/*
* 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 ARM CM4F port.
*----------------------------------------------------------*/
/* Scheduler includes. */
#include "FreeRTOS.h"
#include "task.h"
#ifndef __TI_VFP_SUPPORT__
#error This port can only be used when the project options are configured to enable hardware floating point support.
#endif
#if ( configMAX_SYSCALL_INTERRUPT_PRIORITY == 0 )
#error configMAX_SYSCALL_INTERRUPT_PRIORITY must not be set to 0. See http: /*www.FreeRTOS.org/RTOS-Cortex-M3-M4.html */
#endif
/* Constants required to manipulate the core. Registers first... */
#define portNVIC_SYSTICK_CTRL_REG ( *( ( volatile uint32_t * ) 0xe000e010 ) )
#define portNVIC_SYSTICK_LOAD_REG ( *( ( volatile uint32_t * ) 0xe000e014 ) )
#define portNVIC_SYSTICK_CURRENT_VALUE_REG ( *( ( volatile uint32_t * ) 0xe000e018 ) )
#define portNVIC_SHPR3_REG ( *( ( volatile uint32_t * ) 0xe000ed20 ) )
/* ...then bits in the registers. */
#define portNVIC_SYSTICK_CLK_BIT ( 1UL << 2UL )
#define portNVIC_SYSTICK_INT_BIT ( 1UL << 1UL )
#define portNVIC_SYSTICK_ENABLE_BIT ( 1UL << 0UL )
#define portNVIC_SYSTICK_COUNT_FLAG_BIT ( 1UL << 16UL )
#define portNVIC_PENDSVCLEAR_BIT ( 1UL << 27UL )
#define portNVIC_PEND_SYSTICK_SET_BIT ( 1UL << 26UL )
#define portNVIC_PEND_SYSTICK_CLEAR_BIT ( 1UL << 25UL )
#define portMIN_INTERRUPT_PRIORITY ( 255UL )
#define portNVIC_PENDSV_PRI ( ( ( uint32_t ) portMIN_INTERRUPT_PRIORITY ) << 16UL )
#define portNVIC_SYSTICK_PRI ( ( ( uint32_t ) portMIN_INTERRUPT_PRIORITY ) << 24UL )
/* Constants required to check the validity of an interrupt priority. */
#define portFIRST_USER_INTERRUPT_NUMBER ( 16 )
#define portNVIC_IP_REGISTERS_OFFSET_16 ( 0xE000E3F0 )
#define portAIRCR_REG ( *( ( volatile uint32_t * ) 0xE000ED0C ) )
#define portMAX_8_BIT_VALUE ( ( uint8_t ) 0xff )
#define portTOP_BIT_OF_BYTE ( ( uint8_t ) 0x80 )
#define portMAX_PRIGROUP_BITS ( ( uint8_t ) 7 )
#define portPRIORITY_GROUP_MASK ( 0x07UL << 8UL )
#define portPRIGROUP_SHIFT ( 8UL )
/* 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 )
/* The systick is a 24-bit counter. */
#define portMAX_24_BIT_NUMBER ( 0xffffffUL )
/* A fiddle factor to estimate the number of SysTick counts that would have
* occurred while the SysTick counter is stopped during tickless idle
* calculations. */
#define portMISSED_COUNTS_FACTOR ( 94UL )
/* 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 )
/* Let the user override the default SysTick clock rate. If defined by the
* user, this symbol must equal the SysTick clock rate when the CLK bit is 0 in the
* configuration register. */
#ifndef configSYSTICK_CLOCK_HZ
#define configSYSTICK_CLOCK_HZ ( configCPU_CLOCK_HZ )
/* Ensure the SysTick is clocked at the same frequency as the core. */
#define portNVIC_SYSTICK_CLK_BIT_CONFIG ( portNVIC_SYSTICK_CLK_BIT )
#else
/* Select the option to clock SysTick not at the same frequency as the core. */
#define portNVIC_SYSTICK_CLK_BIT_CONFIG ( 0 )
#endif
/*
* Setup the timer to generate the tick interrupts. The implementation in this
* file is weak to allow application writers to change the timer used to
* generate the tick interrupt.
