/* | |
* 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 | |
* | |
*/ | |
/* Standard includes. */ | |
#include <stdlib.h> | |
/* Scheduler includes. */ | |
#include "FreeRTOS.h" | |
#include "task.h" | |
/* 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 portINSTRUCTION_SIZE ( ( StackType_t ) 4 ) | |
#define portNO_CRITICAL_SECTION_NESTING ( ( StackType_t ) 0 ) | |
/* Constants required to setup the tick ISR. */ | |
#define portENABLE_TIMER ( ( uint8_t ) 0x01 ) | |
#define portPRESCALE_VALUE 0x00 | |
#define portINTERRUPT_ON_MATCH ( ( uint32_t ) 0x01 ) | |
#define portRESET_COUNT_ON_MATCH ( ( uint32_t ) 0x02 ) | |
/* Constants required to setup the VIC for the tick ISR. */ | |
#define portTIMER_VIC_CHANNEL ( ( uint32_t ) 0x0004 ) | |
#define portTIMER_VIC_CHANNEL_BIT ( ( uint32_t ) 0x0010 ) | |
#define portTIMER_VIC_ENABLE ( ( uint32_t ) 0x0020 ) | |
/* Constants required to handle interrupts. */ | |
#define portTIMER_MATCH_ISR_BIT ( ( uint8_t ) 0x01 ) | |
#define portCLEAR_VIC_INTERRUPT ( ( uint32_t ) 0 ) | |
/*-----------------------------------------------------------*/ | |
/* The code generated by the Keil compiler does not maintain separate | |
stack and frame pointers. The portENTER_CRITICAL macro cannot therefore | |
use the stack as per other ports. Instead 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. */ | |
#define portNO_CRITICAL_NESTING ( ( uint32_t ) 0 ) | |
volatile uint32_t ulCriticalNesting = 9999UL; | |
/*-----------------------------------------------------------*/ | |
/* Setup the timer to generate the tick interrupts. */ | |
static void prvSetupTimerInterrupt( void ); | |
/* | |
* The scheduler can only be started from ARM mode, so | |
* vPortStartFirstSTask() is defined in portISR.c. | |
*/ | |
extern __asm void vPortStartFirstTask( void ); | |
/*-----------------------------------------------------------*/ | |
/* | |
* See header file for description. | |
*/ | |
StackType_t *pxPortInitialiseStack( StackType_t *pxTopOfStack, TaskFunction_t pxCode, void *pvParameters ) | |
{ | |
StackType_t *pxOriginalTOS; | |
/* Setup the initial stack of the task. The stack is set exactly as | |
expected by the portRESTORE_CONTEXT() macro. | |
Remember where the top of the (simulated) stack is before we place | |
anything on it. */ | |
pxOriginalTOS = pxTopOfStack; | |
/* To ensure asserts in tasks.c don't fail, although in this case the assert | |
is not really required. */ | |
pxTopOfStack--; | |
/* First on the stack is the return address - which in this case is the | |
start of the task. The offset is added to make the return address appear | |
as it would within an IRQ ISR. */ | |
*pxTopOfStack = ( StackType_t ) pxCode + portINSTRUCTION_SIZE; | |
pxTopOfStack--; | |
*pxTopOfStack = ( StackType_t ) 0xaaaaaaaa; /* R14 */ | |
pxTopOfStack--; | |
*pxTopOfStack = ( StackType_t ) pxOriginalTOS; /* Stack used when task starts goes in R13. */ | |
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 last thing onto the stack is the status register, which is set for | |
system mode, with interrupts enabled. */ | |
*pxTopOfStack = ( StackType_t ) portINITIAL_SPSR; | |
if( ( ( uint32_t ) pxCode & 0x01UL ) != 0x00UL ) | |
{ | |
/* We want the task to start in thumb mode. */ | |
*pxTopOfStack |= portTHUMB_MODE_BIT; | |
} | |
pxTopOfStack--; | |
/* The code generated by the Keil compiler does not maintain separate | |
stack and frame pointers. The portENTER_CRITICAL macro cannot therefore | |
use the stack as per other ports. Instead 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 is initially set to zero. */ | |
