FreeRTOS/Source/portable/RVDS/ARM_CA9/port.c

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    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.

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*/

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

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

#ifndef configINTERRUPT_CONTROLLER_BASE_ADDRESS
	#error configINTERRUPT_CONTROLLER_BASE_ADDRESS must be defined.  See http://www.freertos.org/Using-FreeRTOS-on-Cortex-A-Embedded-Processors.html
#endif

#ifndef configINTERRUPT_CONTROLLER_CPU_INTERFACE_OFFSET
	#error configINTERRUPT_CONTROLLER_CPU_INTERFACE_OFFSET must be defined.  See http://www.freertos.org/Using-FreeRTOS-on-Cortex-A-Embedded-Processors.html
#endif

#ifndef configUNIQUE_INTERRUPT_PRIORITIES
	#error configUNIQUE_INTERRUPT_PRIORITIES must be defined.  See http://www.freertos.org/Using-FreeRTOS-on-Cortex-A-Embedded-Processors.html
#endif

#ifndef configSETUP_TICK_INTERRUPT
	#error configSETUP_TICK_INTERRUPT() must be defined.  See http://www.freertos.org/Using-FreeRTOS-on-Cortex-A-Embedded-Processors.html
#endif /* configSETUP_TICK_INTERRUPT */

#ifndef configMAX_API_CALL_INTERRUPT_PRIORITY
	#error configMAX_API_CALL_INTERRUPT_PRIORITY must be defined.  See http://www.freertos.org/Using-FreeRTOS-on-Cortex-A-Embedded-Processors.html
#endif

#if configMAX_API_CALL_INTERRUPT_PRIORITY == 0
	#error configMAX_API_CALL_INTERRUPT_PRIORITY must not be set to 0
#endif

#if configMAX_API_CALL_INTERRUPT_PRIORITY > configUNIQUE_INTERRUPT_PRIORITIES
	#error configMAX_API_CALL_INTERRUPT_PRIORITY must be less than or equal to configUNIQUE_INTERRUPT_PRIORITIES as the lower the numeric priority value the higher the logical interrupt priority
#endif

#if configUSE_PORT_OPTIMISED_TASK_SELECTION == 1
	/* Check the configuration. */
	#if( configMAX_PRIORITIES > 32 )
		#error configUSE_PORT_OPTIMISED_TASK_SELECTION can only be set to 1 when configMAX_PRIORITIES is less than or equal to 32.  It is very rare that a system requires more than 10 to 15 difference priorities as tasks that share a priority will time slice.
	#endif
#endif /* configUSE_PORT_OPTIMISED_TASK_SELECTION */

/* In case security extensions are implemented. */
#if configMAX_API_CALL_INTERRUPT_PRIORITY <= ( configUNIQUE_INTERRUPT_PRIORITIES / 2 )
	#error configMAX_API_CALL_INTERRUPT_PRIORITY must be greater than ( configUNIQUE_INTERRUPT_PRIORITIES / 2 )
#endif

/* The number of bits to shift for an interrupt priority is dependent on the
number of bits implemented by the interrupt controller. */
#if configUNIQUE_INTERRUPT_PRIORITIES == 16
	#define portPRIORITY_SHIFT 4
	#define portMAX_BINARY_POINT_VALUE	3
#elif configUNIQUE_INTERRUPT_PRIORITIES == 32
	#define portPRIORITY_SHIFT 3
	#define portMAX_BINARY_POINT_VALUE	2
#elif configUNIQUE_INTERRUPT_PRIORITIES == 64
	#define portPRIORITY_SHIFT 2
	#define portMAX_BINARY_POINT_VALUE	1
#elif configUNIQUE_INTERRUPT_PRIORITIES == 128
	#define portPRIORITY_SHIFT 1
	#define portMAX_BINARY_POINT_VALUE	0
#elif configUNIQUE_INTERRUPT_PRIORITIES == 256
	#define portPRIORITY_SHIFT 0
	#define portMAX_BINARY_POINT_VALUE	0
#else
	#error Invalid configUNIQUE_INTERRUPT_PRIORITIES setting.  configUNIQUE_INTERRUPT_PRIORITIES must be set to the number of unique priorities implemented by the target hardware
#endif

/* A critical section is exited when the critical section nesting count reaches
this value. */
#define portNO_CRITICAL_NESTING			( ( unsigned long ) 0 )

/* In all GICs 255 can be written to the priority mask register to unmask all
(but the lowest) interrupt priority. */
#define portUNMASK_VALUE				( 0xFF )

