/*
    FreeRTOS V6.0.5 - Copyright (C) 2010 Real Time Engineers Ltd.

    ***************************************************************************
    *                                                                         *
    * If you are:                                                             *
    *                                                                         *
    *    + New to FreeRTOS,                                                   *
    *    + Wanting to learn FreeRTOS or multitasking in general quickly       *
    *    + Looking for basic training,                                        *
    *    + Wanting to improve your FreeRTOS skills and productivity           *
    *                                                                         *
    * then take a look at the FreeRTOS eBook                                  *
    *                                                                         *
    *        "Using the FreeRTOS Real Time Kernel - a Practical Guide"        *
    *                  http://www.FreeRTOS.org/Documentation                  *
    *                                                                         *
    * A pdf reference manual is also available.  Both are usually delivered   *
    * to your inbox within 20 minutes to two hours when purchased between 8am *
    * and 8pm GMT (although please allow up to 24 hours in case of            *
    * exceptional circumstances).  Thank you for your support!                *
    *                                                                         *
    ***************************************************************************

    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.

    1 tab == 4 spaces!

    http://www.FreeRTOS.org - Documentation, latest information, license and
    contact details.

    http://www.SafeRTOS.com - A version that is certified for use in safety
    critical systems.

    http://www.OpenRTOS.com - Commercial support, development, porting,
    licensing and training services.
*/


/*-----------------------------------------------------------
 * 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 long ) 0 )

volatile unsigned long 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.						*/
		}
	}
}