FreeRTOS/Source/portable/Tasking/ARM_CM4F/port.c - third_party/github/FreeRTOS/FreeRTOS-Kernel - Git at Google

 /*
     FreeRTOS V7.4.2 - Copyright (C) 2013 Real Time Engineers Ltd.

     FEATURES AND PORTS ARE ADDED TO FREERTOS ALL THE TIME.  PLEASE VISIT
     http://www.FreeRTOS.org TO ENSURE YOU ARE USING THE LATEST VERSION.

     ***************************************************************************
      *                                                                       *
      *    FreeRTOS tutorial books are available in pdf and paperback.        *
      *    Complete, revised, and edited pdf reference manuals are also       *
      *    available.                                                         *
      *                                                                       *
      *    Purchasing FreeRTOS documentation will not only help you, by       *
      *    ensuring you get running as quickly as possible and with an        *
      *    in-depth knowledge of how to use FreeRTOS, it will also help       *
      *    the FreeRTOS project to continue with its mission of providing     *
      *    professional grade, cross platform, de facto standard solutions    *
      *    for microcontrollers - completely free of charge!                  *
      *                                                                       *
      *    >>> See http://www.FreeRTOS.org/Documentation for details. <<<     *
      *                                                                       *
      *    Thank you for using FreeRTOS, and 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 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.  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 Real Time Engineers Ltd., contact details for whom are available
     on the FreeRTOS WEB site.

     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, and our new
     fully thread aware and reentrant UDP/IP stack.

     http://www.OpenRTOS.com - Real Time Engineers ltd license FreeRTOS to High
     Integrity Systems, who sell the code with commercial support,
     indemnification and middleware, under the OpenRTOS brand.

     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.
 */

 /*-----------------------------------------------------------
  * Implementation of functions defined in portable.h for the ARM CM4F port.
  *----------------------------------------------------------*/

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

 /* Constants required to manipulate the NVIC. */
 #define portNVIC_SYSTICK_CTRL		( ( volatile unsigned long * ) 0xe000e010 )
 #define portNVIC_SYSTICK_LOAD		( ( volatile unsigned long * ) 0xe000e014 )
 #define portNVIC_SYSPRI2			( ( volatile unsigned long * ) 0xe000ed20 )
 #define portNVIC_SYSTICK_CLK		0x00000004
 #define portNVIC_SYSTICK_INT		0x00000002
 #define portNVIC_SYSTICK_ENABLE		0x00000001
 #define portNVIC_PENDSV_PRI			( ( ( unsigned long ) configKERNEL_INTERRUPT_PRIORITY ) << 16 )
 #define portNVIC_SYSTICK_PRI		( ( ( unsigned long ) configKERNEL_INTERRUPT_PRIORITY ) << 24 )

 /* Constants required to manipulate the VFP. */
 #define portFPCCR					( ( volatile unsigned long * ) 0xe000ef34 ) /* Floating point context control register. */
 #define portASPEN_AND_LSPEN_BITS	( 0x3UL << 30UL )

 /* Constants required to set up the initial stack. */
 #define portINITIAL_XPSR			( 0x01000000 )
 #define portINITIAL_EXEC_RETURN		( 0xfffffffd )

 /* The priority used by the kernel is assigned to a variable to make access
 from inline assembler easier. */
 const unsigned long ulKernelPriority = configKERNEL_INTERRUPT_PRIORITY;

 /* Each task maintains its own interrupt status in the critical nesting
 variable. */
 static unsigned long ulCriticalNesting = 0xaaaaaaaaUL;

 /*
  * Setup the timer to generate the tick interrupts.
  */
 static void prvSetupTimerInterrupt( void );

 /*
  * Exception handlers.
  */
 void SysTick_Handler( void );

 /*
  * Functions defined in port_asm.asm.
  */
 extern void vPortEnableVFP( void );
 extern void vPortStartFirstTask( void );

 /* This exists purely to allow the const to be used from within the
 port_asm.asm assembly file. */
 const unsigned long ulMaxSyscallInterruptPriorityConst = configMAX_SYSCALL_INTERRUPT_PRIORITY;

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

 /*
  * See header file for description.
  */
 portSTACK_TYPE *pxPortInitialiseStack( portSTACK_TYPE *pxTopOfStack, pdTASK_CODE pxCode, void *pvParameters )
 {
 	/* Simulate the stack frame as it would be created by a context switch
 	interrupt. */

