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/*

    FreeRTOS V6.1.1 - Copyright (C) 2011 Real Time Engineers Ltd.

    ***************************************************************************

    *                                                                         *

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    * A pdf reference manual is also available.  Both are usually delivered   *

    * to your inbox within 20 minutes to two hours when purchased between 8am *

    * and 8pm GMT (although please allow up to 24 hours in case of            *

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    ***************************************************************************

    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.

    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!

    http://www.FreeRTOS.org - Documentation, latest information, license and

    contact details.

    http://www.SafeRTOS.com - A version that is certified for use in safety

    critical systems.

    http://www.OpenRTOS.com - Commercial support, development, porting,

    licensing and training services.

*/

/*

        Change from V4.2.1:

        + Introduced usage of configKERNEL_INTERRUPT_PRIORITY macro to set the

          interrupt priority used by the kernel.

*/

/*-----------------------------------------------------------

 * Implementation of functions defined in portable.h for the ARM CM3 port.

 *----------------------------------------------------------*/

/* Scheduler includes. */

#include "FreeRTOS.h"

#include "task.h"

/* Constants required to manipulate the NVIC. */

#define portNVIC_SYSTICK_CTRL           ( ( volatile unsigned long *) 0xe000e010 )

#define portNVIC_SYSTICK_LOAD           ( ( volatile unsigned long *) 0xe000e014 )

#define portNVIC_INT_CTRL                       ( ( volatile unsigned long *) 0xe000ed04 )

#define portNVIC_SYSPRI2                        ( ( volatile unsigned long *) 0xe000ed20 )

#define portNVIC_SYSTICK_CLK            0x00000004

#define portNVIC_SYSTICK_INT            0x00000002

#define portNVIC_SYSTICK_ENABLE         0x00000001

#define portNVIC_PENDSVSET                      0x10000000

#define portNVIC_PENDSV_PRI                     ( ( ( unsigned long ) configKERNEL_INTERRUPT_PRIORITY ) << 16 )

#define portNVIC_SYSTICK_PRI            ( ( ( unsigned long ) configKERNEL_INTERRUPT_PRIORITY ) << 24 )

/* Constants required to set up the initial stack. */

#define portINITIAL_XPSR                        ( 0x01000000 )

/* For backward compatibility, ensure configKERNEL_INTERRUPT_PRIORITY is

defined.  The value 255 should also ensure backward compatibility.

FreeRTOS.org versions prior to V4.3.0 did not include this definition. */

#ifndef configKERNEL_INTERRUPT_PRIORITY

        #define configKERNEL_INTERRUPT_PRIORITY 0

#endif

/* 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 xPortSysTickHandler( void );

/*

 * Start first task is a separate function so it can be tested in isolation.

 */

extern void vPortStartFirstTask( void );

/*-----------------------------------------------------------*/

/*

 * 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;

}

/*-----------------------------------------------------------*/

/*

 * See header file for description.

 */

portBASE_TYPE xPortStartScheduler( void )

{

        /* Make PendSV and SysTick the lowest priority interrupts. */

        *(portNVIC_SYSPRI2) |= portNVIC_PENDSV_PRI;

        *(portNVIC_SYSPRI2) |= 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. */

        vPortStartFirstTask();

        /* 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) = portNVIC_PENDSVSET;

}

/*-----------------------------------------------------------*/

void vPortEnterCritical( void )

{

        portDISABLE_INTERRUPTS();

        uxCriticalNesting++;

}

/*-----------------------------------------------------------*/

void vPortExitCritical( void )

{

        uxCriticalNesting--;

        if( uxCriticalNesting == 0 )

        {

                portENABLE_INTERRUPTS();

        }

}

/*-----------------------------------------------------------*/

void xPortSysTickHandler( void )

{

unsigned long ulDummy;

        /* If using preemption, also force a context switch. */

        #if configUSE_PREEMPTION == 1

                *(portNVIC_INT_CTRL) = portNVIC_PENDSVSET;

        #endif

        ulDummy = portSET_INTERRUPT_MASK_FROM_ISR();

        {

                vTaskIncrementTick();

        }

        portCLEAR_INTERRUPT_MASK_FROM_ISR( ulDummy );

}

/*-----------------------------------------------------------*/

/*

 * Setup the systick timer to generate the tick interrupts at the required

 * frequency.

 */

void prvSetupTimerInterrupt( void )

{

        /* Configure SysTick to interrupt at the requested rate. */

        *(portNVIC_SYSTICK_LOAD) = ( configCPU_CLOCK_HZ / configTICK_RATE_HZ ) - 1UL;

        *(portNVIC_SYSTICK_CTRL) = portNVIC_SYSTICK_CLK | portNVIC_SYSTICK_INT | portNVIC_SYSTICK_ENABLE;

}

/*-----------------------------------------------------------*/