/*
    FreeRTOS V6.0.0 - Copyright (C) 2009 Real Time Engineers Ltd.

    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 exception 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.
    Alternative commercial license and support terms are also available upon
    request.  See the licensing section of http://www.FreeRTOS.org for full
    license details.

    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 along
    with FreeRTOS; if not, write to the Free Software Foundation, Inc., 59
    Temple Place, Suite 330, Boston, MA  02111-1307  USA.


    ***************************************************************************
    *                                                                         *
    * The FreeRTOS eBook and reference manual are available to purchase for a *
    * small fee. Help yourself get started quickly while also helping the     *
    * FreeRTOS project! See http://www.FreeRTOS.org/Documentation for details *
    *                                                                         *
    ***************************************************************************

    1 tab == 4 spaces!

    Please ensure to read the configuration and relevant port sections of the
    online documentation.

    http://www.FreeRTOS.org - Documentation, latest information, license and
    contact details.

    http://www.SafeRTOS.com - A version that is certified for use in safety
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*/

/*-----------------------------------------------------------
 * Implementation of functions defined in portable.h for the PIC32MX port.
  *----------------------------------------------------------*/

/* Scheduler include files. */
#include "FreeRTOS.h"
#include "task.h"

/* Hardware specifics. */
#define portTIMER_PRESCALE 8

/* Bits within various registers. */
#define portIE_BIT					( 0x00000001 )
#define portEXL_BIT					( 0x00000002 )
#define portSW0_ENABLE				( 0x00000100 )

/* The EXL bit is set to ensure interrupts do not occur while the context of
the first task is being restored. */
#define portINITIAL_SR				( portIE_BIT | portEXL_BIT | portSW0_ENABLE )

/* Records the interrupt nesting depth.  This starts at one as it will be
decremented to 0 when the first task starts. */
volatile unsigned portBASE_TYPE uxInterruptNesting = 0x01;

/* Stores the task stack pointer when a switch is made to use the system stack. */
unsigned portBASE_TYPE uxSavedTaskStackPointer = 0;

/* The stack used by interrupt service routines that cause a context switch. */
portSTACK_TYPE xISRStack[ configISR_STACK_SIZE ] = { 0 };

/* The top of stack value ensures there is enough space to store 6 registers on 
the callers stack, as some functions seem to want to do this. */
const portBASE_TYPE * const xISRStackTop = &( xISRStack[ configISR_STACK_SIZE - 7 ] );

/* Place the prototype here to ensure the interrupt vector is correctly installed. */
extern void __attribute__( (interrupt(ipl1), vector(_TIMER_1_VECTOR))) vT1InterruptHandler( void );

/*
 * The software interrupt handler that performs the yield.
 */
void __attribute__( (interrupt(ipl1), vector(_CORE_SOFTWARE_0_VECTOR))) vPortYieldISR( void );

/*-----------------------------------------------------------*/

/* 
 * See header file for description. 
 */
portSTACK_TYPE *pxPortInitialiseStack( portSTACK_TYPE *pxTopOfStack, pdTASK_CODE pxCode, void *pvParameters )
{
	*pxTopOfStack = (portSTACK_TYPE) 0xDEADBEEF;
	pxTopOfStack--;

	*pxTopOfStack = (portSTACK_TYPE) 0x12345678;	/* Word to which the stack pointer will be left pointing after context restore. */
	pxTopOfStack--;

	*pxTopOfStack = (portSTACK_TYPE) _CP0_GET_CAUSE();
	pxTopOfStack--;

	*pxTopOfStack = (portSTACK_TYPE) portINITIAL_SR; /* CP0_STATUS */
	pxTopOfStack--;

	*pxTopOfStack = (portSTACK_TYPE) pxCode; 		/* CP0_EPC */
	pxTopOfStack--;

	*pxTopOfStack = (portSTACK_TYPE) NULL;  		/* ra */
	pxTopOfStack -= 15;

	*pxTopOfStack = (portSTACK_TYPE) pvParameters; /* Parameters to pass in */
	pxTopOfStack -= 14;

	*pxTopOfStack = (portSTACK_TYPE) 0x00000000; 	/* critical nesting level - no longer used. */
	pxTopOfStack--;
	
	return pxTopOfStack;
}
/*-----------------------------------------------------------*/

/*
 * Setup a timer for a regular tick.
 */
void prvSetupTimerInterrupt( void )
{
const unsigned long ulCompareMatch = ( (configPERIPHERAL_CLOCK_HZ / portTIMER_PRESCALE) / configTICK_RATE_HZ ) - 1;

	OpenTimer1( ( T1_ON | T1_PS_1_8 | T1_SOURCE_INT ), ulCompareMatch );
	ConfigIntTimer1( T1_INT_ON | configKERNEL_INTERRUPT_PRIORITY );
}
/*-----------------------------------------------------------*/

void vPortEndScheduler(void)
{
	/* It is unlikely that the scheduler for the PIC port will get stopped
	once running.  If required disable the tick interrupt here, then return 
	to xPortStartScheduler(). */
	for( ;; );
}
/*-----------------------------------------------------------*/

portBASE_TYPE xPortStartScheduler( void )
{
extern void vPortStartFirstTask( void );
extern void *pxCurrentTCB;

	/* Setup the software interrupt. */
	mConfigIntCoreSW0( CSW_INT_ON | CSW_INT_PRIOR_1 | CSW_INT_SUB_PRIOR_0 );

	/* Setup the timer to generate the tick.  Interrupts will have been 
	disabled by the time we get here. */
	prvSetupTimerInterrupt();

	/* Kick off the highest priority task that has been created so far. 
	Its stack location is loaded into uxSavedTaskStackPointer. */
	uxSavedTaskStackPointer = *( unsigned portBASE_TYPE * ) pxCurrentTCB;
	vPortStartFirstTask();

	/* Should never get here as the tasks will now be executing. */
	return pdFALSE;
}
/*-----------------------------------------------------------*/

void vPortIncrementTick( void )
{
unsigned portBASE_TYPE uxSavedStatus;

	uxSavedStatus = uxPortSetInterruptMaskFromISR();
		vTaskIncrementTick();
	vPortClearInterruptMaskFromISR( uxSavedStatus );
	
	/* If we are using the preemptive scheduler then we might want to select
	a different task to execute. */
	#if configUSE_PREEMPTION == 1
		SetCoreSW0();
	#endif /* configUSE_PREEMPTION */

	/* Clear timer 0 interrupt. */
	mT1ClearIntFlag();
}
/*-----------------------------------------------------------*/

unsigned portBASE_TYPE uxPortSetInterruptMaskFromISR( void )
{
unsigned portBASE_TYPE uxSavedStatusRegister;

	asm volatile ( "di" );
	uxSavedStatusRegister = _CP0_GET_STATUS() | 0x01;
	_CP0_SET_STATUS( ( uxSavedStatusRegister | ( configMAX_SYSCALL_INTERRUPT_PRIORITY << portIPL_SHIFT ) ) );

	return uxSavedStatusRegister;
}
/*-----------------------------------------------------------*/

void vPortClearInterruptMaskFromISR( unsigned portBASE_TYPE uxSavedStatusRegister )
{
	_CP0_SET_STATUS( uxSavedStatusRegister );
}
/*-----------------------------------------------------------*/