/*
* FreeRTOS Kernel V10.6.2
* 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();
}
}
}
/*-----------------------------------------------------------*/