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    ***************************************************************************
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    ***************************************************************************

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*/

/*-----------------------------------------------------------
 * Implementation of functions defined in portable.h for the MicroBlaze port.
 *----------------------------------------------------------*/


/* Scheduler includes. */
#include "FreeRTOS.h"
#include "task.h"

/* Standard includes. */
#include <string.h>

/* Hardware includes. */
#include <xintc.h>
#include <xintc_i.h>
#include <xtmrctr.h>

/* Tasks are started with interrupts enabled. */
#define portINITIAL_MSR_STATE		( ( StackType_t ) 0x02 )

/* Tasks are started with a critical section nesting of 0 - however prior
to the scheduler being commenced we don't want the critical nesting level
to reach zero, so it is initialised to a high value. */
#define portINITIAL_NESTING_VALUE	( 0xff )

/* Our hardware setup only uses one counter. */
#define portCOUNTER_0 				0

/* The stack used by the ISR is filled with a known value to assist in
debugging. */
#define portISR_STACK_FILL_VALUE	0x55555555

/* Counts the nesting depth of calls to portENTER_CRITICAL().  Each task 
maintains it's own count, so this variable is saved as part of the task
context. */
volatile UBaseType_t uxCriticalNesting = portINITIAL_NESTING_VALUE;

/* To limit the amount of stack required by each task, this port uses a
separate stack for interrupts. */
uint32_t *pulISRStack;

/*-----------------------------------------------------------*/

/*
 * Sets up the periodic ISR used for the RTOS tick.  This uses timer 0, but
 * could have alternatively used the watchdog timer or timer 1.
 */
static void prvSetupTimerInterrupt( void );
/*-----------------------------------------------------------*/

/* 
 * Initialise the stack of a task to look exactly as if a call to 
 * portSAVE_CONTEXT had been made.
 * 
 * See the header file portable.h.
 */
StackType_t *pxPortInitialiseStack( StackType_t *pxTopOfStack, TaskFunction_t pxCode, void *pvParameters )
{
extern void *_SDA2_BASE_, *_SDA_BASE_;
const uint32_t ulR2 = ( uint32_t ) &_SDA2_BASE_;
const uint32_t ulR13 = ( uint32_t ) &_SDA_BASE_;

	/* Place a few bytes of known values on the bottom of the stack. 
	This is essential for the Microblaze port and these lines must
	not be omitted.  The parameter value will overwrite the 
	0x22222222 value during the function prologue. */
	*pxTopOfStack = ( StackType_t ) 0x11111111;
	pxTopOfStack--;
	*pxTopOfStack = ( StackType_t ) 0x22222222;
	pxTopOfStack--;
	*pxTopOfStack = ( StackType_t ) 0x33333333;
	pxTopOfStack--; 

	/* First stack an initial value for the critical section nesting.  This
	is initialised to zero as tasks are started with interrupts enabled. */
	*pxTopOfStack = ( StackType_t ) 0x00;	/* R0. */

