port.c

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/*
	FreeRTOS.org V4.0.5 - Copyright (C) 2003-2006 Richard Barry.

	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 as published by
	the Free Software Foundation; either version 2 of the License, or
	(at your option) any later version.

	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

	A special exception to the GPL can be applied should you wish to distribute
	a combined work that includes FreeRTOS, without being obliged to provide
	the source code for any proprietary components.  See the licensing section
	of http://www.FreeRTOS.org for full details of how and when the exception
	can be applied.

	***************************************************************************
	See http://www.FreeRTOS.org for documentation, latest information, license
	and contact details.  Please ensure to read the configuration and relevant
	port sections of the online documentation.
	***************************************************************************
*/

/*-----------------------------------------------------------
 * Implementation of functions defined in portable.h for the ST STR91x ARM7
 * port.
 *----------------------------------------------------------*/

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

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

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

/* Constants required to setup the initial stack. */
#ifndef _RUN_TASK_IN_ARM_MODE_
	#define portINITIAL_SPSR			( ( portSTACK_TYPE ) 0x3f ) /* System mode, THUMB mode, interrupts enabled. */
#else
	#define portINITIAL_SPSR 			( ( portSTACK_TYPE ) 0x1f ) /* System mode, ARM mode, interrupts enabled. */
#endif
#define portINSTRUCTION_SIZE			( ( portSTACK_TYPE ) 4 )

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


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

/* 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. */
unsigned portLONG ulCriticalNesting = ( unsigned portLONG ) 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. */
__arm __irq void vPortNonPreemptiveTick( void );
void WDG_IRQHandler( void );

/* VIC interrupt default handler. */
static void prvDefaultHandler( 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 status register is set for system mode, with interrupts enabled. */
	*pxTopOfStack = ( portSTACK_TYPE ) 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;	
}
/*-----------------------------------------------------------*/

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

/* This function is called from an asm wrapper, so does not require the __irq
keyword. */
void WDG_IRQHandler( void )
{
	/* Increment the tick counter. */
	vTaskIncrementTick();

	#if configUSE_PREEMPTION == 1
		/* The new tick value might unblock a task.  Ensure the highest task that
		is ready to execute is the task that will execute when the tick ISR
		exits. */
		vTaskSwitchContext();
	#endif
		
	/* Clear the interrupt in the watchdog. */
	WDG->SR &= ~0x0001;
}
/*-----------------------------------------------------------*/

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

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;
	long err, err_min=n;

	*a = a0 = ((n-1)/65536ul) + 1;
	*b = b0 = n / *a;

	for (; *a <= 256; (*a)++)
	{
		*b = n / *a;
		err = (long)*a * (long)*b - (long)n;
		if (abs(err) > (*a / 2))
		{
			(*b)++;
			err = (long)*a * (long)*b - (long)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;
unsigned portSHORT a;
unsigned portLONG 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 = ( unsigned portLONG ) prvDefaultHandler;
	VIC1->DVAR = ( unsigned portLONG ) prvDefaultHandler;
	
	WDG_Cmd(ENABLE);
}

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

__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 )
{
}