/* * FreeRTOS Kernel V10.3.1 * Copyright (C) 2020 Amazon.com, Inc. or its affiliates. All Rights Reserved. * * 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. * * http://www.FreeRTOS.org * http://aws.amazon.com/freertos * * 1 tab == 4 spaces! */ /*----------------------------------------------------------- * Implementation of functions defined in portable.h for the ARM CM0 port. *----------------------------------------------------------*/ /* IAR includes. */ #include "intrinsics.h" /* Scheduler includes. */ #include "FreeRTOS.h" #include "task.h" /* Constants required to manipulate the NVIC. */ #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_INT_CTRL_REG ( *( ( volatile uint32_t * ) 0xe000ed04 ) ) #define portNVIC_SHPR3_REG ( *( ( volatile uint32_t * ) 0xe000ed20 ) ) #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 portMIN_INTERRUPT_PRIORITY ( 255UL ) #define portNVIC_PENDSV_PRI ( portMIN_INTERRUPT_PRIORITY << 16UL ) #define portNVIC_SYSTICK_PRI ( portMIN_INTERRUPT_PRIORITY << 24UL ) /* Constants required to set up the initial stack. */ #define portINITIAL_XPSR ( 0x01000000 ) /* For backward compatibility, ensure configKERNEL_INTERRUPT_PRIORITY is * defined. The value 255 should also ensure backward compatibility. * FreeRTOS.org versions prior to V4.3.0 did not include this definition. */ #ifndef configKERNEL_INTERRUPT_PRIORITY #define configKERNEL_INTERRUPT_PRIORITY 0 #endif /* Each task maintains its own interrupt status in the critical nesting * variable. */ static UBaseType_t uxCriticalNesting = 0xaaaaaaaa; /* 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. */ #ifndef portMISSED_COUNTS_FACTOR #define portMISSED_COUNTS_FACTOR ( 45UL ) #endif /* 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 */ /* * 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. */ #pragma weak vPortSetupTimerInterrupt 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 ); /* * Used to catch tasks that attempt to return from their implementing function. */ static void prvTaskExitError( void ); /*-----------------------------------------------------------*/ /* * 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. */ pxTopOfStack--; /* Offset added to account for the way the MCU uses the stack on entry/exit of interrupts. */ *pxTopOfStack = portINITIAL_XPSR; /* xPSR */ pxTopOfStack--; *pxTopOfStack = ( StackType_t ) pxCode; /* PC */ pxTopOfStack--; *pxTopOfStack = ( StackType_t ) prvTaskExitError; /* LR */ pxTopOfStack -= 5; /* R12, R3, R2 and R1. */ *pxTopOfStack = ( StackType_t ) pvParameters; /* R0 */ pxTopOfStack -= 8; /* R11..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 ) { /* 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; /* 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 vPortYield( void ) { /* Set a PendSV to request a context switch. */ portNVIC_INT_CTRL_REG = portNVIC_PENDSVSET; /* Barriers are normally not required but do ensure the code is completely * within the specified behaviour for the architecture. */ __DSB(); __ISB(); } /*-----------------------------------------------------------*/ void vPortEnterCritical( void ) { portDISABLE_INTERRUPTS(); uxCriticalNesting++; __DSB(); __ISB(); } /*-----------------------------------------------------------*/ void vPortExitCritical( void ) { configASSERT( uxCriticalNesting ); uxCriticalNesting--; if( uxCriticalNesting == 0 ) { portENABLE_INTERRUPTS(); } } /*-----------------------------------------------------------*/ void xPortSysTickHandler( void ) { uint32_t ulPreviousMask; ulPreviousMask = portSET_INTERRUPT_MASK_FROM_ISR(); { /* Increment the RTOS tick. */ if( xTaskIncrementTick() != pdFALSE ) { /* Pend a context switch. */ portNVIC_INT_CTRL_REG = portNVIC_PENDSVSET; } } portCLEAR_INTERRUPT_MASK_FROM_ISR( ulPreviousMask ); } /*-----------------------------------------------------------*/ /* * Setup the systick timer to generate the tick interrupts at the required * frequency. */ void