*/
void vPortSetupTimerInterrupt( void );
/*
* Exception handlers.
*/
void xPortSysTickHandler( void );
/*
* Start first task is a separate function so it can be tested in isolation.
*/
extern void vPortStartFirstTask( void );
/*
* Turn the VFP on.
*/
extern void vPortEnableVFP( void );
/*
* Used to catch tasks that attempt to return from their implementing function.
*/
static void prvTaskExitError( void );
/*-----------------------------------------------------------*/
/* Required to allow portasm.asm access the configMAX_SYSCALL_INTERRUPT_PRIORITY
* setting. */
const uint32_t ulMaxSyscallInterruptPriority = configMAX_SYSCALL_INTERRUPT_PRIORITY;
/* Each task maintains its own interrupt status in the critical nesting
* variable. */
static UBaseType_t uxCriticalNesting = 0xaaaaaaaa;
/*
* The number of SysTick increments that make up one tick period.
*/
#if ( configUSE_TICKLESS_IDLE == 1 )
static uint32_t ulTimerCountsForOneTick = 0;
#endif /* configUSE_TICKLESS_IDLE */
/*
* The maximum number of tick periods that can be suppressed is limited by the
* 24 bit resolution of the SysTick timer.
*/
#if ( configUSE_TICKLESS_IDLE == 1 )
static uint32_t xMaximumPossibleSuppressedTicks = 0;
#endif /* configUSE_TICKLESS_IDLE */
/*
* Compensate for the CPU cycles that pass while the SysTick is stopped (low
* power functionality only.
*/
#if ( configUSE_TICKLESS_IDLE == 1 )
static uint32_t ulStoppedTimerCompensation = 0;
#endif /* configUSE_TICKLESS_IDLE */
/*
* Used by the portASSERT_IF_INTERRUPT_PRIORITY_INVALID() macro to ensure
* FreeRTOS API functions are not called from interrupts that have been assigned
* a priority above configMAX_SYSCALL_INTERRUPT_PRIORITY.
*/
#if ( configASSERT_DEFINED == 1 )
static uint8_t ucMaxSysCallPriority = 0;
static uint32_t ulMaxPRIGROUPValue = 0;
static const volatile uint8_t * const pcInterruptPriorityRegisters = ( uint8_t * ) portNVIC_IP_REGISTERS_OFFSET_16;
#endif /* configASSERT_DEFINED */
/*-----------------------------------------------------------*/
/*
* 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 ) prvTaskExitError; /* 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( uxCriticalNesting == ~0UL );
portDISABLE_INTERRUPTS();
for( ; ; )
{
}
}
/*-----------------------------------------------------------*/
/*
* See header file for description.
*/
BaseType_t xPortStartScheduler( void )
{
#if ( configASSERT_DEFINED == 1 )
{
volatile uint8_t ucOriginalPriority;
volatile uint32_t ulImplementedPrioBits = 0;
volatile uint8_t * const pucFirstUserPriorityRegister = ( uint8_t * ) ( portNVIC_IP_REGISTERS_OFFSET_16 + portFIRST_USER_INTERRUPT_NUMBER );
volatile uint8_t ucMaxPriorityValue;
/* Determine the maximum priority from which ISR safe FreeRTOS API
* functions can be called. ISR safe functions are those that end in
* "FromISR". FreeRTOS maintains separate thread and ISR API functions to
* ensure interrupt entry is as fast and simple as possible.
