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https://github.com/FreeRTOS/FreeRTOS-Kernel.git
synced 2025-08-19 09:38:32 -04:00
Updates to the Cortex-M tickless idle code to reduce clock slippage.
Updates to prevent the vTaskSwitchContext() function being removed from GCC builds when link time optimisation is used.
This commit is contained in:
Richard Barry
parent
7ee26c1b5e
commit
464c2660ad
16 changed files with 686 additions and 505 deletions
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@ -114,9 +114,6 @@ is defined. */
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#define portNVIC_PENDSVCLEAR_BIT ( 1UL << 27UL )
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#define portNVIC_PEND_SYSTICK_CLEAR_BIT ( 1UL << 25UL )
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/* Masks off all bits but the VECTACTIVE bits in the ICSR register. */
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#define portVECTACTIVE_MASK ( 0xFFUL )
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#define portNVIC_PENDSV_PRI ( ( ( uint32_t ) configKERNEL_INTERRUPT_PRIORITY ) << 16UL )
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#define portNVIC_SYSTICK_PRI ( ( ( uint32_t ) configKERNEL_INTERRUPT_PRIORITY ) << 24UL )
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@ -130,6 +127,9 @@ is defined. */
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#define portPRIORITY_GROUP_MASK ( 0x07UL << 8UL )
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#define portPRIGROUP_SHIFT ( 8UL )
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/* Masks off all bits but the VECTACTIVE bits in the ICSR register. */
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#define portVECTACTIVE_MASK ( 0xFFUL )
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/* Constants required to set up the initial stack. */
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#define portINITIAL_XPSR ( 0x01000000 )
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@ -145,10 +145,6 @@ calculations. */
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have bit-0 clear, as it is loaded into the PC on exit from an ISR. */
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#define portSTART_ADDRESS_MASK ( ( StackType_t ) 0xfffffffeUL )
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/* Each task maintains its own interrupt status in the critical nesting
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variable. */
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static UBaseType_t uxCriticalNesting = 0xaaaaaaaa;
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/*
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* Setup the timer to generate the tick interrupts. The implementation in this
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* file is weak to allow application writers to change the timer used to
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@ -175,10 +171,14 @@ static void prvTaskExitError( void );
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/*-----------------------------------------------------------*/
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/* Each task maintains its own interrupt status in the critical nesting
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variable. */
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static UBaseType_t uxCriticalNesting = 0xaaaaaaaa;
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/*
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* The number of SysTick increments that make up one tick period.
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*/
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#if configUSE_TICKLESS_IDLE == 1
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#if( configUSE_TICKLESS_IDLE == 1 )
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static uint32_t ulTimerCountsForOneTick = 0;
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#endif /* configUSE_TICKLESS_IDLE */
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@ -186,7 +186,7 @@ static void prvTaskExitError( void );
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* The maximum number of tick periods that can be suppressed is limited by the
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* 24 bit resolution of the SysTick timer.
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*/
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#if configUSE_TICKLESS_IDLE == 1
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#if( configUSE_TICKLESS_IDLE == 1 )
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static uint32_t xMaximumPossibleSuppressedTicks = 0;
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#endif /* configUSE_TICKLESS_IDLE */
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@ -194,7 +194,7 @@ static void prvTaskExitError( void );
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* Compensate for the CPU cycles that pass while the SysTick is stopped (low
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* power functionality only.
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*/
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#if configUSE_TICKLESS_IDLE == 1
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#if( configUSE_TICKLESS_IDLE == 1 )
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static uint32_t ulStoppedTimerCompensation = 0;
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#endif /* configUSE_TICKLESS_IDLE */
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@ -313,6 +313,10 @@ BaseType_t xPortStartScheduler( void )
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/* Read the value back to see how many bits stuck. */
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ucMaxPriorityValue = *pucFirstUserPriorityRegister;
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/* The kernel interrupt priority should be set to the lowest
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priority. */
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configASSERT( ucMaxPriorityValue == ( configKERNEL_INTERRUPT_PRIORITY & ucMaxPriorityValue ) );
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/* Use the same mask on the maximum system call priority. */
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ucMaxSysCallPriority = configMAX_SYSCALL_INTERRUPT_PRIORITY & ucMaxPriorityValue;
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@ -467,11 +471,11 @@ void xPortSysTickHandler( void )
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}
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/*-----------------------------------------------------------*/
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#if configUSE_TICKLESS_IDLE == 1
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#if( configUSE_TICKLESS_IDLE == 1 )
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__weak void vPortSuppressTicksAndSleep( TickType_t xExpectedIdleTime )
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{
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uint32_t ulReloadValue, ulCompleteTickPeriods, ulCompletedSysTickDecrements, ulSysTickCTRL;
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uint32_t ulReloadValue, ulCompleteTickPeriods, ulCompletedSysTickDecrements;
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TickType_t xModifiableIdleTime;
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/* Make sure the SysTick reload value does not overflow the counter. */
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@ -547,23 +551,41 @@ void xPortSysTickHandler( void )
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}
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configPOST_SLEEP_PROCESSING( xExpectedIdleTime );
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/* Stop SysTick. Again, the time the SysTick is stopped for is
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accounted for as best it can be, but using the tickless mode will
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inevitably result in some tiny drift of the time maintained by the
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kernel with respect to calendar time. */
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ulSysTickCTRL = portNVIC_SYSTICK_CTRL_REG;
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portNVIC_SYSTICK_CTRL_REG = ( ulSysTickCTRL & ~portNVIC_SYSTICK_ENABLE_BIT );
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/* Re-enable interrupts - see comments above __disable_irq() call
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above. */
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/* Re-enable interrupts to allow the interrupt that brought the MCU
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out of sleep mode to execute immediately. see comments above
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__disable_interrupt() call above. */