/* Tasks are not created with a floating point context, but can be given a
floating point context after they have been created.  A variable is stored as
part of the tasks context that holds portNO_FLOATING_POINT_CONTEXT if the task
does not have an FPU context, or any other value if the task does have an FPU
context. */
#define portNO_FLOATING_POINT_CONTEXT	( ( portSTACK_TYPE ) 0 )

/* Interrupt controller access addresses. */
#define portICCPMR_PRIORITY_MASK_OFFSET  		( 0x04 )
#define portICCIAR_INTERRUPT_ACKNOWLEDGE_OFFSET ( 0x0C )
#define portICCEOIR_END_OF_INTERRUPT_OFFSET 	( 0x10 )
#define portICCBPR_BINARY_POINT_OFFSET			( 0x08 )
#define portICCRPR_RUNNING_PRIORITY_OFFSET		( 0x14 )
#define portINTERRUPT_CONTROLLER_CPU_INTERFACE_ADDRESS 		( configINTERRUPT_CONTROLLER_BASE_ADDRESS + configINTERRUPT_CONTROLLER_CPU_INTERFACE_OFFSET )
#define portICCPMR_PRIORITY_MASK_REGISTER 					( *( ( volatile unsigned long * ) ( portINTERRUPT_CONTROLLER_CPU_INTERFACE_ADDRESS + portICCPMR_PRIORITY_MASK_OFFSET ) ) )
#define portICCIAR_INTERRUPT_ACKNOWLEDGE_REGISTER_ADDRESS 	( portINTERRUPT_CONTROLLER_CPU_INTERFACE_ADDRESS + portICCIAR_INTERRUPT_ACKNOWLEDGE_OFFSET )
#define portICCEOIR_END_OF_INTERRUPT_REGISTER_ADDRESS 		( portINTERRUPT_CONTROLLER_CPU_INTERFACE_ADDRESS + portICCEOIR_END_OF_INTERRUPT_OFFSET )
#define portICCPMR_PRIORITY_MASK_REGISTER_ADDRESS 			( portINTERRUPT_CONTROLLER_CPU_INTERFACE_ADDRESS + portICCPMR_PRIORITY_MASK_OFFSET )
#define portICCBPR_BINARY_POINT_REGISTER 					( *( ( const volatile unsigned long * ) ( portINTERRUPT_CONTROLLER_CPU_INTERFACE_ADDRESS + portICCBPR_BINARY_POINT_OFFSET ) ) )
#define portICCRPR_RUNNING_PRIORITY_REGISTER 				( *( ( const volatile unsigned char * ) ( portINTERRUPT_CONTROLLER_CPU_INTERFACE_ADDRESS + portICCRPR_RUNNING_PRIORITY_OFFSET ) ) )

/* Used by portASSERT_IF_INTERRUPT_PRIORITY_INVALID() when ensuring the binary
point is zero. */
#define portBINARY_POINT_BITS			( ( unsigned char ) 0x03 )

/* Constants required to setup the initial task context. */
#define portINITIAL_SPSR				( ( portSTACK_TYPE ) 0x1f ) /* System mode, ARM mode, interrupts enabled. */
#define portTHUMB_MODE_BIT				( ( portSTACK_TYPE ) 0x20 )
#define portINTERRUPT_ENABLE_BIT		( 0x80UL )
#define portTHUMB_MODE_ADDRESS			( 0x01UL )

/* Masks all bits in the APSR other than the mode bits. */
#define portAPSR_MODE_BITS_MASK			( 0x1F )

/* The value of the mode bits in the APSR when the CPU is executing in user
mode. */
#define portAPSR_USER_MODE				( 0x10 )

/* Macro to unmask all interrupt priorities. */
#define portCLEAR_INTERRUPT_MASK()											\
{																			\
	__disable_irq();														\
	portICCPMR_PRIORITY_MASK_REGISTER = portUNMASK_VALUE;					\
	__asm(	"DSB		\n"													\
			"ISB		\n" );												\
	__enable_irq();															\
}

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

/*
 * Starts the first task executing.  This function is necessarily written in
 * assembly code so is implemented in portASM.s.
 */
extern void vPortRestoreTaskContext( void );

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

/* A variable is used to keep track of the critical section nesting.  This
variable has to be stored as part of the task context and must be initialised to
a non zero value to ensure interrupts don't inadvertently become unmasked before
the scheduler starts.  As it is stored as part of the task context it will
automatically be set to 0 when the first task is started. */
volatile unsigned long ulCriticalNesting = 9999UL;

