r0						\n"
	"	bl vTaskSwitchContext				\n"
	"	mov r0, #0							\n"
	"	msr basepri, r0						\n"
	"	ldmia sp!, {r3, r14}				\n"
	"										\n"	/* Restore the context, including the critical nesting count. */
	"	ldr r1, [r3]						\n"
	"	ldr r0, [r1]						\n" /* The first item in pxCurrentTCB is the task top of stack. */
	"	ldmia r0!, {r4-r11}					\n" /* Pop the registers. */
	"	msr psp, r0							\n"
	"	bx r14								\n"
	"										\n"
	"	.align 2							\n"
	"pxCurrentTCBConst: .word pxCurrentTCB	\n"
	::"i"(configMAX_SYSCALL_INTERRUPT_PRIORITY)
	);
}
/*-----------------------------------------------------------*/

void xPortSysTickHandler( void )
{
	/* If using preemption, also force a context switch. */
	#if configUSE_PREEMPTION == 1
		portNVIC_INT_CTRL_REG = portNVIC_PENDSVSET_BIT;
	#endif

	#if configUSE_TICKLESS_IDLE == 1
		portNVIC_SYSTICK_LOAD_REG = ulTimerReloadValueForOneTick;
	#endif

	( void ) portSET_INTERRUPT_MASK_FROM_ISR();
	{
		vTaskIncrementTick();
	}
	portCLEAR_INTERRUPT_MASK_FROM_ISR( 0 );
}
/*-----------------------------------------------------------*/

#if configUSE_TICKLESS_IDLE == 1

	__attribute__((weak)) void vPortSuppressTicksAndSleep( portTickType xExpectedIdleTime )
	{
	unsigned long ulReloadValue, ulCompleteTickPeriods, ulCompletedSysTickIncrements;

		/* Make sure the SysTick reload value does not overflow the counter. */
		if( xExpectedIdleTime > xMaximumPossibleSuppressedTicks )
		{
			xExpectedIdleTime = xMaximumPossibleSuppressedTicks;
		}

		/* Calculate the reload value required to wait xExpectedIdleTime
		tick periods.  -1 is used because this code will execute part way
		through one of the tick periods, and the fraction of a tick period is
		accounted for later. */
		ulReloadValue = ( ulTimerReloadValueForOneTick * ( xExpectedIdleTime - 1UL ) );
		if( ulReloadValue > ulStoppedTimerCompensation )
		{
			ulReloadValue -= ulStoppedTimerCompensation;
		}

		/* Stop the SysTick momentarily.  The time the SysTick is stopped for
		is accounted for as best it can be, but using the tickless mode will
		inevitably result in some tiny drift of the time maintained by the
		kernel with respect to calendar time. */
		portNVIC_SYSTICK_CTRL_REG = portNVIC_SYSTICK_CLK_BIT | portNVIC_SYSTICK_INT_BIT;

		/* If a context switch is pending then abandon the low power entry as
		the context switch might have been pended by an external interrupt that
		requires processing. */
		if( ( portNVIC_INT_CTRL_REG & portNVIC_PENDSVSET_BIT ) != 0 )
		{
			/* Restart SysTick. */
			portNVIC_SYSTICK_CTRL_REG = portNVIC_SYSTICK_CLK_BIT | portNVIC_SYSTICK_INT_BIT | portNVIC_SYSTICK_ENABLE_BIT;
		}
		else
		{
			/* Adjust the reload value to take into account that the current
			time slice is already partially complete. */
			ulReloadValue += ( portNVIC_SYSTICK_LOAD_REG - ( portNVIC_SYSTICK_LOAD_REG - portNVIC_SYSTICK_CURRENT_VALUE_REG ) );
			portNVIC_SYSTICK_LOAD_REG = ulReloadValue;

			/* Clear the SysTick count flag and set the count value back to
			zero. */
			portNVIC_SYSTICK_CURRENT_VALUE_REG = 0UL;

			/* Restart SysTick. */
			portNVIC_SYSTICK_CTRL_REG = portNVIC_SYSTICK_CLK_BIT | portNVIC_SYSTICK_INT_BIT | portNVIC_SYSTICK_ENABLE_BIT;

