| /* | |
| * 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 CM0 port. | |
| *----------------------------------------------------------*/ | |
| /* 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 portNVIC_PENDSVSET_BIT ( 1UL << 28UL ) | |
| #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 ) | |
| /* 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 | |
| /* Let the user override the pre-loading of the initial LR with the address of | |
| * prvTaskExitError() in case it messes up unwinding of the stack in the | |
| * debugger. */ | |
| #ifdef configTASK_RETURN_ADDRESS | |
| #define portTASK_RETURN_ADDRESS configTASK_RETURN_ADDRESS | |
| #else | |
| #define portTASK_RETURN_ADDRESS prvTaskExitError | |
| #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 xPortPendSVHandler( void ) __attribute__( ( naked ) ); | |
| void xPortSysTickHandler( void ); | |
| void vPortSVCHandler( void ); | |
| /* | |
| * Start first task is a separate function so it can be tested in isolation. | |
| */ | |
| static void vPortStartFirstTask( void ) __attribute__( ( naked ) ); | |
| /* | |
| * Used to catch tasks that attempt to return from their implementing function. | |
| */ | |
| static void prvTaskExitError( void ); | |
| /*-----------------------------------------------------------*/ | |
| /* 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 */ | |
| /*-----------------------------------------------------------*/ | |
| /* | |
| * 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 ) portTASK_RETURN_ADDRESS; /* LR */ | |
| pxTopOfStack -= 5; /* R12, R3, R2 and R1. */ | |
| *pxTopOfStack = ( StackType_t ) pvParameters; /* R0 */ | |
| pxTopOfStack -= 8; /* R11..R4. */ | |
| return pxTopOfStack; | |
| } | |
| /*-----------------------------------------------------------*/ | |
| static void prvTaskExitError( void ) | |
| { | |
| volatile uint32_t ulDummy = 0UL; | |
| /* 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(); | |
| while( ulDummy == 0 ) | |
| { | |
| /* This file calls prvTaskExitError() after the scheduler has been | |
| * started to remove a compiler warning about the function being defined | |
| * but never called. ulDummy is used purely to quieten other warnings | |
| * about code appearing after this function is called - making ulDummy | |
| * volatile makes the compiler think the function could return and | |
| * therefore not output an 'unreachable code' warning for code that appears | |
| * after it. */ | |
| } | |
| } | |
| /*-----------------------------------------------------------*/ | |
| void vPortSVCHandler( void ) | |
| { | |
| /* This function is no longer used, but retained for backward | |
| * compatibility. */ | |
| } | |
| /*-----------------------------------------------------------*/ | |
| void vPortStartFirstTask( void ) | |
| { | |
| /* The MSP stack is not reset as, unlike on M3/4 parts, there is no vector | |
| * table offset register that can be used to locate the initial stack value. | |
| * Not all M0 parts have the application vector table at address 0. */ | |
| __asm volatile ( | |
| " .syntax unified \n" | |
| " ldr r2, pxCurrentTCBConst2 \n"/* Obtain location of pxCurrentTCB. */ | |
| " ldr r3, [r2] \n" | |
| " ldr r0, [r3] \n"/* The first item in pxCurrentTCB is the task top of stack. */ | |
| " adds r0, #32 \n"/* Discard everything up to r0. */ | |
| " msr psp, r0 \n"/* This is now the new top of stack to use in the task. */ | |
| " movs r0, #2 \n"/* Switch to the psp stack. */ | |
| " msr CONTROL, r0 \n" | |
| " isb \n" | |
| " pop {r0-r5} \n"/* Pop the registers that are saved automatically. */ | |
| " mov lr, r5 \n"/* lr is now in r5. */ | |
| " pop {r3} \n"/* Return address is now in r3. */ | |
| " pop {r2} \n"/* Pop and discard XPSR. */ | |
| " cpsie i \n"/* The first task has its context and interrupts can be enabled. */ | |
| " bx r3 \n"/* Finally, jump to the user defined task code. */ | |
| " \n" | |
| " .align 4 \n" | |
| "pxCurrentTCBConst2: .word pxCurrentTCB " | |
| ); | |
| } | |
| /*-----------------------------------------------------------*/ | |
| /* | |
| * See header file for description. | |
| */ | |
| BaseType_t xPortStartScheduler( void ) | |
| { | |
| /* Make PendSV, CallSV and SysTick the same priority as the kernel. */ | |
| 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 never get here as the tasks will now be executing! Call the task | |
| * exit error function to prevent compiler warnings about a static function | |
| * not being called in the case that the application writer overrides this | |
| * functionality by defining configTASK_RETURN_ADDRESS. Call | |