/* Used to pass constants into the ASM code.  The address at which variables are
placed is the constant value so indirect loads in the asm code are not
required. */
unsigned long ulICCIAR __attribute__( ( at( portICCIAR_INTERRUPT_ACKNOWLEDGE_REGISTER_ADDRESS ) ) );
unsigned long ulICCEOIR __attribute__( ( at( portICCEOIR_END_OF_INTERRUPT_REGISTER_ADDRESS ) ) );
unsigned long ulICCPMR __attribute__( ( at( portICCPMR_PRIORITY_MASK_REGISTER_ADDRESS ) ) );
unsigned long ulAsmAPIPriorityMask __attribute__( ( at( configMAX_API_CALL_INTERRUPT_PRIORITY << portPRIORITY_SHIFT ) ) );

/* Saved as part of the task context.  If ulPortTaskHasFPUContext is non-zero then
a floating point context must be saved and restored for the task. */
unsigned long ulPortTaskHasFPUContext = pdFALSE;

/* Set to 1 to pend a context switch from an ISR. */
unsigned long ulPortYieldRequired = pdFALSE;

/* Counts the interrupt nesting depth.  A context switch is only performed if
if the nesting depth is 0. */
unsigned long ulPortInterruptNesting = 0UL;

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

/*
 * See header file for description.
 */
portSTACK_TYPE *pxPortInitialiseStack( portSTACK_TYPE *pxTopOfStack, pdTASK_CODE pxCode, void *pvParameters )
{
	/* Setup the initial stack of the task.  The stack is set exactly as
	expected by the portRESTORE_CONTEXT() macro.

	The fist real value on the stack is the status register, which is set for
	system mode, with interrupts enabled.  A few NULLs are added first to ensure
	GDB does not try decoding a non-existent return address. */
	*pxTopOfStack = NULL;
	pxTopOfStack--;
	*pxTopOfStack = NULL;
	pxTopOfStack--;
	*pxTopOfStack = NULL;
	pxTopOfStack--;
	*pxTopOfStack = ( portSTACK_TYPE ) portINITIAL_SPSR;

	if( ( ( unsigned long ) pxCode & portTHUMB_MODE_ADDRESS ) != 0x00UL )
	{
		/* The task will start in THUMB mode. */
		*pxTopOfStack |= portTHUMB_MODE_BIT;
	}

	pxTopOfStack--;

	/* Next the return address, which in this case is the start of the task. */
	*pxTopOfStack = ( portSTACK_TYPE ) pxCode;
	pxTopOfStack--;

	/* Next all the registers other than the stack pointer. */
	*pxTopOfStack = ( portSTACK_TYPE ) 0x00000000;	/* R14 */
	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--;
	*pxTopOfStack = ( portSTACK_TYPE ) pvParameters; /* R0 */
	pxTopOfStack--;

	/* The task will start with a critical nesting count of 0 as interrupts are
	enabled. */
	*pxTopOfStack = portNO_CRITICAL_NESTING;
	pxTopOfStack--;

	/* The task will start without a floating point context.  A task that uses
	the floating point hardware must call vPortTaskUsesFPU() before executing
	any floating point instructions. */
	*pxTopOfStack = portNO_FLOATING_POINT_CONTEXT;

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

portBASE_TYPE xPortStartScheduler( void )
{
unsigned long ulAPSR;

	/* Only continue if the CPU is not in User mode.  The CPU must be in a
	Privileged mode for the scheduler to start. */
	__asm( "MRS ulAPSR, APSR" );
	ulAPSR &= portAPSR_MODE_BITS_MASK;
	configASSERT( ulAPSR != portAPSR_USER_MODE );

	if( ulAPSR != portAPSR_USER_MODE )
	{
		/* Only continue if the binary point value is set to its lowest possible
		setting.  See the comments in vPortValidateInterruptPriority() below for
		more information. */
		configASSERT( ( portICCBPR_BINARY_POINT_REGISTER & portBINARY_POINT_BITS ) <= portMAX_BINARY_POINT_VALUE );
		
		if( ( portICCBPR_BINARY_POINT_REGISTER & portBINARY_POINT_BITS ) <= portMAX_BINARY_POINT_VALUE )
		{	
			/* Start the timer that generates the tick ISR. */
			configSETUP_TICK_INTERRUPT();

			__enable_irq();
			vPortRestoreTaskContext();
		}
	}

	/* Will only get here if xTaskStartScheduler() was called with the CPU in
	a non-privileged mode or the binary point register was not set to its lowest
	possible value. */
	return 0;
}
/*-----------------------------------------------------------*/

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

void vPortEnterCritical( void )
{
	/* Disable interrupts as per portDISABLE_INTERRUPTS(); 	*/
	ulPortSetInterruptMask();

	/* 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 the critical section is being
		exited. */
		ulCriticalNesting--;