	/* Place an initial value for all the general purpose registers. */
	pxTopOfStack--;
	*pxTopOfStack = ( StackType_t ) ulR2;	/* R2 - small data area. */
	pxTopOfStack--;
	*pxTopOfStack = ( StackType_t ) 0x03;	/* R3. */
	pxTopOfStack--;
	*pxTopOfStack = ( StackType_t ) 0x04;	/* R4. */
	pxTopOfStack--;
	*pxTopOfStack = ( StackType_t ) pvParameters;/* R5 contains the function call parameters. */
	pxTopOfStack--;
	*pxTopOfStack = ( StackType_t ) 0x06;	/* R6. */
	pxTopOfStack--;
	*pxTopOfStack = ( StackType_t ) 0x07;	/* R7. */
	pxTopOfStack--;
	*pxTopOfStack = ( StackType_t ) 0x08;	/* R8. */
	pxTopOfStack--;
	*pxTopOfStack = ( StackType_t ) 0x09;	/* R9. */
	pxTopOfStack--;
	*pxTopOfStack = ( StackType_t ) 0x0a;	/* R10. */
	pxTopOfStack--;
	*pxTopOfStack = ( StackType_t ) 0x0b;	/* R11. */
	pxTopOfStack--;
	*pxTopOfStack = ( StackType_t ) 0x0c;	/* R12. */
	pxTopOfStack--;
	*pxTopOfStack = ( StackType_t ) ulR13;	/* R13 - small data read write area. */
	pxTopOfStack--;
	*pxTopOfStack = ( StackType_t ) pxCode;	/* R14. */
	pxTopOfStack--;
	*pxTopOfStack = ( StackType_t ) 0x0f;	/* R15. */
	pxTopOfStack--;
	*pxTopOfStack = ( StackType_t ) 0x10;	/* R16. */
	pxTopOfStack--;
	*pxTopOfStack = ( StackType_t ) 0x11;	/* R17. */
	pxTopOfStack--;
	*pxTopOfStack = ( StackType_t ) 0x12;	/* R18. */
	pxTopOfStack--;
	*pxTopOfStack = ( StackType_t ) 0x13;	/* R19. */
	pxTopOfStack--;
	*pxTopOfStack = ( StackType_t ) 0x14;	/* R20. */
	pxTopOfStack--;
	*pxTopOfStack = ( StackType_t ) 0x15;	/* R21. */
	pxTopOfStack--;
	*pxTopOfStack = ( StackType_t ) 0x16;	/* R22. */
	pxTopOfStack--;
	*pxTopOfStack = ( StackType_t ) 0x17;	/* R23. */
	pxTopOfStack--;
	*pxTopOfStack = ( StackType_t ) 0x18;	/* R24. */
	pxTopOfStack--;
	*pxTopOfStack = ( StackType_t ) 0x19;	/* R25. */
	pxTopOfStack--;
	*pxTopOfStack = ( StackType_t ) 0x1a;	/* R26. */
	pxTopOfStack--;
	*pxTopOfStack = ( StackType_t ) 0x1b;	/* R27. */
	pxTopOfStack--;
	*pxTopOfStack = ( StackType_t ) 0x1c;	/* R28. */
	pxTopOfStack--;
	*pxTopOfStack = ( StackType_t ) 0x1d;	/* R29. */
	pxTopOfStack--;
	*pxTopOfStack = ( StackType_t ) 0x1e;	/* R30. */
	pxTopOfStack--;

	/* The MSR is stacked between R30 and R31. */
	*pxTopOfStack = portINITIAL_MSR_STATE;
	pxTopOfStack--;

	*pxTopOfStack = ( StackType_t ) 0x1f;	/* R31. */
	pxTopOfStack--;

	/* Return a pointer to the top of the stack we have generated so this can
	be stored in the task control block for the task. */
	return pxTopOfStack;
}
/*-----------------------------------------------------------*/

BaseType_t xPortStartScheduler( void )
{
extern void ( __FreeRTOS_interrupt_Handler )( void );
extern void ( vStartFirstTask )( void );


	/* Setup the FreeRTOS interrupt handler.  Code copied from crt0.s. */
	asm volatile ( 	"la	r6, r0, __FreeRTOS_interrupt_handler		\n\t" \
					"sw	r6, r1, r0									\n\t" \
					"lhu r7, r1, r0									\n\t" \
					"shi r7, r0, 0x12								\n\t" \
					"shi r6, r0, 0x16 " );

	/* Setup the hardware to generate the tick.  Interrupts are disabled when
	this function is called. */
	prvSetupTimerInterrupt();

	/* Allocate the stack to be used by the interrupt handler. */
	pulISRStack = ( uint32_t * ) pvPortMalloc( configMINIMAL_STACK_SIZE * sizeof( StackType_t ) );

	/* Restore the context of the first task that is going to run. */
	if( pulISRStack != NULL )
	{
		/* Fill the ISR stack with a known value to facilitate debugging. */
		memset( pulISRStack, portISR_STACK_FILL_VALUE, configMINIMAL_STACK_SIZE * sizeof( StackType_t ) );
		pulISRStack += ( configMINIMAL_STACK_SIZE - 1 );

		/* Kick off the first task. */
		vStartFirstTask();
	}

	/* Should not get here as the tasks are now running! */
	return pdFALSE;
}
/*-----------------------------------------------------------*/

void vPortEndScheduler( void )
{
	/* Not implemented. */
}
/*-----------------------------------------------------------*/

/*
 * Manual context switch called by portYIELD or taskYIELD.  
 */
void vPortYield( void )
{
extern void VPortYieldASM( void );

	/* Perform the context switch in a critical section to assure it is
	not interrupted by the tick ISR.  It is not a problem to do this as
	each task maintains it's own interrupt status. */
	portENTER_CRITICAL();
		/* Jump directly to the yield function to ensure there is no
		compiler generated prologue code. */
		asm volatile (	"bralid r14, VPortYieldASM		\n\t" \
						"or r0, r0, r0					\n\t" );
	portEXIT_CRITICAL();
}
/*-----------------------------------------------------------*/

