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/*

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

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

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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.

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

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*/

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

 * Implementation of functions defined in portable.h for the Atmel ARM7 port.

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

/* Standard includes. */

#include <stdlib.h>

/* Scheduler includes. */

#include "FreeRTOS.h"

#include "task.h"

/* Constants required to setup the initial stack. */

#define portINITIAL_SPSR                                ( ( portSTACK_TYPE ) 0x1f ) /* System mode, ARM mode, interrupts enabled. */

#define portTHUMB_MODE_BIT                              ( ( portSTACK_TYPE ) 0x20 )

#define portINSTRUCTION_SIZE                    ( ( portSTACK_TYPE ) 4 )

/* Constants required to setup the PIT. */

#define portPIT_CLOCK_DIVISOR                   ( ( unsigned long ) 16 )

#define portPIT_COUNTER_VALUE                   ( ( ( configCPU_CLOCK_HZ / portPIT_CLOCK_DIVISOR ) / 1000UL ) * portTICK_RATE_MS )

/* Constants required to handle critical sections. */

#define portNO_CRITICAL_NESTING                 ( ( unsigned long ) 0 )

#define portINT_LEVEL_SENSITIVE  0

#define portPIT_ENABLE          ( ( unsigned short ) 0x1 << 24 )

#define portPIT_INT_ENABLE      ( ( unsigned short ) 0x1 << 25 )

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

/* Setup the PIT to generate the tick interrupts. */

static void prvSetupTimerInterrupt( void );

/* ulCriticalNesting will get set to zero when the first task starts.  It

cannot be initialised to 0 as this will cause interrupts to be enabled

during the kernel initialisation process. */

unsigned long ulCriticalNesting = ( unsigned long ) 9999;

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

/*

 * Initialise the stack of a task to look exactly as if a call to

 * portSAVE_CONTEXT had been called.

 *

 * See header file for description.

 */

portSTACK_TYPE *pxPortInitialiseStack( portSTACK_TYPE *pxTopOfStack, pdTASK_CODE pxCode, void *pvParameters )

{

portSTACK_TYPE *pxOriginalTOS;

        pxOriginalTOS = pxTopOfStack;

        /* Setup the initial stack of the task.  The stack is set exactly as

        expected by the portRESTORE_CONTEXT() macro. */

        /* First on the stack is the return address - which in this case is the

        start of the task.  The offset is added to make the return address appear

        as it would within an IRQ ISR. */

        *pxTopOfStack = ( portSTACK_TYPE ) pxCode + portINSTRUCTION_SIZE;

        pxTopOfStack--;

        *pxTopOfStack = ( portSTACK_TYPE ) 0xaaaaaaaa;  /* R14 */

        pxTopOfStack--;

        *pxTopOfStack = ( portSTACK_TYPE ) pxOriginalTOS; /* Stack used when task starts goes in R13. */

        pxTopOfStack--;

        *pxTopOfStack = ( portSTACK_TYPE ) 0x12121212;  /* R12 */

        pxTopOfStack--;

        *pxTopOfStack = ( portSTACK_TYPE ) 0x11111111;  /* R11 */

        pxTopOfStack--;

        *pxTopOfStack = ( portSTACK_TYPE ) 0x10101010;  /* R10 */

        pxTopOfStack--;

        *pxTopOfStack = ( portSTACK_TYPE ) 0x09090909;  /* R9 */

        pxTopOfStack--;

        *pxTopOfStack = ( portSTACK_TYPE ) 0x08080808;  /* R8 */

        pxTopOfStack--;

        *pxTopOfStack = ( portSTACK_TYPE ) 0x07070707;  /* R7 */

        pxTopOfStack--;

        *pxTopOfStack = ( portSTACK_TYPE ) 0x06060606;  /* R6 */

        pxTopOfStack--;

        *pxTopOfStack = ( portSTACK_TYPE ) 0x05050505;  /* R5 */

        pxTopOfStack--;

        *pxTopOfStack = ( portSTACK_TYPE ) 0x04040404;  /* R4 */

        pxTopOfStack--;

        *pxTopOfStack = ( portSTACK_TYPE ) 0x03030303;  /* R3 */

        pxTopOfStack--;

        *pxTopOfStack = ( portSTACK_TYPE ) 0x02020202;  /* R2 */

        pxTopOfStack--;

