/*
    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 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();
		}
	}
}
/*-----------------------------------------------------------*/