/*
    FreeRTOS V8.2.3 - Copyright (C) 2015 Real Time Engineers Ltd.
    All rights reserved

    VISIT http://www.FreeRTOS.org TO ENSURE YOU ARE USING THE LATEST VERSION.

    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.  Full license text is available on the following
    link: http://www.freertos.org/a00114.html

    ***************************************************************************
     *                                                                       *
     *    FreeRTOS provides completely free yet professionally developed,    *
     *    robust, strictly quality controlled, supported, and cross          *
     *    platform software that is more than just the market leader, it     *
     *    is the industry's de facto standard.                               *
     *                                                                       *
     *    Help yourself get started quickly while simultaneously helping     *
     *    to support the FreeRTOS project by purchasing a FreeRTOS           *
     *    tutorial book, reference manual, or both:                          *
     *    http://www.FreeRTOS.org/Documentation                              *
     *                                                                       *
    ***************************************************************************

    http://www.FreeRTOS.org/FAQHelp.html - Having a problem?  Start by reading
    the FAQ page "My application does not run, what could be wrong?".  Have you
    defined configASSERT()?

    http://www.FreeRTOS.org/support - In return for receiving this top quality
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    http://www.FreeRTOS.org/training - Investing in training allows your team to
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    FreeRTOS training directly from Richard Barry, CEO of Real Time Engineers
    Ltd, and the world's leading authority on the world's leading RTOS.

    http://www.FreeRTOS.org/plus - A selection of FreeRTOS ecosystem products,
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    compatible FAT file system, and our tiny thread aware UDP/IP stack.

    http://www.FreeRTOS.org/labs - Where new FreeRTOS products go to incubate.
    Come and try FreeRTOS+TCP, our new open source TCP/IP stack for FreeRTOS.

    http://www.OpenRTOS.com - Real Time Engineers ltd. license FreeRTOS to High
    Integrity Systems ltd. to sell under the OpenRTOS brand.  Low cost OpenRTOS
    licenses offer ticketed support, indemnification and commercial middleware.

    http://www.SafeRTOS.com - High Integrity Systems also provide a safety
    engineered and independently SIL3 certified version for use in safety and
    mission critical applications that require provable dependability.

    1 tab == 4 spaces!
*/

/* Standard includes. */
#include <stdlib.h>

/* Scheduler includes. */
#include "FreeRTOS.h"
#include "task.h"

#if configUSE_PORT_OPTIMISED_TASK_SELECTION == 1
	/* Check the configuration. */
	#if( configMAX_PRIORITIES > 32 )
		#error configUSE_PORT_OPTIMISED_TASK_SELECTION can only be set to 1 when configMAX_PRIORITIES is less than or equal to 32.  It is very rare that a system requires more than 10 to 15 difference priorities as tasks that share a priority will time slice.
	#endif
#endif /* configUSE_PORT_OPTIMISED_TASK_SELECTION */

#ifndef configSETUP_TICK_INTERRUPT
	#error configSETUP_TICK_INTERRUPT() must be defined in FreeRTOSConfig.h to call the function that sets up the tick interrupt.
#endif

#ifndef configCLEAR_TICK_INTERRUPT
	#error configCLEAR_TICK_INTERRUPT must be defined in FreeRTOSConfig.h to clear which ever interrupt was used to generate the tick interrupt.
#endif

/* A critical section is exited when the critical section nesting count reaches
this value. */
#define portNO_CRITICAL_NESTING			( ( uint32_t ) 0 )

/* Tasks are not created with a floating point context, but can be given a
floating point context after they have been created.  A variable is stored as
part of the tasks context that holds portNO_FLOATING_POINT_CONTEXT if the task
does not have an FPU context, or any other value if the task does have an FPU
context. */
#define portNO_FLOATING_POINT_CONTEXT	( ( StackType_t ) 0 )

/* Constants required to setup the initial task context. */
#define portINITIAL_SPSR				( ( StackType_t ) 0x1f ) /* System mode, ARM mode, IRQ enabled FIQ enabled. */
#define portTHUMB_MODE_BIT				( ( StackType_t ) 0x20 )
#define portTHUMB_MODE_ADDRESS			( 0x01UL )

/* Masks all bits in the APSR other than the mode bits. */
#define portAPSR_MODE_BITS_MASK			( 0x1F )

/* The value of the mode bits in the APSR when the CPU is executing in user
mode. */
#define portAPSR_USER_MODE				( 0x10 )