 	/* Offset added to account for the way the MCU uses the stack on entry/exit
 	of interrupts, and to ensure alignment. */
 	pxTopOfStack--;

 	*pxTopOfStack = portINITIAL_XPSR;	/* xPSR */
 	pxTopOfStack--;
 	*pxTopOfStack = ( portSTACK_TYPE ) pxCode;	/* PC */
 	pxTopOfStack--;
 	*pxTopOfStack = 0;	/* LR */

 	/* Save code space by skipping register initialisation. */
 	pxTopOfStack -= 5;	/* R12, R3, R2 and R1. */
 	*pxTopOfStack = ( portSTACK_TYPE ) pvParameters;	/* R0 */

 	/* A save method is being used that requires each task to maintain its
 	own exec return value. */
 	pxTopOfStack--;
 	*pxTopOfStack = portINITIAL_EXEC_RETURN;

 	pxTopOfStack -= 8;	/* R11, R10, R9, R8, R7, R6, R5 and R4. */

 	return pxTopOfStack;
 }
 /*-----------------------------------------------------------*/

 /*
  * See header file for description.
  */
 portBASE_TYPE xPortStartScheduler( void )
 {
 	/* configMAX_SYSCALL_INTERRUPT_PRIORITY must not be set to 0.
 	See http://www.FreeRTOS.org/RTOS-Cortex-M3-M4.html */
 	configASSERT( ( configMAX_SYSCALL_INTERRUPT_PRIORITY ) );

 	/* Make PendSV and SysTick the lowest priority interrupts. */
 	*(portNVIC_SYSPRI2) |= portNVIC_PENDSV_PRI;
 	*(portNVIC_SYSPRI2) |= portNVIC_SYSTICK_PRI;

 	/* Start the timer that generates the tick ISR.  Interrupts are disabled
 	here already. */
 	prvSetupTimerInterrupt();

 	/* Initialise the critical nesting count ready for the first task. */
 	ulCriticalNesting = 0;

 	/* Ensure the VFP is enabled - it should be anyway. */
 	vPortEnableVFP();

 	/* Lazy save always. */
 	*( portFPCCR ) |= portASPEN_AND_LSPEN_BITS;

 	/* Start the first task. */
 	vPortStartFirstTask();

 	/* Should not get here! */
 	return 0;
 }
 /*-----------------------------------------------------------*/

 void vPortEndScheduler( void )
 {
 	/* It is unlikely that the CM4F port will require this function as there
 	is nothing to return to.  */
 }
 /*-----------------------------------------------------------*/

 void vPortYield( void )
 {
 	/* Set a PendSV to request a context switch. */
 	*(portNVIC_INT_CTRL) = portNVIC_PENDSVSET;

 	/* Barriers are normally not required but do ensure the code is completely
 	within the specified behaviour for the architecture. */
 	__DSB();
 	__ISB();
 }
 /*-----------------------------------------------------------*/

 void vPortEnterCritical( void )
 {
 	portDISABLE_INTERRUPTS();
 	ulCriticalNesting++;
 	__DSB();
 	__ISB();
 }
 /*-----------------------------------------------------------*/

 void vPortExitCritical( void )
 {
 	ulCriticalNesting--;
 	if( ulCriticalNesting == 0 )
 	{
 		portENABLE_INTERRUPTS();
 	}
 }
 /*-----------------------------------------------------------*/

 void SysTick_Handler( void )
 {
 unsigned long ulDummy;

 	ulDummy = portSET_INTERRUPT_MASK_FROM_ISR();
 	{
 		if( xTaskIncrementTick() != pdFALSE )
 		{
 			/* Pend a context switch. */
 			*(portNVIC_INT_CTRL) = portNVIC_PENDSVSET;
 		}
 	}
 	portCLEAR_INTERRUPT_MASK_FROM_ISR( ulDummy );
 }
 /*-----------------------------------------------------------*/

 /*
  * Setup the systick timer to generate the tick interrupts at the required
  * frequency.
  */
 void prvSetupTimerInterrupt( void )
 {
 	/* Configure SysTick to interrupt at the requested rate. */
 	*(portNVIC_SYSTICK_LOAD) = ( configCPU_CLOCK_HZ / configTICK_RATE_HZ ) - 1UL;
 	*(portNVIC_SYSTICK_CTRL) = portNVIC_SYSTICK_CLK | portNVIC_SYSTICK_INT | portNVIC_SYSTICK_ENABLE;
 }
 /*-----------------------------------------------------------*/
	/*
	FreeRTOS V7.4.2 - Copyright (C) 2013 Real Time Engineers Ltd.

