/*
    FreeRTOS V9.0.0 - Copyright (C) 2016 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
    embedded software for free we request you assist our global community by
    participating in the support forum.

    http://www.FreeRTOS.org/training - Investing in training allows your team to
    be as productive as possible as early as possible.  Now you can receive
    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,
    including FreeRTOS+Trace - an indispensable productivity tool, a DOS
    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>

/* IAR includes. */
#include <intrinsics.h>

/* Scheduler includes. */
#include "FreeRTOS.h"
#include "task.h"

#ifndef configINTERRUPT_CONTROLLER_BASE_ADDRESS
	#error configINTERRUPT_CONTROLLER_BASE_ADDRESS must be defined.  See http://www.freertos.org/Using-FreeRTOS-on-Cortex-A-Embedded-Processors.html
#endif

#ifndef configINTERRUPT_CONTROLLER_CPU_INTERFACE_OFFSET
	#error configINTERRUPT_CONTROLLER_CPU_INTERFACE_OFFSET must be defined.  See http://www.freertos.org/Using-FreeRTOS-on-Cortex-A-Embedded-Processors.html
#endif

#ifndef configUNIQUE_INTERRUPT_PRIORITIES
	#error configUNIQUE_INTERRUPT_PRIORITIES must be defined.  See http://www.freertos.org/Using-FreeRTOS-on-Cortex-A-Embedded-Processors.html
#endif

#ifndef configSETUP_TICK_INTERRUPT
	#error configSETUP_TICK_INTERRUPT() must be defined.  See http://www.freertos.org/Using-FreeRTOS-on-Cortex-A-Embedded-Processors.html
#endif /* configSETUP_TICK_INTERRUPT */

#ifndef configMAX_API_CALL_INTERRUPT_PRIORITY
	#error configMAX_API_CALL_INTERRUPT_PRIORITY must be defined.  See http://www.freertos.org/Using-FreeRTOS-on-Cortex-A-Embedded-Processors.html
#endif

#if configMAX_API_CALL_INTERRUPT_PRIORITY == 0
	#error configMAX_API_CALL_INTERRUPT_PRIORITY must not be set to 0
#endif

#if configMAX_API_CALL_INTERRUPT_PRIORITY > configUNIQUE_INTERRUPT_PRIORITIES
	#error configMAX_API_CALL_INTERRUPT_PRIORITY must be less than or equal to configUNIQUE_INTERRUPT_PRIORITIES as the lower the numeric priority value the higher the logical interrupt priority
#endif

#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 */

/* In case security extensions are implemented. */
#if configMAX_API_CALL_INTERRUPT_PRIORITY <= ( configUNIQUE_INTERRUPT_PRIORITIES / 2 )
	#error configMAX_API_CALL_INTERRUPT_PRIORITY must be greater than ( configUNIQUE_INTERRUPT_PRIORITIES / 2 )
#endif

#ifndef configCLEAR_TICK_INTERRUPT
	#define configCLEAR_TICK_INTERRUPT()
#endif

/* A critical section is exited when the critical section nesting count reaches
this value. */
#define portNO_CRITICAL_NESTING			( ( uint32_t ) 0 )

/* In all GICs 255 can be written to the priority mask register to unmask all
(but the lowest) interrupt priority. */
#define portUNMASK_VALUE				( 0xFFUL )

/* 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, interrupts enabled. */
#define portTHUMB_MODE_BIT				( ( StackType_t ) 0x20 )
#define portTHUMB_MODE_ADDRESS			( 0x01UL )

/* Used by portASSERT_IF_INTERRUPT_PRIORITY_INVALID() when ensuring the binary
point is zero. */
#define portBINARY_POINT_BITS			( ( uint8_t ) 0x03 )

/* 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 )

/* Macro to unmask all interrupt priorities. */
#define portCLEAR_INTERRUPT_MASK()											\
{																			\
	__disable_irq();														\
	portICCPMR_PRIORITY_MASK_REGISTER = portUNMASK_VALUE;					\
	__asm(	"DSB		\n"													\
			"ISB		\n" );												\
	__enable_irq();															\
}

/*-----------------------------------------------------------*/

/*
 * 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. */
uint32_t ulPortTaskHasFPUContext = pdFALSE;

/* Set to 1 to pend a context switch from an ISR. */
uint32_t ulPortYieldRequired = pdFALSE;

/* Counts the interrupt nesting depth.  A context switch is only performed if
if the nesting depth is 0. */
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 = NULL;
	pxTopOfStack--;
	*pxTopOfStack = NULL;
	pxTopOfStack--;
	*pxTopOfStack = 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 ) prvTaskExitError;	/* 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 )
	{
		/* Only continue if the binary point value is set to its lowest possible
		setting.  See the comments in vPortValidateInterruptPriority() below for
		more information. */
		configASSERT( ( portICCBPR_BINARY_POINT_REGISTER & portBINARY_POINT_BITS ) <= portMAX_BINARY_POINT_VALUE );

		if( ( portICCBPR_BINARY_POINT_REGISTER & portBINARY_POINT_BITS ) <= portMAX_BINARY_POINT_VALUE )
		{
			/* Start the timer that generates the tick ISR. */
			configSETUP_TICK_INTERRUPT();

