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/*
FreeRTOS V7.5.0 - Copyright (C) 2013 Real Time Engineers Ltd.
VISIT http://www.FreeRTOS.org TO ENSURE YOU ARE USING THE LATEST VERSION.
***************************************************************************
* *
* FreeRTOS provides completely free yet professionally developed, *
* robust, strictly quality controlled, supported, and cross *
* platform software that has become a de facto standard. *
* *
* Help yourself get started quickly and support the FreeRTOS *
* project by purchasing a FreeRTOS tutorial book, reference *
* manual, or both from: http://www.FreeRTOS.org/Documentation *
* *
* Thank you! *
* *
***************************************************************************
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 modification 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. Full license text is available from the following
link: http://www.freertos.org/a00114.html
1 tab == 4 spaces!
***************************************************************************
* *
* Having a problem? Start by reading the FAQ "My application does *
* not run, what could be wrong?" *
* *
* http://www.FreeRTOS.org/FAQHelp.html *
* *
***************************************************************************
http://www.FreeRTOS.org - Documentation, books, training, latest versions,
license and Real Time Engineers Ltd. contact details.
http://www.FreeRTOS.org/plus - A selection of FreeRTOS ecosystem products,
including FreeRTOS+Trace - an indispensable productivity tool, a DOS
compatible FAT file system, and our tiny thread aware UDP/IP stack.
http://www.OpenRTOS.com - Real Time Engineers ltd license FreeRTOS to High
Integrity Systems to sell under the OpenRTOS brand. Low cost OpenRTOS
licenses offer ticketed support, indemnification and middleware.
http://www.SafeRTOS.com - High Integrity Systems also provide a safety
engineered and independently SIL3 certified version for use in safety and
mission critical applications that require provable dependability.
1 tab == 4 spaces!
*/
/*-----------------------------------------------------------
* 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 interrupts. */
#define portTIMER_MATCH_ISR_BIT ( ( unsigned portCHAR ) 0x01 )
#define portCLEAR_VIC_INTERRUPT ( ( unsigned portLONG ) 0 )
/* Constants required to handle critical sections. */
#define portNO_CRITICAL_NESTING ( ( unsigned portLONG ) 0 )
volatile unsigned portLONG ulCriticalNesting = 9999UL;
/*-----------------------------------------------------------*/
/* ISR to handle manual context switches (from a call to taskYIELD()). */
void vPortYieldProcessor( void ) __attribute__((interrupt("SWI"), naked));
/*
* 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. */
portRESTORE_CONTEXT();
}
/*-----------------------------------------------------------*/
/*
* Called by portYIELD() or taskYIELD() to manually force a context switch.
*
* When a context switch is performed from the task level the saved task
* context is made to look as if it occurred from within the tick ISR. This
* way the same restore context function can be used when restoring the context
* saved from the ISR or that saved from a call to vPortYieldProcessor.
*/
void vPortYieldProcessor( void )
{
/* Within an IRQ ISR the link register has an offset from the true return
address, but an SWI ISR does not. Add the offset manually so the same
ISR return code can be used in both cases. */
__asm volatile ( "ADD LR, LR, #4" );
/* Perform the context switch. First save the context of the current task. */
portSAVE_CONTEXT();
/* Find the highest priority task that is ready to run. */
__asm volatile( "bl vTaskSwitchContext" );
/* Restore the context of the new task. */
portRESTORE_CONTEXT();
}
/*-----------------------------------------------------------*/
/*
* The ISR used for the scheduler tick depends on whether the cooperative or
* the preemptive scheduler is being used.
*/
#if configUSE_PREEMPTION == 0
/* The cooperative scheduler requires a normal IRQ service routine to
simply increment the system tick. */
void vNonPreemptiveTick( void ) __attribute__ ((interrupt ("IRQ")));
void vNonPreemptiveTick( void )
{
xTaskIncrementTick();
T0IR = 2;
VICVectAddr = portCLEAR_VIC_INTERRUPT;
}
#else
/* The preemptive scheduler is defined as "naked" as the full context is
saved on entry as part of the context switch. */
void vPreemptiveTick( void ) __attribute__((naked));
void vPreemptiveTick( void )
{
/* Save the context of the interrupted task. */
portSAVE_CONTEXT();
/* Increment the RTOS tick count, then look for the highest priority
task that is ready to run. */
__asm volatile
(
" bl xTaskIncrementTick \t\n" \
" cmp r0, #0 \t\n" \
" beq SkipContextSwitch \t\n" \
" bl vTaskSwitchContext \t\n" \
"SkipContextSwitch: \t\n"
);
/* Ready for the next interrupt. */
T0IR = 2;
VICVectAddr = portCLEAR_VIC_INTERRUPT;
/* Restore the context of the new task. */
portRESTORE_CONTEXT();
}
#endif
/*-----------------------------------------------------------*/
/*
* 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 */
/* The code generated by the GCC compiler uses the stack in different ways at
different optimisation levels. The interrupt flags can therefore not always
be saved to the stack. Instead the critical section nesting level is stored
in a variable, which is then saved as part of the stack context. */
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. */
}
}
}
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