/*
* FreeRTOS Kernel V10.4.3
* Copyright (C) 2020 Amazon.com, Inc. or its affiliates. All Rights Reserved.
*
* Permission is hereby granted, free of charge, to any person obtaining a copy of
* this software and associated documentation files (the "Software"), to deal in
* the Software without restriction, including without limitation the rights to
* use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
* the Software, and to permit persons to whom the Software is furnished to do so,
* subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in all
* copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
* FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
* COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
* IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
* CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*
* https://www.FreeRTOS.org
* https://github.com/FreeRTOS
*
*/
/*-----------------------------------------------------------
* 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 uint32_t * ) 0xe000e010 )
#define portNVIC_SYSTICK_LOAD ( ( volatile uint32_t * ) 0xe000e014 )
#define portNVIC_SHPR3_REG ( ( volatile uint32_t * ) 0xe000ed20 )
#define portNVIC_SYSTICK_CLK 0x00000004
#define portNVIC_SYSTICK_INT 0x00000002
#define portNVIC_SYSTICK_ENABLE 0x00000001
#define portNVIC_PENDSV_PRI ( ( ( uint32_t ) configKERNEL_INTERRUPT_PRIORITY ) << 16 )
#define portNVIC_SYSTICK_PRI ( ( ( uint32_t ) configKERNEL_INTERRUPT_PRIORITY ) << 24 )
/* Masks off all bits but the VECTACTIVE bits in the ICSR register. */
#define portVECTACTIVE_MASK ( 0xFFUL )
/* Constants required to manipulate the VFP. */
#define portFPCCR ( ( volatile uint32_t * ) 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_EXC_RETURN ( 0xfffffffd )
/* Let the user override the pre-loading of the initial LR with the address of
* prvTaskExitError() in case it messes up unwinding of the stack in the
* debugger. */
#ifdef configTASK_RETURN_ADDRESS
#define portTASK_RETURN_ADDRESS configTASK_RETURN_ADDRESS
#else
#define portTASK_RETURN_ADDRESS prvTaskExitError
#endif
/* For strict compliance with the Cortex-M spec the task start address should
* have bit-0 clear, as it is loaded into the PC on exit from an ISR. */
#define portSTART_ADDRESS_MASK ( ( StackType_t ) 0xfffffffeUL )
/* The priority used by the kernel is assigned to a variable to make access
* from inline assembler easier. */
const uint32_t ulKernelPriority = configKERNEL_INTERRUPT_PRIORITY;
/* Each task maintains its own interrupt status in the critical nesting
* variable. */
static uint32_t 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 );
/*
* Used to catch tasks that attempt to return from their implementing function.
*/
static void prvTaskExitError( void );
/* This exists purely to allow the const to be used from within the
* port_asm.asm assembly file. */
const uint32_t ulMaxSyscallInterruptPriorityConst = configMAX_SYSCALL_INTERRUPT_PRIORITY;
/*-----------------------------------------------------------*/
/*
* See header file for description.
*/
StackType_t * pxPortInitialiseStack( StackType_t * pxTopOfStack,
TaskFunction_t 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 = ( ( StackType_t ) pxCode ) & portSTART_ADDRESS_MASK; /* PC */
pxTopOfStack--;
*pxTopOfStack = ( StackType_t ) portTASK_RETURN_ADDRESS; /* LR */
/* Save code space by skipping register initialisation. */
pxTopOfStack -= 5; /* R12, R3, R2 and R1. */
*pxTopOfStack = ( StackType_t ) pvParameters; /* R0 */
/* A save method is being used that requires each task to maintain its
* own exec return value. */
pxTopOfStack--;
*pxTopOfStack = portINITIAL_EXC_RETURN;
pxTopOfStack -= 8; /* R11, R10, R9, R8, R7, R6, R5 and R4. */
return pxTopOfStack;
}
/*-----------------------------------------------------------*/
static void prvTaskExitError( void )
{
/* A function that implements a task must not exit or attempt to return to
* its caller as there is nothing to return to. If a task wants to exit it
* should instead call vTaskDelete( NULL ).
*
* Artificially force an assert() to be triggered if configASSERT() is
* defined, then stop here so application writers can catch the error. */
configASSERT( ulCriticalNesting == ~0UL );
portDISABLE_INTERRUPTS();
for( ; ; )
{
}
}
/*-----------------------------------------------------------*/
/*
* See header file for description.
*/
BaseType_t xPortStartScheduler( void )
{
/* configMAX_SYSCALL_INTERRUPT_PRIORITY must not be set to 0.
* See https://www.FreeRTOS.org/RTOS-Cortex-M3-M4.html */
configASSERT( ( configMAX_SYSCALL_INTERRUPT_PRIORITY ) );
/* Make PendSV and SysTick the lowest priority interrupts. */
*( portNVIC_SHPR3_REG ) |= portNVIC_PENDSV_PRI;
*( portNVIC_SHPR3_REG ) |= 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 )
{
/* Not implemented in ports where there is nothing to return to.
* Artificially force an assert. */
configASSERT( ulCriticalNesting == 1000UL );
}
/*-----------------------------------------------------------*/
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();
/* This is not the interrupt safe version of the enter critical function so
* assert() if it is being called from an interrupt context. Only API
* functions that end in "FromISR" can be used in an interrupt. Only assert if
* the critical nesting count is 1 to protect against recursive calls if the
* assert function also uses a critical section. */
if( ulCriticalNesting == 1 )
{
configASSERT( ( ( *( portNVIC_INT_CTRL ) ) & portVECTACTIVE_MASK ) == 0 );
}
}
/*-----------------------------------------------------------*/
void vPortExitCritical( void )
{
configASSERT( ulCriticalNesting );
ulCriticalNesting--;
if( ulCriticalNesting == 0 )
{
portENABLE_INTERRUPTS();
}
}
/*-----------------------------------------------------------*/
void SysTick_Handler( void )
{
uint32_t 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;
}
/*-----------------------------------------------------------*/