/*
* 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
*
*/
/*-----------------------------------------------------------
* Implementation of functions defined in portable.h for the Philips ARM7 port.
*----------------------------------------------------------*/
/*
Changes from V3.2.2
+ Bug fix - The prescale value for the timer setup is now written to T0PR
instead of T0PC. This bug would have had no effect unless a prescale
value was actually used.
*/
/* Standard includes. */
#include <stdlib.h>
#include <intrinsics.h>
/* Scheduler includes. */
#include "FreeRTOS.h"
#include "task.h"
/* 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 initial stack. */
#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 )
/* Constants required to setup the PIT. */
#define portPIT_CLOCK_DIVISOR ( ( uint32_t ) 16 )
#define portPIT_COUNTER_VALUE ( ( ( configCPU_CLOCK_HZ / portPIT_CLOCK_DIVISOR ) / 1000UL ) * portTICK_PERIOD_MS )
/* Constants required to handle interrupts. */
#define portTIMER_MATCH_ISR_BIT ( ( uint8_t ) 0x01 )
#define portCLEAR_VIC_INTERRUPT ( ( uint32_t ) 0 )
/* Constants required to handle critical sections. */
#define portNO_CRITICAL_NESTING ( ( uint32_t ) 0 )
#define portINT_LEVEL_SENSITIVE 0
#define portPIT_ENABLE ( ( uint16_t ) 0x1 << 24 )
#define portPIT_INT_ENABLE ( ( uint16_t ) 0x1 << 25 )
/* 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 )
/*-----------------------------------------------------------*/
/* Setup the PIT to generate the tick interrupts. */
static void prvSetupTimerInterrupt( void );
/* ulCriticalNesting will get set to zero when the first task starts. It
cannot be initialised to 0 as this will cause interrupts to be enabled
during the kernel initialisation process. */
uint32_t ulCriticalNesting = ( uint32_t ) 9999;
/*-----------------------------------------------------------*/
/*
* Initialise the stack of a task to look exactly as if a call to
* portSAVE_CONTEXT had been called.
*
* See header file for description.
*/
StackType_t *pxPortInitialiseStack( StackType_t *pxTopOfStack, TaskFunction_t pxCode, void *pvParameters )
{
StackType_t *pxOriginalTOS;
pxOriginalTOS = pxTopOfStack;
/* Setup the initial stack of the task. The stack is set exactly as
expected by the portRESTORE_CONTEXT() macro. */
/* 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--;
/* When the task starts is will expect to find the function parameter in
R0. */
*pxTopOfStack = ( StackType_t ) pvParameters; /* R0 */
pxTopOfStack--;
/* The status register 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--;
/* Interrupt flags cannot always be stored on the stack and will
instead be stored in a variable, which is then saved as part of the
tasks context. */
*pxTopOfStack = portNO_CRITICAL_NESTING;
return pxTopOfStack;
}
/*-----------------------------------------------------------*/
BaseType_t xPortStartScheduler( void )
{
extern void vPortStartFirstTask( void );
/* Start the timer that generates the tick ISR. Interrupts are disabled
here already. */
prvSetupTimerInterrupt();
/* Start the first task. */
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 configUSE_PREEMPTION == 0
/* The cooperative scheduler requires a normal IRQ service routine to
simply increment the system tick. */
static __arm __irq void vPortNonPreemptiveTick( void );
static __arm __irq void vPortNonPreemptiveTick( void )
{
/* Increment the tick count - which may wake some tasks but as the
preemptive scheduler is not being used any woken task is not given
processor time no matter what its priority. */
xTaskIncrementTick();
/* Ready for the next interrupt. */
T0IR = portTIMER_MATCH_ISR_BIT;
VICVectAddr = portCLEAR_VIC_INTERRUPT;
}
#else
/* This function is called from an asm wrapper, so does not require the __irq
keyword. */
void vPortPreemptiveTick( void );
void vPortPreemptiveTick( void )
{
/* Increment the tick counter. */
if( xTaskIncrementTick() != pdFALSE )
{
/* The new tick value might unblock a task. Ensure the highest task that
is ready to execute is the task that will execute when the tick ISR
exits. */
vTaskSwitchContext();
}
/* Ready for the next interrupt. */
T0IR = portTIMER_MATCH_ISR_BIT;
VICVectAddr = portCLEAR_VIC_INTERRUPT;
}
#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
{
extern void ( vPortPreemptiveTickEntry )( void );
VICVectAddr0 = ( uint32_t ) vPortPreemptiveTickEntry;
}
#else
{
extern void ( vNonPreemptiveTick )( void );
VICVectAddr0 = ( int32_t ) vPortNonPreemptiveTick;
}
#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 first! */
__disable_interrupt();
/* 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_interrupt();
}
}
}
/*-----------------------------------------------------------*/