	FEATURES AND PORTS ARE ADDED TO FREERTOS ALL THE TIME. PLEASE VISIT
	http://www.FreeRTOS.org TO ENSURE YOU ARE USING THE LATEST VERSION.

	***************************************************************************
	* *
	* FreeRTOS tutorial books are available in pdf and paperback. *
	* Complete, revised, and edited pdf reference manuals are also *
	* available. *
	* *
	* Purchasing FreeRTOS documentation will not only help you, by *
	* ensuring you get running as quickly as possible and with an *
	* in-depth knowledge of how to use FreeRTOS, it will also help *
	* the FreeRTOS project to continue with its mission of providing *
	* professional grade, cross platform, de facto standard solutions *
	* for microcontrollers - completely free of charge! *
	* *
	* >>> See http://www.FreeRTOS.org/Documentation for details. <<< *
	* *
	* Thank you for using FreeRTOS, and 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 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. 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 Real Time Engineers Ltd., contact details for whom are available
	on the FreeRTOS WEB site.

	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, and our new
	fully thread aware and reentrant UDP/IP stack.

	http://www.OpenRTOS.com - Real Time Engineers ltd license FreeRTOS to High
	Integrity Systems, who sell the code with commercial support,
	indemnification and middleware, under the OpenRTOS brand.

	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.
	*/

	/*-----------------------------------------------------------
	* Implementation of functions defined in portable.h for the ARM CM4F port.
	----------------------------------------------------------/

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

	/* Constants required to manipulate the NVIC. */
	#define portNVIC_SYSTICK_CTRL ( ( volatile unsigned long * ) 0xe000e010 )
	#define portNVIC_SYSTICK_LOAD ( ( volatile unsigned long * ) 0xe000e014 )
	#define portNVIC_SYSPRI2 ( ( volatile unsigned long * ) 0xe000ed20 )
	#define portNVIC_SYSTICK_CLK 0x00000004
	#define portNVIC_SYSTICK_INT 0x00000002
	#define portNVIC_SYSTICK_ENABLE 0x00000001
	#define portNVIC_PENDSV_PRI ( ( ( unsigned long ) configKERNEL_INTERRUPT_PRIORITY ) << 16 )
	#define portNVIC_SYSTICK_PRI ( ( ( unsigned long ) configKERNEL_INTERRUPT_PRIORITY ) << 24 )

	/* Constants required to manipulate the VFP. */
	#define portFPCCR ( ( volatile unsigned long * ) 0xe000ef34 ) /* Floating point context control register. */
	#define portASPEN_AND_LSPEN_BITS ( 0x3UL << 30UL )

	/* Constants required to set up the initial stack. */
	#define portINITIAL_XPSR ( 0x01000000 )
	#define portINITIAL_EXEC_RETURN ( 0xfffffffd )

	/* The priority used by the kernel is assigned to a variable to make access
	from inline assembler easier. */
	const unsigned long ulKernelPriority = configKERNEL_INTERRUPT_PRIORITY;

	/* Each task maintains its own interrupt status in the critical nesting
	variable. */
	static unsigned long ulCriticalNesting = 0xaaaaaaaaUL;

	/*
	* Setup the timer to generate the tick interrupts.
	*/
	static void prvSetupTimerInterrupt( void );

	/*
	* Exception handlers.
	*/
	void SysTick_Handler( void );

	/*
	* Functions defined in port_asm.asm.
	*/
	extern void vPortEnableVFP( void );
	extern void vPortStartFirstTask( void );

	/* This exists purely to allow the const to be used from within the
	port_asm.asm assembly file. */
	const unsigned long ulMaxSyscallInterruptPriorityConst = configMAX_SYSCALL_INTERRUPT_PRIORITY;

	/-----------------------------------------------------------/

	/*
	* See header file for description.
	*/
	portSTACK_TYPE pxPortInitialiseStack( portSTACK_TYPE pxTopOfStack, pdTASK_CODE pxCode, void *pvParameters )
	{
	/* Simulate the stack frame as it would be created by a context switch
	interrupt. */

