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    ***************************************************************************
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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
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    ***************************************************************************
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*/

/*-----------------------------------------------------------
 * Implementation of functions defined in portable.h for the ST STR91x ARM9
 * port.
 *----------------------------------------------------------*/

/* Library includes. */
#include "91x_lib.h"

/* Standard includes. */
#include <stdlib.h>
#include <assert.h>

/* Scheduler includes. */
#include "FreeRTOS.h"
#include "task.h"

#ifndef configUSE_WATCHDOG_TICK
	#error configUSE_WATCHDOG_TICK must be set to either 1 or 0 in FreeRTOSConfig.h to use either the Watchdog or timer 2 to generate the tick interrupt respectively.
#endif

/* Constants required to setup the initial stack. */
#ifndef _RUN_TASK_IN_ARM_MODE_
	#define portINITIAL_SPSR			( ( StackType_t ) 0x3f ) /* System mode, THUMB mode, interrupts enabled. */
#else
	#define portINITIAL_SPSR 			( ( StackType_t ) 0x1f ) /* System mode, ARM mode, interrupts enabled. */
#endif

#define portINSTRUCTION_SIZE			( ( StackType_t ) 4 )

/* Constants required to handle critical sections. */
#define portNO_CRITICAL_NESTING 		( ( uint32_t ) 0 )

#ifndef abs
	#define abs(x) ((x)>0 ? (x) : -(x))
#endif

/**
 * Toggle a led using the following algorithm:
 * if ( GPIO_ReadBit(GPIO9, GPIO_Pin_2) )
 * {
 *   GPIO_WriteBit( GPIO9, GPIO_Pin_2, Bit_RESET );
 * }
 * else
 * {
 *   GPIO_WriteBit( GPIO9, GPIO_Pin_2, Bit_RESET );
 * }
 *
 */
#define TOGGLE_LED(port,pin) 									\
	if ( ((((port)->DR[(pin)<<2])) & (pin)) != Bit_RESET ) 		\
	{															\
    	(port)->DR[(pin) <<2] = 0x00;							\
  	}															\
  	else														\
	{															\
    	(port)->DR[(pin) <<2] = (pin);							\
  	}


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

/* Setup the watchdog 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. */
uint32_t ulCriticalNesting = ( uint32_t ) 9999;

/* Tick interrupt routines for cooperative and preemptive operation
respectively.  The preemptive version is not defined as __irq as it is called
from an asm wrapper function. */
void WDG_IRQHandler( void );

/* VIC interrupt default handler. */
static void prvDefaultHandler( void );

#if configUSE_WATCHDOG_TICK == 0
	/* Used to update the OCR timer register */
	static u16 s_nPulseLength;
#endif

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

/*
 * Initialise the stack of a task to look exactly as if a call to
 * portSAVE_CONTEXT had been called.
 *
 * See header file for description.
 */
StackType_t *pxPortInitialiseStack( StackType_t *pxTopOfStack, TaskFunction_t pxCode, void *pvParameters )
{
	StackType_t *pxOriginalTOS;

	pxOriginalTOS = pxTopOfStack;

	/* To ensure asserts in tasks.c don't fail, although in this case the assert
	is not really required. */
	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 = ( StackType_t ) pxCode + portINSTRUCTION_SIZE;		
	pxTopOfStack--;