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__enable_irq();
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__dsb( portSY_FULL_READ_WRITE );
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__isb( portSY_FULL_READ_WRITE );
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if( ( ulSysTickCTRL & portNVIC_SYSTICK_COUNT_FLAG_BIT ) != 0 )
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/* Disable interrupts again because the clock is about to be stopped
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and interrupts that execute while the clock is stopped will increase
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any slippage between the time maintained by the RTOS and calendar
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time. */
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__disable_irq();
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__dsb( portSY_FULL_READ_WRITE );
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__isb( portSY_FULL_READ_WRITE );
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/* Disable the SysTick clock without reading the
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portNVIC_SYSTICK_CTRL_REG register to ensure the
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portNVIC_SYSTICK_COUNT_FLAG_BIT is not cleared if it is set. Again,
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the time the SysTick is stopped for is accounted for as best it can
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be, but using the tickless mode will inevitably result in some tiny
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drift of the time maintained by the kernel with respect to calendar
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time*/
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portNVIC_SYSTICK_CTRL_REG = ( portNVIC_SYSTICK_CLK_BIT | portNVIC_SYSTICK_INT_BIT );
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/* Determine if the SysTick clock has already counted to zero and
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been set back to the current reload value (the reload back being
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correct for the entire expected idle time) or if the SysTick is yet
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to count to zero (in which case an interrupt other than the SysTick
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must have brought the system out of sleep mode). */
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if( ( portNVIC_SYSTICK_CTRL_REG & portNVIC_SYSTICK_COUNT_FLAG_BIT ) != 0 )
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{
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uint32_t ulCalculatedLoadValue;
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/* The tick interrupt has already executed, and the SysTick
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count reloaded with ulReloadValue. Reset the
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/* The tick interrupt is already pending, and the SysTick count
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reloaded with ulReloadValue. Reset the
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portNVIC_SYSTICK_LOAD_REG with whatever remains of this tick
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period. */
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ulCalculatedLoadValue = ( ulTimerCountsForOneTick - 1UL ) - ( ulReloadValue - portNVIC_SYSTICK_CURRENT_VALUE_REG );
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@ -578,11 +600,9 @@ void xPortSysTickHandler( void )
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portNVIC_SYSTICK_LOAD_REG = ulCalculatedLoadValue;
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/* The tick interrupt handler will already have pended the tick
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processing in the kernel. As the pending tick will be
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processed as soon as this function exits, the tick value
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maintained by the tick is stepped forward by one less than the
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time spent waiting. */
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/* As the pending tick will be processed as soon as this
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function exits, the tick value maintained by the tick is stepped
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forward by one less than the time spent waiting. */
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ulCompleteTickPeriods = xExpectedIdleTime - 1UL;
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}
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else
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@ -604,17 +624,14 @@ void xPortSysTickHandler( void )
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/* Restart SysTick so it runs from portNVIC_SYSTICK_LOAD_REG
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again, then set portNVIC_SYSTICK_LOAD_REG back to its standard
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value. The critical section is used to ensure the tick interrupt
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can only execute once in the case that the reload register is near
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zero. */
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value. */
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portNVIC_SYSTICK_CURRENT_VALUE_REG = 0UL;
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portENTER_CRITICAL();
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{
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portNVIC_SYSTICK_CTRL_REG |= portNVIC_SYSTICK_ENABLE_BIT;
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vTaskStepTick( ulCompleteTickPeriods );
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portNVIC_SYSTICK_LOAD_REG = ulTimerCountsForOneTick - 1UL;
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}
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portEXIT_CRITICAL();
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portNVIC_SYSTICK_CTRL_REG |= portNVIC_SYSTICK_ENABLE_BIT;
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vTaskStepTick( ulCompleteTickPeriods );
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portNVIC_SYSTICK_LOAD_REG = ulTimerCountsForOneTick - 1UL;
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/* Exit with interrpts enabled. */
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__enable_irq();
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}
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}
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@ -626,12 +643,12 @@ void xPortSysTickHandler( void )
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* Setup the SysTick timer to generate the tick interrupts at the required
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* frequency.
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*/
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#if configOVERRIDE_DEFAULT_TICK_CONFIGURATION == 0
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#if( configOVERRIDE_DEFAULT_TICK_CONFIGURATION == 0 )
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void vPortSetupTimerInterrupt( void )
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{
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/* Calculate the constants required to configure the tick interrupt. */
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#if configUSE_TICKLESS_IDLE == 1
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#if( configUSE_TICKLESS_IDLE == 1 )
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{
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ulTimerCountsForOneTick = ( configSYSTICK_CLOCK_HZ / configTICK_RATE_HZ );
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xMaximumPossibleSuppressedTicks = portMAX_24_BIT_NUMBER / ulTimerCountsForOneTick;
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@ -714,7 +731,7 @@ __asm uint32_t vPortGetIPSR( void )
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devices by calling NVIC_SetPriorityGrouping( 0 ); before starting the
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scheduler. Note however that some vendor specific peripheral libraries
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assume a non-zero priority group setting, in which cases using a value
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of zero will result in unpredicable behaviour. */
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of zero will result in unpredictable behaviour. */
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configASSERT( ( portAIRCR_REG & portPRIORITY_GROUP_MASK ) <= ulMaxPRIGROUPValue );
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}
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