*
* Save the interrupt priority value that is about to be clobbered. */
ucOriginalPriority = *pucFirstUserPriorityRegister;
/* Determine the number of priority bits available. First write to all
* possible bits. */
*pucFirstUserPriorityRegister = portMAX_8_BIT_VALUE;
/* Read the value back to see how many bits stuck. */
ucMaxPriorityValue = *pucFirstUserPriorityRegister;
/* Use the same mask on the maximum system call priority. */
ucMaxSysCallPriority = configMAX_SYSCALL_INTERRUPT_PRIORITY & ucMaxPriorityValue;
/* Check that the maximum system call priority is nonzero after
* accounting for the number of priority bits supported by the
* hardware. A priority of 0 is invalid because setting the BASEPRI
* register to 0 unmasks all interrupts, and interrupts with priority 0
* cannot be masked using BASEPRI.
* See https://www.FreeRTOS.org/RTOS-Cortex-M3-M4.html */
configASSERT( ucMaxSysCallPriority );
/* Check that the bits not implemented in hardware are zero in
* configMAX_SYSCALL_INTERRUPT_PRIORITY. */
configASSERT( ( configMAX_SYSCALL_INTERRUPT_PRIORITY & ( ~ucMaxPriorityValue ) ) == 0U );
/* Calculate the maximum acceptable priority group value for the number
* of bits read back. */
while( ( ucMaxPriorityValue & portTOP_BIT_OF_BYTE ) == portTOP_BIT_OF_BYTE )
{
ulImplementedPrioBits++;
ucMaxPriorityValue <<= ( uint8_t ) 0x01;
}
if( ulImplementedPrioBits == 8 )
{
/* When the hardware implements 8 priority bits, there is no way for
* the software to configure PRIGROUP to not have sub-priorities. As
* a result, the least significant bit is always used for sub-priority
* and there are 128 preemption priorities and 2 sub-priorities.
*
* This may cause some confusion in some cases - for example, if
* configMAX_SYSCALL_INTERRUPT_PRIORITY is set to 5, both 5 and 4
* priority interrupts will be masked in Critical Sections as those
* are at the same preemption priority. This may appear confusing as
* 4 is higher (numerically lower) priority than
* configMAX_SYSCALL_INTERRUPT_PRIORITY and therefore, should not
* have been masked. Instead, if we set configMAX_SYSCALL_INTERRUPT_PRIORITY
* to 4, this confusion does not happen and the behaviour remains the same.
*
* The following assert ensures that the sub-priority bit in the
* configMAX_SYSCALL_INTERRUPT_PRIORITY is clear to avoid the above mentioned
* confusion. */
configASSERT( ( configMAX_SYSCALL_INTERRUPT_PRIORITY & 0x1U ) == 0U );
ulMaxPRIGROUPValue = 0;
}
else
{
ulMaxPRIGROUPValue = portMAX_PRIGROUP_BITS - ulImplementedPrioBits;
}
/* Shift the priority group value back to its position within the AIRCR
* register. */
ulMaxPRIGROUPValue <<= portPRIGROUP_SHIFT;
ulMaxPRIGROUPValue &= portPRIORITY_GROUP_MASK;
/* Restore the clobbered interrupt priority register to its original
* value. */
*pucFirstUserPriorityRegister = ucOriginalPriority;
}
#endif /* configASSERT_DEFINED */
/* 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. */
vPortSetupTimerInterrupt();
/* Initialise the critical nesting count ready for the first task. */
uxCriticalNesting = 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( uxCriticalNesting == 1000UL );
}
/*-----------------------------------------------------------*/
void vPortEnterCritical( void )
{
portDISABLE_INTERRUPTS();