	*pxTopOfStack = ( StackType_t ) 0xaaaaaaaa;	/* R14 */
	pxTopOfStack--;	
	*pxTopOfStack = ( StackType_t ) pxOriginalTOS; /* Stack used when task starts goes in R13. */
	pxTopOfStack--;
	*pxTopOfStack = ( StackType_t ) 0x12121212;	/* R12 */
	pxTopOfStack--;	
	*pxTopOfStack = ( StackType_t ) 0x11111111;	/* R11 */
	pxTopOfStack--;	
	*pxTopOfStack = ( StackType_t ) 0x10101010;	/* R10 */
	pxTopOfStack--;	
	*pxTopOfStack = ( StackType_t ) 0x09090909;	/* R9 */
	pxTopOfStack--;	
	*pxTopOfStack = ( StackType_t ) 0x08080808;	/* R8 */
	pxTopOfStack--;	
	*pxTopOfStack = ( StackType_t ) 0x07070707;	/* R7 */
	pxTopOfStack--;	
	*pxTopOfStack = ( StackType_t ) 0x06060606;	/* R6 */
	pxTopOfStack--;	
	*pxTopOfStack = ( StackType_t ) 0x05050505;	/* R5 */
	pxTopOfStack--;	
	*pxTopOfStack = ( StackType_t ) 0x04040404;	/* R4 */
	pxTopOfStack--;	
	*pxTopOfStack = ( StackType_t ) 0x03030303;	/* R3 */
	pxTopOfStack--;	
	*pxTopOfStack = ( StackType_t ) 0x02020202;	/* R2 */
	pxTopOfStack--;	
	*pxTopOfStack = ( StackType_t ) 0x01010101;	/* R1 */
	pxTopOfStack--;	

	/* When the task starts is will expect to find the function parameter in
	R0. */
	*pxTopOfStack = ( StackType_t ) pvParameters; /* R0 */
	pxTopOfStack--;

	/* The status register is set for system mode, with interrupts enabled. */
	*pxTopOfStack = ( StackType_t ) portINITIAL_SPSR;
	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;	
}
/*-----------------------------------------------------------*/

BaseType_t 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.  */
}
/*-----------------------------------------------------------*/

/* This function is called from an asm wrapper, so does not require the __irq
keyword. */
#if configUSE_WATCHDOG_TICK == 1

	static void prvFindFactors(u32 n, u16 *a, u32 *b)
	{
		/* This function is copied from the ST STR7 library and is
		copyright STMicroelectronics.  Reproduced with permission. */
	
		u32 b0;
		u16 a0;
		int32_t err, err_min=n;
	
		*a = a0 = ((n-1)/65536ul) + 1;
		*b = b0 = n / *a;
	
		for (; *a <= 256; (*a)++)
		{
			*b = n / *a;
			err = (int32_t)*a * (int32_t)*b - (int32_t)n;
			if (abs(err) > (*a / 2))
			{
				(*b)++;
				err = (int32_t)*a * (int32_t)*b - (int32_t)n;
			}
			if (abs(err) < abs(err_min))
			{
				err_min = err;
				a0 = *a;
				b0 = *b;
				if (err == 0) break;
			}
		}
	
		*a = a0;
		*b = b0;
	}
	/*-----------------------------------------------------------*/

	static void prvSetupTimerInterrupt( void )
	{
	WDG_InitTypeDef xWdg;
	uint16_t a;
	uint32_t n = configCPU_PERIPH_HZ / configTICK_RATE_HZ, b;
	
		/* Configure the watchdog as a free running timer that generates a
		periodic interrupt. */
	
		SCU_APBPeriphClockConfig( __WDG, ENABLE );
		WDG_DeInit();
		WDG_StructInit(&xWdg);
		prvFindFactors( n, &a, &b );
		xWdg.WDG_Prescaler = a - 1;
		xWdg.WDG_Preload = b - 1;
		WDG_Init( &xWdg );
		WDG_ITConfig(ENABLE);
		
		/* Configure the VIC for the WDG interrupt. */
		VIC_Config( WDG_ITLine, VIC_IRQ, 10 );
		VIC_ITCmd( WDG_ITLine, ENABLE );
		
		/* Install the default handlers for both VIC's. */
		VIC0->DVAR = ( uint32_t ) prvDefaultHandler;
		VIC1->DVAR = ( uint32_t ) prvDefaultHandler;
		