vPortSetupTimerInterrupt( void ) { /* Calculate the constants required to configure the tick interrupt. */ #if ( configUSE_TICKLESS_IDLE == 1 ) { ulTimerCountsForOneTick = ( configCPU_CLOCK_HZ / configTICK_RATE_HZ ); xMaximumPossibleSuppressedTicks = portMAX_24_BIT_NUMBER / ulTimerCountsForOneTick; ulStoppedTimerCompensation = portMISSED_COUNTS_FACTOR; } #endif /* configUSE_TICKLESS_IDLE */ /* Stop and reset 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 = ( configCPU_CLOCK_HZ / configTICK_RATE_HZ ) - 1UL; portNVIC_SYSTICK_CTRL_REG = portNVIC_SYSTICK_CLK_BIT | portNVIC_SYSTICK_INT_BIT | portNVIC_SYSTICK_ENABLE_BIT; } /*-----------------------------------------------------------*/ #if ( configUSE_TICKLESS_IDLE == 1 ) __weak void vPortSuppressTicksAndSleep( TickType_t xExpectedIdleTime ) { uint32_t ulReloadValue, ulCompleteTickPeriods, ulCompletedSysTickDecrements; TickType_t xModifiableIdleTime; /* Make sure the SysTick reload value does not overflow the counter. */ if( xExpectedIdleTime > xMaximumPossibleSuppressedTicks ) { xExpectedIdleTime = xMaximumPossibleSuppressedTicks; } /* 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_ENABLE_BIT; /* Calculate the reload value required to wait xExpectedIdleTime * tick periods. -1 is used because this code will execute part way * through one of the tick periods. */ ulReloadValue = portNVIC_SYSTICK_CURRENT_VALUE_REG + ( ulTimerCountsForOneTick * ( xExpectedIdleTime - 1UL ) ); if( ulReloadValue > ulStoppedTimerCompensation ) { ulReloadValue -= ulStoppedTimerCompensation; } /* Enter a critical section but don't use the taskENTER_CRITICAL() * method as that will mask interrupts that should exit sleep mode. */ __disable_interrupt(); __DSB(); __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 ) { /* Restart from whatever is left in the count register to complete * this tick period. */ portNVIC_SYSTICK_LOAD_REG = portNVIC_SYSTICK_CURRENT_VALUE_REG; /* Restart SysTick. */ portNVIC_SYSTICK_CTRL_REG |= portNVIC_SYSTICK_ENABLE_BIT; /* Reset the reload register to the value required for normal tick * periods. */ portNVIC_SYSTICK_LOAD_REG = ulTimerCountsForOneTick - 1UL; /* Re-enable interrupts - see comments above __disable_interrupt() * call above. */ __enable_interrupt(); } else { /* 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 ) { __DSB(); __WFI(); __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 * __disable_interrupt() call above. */ __enable_interrupt(); __DSB(); __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. */ __disable_interrupt(); __DSB(); __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 | portNVIC_SYSTICK_INT_BIT ); /* Determine if the SysTick clock has already counted to zero and * been set back to the current reload value (the reload back being * correct for the entire expected idle time) or if the SysTick is yet * to count to zero (in which case an interrupt other than the SysTick * must have brought the system out of sleep mode). */ if( ( portNVIC_SYSTICK_CTRL_REG & portNVIC_SYSTICK_COUNT_FLAG_BIT ) != 0 ) { uint32_t ulCalculatedLoadValue; /* The tick interrupt is already pending, and the SysTick count * reloaded with ulReloadValue. Reset the * portNVIC_SYSTICK_LOAD_REG with whatever remains of this 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. */ 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. * Work out how long the sleep lasted rounded to complete tick * periods (not the ulReload value which accounted for part * ticks). */ ulCompletedSysTickDecrements = ( xExpectedIdleTime * ulTimerCountsForOneTick ) - portNVIC_SYSTICK_CURRENT_VALUE_REG; /* 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. */ portNVIC_SYSTICK_CURRENT_VALUE_REG = 0UL; portNVIC_SYSTICK_CTRL_REG |= portNVIC_SYSTICK_ENABLE_BIT; vTaskStepTick( ulCompleteTickPeriods ); portNVIC_SYSTICK_LOAD_REG = ulTimerCountsForOneTick - 1UL; /* Exit with interrpts enabled. */ __enable_interrupt(); } } #endif /* configUSE_TICKLESS_IDLE */