uxCriticalNesting++;
/* 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( uxCriticalNesting == 1 )
{
configASSERT( ( portNVIC_INT_CTRL_REG & portVECTACTIVE_MASK ) == 0 );
}
}
/*-----------------------------------------------------------*/
void vPortExitCritical( void )
{
configASSERT( uxCriticalNesting );
uxCriticalNesting--;
if( uxCriticalNesting == 0 )
{
portENABLE_INTERRUPTS();
}
}
/*-----------------------------------------------------------*/
void xPortSysTickHandler( void )
{
/* The SysTick runs at the lowest interrupt priority, so when this interrupt
* executes all interrupts must be unmasked. There is therefore no need to
* save and then restore the interrupt mask value as its value is already
* known. */
( void ) portSET_INTERRUPT_MASK_FROM_ISR();
{
/* Increment the RTOS tick. */
if( xTaskIncrementTick() != pdFALSE )
{
/* A context switch is required. Context switching is performed in
* the PendSV interrupt. Pend the PendSV interrupt. */
portNVIC_INT_CTRL_REG = portNVIC_PENDSVSET_BIT;
}
}
portCLEAR_INTERRUPT_MASK_FROM_ISR( 0 );
}
/*-----------------------------------------------------------*/
#if ( configUSE_TICKLESS_IDLE == 1 )
#pragma WEAK( vPortSuppressTicksAndSleep )
void vPortSuppressTicksAndSleep( TickType_t xExpectedIdleTime )
{
uint32_t ulReloadValue, ulCompleteTickPeriods, ulCompletedSysTickDecrements, ulSysTickDecrementsLeft;
TickType_t xModifiableIdleTime;
/* Make sure the SysTick reload value does not overflow the counter. */
if( xExpectedIdleTime > xMaximumPossibleSuppressedTicks )
{
xExpectedIdleTime = xMaximumPossibleSuppressedTicks;
}
/* Enter a critical section but don't use the taskENTER_CRITICAL()
* method as that will mask interrupts that should exit sleep mode. */
__asm( " cpsid i" );
__asm( " dsb" );
__asm( " isb" );
/* If a context switch is pending or a task is waiting for the scheduler
* to be unsuspended then abandon the low power entry. */
if( eTaskConfirmSleepModeStatus() == eAbortSleep )
{
/* Re-enable interrupts - see comments above the cpsid instruction
* above. */
__asm( " cpsie i" );
}
else
{
/* Stop the SysTick momentarily. The time the SysTick is stopped for
* is accounted for as best it can be, but using the tickless mode will
* inevitably result in some tiny drift of the time maintained by the
* kernel with respect to calendar time. */
portNVIC_SYSTICK_CTRL_REG = ( portNVIC_SYSTICK_CLK_BIT_CONFIG | portNVIC_SYSTICK_INT_BIT );
/* Use the SysTick current-value register to determine the number of
* SysTick decrements remaining until the next tick interrupt. If the
* current-value register is zero, then there are actually
* ulTimerCountsForOneTick decrements remaining, not zero, because the
* SysTick requests the interrupt when decrementing from 1 to 0. */
ulSysTickDecrementsLeft = portNVIC_SYSTICK_CURRENT_VALUE_REG;
if( ulSysTickDecrementsLeft == 0 )
{
ulSysTickDecrementsLeft = ulTimerCountsForOneTick;
}
/* Calculate the reload value required to wait xExpectedIdleTime
* tick periods. -1 is used because this code normally executes part
* way through the first tick period. But if the SysTick IRQ is now
* pending, then clear the IRQ, suppressing the first tick, and correct
* the reload value to reflect that the second tick period is already