        *pxTopOfStack = ( portSTACK_TYPE ) 0x01010101;  /* R1 */

        pxTopOfStack--;

        /* When the task starts is will expect to find the function parameter in

        R0. */

        *pxTopOfStack = ( portSTACK_TYPE ) pvParameters; /* R0 */

        pxTopOfStack--;

        /* The status register is set for system mode, with interrupts enabled. */

        *pxTopOfStack = ( portSTACK_TYPE ) portINITIAL_SPSR;

        if( ( ( unsigned long ) pxCode & 0x01UL ) != 0x00UL )

        {

                /* We want the task to start in thumb mode. */

                *pxTopOfStack |= portTHUMB_MODE_BIT;

        }

        pxTopOfStack--;

        /* Interrupt flags cannot always be stored on the stack and will

        instead be stored in a variable, which is then saved as part of the

        tasks context. */

        *pxTopOfStack = portNO_CRITICAL_NESTING;

        return pxTopOfStack;

}

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

portBASE_TYPE xPortStartScheduler( void )

{

extern void vPortStartFirstTask( void );

        /* Start the timer that generates the tick ISR.  Interrupts are disabled

        here already. */

        prvSetupTimerInterrupt();

        /* Start the first task. */

        vPortStartFirstTask();

        /* Should not get here! */

        return 0;

}

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

void vPortEndScheduler( void )

{

        /* It is unlikely that the ARM port will require this function as there

        is nothing to return to.  */

}

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

#if configUSE_PREEMPTION == 0

        /* The cooperative scheduler requires a normal IRQ service routine to

        simply increment the system tick. */

        static __arm __irq void vPortNonPreemptiveTick( void );

        static __arm __irq void vPortNonPreemptiveTick( void )

        {

                unsigned long ulDummy;

                /* Increment the tick count - which may wake some tasks but as the

                preemptive scheduler is not being used any woken task is not given

                processor time no matter what its priority. */

                vTaskIncrementTick();

                /* Clear the PIT interrupt. */

                ulDummy = AT91C_BASE_PITC->PITC_PIVR;

                /* End the interrupt in the AIC. */

                AT91C_BASE_AIC->AIC_EOICR = ulDummy;

        }

#else

        /* Currently the IAR port requires the preemptive tick function to be

        defined in an asm file. */

#endif

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

static void prvSetupTimerInterrupt( void )

{

AT91PS_PITC pxPIT = AT91C_BASE_PITC;

        /* Setup the AIC for PIT interrupts.  The interrupt routine chosen depends

        on whether the preemptive or cooperative scheduler is being used. */

        #if configUSE_PREEMPTION == 0

                AT91F_AIC_ConfigureIt( AT91C_BASE_AIC, AT91C_ID_SYS, AT91C_AIC_PRIOR_HIGHEST, portINT_LEVEL_SENSITIVE, ( void (*)(void) ) vPortNonPreemptiveTick );

        #else

                extern void ( vPortPreemptiveTick )( void );

                AT91F_AIC_ConfigureIt( AT91C_BASE_AIC, AT91C_ID_SYS, AT91C_AIC_PRIOR_HIGHEST, portINT_LEVEL_SENSITIVE, ( void (*)(void) ) vPortPreemptiveTick );

        #endif

        /* Configure the PIT period. */

        pxPIT->PITC_PIMR = portPIT_ENABLE | portPIT_INT_ENABLE | portPIT_COUNTER_VALUE;

        /* Enable the interrupt.  Global interrupts are disables at this point so

        this is safe. */

        AT91F_AIC_EnableIt( AT91C_BASE_AIC, AT91C_ID_SYS );

}

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

void vPortEnterCritical( void )

{

        /* Disable interrupts first! */

        __disable_interrupt();

        /* 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++;

}

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

void vPortExitCritical( void )

{

        if( ulCriticalNesting > portNO_CRITICAL_NESTING )

        {

                /* Decrement the nesting count as we are leaving a critical section. */

                ulCriticalNesting--;

                /* If the nesting level has reached zero then interrupts should be

                re-enabled. */

                if( ulCriticalNesting == portNO_CRITICAL_NESTING )

                {

                        __enable_interrupt();

                }

        }

}

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