/*
 * Hardware initialisation to generate the RTOS tick.   
 */
static void prvSetupTimerInterrupt( void )
{
XTmrCtr xTimer;
const uint32_t ulCounterValue = configCPU_CLOCK_HZ / configTICK_RATE_HZ;
UBaseType_t uxMask;

	/* The OPB timer1 is used to generate the tick.  Use the provided library
	functions to enable the timer and set the tick frequency. */
	XTmrCtr_mDisable( XPAR_OPB_TIMER_1_BASEADDR, XPAR_OPB_TIMER_1_DEVICE_ID );
	XTmrCtr_Initialize( &xTimer, XPAR_OPB_TIMER_1_DEVICE_ID );
   	XTmrCtr_mSetLoadReg( XPAR_OPB_TIMER_1_BASEADDR, portCOUNTER_0, ulCounterValue );
	XTmrCtr_mSetControlStatusReg( XPAR_OPB_TIMER_1_BASEADDR, portCOUNTER_0, XTC_CSR_LOAD_MASK | XTC_CSR_INT_OCCURED_MASK );

	/* Set the timer interrupt enable bit while maintaining the other bit 
	states. */
	uxMask = XIntc_In32( ( XPAR_OPB_INTC_0_BASEADDR + XIN_IER_OFFSET ) );
	uxMask |= XPAR_OPB_TIMER_1_INTERRUPT_MASK;
	XIntc_Out32( ( XPAR_OPB_INTC_0_BASEADDR + XIN_IER_OFFSET ), ( uxMask ) );	
	
	XTmrCtr_Start( &xTimer, XPAR_OPB_TIMER_1_DEVICE_ID );
	XTmrCtr_mSetControlStatusReg(XPAR_OPB_TIMER_1_BASEADDR, portCOUNTER_0, XTC_CSR_ENABLE_TMR_MASK | XTC_CSR_ENABLE_INT_MASK | XTC_CSR_AUTO_RELOAD_MASK | XTC_CSR_DOWN_COUNT_MASK | XTC_CSR_INT_OCCURED_MASK );
	XIntc_mAckIntr( XPAR_INTC_SINGLE_BASEADDR, 1 );
}
/*-----------------------------------------------------------*/

/*
 * The interrupt handler placed in the interrupt vector when the scheduler is
 * started.  The task context has already been saved when this is called.
 * This handler determines the interrupt source and calls the relevant 
 * peripheral handler.
 */
void vTaskISRHandler( void )
{
static uint32_t ulPending;    

	/* Which interrupts are pending? */
	ulPending = XIntc_In32( ( XPAR_INTC_SINGLE_BASEADDR + XIN_IVR_OFFSET ) );

	if( ulPending < XPAR_INTC_MAX_NUM_INTR_INPUTS )
	{
		static XIntc_VectorTableEntry *pxTablePtr;
		static XIntc_Config *pxConfig;
		static uint32_t ulInterruptMask;

		ulInterruptMask = ( uint32_t ) 1 << ulPending;

		/* Get the configuration data using the device ID */
		pxConfig = &XIntc_ConfigTable[ ( uint32_t ) XPAR_INTC_SINGLE_DEVICE_ID ];

		pxTablePtr = &( pxConfig->HandlerTable[ ulPending ] );
		if( pxConfig->AckBeforeService & ( ulInterruptMask  ) )
		{
			XIntc_mAckIntr( pxConfig->BaseAddress, ulInterruptMask );
			pxTablePtr->Handler( pxTablePtr->CallBackRef );
		}
		else
		{
			pxTablePtr->Handler( pxTablePtr->CallBackRef );
			XIntc_mAckIntr( pxConfig->BaseAddress, ulInterruptMask );
		}
	}
}
/*-----------------------------------------------------------*/

/* 
 * Handler for the timer interrupt.
 */
void vTickISR( void *pvBaseAddress )
{
uint32_t ulCSR;

	/* Increment the RTOS tick - this might cause a task to unblock. */
	if( xTaskIncrementTick() != pdFALSE )
	{
		vTaskSwitchContext();
	}

	/* Clear the timer interrupt */
	ulCSR = XTmrCtr_mGetControlStatusReg(XPAR_OPB_TIMER_1_BASEADDR, 0);	
	XTmrCtr_mSetControlStatusReg( XPAR_OPB_TIMER_1_BASEADDR, portCOUNTER_0, ulCSR );
}
/*-----------------------------------------------------------*/