* underway. The expected idle time is always at least two ticks. */
ulReloadValue = ulSysTickDecrementsLeft + ( ulTimerCountsForOneTick * ( xExpectedIdleTime - 1UL ) );
if( ( portNVIC_INT_CTRL_REG & portNVIC_PEND_SYSTICK_SET_BIT ) != 0 )
{
portNVIC_INT_CTRL_REG = portNVIC_PEND_SYSTICK_CLEAR_BIT;
ulReloadValue -= ulTimerCountsForOneTick;
}
if( ulReloadValue > ulStoppedTimerCompensation )
{
ulReloadValue -= ulStoppedTimerCompensation;
}
/* Set the new reload value. */
portNVIC_SYSTICK_LOAD_REG = ulReloadValue;
/* Clear the SysTick count flag and set the count value back to
* zero. */
portNVIC_SYSTICK_CURRENT_VALUE_REG = 0UL;
/* Restart SysTick. */
portNVIC_SYSTICK_CTRL_REG |= portNVIC_SYSTICK_ENABLE_BIT;
/* Sleep until something happens. configPRE_SLEEP_PROCESSING() can
* set its parameter to 0 to indicate that its implementation contains
* its own wait for interrupt or wait for event instruction, and so wfi
* should not be executed again. However, the original expected idle
* time variable must remain unmodified, so a copy is taken. */
xModifiableIdleTime = xExpectedIdleTime;
configPRE_SLEEP_PROCESSING( xModifiableIdleTime );
if( xModifiableIdleTime > 0 )
{
__asm( " dsb" );
__asm( " wfi" );
__asm( " isb" );
}
configPOST_SLEEP_PROCESSING( xExpectedIdleTime );
/* Re-enable interrupts to allow the interrupt that brought the MCU
* out of sleep mode to execute immediately. See comments above
* the cpsid instruction above. */
__asm( " cpsie i" );
__asm( " dsb" );
__asm( " isb" );
/* Disable interrupts again because the clock is about to be stopped
* and interrupts that execute while the clock is stopped will increase
* any slippage between the time maintained by the RTOS and calendar
* time. */
__asm( " cpsid i" );
__asm( " dsb" );
__asm( " isb" );
/* Disable the SysTick clock without reading the
* portNVIC_SYSTICK_CTRL_REG register to ensure the
* portNVIC_SYSTICK_COUNT_FLAG_BIT is not cleared if it is set. Again,
* the time the SysTick is stopped for is accounted for as best it can
* be, but using the tickless mode will inevitably result in some tiny
* drift of the time maintained by the kernel with respect to calendar
* time*/
portNVIC_SYSTICK_CTRL_REG = ( portNVIC_SYSTICK_CLK_BIT_CONFIG | portNVIC_SYSTICK_INT_BIT );
/* Determine whether the SysTick has already counted to zero. */
if( ( portNVIC_SYSTICK_CTRL_REG & portNVIC_SYSTICK_COUNT_FLAG_BIT ) != 0 )
{
uint32_t ulCalculatedLoadValue;
/* The tick interrupt ended the sleep (or is now pending), and
* a new tick period has started. Reset portNVIC_SYSTICK_LOAD_REG
* with whatever remains of the new tick period. */
ulCalculatedLoadValue = ( ulTimerCountsForOneTick - 1UL ) - ( ulReloadValue - portNVIC_SYSTICK_CURRENT_VALUE_REG );
/* Don't allow a tiny value, or values that have somehow
* underflowed because the post sleep hook did something
* that took too long or because the SysTick current-value register
* is zero. */
if( ( ulCalculatedLoadValue <= ulStoppedTimerCompensation ) || ( ulCalculatedLoadValue > ulTimerCountsForOneTick ) )
{
ulCalculatedLoadValue = ( ulTimerCountsForOneTick - 1UL );
}
portNVIC_SYSTICK_LOAD_REG = ulCalculatedLoadValue;
/* As the pending tick will be processed as soon as this