			/* Sleep until something happens. */
			portPRE_SLEEP_PROCESSING();
			__asm volatile( "wfi" );
			portPOST_SLEEP_PROCESSING();

			/* Stop SysTick.  Again, the time the SysTick is stopped for is
			accounted for as best it can be, but using the tickless mode will
			inevitably result in some tiny drift of the time maintained by the
			kernel with respect to calendar time. */
			portNVIC_SYSTICK_CTRL_REG = portNVIC_SYSTICK_CLK_BIT | portNVIC_SYSTICK_INT_BIT;

			if( ( portNVIC_SYSTICK_CTRL_REG & portNVIC_SYSTICK_COUNT_FLAG_BIT ) != 0 )
			{
				/* The tick interrupt has already executed, and the SysTick
				count reloaded with the portNVIC_SYSTICK_LOAD_REG value.
				Reset the portNVIC_SYSTICK_LOAD_REG with whatever remains of
				this tick period. */
				portNVIC_SYSTICK_LOAD_REG = ulTimerReloadValueForOneTick - ( ulReloadValue - portNVIC_SYSTICK_CURRENT_VALUE_REG );

				/* The tick interrupt handler will already have pended the tick
				processing in the kernel.  As the pending tick will be
				processed as soon as this function exits, the tick value
				maintained by the tick is stepped forward by one less than the
				time spent waiting. */
				ulCompleteTickPeriods = xExpectedIdleTime - 1UL;
			}
			else
			{
				/* Something other than the tick interrupt ended the sleep.
				Work out how long the sleep lasted. */
				ulCompletedSysTickIncrements = ( xExpectedIdleTime * ulTimerReloadValueForOneTick ) - portNVIC_SYSTICK_CURRENT_VALUE_REG;

				/* How many complete tick periods passed while the processor
				was waiting? */
				ulCompleteTickPeriods = ulCompletedSysTickIncrements / ulTimerReloadValueForOneTick;

				/* The reload value is set to whatever fraction of a single tick
				period remains. */
				portNVIC_SYSTICK_LOAD_REG = ( ( ulCompleteTickPeriods + 1 ) * ulTimerReloadValueForOneTick ) - ulCompletedSysTickIncrements;
			}

			/* Restart SysTick so it runs from portNVIC_SYSTICK_LOAD_REG
			again, then set portNVIC_SYSTICK_LOAD_REG back to its standard
			value. */
			portNVIC_SYSTICK_CURRENT_VALUE_REG = 0UL;
			portNVIC_SYSTICK_CTRL_REG = portNVIC_SYSTICK_CLK_BIT | portNVIC_SYSTICK_INT_BIT | portNVIC_SYSTICK_ENABLE_BIT;

			vTaskStepTick( ulCompleteTickPeriods );
		}
	}

#endif /* #if configUSE_TICKLESS_IDLE */
/*-----------------------------------------------------------*/

/*
 * Setup the systick timer to generate the tick interrupts at the required
 * frequency.
 */
void prvSetupTimerInterrupt( void )
{
	/* Calculate the constants required to configure the tick interrupt. */
	ulTimerReloadValueForOneTick = ( configSYSTICK_CLOCK_HZ / configTICK_RATE_HZ ) - 1UL;
	#if configUSE_TICKLESS_IDLE == 1
		xMaximumPossibleSuppressedTicks = 0xffffffUL / ( ( configSYSTICK_CLOCK_HZ / configTICK_RATE_HZ ) - 1UL );
	#endif /* configUSE_TICKLESS_IDLE */

	/* Configure SysTick to interrupt at the requested rate. */
	portNVIC_SYSTICK_LOAD_REG = ulTimerReloadValueForOneTick;
	portNVIC_SYSTICK_CTRL_REG = portNVIC_SYSTICK_CLK_BIT | portNVIC_SYSTICK_INT_BIT | portNVIC_SYSTICK_ENABLE_BIT;
}
/*-----------------------------------------------------------*/