		WDG_Cmd(ENABLE);
	}
	/*-----------------------------------------------------------*/

	void WDG_IRQHandler( void )
	{
		{
			/* Increment the tick counter. */
			if( xTaskIncrementTick() != pdFALSE )
			{		
				/* Select a new task to execute. */
				vTaskSwitchContext();
			}
		
			/* Clear the interrupt in the watchdog. */
			WDG->SR &= ~0x0001;
		}
	}

#else

	static void prvFindFactors(u32 n, u8 *a, u16 *b)
	{
		/* This function is copied from the ST STR7 library and is
		copyright STMicroelectronics.  Reproduced with permission. */
	
		u16 b0;
		u8 a0;
		int32_t err, err_min=n;
	
	
		*a = a0 = ((n-1)/256) + 1;
		*b = b0 = n / *a;
	
		for (; *a <= 256; (*a)++)
		{
			*b = n / *a;
			err = (int32_t)*a * (int32_t)*b - (int32_t)n;
			if (abs(err) > (*a / 2))
			{
				(*b)++;
				err = (int32_t)*a * (int32_t)*b - (int32_t)n;
			}
			if (abs(err) < abs(err_min))
			{
				err_min = err;
				a0 = *a;
				b0 = *b;
				if (err == 0) break;
			}
		}
	
		*a = a0;
		*b = b0;
	}
	/*-----------------------------------------------------------*/

	static void prvSetupTimerInterrupt( void )
	{
		uint8_t a;
		uint16_t b;
		uint32_t n = configCPU_PERIPH_HZ / configTICK_RATE_HZ;
		
		TIM_InitTypeDef timer;
		
		SCU_APBPeriphClockConfig( __TIM23, ENABLE );
		TIM_DeInit(TIM2);
		TIM_StructInit(&timer);
		prvFindFactors( n, &a, &b );
		
		timer.TIM_Mode           = TIM_OCM_CHANNEL_1;
		timer.TIM_OC1_Modes      = TIM_TIMING;
		timer.TIM_Clock_Source   = TIM_CLK_APB;
		timer.TIM_Clock_Edge     = TIM_CLK_EDGE_RISING;
		timer.TIM_Prescaler      = a-1;
		timer.TIM_Pulse_Level_1  = TIM_HIGH;
		timer.TIM_Pulse_Length_1 = s_nPulseLength  = b-1;
		
		TIM_Init (TIM2, &timer);
		TIM_ITConfig(TIM2, TIM_IT_OC1, ENABLE);
		/* Configure the VIC for the WDG interrupt. */
		VIC_Config( TIM2_ITLine, VIC_IRQ, 10 );
		VIC_ITCmd( TIM2_ITLine, ENABLE );
		
		/* Install the default handlers for both VIC's. */
		VIC0->DVAR = ( uint32_t ) prvDefaultHandler;
		VIC1->DVAR = ( uint32_t ) prvDefaultHandler;
		
		TIM_CounterCmd(TIM2, TIM_CLEAR);
		TIM_CounterCmd(TIM2, TIM_START);
	}
	/*-----------------------------------------------------------*/

	void TIM2_IRQHandler( void )
	{
		/* Reset the timer counter to avioid overflow. */
		TIM2->OC1R += s_nPulseLength;
		
		/* Increment the tick counter. */
		if( xTaskIncrementTick() != pdFALSE )
		{
			/* Select a new task to run. */
			vTaskSwitchContext();
		}
		
		/* Clear the interrupt in the watchdog. */
		TIM2->SR &= ~TIM_FLAG_OC1;
	}

#endif /* USE_WATCHDOG_TICK */

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

__arm __interwork void vPortEnterCritical( void )
{
	/* Disable interrupts first! */
	portDISABLE_INTERRUPTS();

	/* 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++;
}
/*-----------------------------------------------------------*/

__arm __interwork 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 )
		{
			portENABLE_INTERRUPTS();
		}
	}
}
/*-----------------------------------------------------------*/

static void prvDefaultHandler( void )
{
}