* function exits, the tick value maintained by the tick is stepped
* forward by one less than the time spent waiting. */
ulCompleteTickPeriods = xExpectedIdleTime - 1UL;
}
else
{
/* Something other than the tick interrupt ended the sleep. */
/* Use the SysTick current-value register to determine the
* number of SysTick decrements remaining until the expected idle
* time would have ended. */
ulSysTickDecrementsLeft = portNVIC_SYSTICK_CURRENT_VALUE_REG;
#if ( portNVIC_SYSTICK_CLK_BIT_CONFIG != portNVIC_SYSTICK_CLK_BIT )
{
/* If the SysTick is not using the core clock, the current-
* value register might still be zero here. In that case, the
* SysTick didn't load from the reload register, and there are
* ulReloadValue decrements remaining in the expected idle
* time, not zero. */
if( ulSysTickDecrementsLeft == 0 )
{
ulSysTickDecrementsLeft = ulReloadValue;
}
}
#endif /* portNVIC_SYSTICK_CLK_BIT_CONFIG */
/* Work out how long the sleep lasted rounded to complete tick
* periods (not the ulReload value which accounted for part
* ticks). */
ulCompletedSysTickDecrements = ( xExpectedIdleTime * ulTimerCountsForOneTick ) - ulSysTickDecrementsLeft;
/* How many complete tick periods passed while the processor
* was waiting? */
ulCompleteTickPeriods = ulCompletedSysTickDecrements / ulTimerCountsForOneTick;
/* The reload value is set to whatever fraction of a single tick
* period remains. */
portNVIC_SYSTICK_LOAD_REG = ( ( ulCompleteTickPeriods + 1UL ) * ulTimerCountsForOneTick ) - ulCompletedSysTickDecrements;
}
/* Restart SysTick so it runs from portNVIC_SYSTICK_LOAD_REG again,
* then set portNVIC_SYSTICK_LOAD_REG back to its standard value. If
* the SysTick is not using the core clock, temporarily configure it to
* use the core clock. This configuration forces the SysTick to load
* from portNVIC_SYSTICK_LOAD_REG immediately instead of at the next
* cycle of the other clock. Then portNVIC_SYSTICK_LOAD_REG is ready
* to receive the standard value immediately. */
portNVIC_SYSTICK_CURRENT_VALUE_REG = 0UL;
portNVIC_SYSTICK_CTRL_REG = portNVIC_SYSTICK_CLK_BIT | portNVIC_SYSTICK_INT_BIT | portNVIC_SYSTICK_ENABLE_BIT;
#if ( portNVIC_SYSTICK_CLK_BIT_CONFIG == portNVIC_SYSTICK_CLK_BIT )
{
portNVIC_SYSTICK_LOAD_REG = ulTimerCountsForOneTick - 1UL;
}
#else
{
/* The temporary usage of the core clock has served its purpose,
* as described above. Resume usage of the other clock. */
portNVIC_SYSTICK_CTRL_REG = portNVIC_SYSTICK_CLK_BIT | portNVIC_SYSTICK_INT_BIT;
if( ( portNVIC_SYSTICK_CTRL_REG & portNVIC_SYSTICK_COUNT_FLAG_BIT ) != 0 )
{
/* The partial tick period already ended. Be sure the SysTick
* counts it only once. */
portNVIC_SYSTICK_CURRENT_VALUE_REG = 0;
}
portNVIC_SYSTICK_LOAD_REG = ulTimerCountsForOneTick - 1UL;
portNVIC_SYSTICK_CTRL_REG = portNVIC_SYSTICK_CLK_BIT_CONFIG | portNVIC_SYSTICK_INT_BIT | portNVIC_SYSTICK_ENABLE_BIT;
}
#endif /* portNVIC_SYSTICK_CLK_BIT_CONFIG */
/* Step the tick to account for any tick periods that elapsed. */
vTaskStepTick( ulCompleteTickPeriods );
/* Exit with interrupts enabled. */
__asm( " cpsie i" );
}
}
#endif /* configUSE_TICKLESS_IDLE */
/*-----------------------------------------------------------*/
/*
* Setup the systick timer to generate the tick interrupts at the required
* frequency.