	/* Offset added to account for the way the MCU uses the stack on entry/exit
	of interrupts, and to ensure alignment. */
	pxTopOfStack--;

	pxTopOfStack = portINITIAL_XPSR; / xPSR */
	pxTopOfStack--;
	pxTopOfStack = ( portSTACK_TYPE ) pxCode; / PC */
	pxTopOfStack--;
	pxTopOfStack = 0; / LR */

	/* Save code space by skipping register initialisation. */
	pxTopOfStack -= 5; /* R12, R3, R2 and R1. */
	pxTopOfStack = ( portSTACK_TYPE ) pvParameters; / R0 */

	/* A save method is being used that requires each task to maintain its
	own exec return value. */
	pxTopOfStack--;
	*pxTopOfStack = portINITIAL_EXEC_RETURN;

	pxTopOfStack -= 8; /* R11, R10, R9, R8, R7, R6, R5 and R4. */

	return pxTopOfStack;
	}
	/-----------------------------------------------------------/

	/*
	* See header file for description.
	*/
	portBASE_TYPE xPortStartScheduler( void )
	{
	/* configMAX_SYSCALL_INTERRUPT_PRIORITY must not be set to 0.
	See http://www.FreeRTOS.org/RTOS-Cortex-M3-M4.html */
	configASSERT( ( configMAX_SYSCALL_INTERRUPT_PRIORITY ) );

	/* Make PendSV and SysTick the lowest priority interrupts. */
	*(portNVIC_SYSPRI2) \|= portNVIC_PENDSV_PRI;
	*(portNVIC_SYSPRI2) \|= portNVIC_SYSTICK_PRI;

	/* Start the timer that generates the tick ISR. Interrupts are disabled
	here already. */
	prvSetupTimerInterrupt();

	/* Initialise the critical nesting count ready for the first task. */
	ulCriticalNesting = 0;

	/* Ensure the VFP is enabled - it should be anyway. */
	vPortEnableVFP();

	/* Lazy save always. */
	*( portFPCCR ) \|= portASPEN_AND_LSPEN_BITS;

	/* Start the first task. */
	vPortStartFirstTask();

	/* Should not get here! */
	return 0;
	}
	/-----------------------------------------------------------/

	void vPortEndScheduler( void )
	{
	/* It is unlikely that the CM4F port will require this function as there
	is nothing to return to. */
	}
	/-----------------------------------------------------------/

	void vPortYield( void )
	{
	/* Set a PendSV to request a context switch. */
	*(portNVIC_INT_CTRL) = portNVIC_PENDSVSET;

	/* Barriers are normally not required but do ensure the code is completely
	within the specified behaviour for the architecture. */
	__DSB();
	__ISB();
	}
	/-----------------------------------------------------------/

	void vPortEnterCritical( void )
	{
	portDISABLE_INTERRUPTS();
	ulCriticalNesting++;
	__DSB();
	__ISB();
	}
	/-----------------------------------------------------------/

	void vPortExitCritical( void )
	{
	ulCriticalNesting--;
	if( ulCriticalNesting == 0 )
	{
	portENABLE_INTERRUPTS();
	}
	}
	/-----------------------------------------------------------/

	void SysTick_Handler( void )
	{
	unsigned long ulDummy;

	ulDummy = portSET_INTERRUPT_MASK_FROM_ISR();
	{
	if( xTaskIncrementTick() != pdFALSE )
	{
	/* Pend a context switch. */
	*(portNVIC_INT_CTRL) = portNVIC_PENDSVSET;
	}
	}
	portCLEAR_INTERRUPT_MASK_FROM_ISR( ulDummy );
	}
	/-----------------------------------------------------------/

	/*
	* Setup the systick timer to generate the tick interrupts at the required
	* frequency.
	*/
	void prvSetupTimerInterrupt( void )
	{
	/* Configure SysTick to interrupt at the requested rate. */
	*(portNVIC_SYSTICK_LOAD) = ( configCPU_CLOCK_HZ / configTICK_RATE_HZ ) - 1UL;
	*(portNVIC_SYSTICK_CTRL) = portNVIC_SYSTICK_CLK \| portNVIC_SYSTICK_INT \| portNVIC_SYSTICK_ENABLE;
	}
	/-----------------------------------------------------------/