/* | |
* FreeRTOS Kernel <DEVELOPMENT BRANCH> | |
* Copyright (C) 2021 Amazon.com, Inc. or its affiliates. All Rights Reserved. | |
* | |
* SPDX-License-Identifier: MIT | |
* | |
* 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 | |
* | |
*/ | |
/* IAR includes. */ | |
#include <intrinsics.h> | |
/* Scheduler includes. */ | |
#include "FreeRTOS.h" | |
#include "task.h" | |
#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 */ | |
#ifndef configSETUP_TICK_INTERRUPT | |
#error configSETUP_TICK_INTERRUPT() must be defined in FreeRTOSConfig.h to call the function that sets up the tick interrupt. A default that uses the PIT is provided in the official demo application. | |
#endif | |
#ifndef configCLEAR_TICK_INTERRUPT | |
#error configCLEAR_TICK_INTERRUPT must be defined in FreeRTOSConfig.h to clear which ever interrupt was used to generate the tick interrupt. A default that uses the PIT is provided in the official demo application. | |
#endif | |
/* A critical section is exited when the critical section nesting count reaches | |
this value. */ | |
#define portNO_CRITICAL_NESTING ( ( uint32_t ) 0 ) | |
/* 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 ( ( StackType_t ) 0 ) | |
/* Constants required to setup the initial task context. */ | |
#define portINITIAL_SPSR ( ( StackType_t ) 0x1f ) /* System mode, ARM mode, interrupts enabled. */ | |
#define portTHUMB_MODE_BIT ( ( StackType_t ) 0x20 ) | |
#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 ) | |
/*-----------------------------------------------------------*/ | |
/* | |
* Starts the first task executing. This function is necessarily written in | |
* assembly code so is implemented in portASM.s. | |
*/ | |
extern void vPortRestoreTaskContext( void ); | |
/* | |
* Used to catch tasks that attempt to return from their implementing function. | |
*/ | |
static void prvTaskExitError( 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 uint32_t ulCriticalNesting = 9999UL; | |
/* 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. */ | |
uint32_t ulPortTaskHasFPUContext = pdFALSE; | |
/* Set to 1 to pend a context switch from an ISR. */ | |
uint32_t ulPortYieldRequired = pdFALSE; | |
/* Counts the interrupt nesting depth. A context switch is only performed if | |
if the nesting depth is 0. */ | |
uint32_t ulPortInterruptNesting = 0UL; | |
/*-----------------------------------------------------------*/ | |
/* | |
* See header file for description. | |
*/ | |
StackType_t *pxPortInitialiseStack( StackType_t *pxTopOfStack, TaskFunction_t 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 = ( StackType_t ) portINITIAL_SPSR; | |
if( ( ( uint32_t ) 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 = ( StackType_t ) pxCode; | |
pxTopOfStack--; | |
/* Next all the registers other than the stack pointer. */ | |
*pxTopOfStack = ( StackType_t ) prvTaskExitError; /* R14 */ | |
pxTopOfStack--; | |
*pxTopOfStack = ( StackType_t ) 0x12121212; /* R12 */ | |
pxTopOfStack--; | |
*pxTopOfStack = ( StackType_t ) 0x11111111; /* R11 */ | |
pxTopOfStack--; | |
*pxTopOfStack = ( StackType_t ) 0x10101010; /* R10 */ | |
pxTopOfStack--; | |
*pxTopOfStack = ( StackType_t ) 0x09090909; /* R9 */ | |
pxTopOfStack--; | |
*pxTopOfStack = ( StackType_t ) 0x08080808; /* R8 */ | |
pxTopOfStack--; | |
*pxTopOfStack = ( StackType_t ) 0x07070707; /* R7 */ | |
pxTopOfStack--; | |
*pxTopOfStack = ( StackType_t ) 0x06060606; /* R6 */ | |
pxTopOfStack--; | |
*pxTopOfStack = ( StackType_t ) 0x05050505; /* R5 */ | |
pxTopOfStack--; | |
*pxTopOfStack = ( StackType_t ) 0x04040404; /* R4 */ | |
pxTopOfStack--; | |
*pxTopOfStack = ( StackType_t ) 0x03030303; /* R3 */ | |
pxTopOfStack--; | |
*pxTopOfStack = ( StackType_t ) 0x02020202; /* R2 */ | |
pxTopOfStack--; | |
*pxTopOfStack = ( StackType_t ) 0x01010101; /* R1 */ | |
pxTopOfStack--; | |
*pxTopOfStack = ( StackType_t ) 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; | |
} | |
/*-----------------------------------------------------------*/ | |
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( ulPortInterruptNesting == ~0UL ); | |
portDISABLE_INTERRUPTS(); | |
for( ;; ); | |
} | |
/*-----------------------------------------------------------*/ | |
BaseType_t xPortStartScheduler( void ) | |
{ | |
uint32_t 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 volatile ( "MRS %0, APSR" : "=r" ( ulAPSR ) ); | |
ulAPSR &= portAPSR_MODE_BITS_MASK; | |
configASSERT( ulAPSR != portAPSR_USER_MODE ); | |
if( ulAPSR != portAPSR_USER_MODE ) | |
{ | |
/* Start the timer that generates the tick ISR. */ | |
configSETUP_TICK_INTERRUPT(); | |
vPortRestoreTaskContext(); | |
} | |
/* Will only get here if vTaskStartScheduler() 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 ) | |
{ | |
/* Not implemented in ports where there is nothing to return to. | |
Artificially force an assert. */ | |
configASSERT( ulCriticalNesting == 1000UL ); | |
} | |
/*-----------------------------------------------------------*/ | |
void vPortEnterCritical( void ) | |
{ | |
portDISABLE_INTERRUPTS(); | |
/* 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++; | |
/* 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( ulPortInterruptNesting == 0 ); | |
} | |
} | |
/*-----------------------------------------------------------*/ | |
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. */ | |
portENABLE_INTERRUPTS(); | |
} | |
} | |
} | |
/*-----------------------------------------------------------*/ | |
void FreeRTOS_Tick_Handler( void ) | |
{ | |
portDISABLE_INTERRUPTS(); | |
/* Increment the RTOS tick. */ | |
if( xTaskIncrementTick() != pdFALSE ) | |
{ | |
ulPortYieldRequired = pdTRUE; | |
} | |
portENABLE_INTERRUPTS(); | |
configCLEAR_TICK_INTERRUPT(); | |
} | |
/*-----------------------------------------------------------*/ | |
void vPortTaskUsesFPU( void ) | |
{ | |
uint32_t 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, %0" :: "r" (ulInitialFPSCR) ); | |
} | |
/*-----------------------------------------------------------*/ | |