| * vTaskSwitchContext() so link time optimisation does not remove the | |
| * symbol. */ | |
| vTaskSwitchContext(); | |
| prvTaskExitError(); | |
| /* 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_BIT; | |
| /* Barriers are normally not required but do ensure the code is completely | |
| * within the specified behaviour for the architecture. */ | |
| __asm volatile ( "dsb" ::: "memory" ); | |
| __asm volatile ( "isb" ); | |
| } | |
| /*-----------------------------------------------------------*/ | |
| void vPortEnterCritical( void ) | |
| { | |
| portDISABLE_INTERRUPTS(); | |
| uxCriticalNesting++; | |
| __asm volatile ( "dsb" ::: "memory" ); | |
| __asm volatile ( "isb" ); | |
| } | |
| /*-----------------------------------------------------------*/ | |
| void vPortExitCritical( void ) | |
| { | |
| configASSERT( uxCriticalNesting ); | |
| uxCriticalNesting--; | |
| if( uxCriticalNesting == 0 ) | |
| { | |
| portENABLE_INTERRUPTS(); | |
| } | |
| } | |
| /*-----------------------------------------------------------*/ | |
| uint32_t ulSetInterruptMaskFromISR( void ) | |
| { | |
| __asm volatile ( | |
| " mrs r0, PRIMASK \n" | |
| " cpsid i \n" | |
| " bx lr " | |
| ::: "memory" | |
| ); | |
| } | |
| /*-----------------------------------------------------------*/ | |
| void vClearInterruptMaskFromISR( __attribute__( ( unused ) ) uint32_t ulMask ) | |
| { | |
| __asm volatile ( | |
| " msr PRIMASK, r0 \n" | |
| " bx lr " | |
| ::: "memory" | |
| ); | |
| } | |
| /*-----------------------------------------------------------*/ | |
| void xPortPendSVHandler( void ) | |
| { | |
| /* This is a naked function. */ | |
| __asm volatile | |
| ( | |
| " .syntax unified \n" | |
| " mrs r0, psp \n" | |
| " \n" | |
| " ldr r3, pxCurrentTCBConst \n"/* Get the location of the current TCB. */ | |
| " ldr r2, [r3] \n" | |
| " \n" | |
| " subs r0, r0, #32 \n"/* Make space for the remaining low registers. */ | |
| " str r0, [r2] \n"/* Save the new top of stack. */ | |
| " stmia r0!, {r4-r7} \n"/* Store the low registers that are not saved automatically. */ | |
| " mov r4, r8 \n"/* Store the high registers. */ | |
| " mov r5, r9 \n" | |
| " mov r6, r10 \n" | |
| " mov r7, r11 \n" | |
| " stmia r0!, {r4-r7} \n" | |
| " \n" | |
| " push {r3, r14} \n" | |
| " cpsid i \n" | |
| " bl vTaskSwitchContext \n" | |
| " cpsie i \n" | |
| " pop {r2, r3} \n"/* lr goes in r3. r2 now holds tcb pointer. */ | |
| " \n" | |
| " ldr r1, [r2] \n" | |
| " ldr r0, [r1] \n"/* The first item in pxCurrentTCB is the task top of stack. */ | |
| " adds r0, r0, #16 \n"/* Move to the high registers. */ | |
| " ldmia r0!, {r4-r7} \n"/* Pop the high registers. */ | |
| " mov r8, r4 \n" | |
| " mov r9, r5 \n" | |
| " mov r10, r6 \n" | |
| " mov r11, r7 \n" | |
| " \n" | |
| " msr psp, r0 \n"/* Remember the new top of stack for the task. */ | |
| " \n" | |
| " subs r0, r0, #32 \n"/* Go back for the low registers that are not automatically restored. */ | |
| " ldmia r0!, {r4-r7} \n"/* Pop low registers. */ | |
| " \n" | |
| " bx r3 \n" | |
| " \n" | |
| " .align 4 \n" | |
| "pxCurrentTCBConst: .word pxCurrentTCB " | |
| ); | |
| } | |
| /*-----------------------------------------------------------*/ | |
| 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_BIT; | |
| } | |
| } | |
| portCLEAR_INTERRUPT_MASK_FROM_ISR( ulPreviousMask ); | |
| } | |
| /*-----------------------------------------------------------*/ | |
| /* | |
| * Setup the systick timer to generate the tick interrupts at the required | |
| * frequency. | |
| */ | |
| __attribute__( ( weak ) ) 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 ) | |
| __attribute__( ( 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. */ | |
| __asm volatile ( "cpsid i" ::: "memory" ); | |
| __asm volatile ( "dsb" ); | |
| __asm volatile ( "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 the cpsid instruction() | |
| * above. */ | |
| __asm volatile ( "cpsie i" ::: "memory" ); | |
| } | |
| 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 ) | |
| { | |
| __asm volatile ( "dsb" ::: "memory" ); | |
| __asm volatile ( "wfi" ); | |
| __asm volatile ( "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. */ | |
| __asm volatile ( "cpsie i" ::: "memory" ); | |
| __asm volatile ( "dsb" ); | |
| __asm volatile ( "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 volatile ( "cpsid i" ::: "memory" ); | |
| __asm volatile ( "dsb" ); | |
| __asm volatile ( "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. */ | |
| __asm volatile ( "cpsie i" ::: "memory" ); | |
| } | |
| } | |
| #endif /* configUSE_TICKLESS_IDLE */ |