portisr.c

FreeRTOS - V5.1.1 Last Update: Nov 20 2008 http://sourceforge.net/projects/freertos/

/*
	FreeRTOS.org V5.1.1 - Copyright (C) 2003-2008 Richard Barry.

	This file is part of the FreeRTOS.org distribution.

	FreeRTOS.org 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.org 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.org; 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.org, 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.

    ***************************************************************************
    ***************************************************************************
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	Please ensure to read the configuration and relevant port sections of the
	online documentation.

	http://www.FreeRTOS.org - Documentation, latest information, license and 
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*/


/*-----------------------------------------------------------
 * Components that can be compiled to either ARM or THUMB mode are
 * contained in port.c  The ISR routines, which can only be compiled
 * to ARM mode, are contained in this file.
 *----------------------------------------------------------*/

/*
*/

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

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

volatile unsigned portLONG ulCriticalNesting = 9999UL;

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

/* 
 * The scheduler can only be started from ARM mode, hence the inclusion of this
 * function here.
 */
void vPortISRStartFirstTask( void );
/*-----------------------------------------------------------*/

void vPortISRStartFirstTask( void )
{
	/* Simply start the scheduler.  This is included here as it can only be
	called from ARM mode. */
	asm volatile (														\
	"LDR		R0, =pxCurrentTCB								\n\t"	\
	"LDR		R0, [R0]										\n\t"	\
	"LDR		LR, [R0]										\n\t"	\
																		\
	/* The critical nesting depth is the first item on the stack. */	\
	/* Load it into the ulCriticalNesting variable. */					\
	"LDR		R0, =ulCriticalNesting							\n\t"	\
	"LDMFD	LR!, {R1}											\n\t"	\
	"STR		R1, [R0]										\n\t"	\
																		\
	/* Get the SPSR from the stack. */									\
	"LDMFD	LR!, {R0}											\n\t"	\
	"MSR		SPSR, R0										\n\t"	\
																		\
	/* Restore all system mode registers for the task. */				\
	"LDMFD	LR, {R0-R14}^										\n\t"	\
	"NOP														\n\t"	\
																		\
	/* Restore the return address. */									\
	"LDR		LR, [LR, #+60]									\n\t"	\
																		\
	/* And return - correcting the offset in the LR to obtain the */	\
	/* correct address. */												\
	"SUBS PC, LR, #4											\n\t"	\
	);																	
}
/*-----------------------------------------------------------*/

void vPortTickISR( void )
{
	/* Increment the RTOS tick count, then look for the highest priority 
	task that is ready to run. */
	vTaskIncrementTick();
	
	#if configUSE_PREEMPTION == 1
		vTaskSwitchContext();
	#endif
			
	/* Ready for the next interrupt. */
	TB_ClearITPendingBit( TB_IT_Update );	
}

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

/*
 * The interrupt management utilities can only be called from ARM mode.  When
 * THUMB_INTERWORK is defined the utilities are defined as functions here to
 * ensure a switch to ARM mode.  When THUMB_INTERWORK is not defined then
 * the utilities are defined as macros in portmacro.h - as per other ports.
 */
#ifdef THUMB_INTERWORK

	void vPortDisableInterruptsFromThumb( void ) __attribute__ ((naked));
	void vPortEnableInterruptsFromThumb( void ) __attribute__ ((naked));

	void vPortDisableInterruptsFromThumb( void )
	{
		asm volatile ( 
			"STMDB	SP!, {R0}		\n\t"	/* Push R0.									*/
			"MRS	R0, CPSR		\n\t"	/* Get CPSR.								*/
			"ORR	R0, R0, #0xC0	\n\t"	/* Disable IRQ, FIQ.						*/
			"MSR	CPSR, R0		\n\t"	/* Write back modified value.				*/
			"LDMIA	SP!, {R0}		\n\t"	/* Pop R0.									*/
			"BX		R14" );					/* Return back to thumb.					*/
	}
			
	void vPortEnableInterruptsFromThumb( void )
	{
		asm volatile ( 
			"STMDB	SP!, {R0}		\n\t"	/* Push R0.									*/	
			"MRS	R0, CPSR		\n\t"	/* Get CPSR.								*/	
			"BIC	R0, R0, #0xC0	\n\t"	/* Enable IRQ, FIQ.							*/	
			"MSR	CPSR, R0		\n\t"	/* Write back modified value.				*/	
			"LDMIA	SP!, {R0}		\n\t"	/* Pop R0.									*/
			"BX		R14" );					/* Return back to thumb.					*/
	}

#endif /* THUMB_INTERWORK */
/*-----------------------------------------------------------*/

void vPortEnterCritical( void )
{
	/* Disable interrupts as per portDISABLE_INTERRUPTS(); 							*/
	asm volatile ( 
		"STMDB	SP!, {R0}			\n\t"	/* Push R0.								*/
		"MRS	R0, CPSR			\n\t"	/* Get CPSR.							*/
		"ORR	R0, R0, #0xC0		\n\t"	/* Disable IRQ, FIQ.					*/
		"MSR	CPSR, R0			\n\t"	/* Write back modified value.			*/
		"LDMIA	SP!, {R0}" );				/* Pop R0.								*/

	/* 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 interrupts as per portEXIT_CRITICAL().					*/
			asm volatile ( 
				"STMDB	SP!, {R0}		\n\t"	/* Push R0.						*/	
				"MRS	R0, CPSR		\n\t"	/* Get CPSR.					*/	
				"BIC	R0, R0, #0xC0	\n\t"	/* Enable IRQ, FIQ.				*/	
				"MSR	CPSR, R0		\n\t"	/* Write back modified value.	*/	
				"LDMIA	SP!, {R0}" );			/* Pop R0.						*/
		}
	}
}