/*
    FreeRTOS V6.0.2 - Copyright (C) 2010 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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*/


/*-----------------------------------------------------------
 * Implementation of functions defined in portable.h for the Atmel AT91R40008
 * port.
 *
 * Components that can be compiled to either ARM or THUMB mode are
 * contained in this file.  The ISR routines, which can only be compiled
 * to ARM mode are contained in portISR.c.
 *----------------------------------------------------------*/

/* Standard includes. */
#include <stdlib.h>

/* Scheduler includes. */
#include "FreeRTOS.h"
#include "task.h"

/* Hardware specific definitions. */
#include "AT91R40008.h"
#include "pio.h"
#include "aic.h"
#include "tc.h"

/* Constants required to setup the task context. */
#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 )
#define portNO_CRITICAL_SECTION_NESTING	( ( portSTACK_TYPE ) 0 )
#define portTICK_PRIORITY_6				( 6 )
/*-----------------------------------------------------------*/

/* Setup the timer to generate the tick interrupts. */
static void prvSetupTimerInterrupt( void );

/* 
 * The scheduler can only be started from ARM mode, so 
 * vPortISRStartFirstSTask() is defined in portISR.c. 
 */
extern void vPortISRStartFirstTask( void );

/*-----------------------------------------------------------*/

/* 
 * 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 last thing onto the stack is the status register, which is set for
	system mode, with interrupts enabled. */
	*pxTopOfStack = ( portSTACK_TYPE ) portINITIAL_SPSR;

	#ifdef THUMB_INTERWORK
	{
		/* We want the task to start in thumb mode. */
		*pxTopOfStack |= portTHUMB_MODE_BIT;
	}
	#endif

	pxTopOfStack--;

	/* Some optimisation levels use the stack differently to others.  This 
	means the 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_SECTION_NESTING;

	return pxTopOfStack;
}
/*-----------------------------------------------------------*/

portBASE_TYPE xPortStartScheduler( void )
{
	/* Start the timer that generates the tick ISR.  Interrupts are disabled
	here already. */
	prvSetupTimerInterrupt();

	/* Start the first task. */
	vPortISRStartFirstTask();	

	/* 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.  */
}
/*-----------------------------------------------------------*/

/*
 * Setup the tick timer to generate the tick interrupts at the required frequency.
 */
static void prvSetupTimerInterrupt( void )
{
volatile unsigned long ulDummy;

	/* Enable clock to the tick timer... */
	AT91C_BASE_PS->PS_PCER = portTIMER_CLK_ENABLE_BIT;

	/* Stop the tick timer... */
	portTIMER_REG_BASE_PTR->TC_CCR = TC_CLKDIS;

	/* Start with tick timer interrupts disabled... */
	portTIMER_REG_BASE_PTR->TC_IDR = 0xFFFFFFFF;

	/* Clear any pending tick timer interrupts... */
	ulDummy = portTIMER_REG_BASE_PTR->TC_SR;

	/* Store interrupt handler function address in tick timer vector register...
	The ISR installed depends on whether the preemptive or cooperative
	scheduler is being used. */
	#if configUSE_PREEMPTION == 1
	{
		extern void ( vPreemptiveTick )( void );
		AT91C_BASE_AIC->AIC_SVR[portTIMER_AIC_CHANNEL] = ( unsigned long ) vPreemptiveTick;
	}
	#else  // else use cooperative scheduler
	{
		extern void ( vNonPreemptiveTick )( void );
		AT91C_BASE_AIC->AIC_SVR[portTIMER_AIC_CHANNEL] = ( unsigned long ) vNonPreemptiveTick;
	}
	#endif

	/* Tick timer interrupt level-sensitive, priority 6... */
	AT91C_BASE_AIC->AIC_SMR[ portTIMER_AIC_CHANNEL ] = AIC_SRCTYPE_INT_LEVEL_SENSITIVE | portTICK_PRIORITY_6;

	/* Enable the tick timer interrupt...

	First at timer level */
	portTIMER_REG_BASE_PTR->TC_IER = TC_CPCS;

	/* Then at the AIC level. */
	AT91C_BASE_AIC->AIC_IECR = (1 << portTIMER_AIC_CHANNEL);

	/* Calculate timer compare value to achieve the desired tick rate... */
	if( (configCPU_CLOCK_HZ / (configTICK_RATE_HZ * 2) ) <= 0xFFFF )
	{
		/* The tick rate is fast enough for us to use the faster timer input
		clock (main clock / 2). */
		portTIMER_REG_BASE_PTR->TC_CMR = TC_WAVE | TC_CLKS_MCK2 | TC_BURST_NONE | TC_CPCTRG;
		portTIMER_REG_BASE_PTR->TC_RC  = configCPU_CLOCK_HZ / (configTICK_RATE_HZ * 2);
	}
	else
	{
		/* We must use a slower timer input clock (main clock / 8) because the
		tick rate is too slow for the faster input clock. */
		portTIMER_REG_BASE_PTR->TC_CMR = TC_WAVE | TC_CLKS_MCK8 | TC_BURST_NONE | TC_CPCTRG;
		portTIMER_REG_BASE_PTR->TC_RC  = configCPU_CLOCK_HZ / (configTICK_RATE_HZ * 8);
	}

	/* Start tick timer... */
	portTIMER_REG_BASE_PTR->TC_CCR = TC_SWTRG | TC_CLKEN;
}
/*-----------------------------------------------------------*/