/* Let the user override the pre-loading of the initial LR with the address of
prvTaskExitError() in case it messes up unwinding of the stack in the
debugger. */
#ifdef configTASK_RETURN_ADDRESS
	#define portTASK_RETURN_ADDRESS	configTASK_RETURN_ADDRESS
#else
	#define portTASK_RETURN_ADDRESS	prvTaskExitError
#endif

/*-----------------------------------------------------------*/

/*
 * Starts the first task executing.  This function is necessarily written in
 * assembly code so is implemented in portASM.s.
 */
extern void vPortRestoreTaskContext( void );

/*
 * Used to catch tasks that attempt to return from their implementing function.
 */
static void prvTaskExitError( void );

/*-----------------------------------------------------------*/

/* A variable is used to keep track of the critical section nesting.  This
variable has to be stored as part of the task context and must be initialised to
a non zero value to ensure interrupts don't inadvertently become unmasked before
the scheduler starts.  As it is stored as part of the task context it will
automatically be set to 0 when the first task is started. */
volatile uint32_t ulCriticalNesting = 9999UL;

/* Saved as part of the task context.  If ulPortTaskHasFPUContext is non-zero then
a floating point context must be saved and restored for the task. */
volatile uint32_t ulPortTaskHasFPUContext = pdFALSE;

/* Set to 1 to pend a context switch from an ISR. */
volatile uint32_t ulPortYieldRequired = pdFALSE;

/* Counts the interrupt nesting depth.  A context switch is only performed if
if the nesting depth is 0. */
volatile uint32_t ulPortInterruptNesting = 0UL;

/*-----------------------------------------------------------*/

/*
 * See header file for description.
 */
StackType_t *pxPortInitialiseStack( StackType_t *pxTopOfStack, TaskFunction_t pxCode, void *pvParameters )
{
	/* Setup the initial stack of the task.  The stack is set exactly as
	expected by the portRESTORE_CONTEXT() macro.

	The fist real value on the stack is the status register, which is set for
	system mode, with interrupts enabled.  A few NULLs are added first to ensure
	GDB does not try decoding a non-existent return address. */
	*pxTopOfStack = ( StackType_t ) NULL;
	pxTopOfStack--;
	*pxTopOfStack = ( StackType_t ) NULL;
	pxTopOfStack--;
	*pxTopOfStack = ( StackType_t ) NULL;
	pxTopOfStack--;
	*pxTopOfStack = ( StackType_t ) portINITIAL_SPSR;

	if( ( ( uint32_t ) pxCode & portTHUMB_MODE_ADDRESS ) != 0x00UL )
	{
		/* The task will start in THUMB mode. */
		*pxTopOfStack |= portTHUMB_MODE_BIT;
	}

	pxTopOfStack--;

	/* Next the return address, which in this case is the start of the task. */
	*pxTopOfStack = ( StackType_t ) pxCode;
	pxTopOfStack--;

	/* Next all the registers other than the stack pointer. */
	*pxTopOfStack = ( StackType_t ) portTASK_RETURN_ADDRESS;	/* R14 */
	pxTopOfStack--;
	*pxTopOfStack = ( StackType_t ) 0x12121212;	/* R12 */
	pxTopOfStack--;
	*pxTopOfStack = ( StackType_t ) 0x11111111;	/* R11 */
	pxTopOfStack--;
	*pxTopOfStack = ( StackType_t ) 0x10101010;	/* R10 */
	pxTopOfStack--;
	*pxTopOfStack = ( StackType_t ) 0x09090909;	/* R9 */
	pxTopOfStack--;
	*pxTopOfStack = ( StackType_t ) 0x08080808;	/* R8 */
	pxTopOfStack--;
	*pxTopOfStack = ( StackType_t ) 0x07070707;	/* R7 */
	pxTopOfStack--;
	*pxTopOfStack = ( StackType_t ) 0x06060606;	/* R6 */
	pxTopOfStack--;
	*pxTopOfStack = ( StackType_t ) 0x05050505;	/* R5 */
	pxTopOfStack--;
	*pxTopOfStack = ( StackType_t ) 0x04040404;	/* R4 */
	pxTopOfStack--;
	*pxTopOfStack = ( StackType_t ) 0x03030303;	/* R3 */
	pxTopOfStack--;
	*pxTopOfStack = ( StackType_t ) 0x02020202;	/* R2 */
	pxTopOfStack--;
	*pxTopOfStack = ( StackType_t ) 0x01010101;	/* R1 */
	pxTopOfStack--;
	*pxTopOfStack = ( StackType_t ) pvParameters; /* R0 */
	pxTopOfStack--;

	/* The task will start with a critical nesting count of 0 as interrupts are
	enabled. */
	*pxTopOfStack = portNO_CRITICAL_NESTING;
	pxTopOfStack--;

	/* The task will start without a floating point context.  A task that uses
	the floating point hardware must call vPortTaskUsesFPU() before executing
	any floating point instructions. */
	*pxTopOfStack = portNO_FLOATING_POINT_CONTEXT;

	return pxTopOfStack;
}
/*-----------------------------------------------------------*/

static void prvTaskExitError( void )
{
	/* A function that implements a task must not exit or attempt to return to
	its caller as there is nothing to return to.  If a task wants to exit it
	should instead call vTaskDelete( NULL ).