*pxTopOfStack = portNO_CRITICAL_SECTION_NESTING; | |
return pxTopOfStack; | |
} | |
/*-----------------------------------------------------------*/ | |
BaseType_t xPortStartScheduler( void ) | |
{ | |
/* Start the timer that generates the tick ISR. */ | |
prvSetupTimerInterrupt(); | |
/* Start the first task. This is done from portISR.c as ARM mode must be | |
used. */ | |
vPortStartFirstTask(); | |
/* Should not get here! */ | |
return 0; | |
} | |
/*-----------------------------------------------------------*/ | |
void vPortEndScheduler( void ) | |
{ | |
/* It is unlikely that the ARM port will require this function as there | |
is nothing to return to. If this is required - stop the tick ISR then | |
return back to main. */ | |
} | |
/*-----------------------------------------------------------*/ | |
#if configUSE_PREEMPTION == 0 | |
/* | |
* The cooperative scheduler requires a normal IRQ service routine to | |
* simply increment the system tick. | |
*/ | |
void vNonPreemptiveTick( void ) __irq; | |
void vNonPreemptiveTick( void ) __irq | |
{ | |
/* Increment the tick count - this may make a delaying task ready | |
to run - but a context switch is not performed. */ | |
xTaskIncrementTick(); | |
T0IR = portTIMER_MATCH_ISR_BIT; /* Clear the timer event */ | |
VICVectAddr = portCLEAR_VIC_INTERRUPT; /* Acknowledge the Interrupt */ | |
} | |
#else | |
/* | |
************************************************************************** | |
* The preemptive scheduler ISR is written in assembler and can be found | |
* in the portASM.s file. This will only get used if portUSE_PREEMPTION | |
* is set to 1 in portmacro.h | |
************************************************************************** | |
*/ | |
void vPreemptiveTick( void ); | |
#endif | |
/*-----------------------------------------------------------*/ | |
static void prvSetupTimerInterrupt( void ) | |
{ | |
uint32_t ulCompareMatch; | |
/* A 1ms tick does not require the use of the timer prescale. This is | |
defaulted to zero but can be used if necessary. */ | |
T0PR = portPRESCALE_VALUE; | |
/* Calculate the match value required for our wanted tick rate. */ | |
ulCompareMatch = configCPU_CLOCK_HZ / configTICK_RATE_HZ; | |
/* Protect against divide by zero. Using an if() statement still results | |
in a warning - hence the #if. */ | |
#if portPRESCALE_VALUE != 0 | |
{ | |
ulCompareMatch /= ( portPRESCALE_VALUE + 1 ); | |
} | |
#endif | |
T0MR0 = ulCompareMatch; | |
/* Generate tick with timer 0 compare match. */ | |
T0MCR = portRESET_COUNT_ON_MATCH | portINTERRUPT_ON_MATCH; | |
/* Setup the VIC for the timer. */ | |
VICIntSelect &= ~( portTIMER_VIC_CHANNEL_BIT ); | |
VICIntEnable |= portTIMER_VIC_CHANNEL_BIT; | |
/* The ISR installed depends on whether the preemptive or cooperative | |
scheduler is being used. */ | |
#if configUSE_PREEMPTION == 1 | |
{ | |
VICVectAddr0 = ( uint32_t ) vPreemptiveTick; | |
} | |
#else | |
{ | |
VICVectAddr0 = ( uint32_t ) vNonPreemptiveTick; | |
} | |
#endif | |
VICVectCntl0 = portTIMER_VIC_CHANNEL | portTIMER_VIC_ENABLE; | |
/* Start the timer - interrupts are disabled when this function is called | |
so it is okay to do this here. */ | |
T0TCR = portENABLE_TIMER; | |
} | |
/*-----------------------------------------------------------*/ | |
void vPortEnterCritical( void ) | |
{ | |
/* Disable interrupts as per portDISABLE_INTERRUPTS(); */ | |
__disable_irq(); | |
/* 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(). */ | |
__enable_irq(); | |
} | |
} | |
} | |
/*-----------------------------------------------------------*/ | |