		/* If the nesting level has reached zero then all interrupt
		priorities must be re-enabled. */
		if( ulCriticalNesting == portNO_CRITICAL_NESTING )
		{
			/* Critical nesting has reached zero so all interrupt priorities
			should be unmasked. */
			portCLEAR_INTERRUPT_MASK();
		}
	}
}
/*-----------------------------------------------------------*/

void FreeRTOS_Tick_Handler( void )
{
	/* Set interrupt mask before altering scheduler structures.   The tick
	handler runs at the lowest priority, so interrupts cannot already be masked,
	so there is no need to save and restore the current mask value. */
	__disable_irq();
	portICCPMR_PRIORITY_MASK_REGISTER = ( configMAX_API_CALL_INTERRUPT_PRIORITY << portPRIORITY_SHIFT );
	__asm(	"DSB		\n"
			"ISB		\n" );
	__enable_irq();

	/* Increment the RTOS tick. */
	if( xTaskIncrementTick() != pdFALSE )
	{
		ulPortYieldRequired = pdTRUE;
	}

	/* Ensure all interrupt priorities are active again. */
	portCLEAR_INTERRUPT_MASK();
}
/*-----------------------------------------------------------*/

void vPortTaskUsesFPU( void )
{
unsigned long ulInitialFPSCR = 0;

	/* A task is registering the fact that it needs an FPU context.  Set the
	FPU flag (which is saved as part of the task context). */
	ulPortTaskHasFPUContext = pdTRUE;

	/* Initialise the floating point status register. */
	__asm( "FMXR 	FPSCR, ulInitialFPSCR" );
}
/*-----------------------------------------------------------*/

void vPortClearInterruptMask( unsigned long ulNewMaskValue )
{
	if( ulNewMaskValue == pdFALSE )
	{
		portCLEAR_INTERRUPT_MASK();
	}
}
/*-----------------------------------------------------------*/

unsigned long ulPortSetInterruptMask( void )
{
unsigned long ulReturn;

	__disable_irq();
	if( portICCPMR_PRIORITY_MASK_REGISTER == ( configMAX_API_CALL_INTERRUPT_PRIORITY << portPRIORITY_SHIFT ) )
	{
		/* Interrupts were already masked. */
		ulReturn = pdTRUE;
	}
	else
	{
		ulReturn = pdFALSE;
		portICCPMR_PRIORITY_MASK_REGISTER = ( configMAX_API_CALL_INTERRUPT_PRIORITY << portPRIORITY_SHIFT );
		__asm(	"DSB		\n"
				"ISB		\n" );
	}
	__enable_irq();

	return ulReturn;
}
/*-----------------------------------------------------------*/

#if( configASSERT_DEFINED == 1 )

	void vPortValidateInterruptPriority( void )
	{
		/* The following assertion will fail if a service routine (ISR) for
		an interrupt that has been assigned a priority above
		configMAX_SYSCALL_INTERRUPT_PRIORITY calls an ISR safe FreeRTOS API
		function.  ISR safe FreeRTOS API functions must *only* be called
		from interrupts that have been assigned a priority at or below
		configMAX_SYSCALL_INTERRUPT_PRIORITY.

		Numerically low interrupt priority numbers represent logically high
		interrupt priorities, therefore the priority of the interrupt must
		be set to a value equal to or numerically *higher* than
		configMAX_SYSCALL_INTERRUPT_PRIORITY.

		FreeRTOS maintains separate thread and ISR API functions to ensure
		interrupt entry is as fast and simple as possible.

		The following links provide detailed information:
		http://www.freertos.org/RTOS-Cortex-M3-M4.html
		http://www.freertos.org/FAQHelp.html */
		configASSERT( portICCRPR_RUNNING_PRIORITY_REGISTER >= ( configMAX_API_CALL_INTERRUPT_PRIORITY << portPRIORITY_SHIFT ) );

		/* Priority grouping:  The interrupt controller (GIC) allows the bits
		that define each interrupt's priority to be split between bits that
		define the interrupt's pre-emption priority bits and bits that define
		the interrupt's sub-priority.  For simplicity all bits must be defined
		to be pre-emption priority bits.  The following assertion will fail if
		this is not the case (if some bits represent a sub-priority).

		The priority grouping is configured by the GIC's binary point register
		(ICCBPR).  Writting 0 to ICCBPR will ensure it is set to its lowest
		possible value (which may be above 0). */
		configASSERT( portICCBPR_BINARY_POINT_REGISTER <= portMAX_BINARY_POINT_VALUE );
	}

#endif /* configASSERT_DEFINED */