	Artificially force an assert() to be triggered if configASSERT() is
	defined, then stop here so application writers can catch the error. */
	configASSERT( ulPortInterruptNesting == ~0UL );
	portDISABLE_INTERRUPTS();
	for( ;; );
}
/*-----------------------------------------------------------*/

BaseType_t xPortStartScheduler( void )
{
uint32_t ulAPSR;

	/* Only continue if the CPU is not in User mode.  The CPU must be in a
	Privileged mode for the scheduler to start. */
	__asm volatile ( "MRS %0, APSR" : "=r" ( ulAPSR ) );
	ulAPSR &= portAPSR_MODE_BITS_MASK;
	configASSERT( ulAPSR != portAPSR_USER_MODE );

	if( ulAPSR != portAPSR_USER_MODE )
	{
		/* Start the timer that generates the tick ISR. */
		portDISABLE_INTERRUPTS();
		configSETUP_TICK_INTERRUPT();

		/* Start the first task executing. */
		vPortRestoreTaskContext();
	}

	/* Will only get here if xTaskStartScheduler() was called with the CPU in
	a non-privileged mode or the binary point register was not set to its lowest
	possible value.  prvTaskExitError() is referenced to prevent a compiler
	warning about it being defined but not referenced in the case that the user
	defines their own exit address. */
	( void ) prvTaskExitError;
	return 0;
}
/*-----------------------------------------------------------*/

void vPortEndScheduler( void )
{
	/* Not implemented in ports where there is nothing to return to.
	Artificially force an assert. */
	configASSERT( ulCriticalNesting == 1000UL );
}
/*-----------------------------------------------------------*/

void vPortEnterCritical( void )
{
	portDISABLE_INTERRUPTS();

	/* Now interrupts are disabled ulCriticalNesting can be accessed
	directly.  Increment ulCriticalNesting to keep a count of how many times
	portENTER_CRITICAL() has been called. */
	ulCriticalNesting++;

	/* This is not the interrupt safe version of the enter critical function so
	assert() if it is being called from an interrupt context.  Only API
	functions that end in "FromISR" can be used in an interrupt.  Only assert if
	the critical nesting count is 1 to protect against recursive calls if the
	assert function also uses a critical section. */
	if( ulCriticalNesting == 1 )
	{
		configASSERT( ulPortInterruptNesting == 0 );
	}
}
/*-----------------------------------------------------------*/

void vPortExitCritical( void )
{
	if( ulCriticalNesting > portNO_CRITICAL_NESTING )
	{
		/* Decrement the nesting count as the critical section is being
		exited. */
		ulCriticalNesting--;

		/* If the nesting level has reached zero then all interrupt
		priorities must be re-enabled. */
		if( ulCriticalNesting == portNO_CRITICAL_NESTING )
		{
			/* Critical nesting has reached zero so all interrupt priorities
			should be unmasked. */
			portENABLE_INTERRUPTS();
		}
	}
}
/*-----------------------------------------------------------*/

void FreeRTOS_Tick_Handler( void )
{
uint32_t ulInterruptStatus;

	ulInterruptStatus = portSET_INTERRUPT_MASK_FROM_ISR();

	/* Increment the RTOS tick. */
	if( xTaskIncrementTick() != pdFALSE )
	{
		ulPortYieldRequired = pdTRUE;
	}

	portCLEAR_INTERRUPT_MASK_FROM_ISR( ulInterruptStatus );

	configCLEAR_TICK_INTERRUPT();
}
/*-----------------------------------------------------------*/

void vPortTaskUsesFPU( void )
{
uint32_t ulInitialFPSCR = 0;

	/* A task is registering the fact that it needs an FPU context.  Set the
	FPU flag (which is saved as part of the task context). */
	ulPortTaskHasFPUContext = pdTRUE;

	/* Initialise the floating point status register. */
	__asm volatile ( "FMXR 	FPSCR, %0" :: "r" (ulInitialFPSCR) );
}
/*-----------------------------------------------------------*/