			__enable_irq();
			vPortRestoreTaskContext();
		}
	}

	/* Will only get here if vTaskStartScheduler() was called with the CPU in
	a non-privileged mode or the binary point register was not set to its lowest
	possible value. */
	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 )
{
	/* Disable interrupts as per portDISABLE_INTERRUPTS(); 	*/
	ulPortSetInterruptMask();

	/* 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. */
			portCLEAR_INTERRUPT_MASK();
		}
	}
}
/*-----------------------------------------------------------*/

void FreeRTOS_Tick_Handler( void )
{
	/* Set interrupt mask before altering scheduler structures.   The tick
	handler runs at the lowest priority, so interrupts cannot already be masked,
	so there is no need to save and restore the current mask value. */
	__disable_irq();
	portICCPMR_PRIORITY_MASK_REGISTER = ( uint32_t ) ( configMAX_API_CALL_INTERRUPT_PRIORITY << portPRIORITY_SHIFT );
	__asm(	"DSB		\n"
			"ISB		\n" );
	__enable_irq();

	/* Increment the RTOS tick. */
	if( xTaskIncrementTick() != pdFALSE )
	{
		ulPortYieldRequired = pdTRUE;
	}

	/* Ensure all interrupt priorities are active again. */
	portCLEAR_INTERRUPT_MASK();
	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( "FMXR 	FPSCR, %0" :: "r" (ulInitialFPSCR) );
}
/*-----------------------------------------------------------*/

void vPortClearInterruptMask( uint32_t ulNewMaskValue )
{
	if( ulNewMaskValue == pdFALSE )
	{
		portCLEAR_INTERRUPT_MASK();
	}
}
/*-----------------------------------------------------------*/

uint32_t ulPortSetInterruptMask( void )
{
uint32_t ulReturn;

	__disable_irq();
	if( portICCPMR_PRIORITY_MASK_REGISTER == ( uint32_t ) ( configMAX_API_CALL_INTERRUPT_PRIORITY << portPRIORITY_SHIFT ) )
	{
		/* Interrupts were already masked. */
		ulReturn = pdTRUE;
	}
	else
	{
		ulReturn = pdFALSE;
		portICCPMR_PRIORITY_MASK_REGISTER = ( uint32_t ) ( configMAX_API_CALL_INTERRUPT_PRIORITY << portPRIORITY_SHIFT );
		__asm(	"DSB		\n"
				"ISB		\n" );
	}
	__enable_irq();

	return ulReturn;
}
/*-----------------------------------------------------------*/

#if( configASSERT_DEFINED == 1 )

	void vPortValidateInterruptPriority( void )
	{
		/* The following assertion will fail if a service routine (ISR) for
		an interrupt that has been assigned a priority above
		configMAX_SYSCALL_INTERRUPT_PRIORITY calls an ISR safe FreeRTOS API
		function.  ISR safe FreeRTOS API functions must *only* be called
		from interrupts that have been assigned a priority at or below
		configMAX_SYSCALL_INTERRUPT_PRIORITY.

		Numerically low interrupt priority numbers represent logically high
		interrupt priorities, therefore the priority of the interrupt must
		be set to a value equal to or numerically *higher* than
		configMAX_SYSCALL_INTERRUPT_PRIORITY.

		FreeRTOS maintains separate thread and ISR API functions to ensure
		interrupt entry is as fast and simple as possible.

		The following links provide detailed information:
		http://www.freertos.org/RTOS-Cortex-M3-M4.html
		http://www.freertos.org/FAQHelp.html */
		configASSERT( portICCRPR_RUNNING_PRIORITY_REGISTER >= ( uint32_t ) ( configMAX_API_CALL_INTERRUPT_PRIORITY << portPRIORITY_SHIFT ) );

		/* Priority grouping:  The interrupt controller (GIC) allows the bits
		that define each interrupt's priority to be split between bits that
		define the interrupt's pre-emption priority bits and bits that define
		the interrupt's sub-priority.  For simplicity all bits must be defined
		to be pre-emption priority bits.  The following assertion will fail if
		this is not the case (if some bits represent a sub-priority).

		The priority grouping is configured by the GIC's binary point register
		(ICCBPR).  Writting 0 to ICCBPR will ensure it is set to its lowest
		possible value (which may be above 0). */
		configASSERT( ( portICCBPR_BINARY_POINT_REGISTER & portBINARY_POINT_BITS ) <= portMAX_BINARY_POINT_VALUE );
	}

#endif /* configASSERT_DEFINED */