*/
#pragma WEAK( vPortSetupTimerInterrupt )
void vPortSetupTimerInterrupt( void )
{
/* Calculate the constants required to configure the tick interrupt. */
#if ( configUSE_TICKLESS_IDLE == 1 )
{
ulTimerCountsForOneTick = ( configSYSTICK_CLOCK_HZ / configTICK_RATE_HZ );
xMaximumPossibleSuppressedTicks = portMAX_24_BIT_NUMBER / ulTimerCountsForOneTick;
ulStoppedTimerCompensation = portMISSED_COUNTS_FACTOR / ( configCPU_CLOCK_HZ / configSYSTICK_CLOCK_HZ );
}
#endif /* configUSE_TICKLESS_IDLE */
/* Stop and clear the SysTick. */
portNVIC_SYSTICK_CTRL_REG = 0UL;
portNVIC_SYSTICK_CURRENT_VALUE_REG = 0UL;
/* Configure SysTick to interrupt at the requested rate. */
portNVIC_SYSTICK_LOAD_REG = ( configSYSTICK_CLOCK_HZ / configTICK_RATE_HZ ) - 1UL;
portNVIC_SYSTICK_CTRL_REG = ( portNVIC_SYSTICK_CLK_BIT_CONFIG | portNVIC_SYSTICK_INT_BIT | portNVIC_SYSTICK_ENABLE_BIT );
}
/*-----------------------------------------------------------*/
#if ( configASSERT_DEFINED == 1 )
void vPortValidateInterruptPriority( void )
{
extern uint32_t ulPortGetIPSR( void );
uint32_t ulCurrentInterrupt;
uint8_t ucCurrentPriority;
ulCurrentInterrupt = ulPortGetIPSR();
/* Is the interrupt number a user defined interrupt? */
if( ulCurrentInterrupt >= portFIRST_USER_INTERRUPT_NUMBER )
{
/* Look up the interrupt's priority. */
ucCurrentPriority = pcInterruptPriorityRegisters[ ulCurrentInterrupt ];
/* The following assertion will fail if a service routine (ISR) for
* an interrupt that has been assigned a priority above
* configMAX_SYSCALL_INTERRUPT_PRIORITY calls an ISR safe FreeRTOS API
* function. ISR safe FreeRTOS API functions must *only* be called
* from interrupts that have been assigned a priority at or below
* configMAX_SYSCALL_INTERRUPT_PRIORITY.
*
* Numerically low interrupt priority numbers represent logically high
* interrupt priorities, therefore the priority of the interrupt must
* be set to a value equal to or numerically *higher* than
* configMAX_SYSCALL_INTERRUPT_PRIORITY.
*
* Interrupts that use the FreeRTOS API must not be left at their
* default priority of zero as that is the highest possible priority,
* which is guaranteed to be above configMAX_SYSCALL_INTERRUPT_PRIORITY,
* and therefore also guaranteed to be invalid.
*
* FreeRTOS maintains separate thread and ISR API functions to ensure
* interrupt entry is as fast and simple as possible.
*
* The following links provide detailed information:
* https://www.FreeRTOS.org/RTOS-Cortex-M3-M4.html
* https://www.FreeRTOS.org/FAQHelp.html */
configASSERT( ucCurrentPriority >= ucMaxSysCallPriority );
}
/* Priority grouping: The interrupt controller (NVIC) allows the bits
* that define each interrupt's priority to be split between bits that
* define the interrupt's pre-emption priority bits and bits that define
* the interrupt's sub-priority. For simplicity all bits must be defined
* to be pre-emption priority bits. The following assertion will fail if
* this is not the case (if some bits represent a sub-priority).
*
* If the application only uses CMSIS libraries for interrupt
* configuration then the correct setting can be achieved on all Cortex-M
* devices by calling NVIC_SetPriorityGrouping( 0 ); before starting the
* scheduler. Note however that some vendor specific peripheral libraries
* assume a non-zero priority group setting, in which cases using a value
* of zero will result in unpredictable behaviour. */
configASSERT( ( portAIRCR_REG & portPRIORITY_GROUP_MASK ) <= ulMaxPRIGROUPValue );
}
#endif /* configASSERT_DEFINED */