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562 lines
21 KiB
C
562 lines
21 KiB
C
/*
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* FreeRTOS Kernel V10.3.1
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* Copyright (C) 2020 Amazon.com, Inc. or its affiliates. All Rights Reserved.
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy of
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* this software and associated documentation files (the "Software"), to deal in
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* the Software without restriction, including without limitation the rights to
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* use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
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* the Software, and to permit persons to whom the Software is furnished to do so,
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* subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in all
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* copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
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* FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
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* COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
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* IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
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* CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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*
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* https://www.FreeRTOS.org
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* https://github.com/FreeRTOS
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*
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*/
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/*-----------------------------------------------------------
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* Implementation of functions defined in portable.h for the ARM CM0 port.
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*----------------------------------------------------------*/
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/* Scheduler includes. */
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#include "FreeRTOS.h"
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#include "task.h"
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/* Constants required to manipulate the NVIC. */
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#define portNVIC_SYSTICK_CTRL_REG ( *( ( volatile uint32_t * ) 0xe000e010 ) )
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#define portNVIC_SYSTICK_LOAD_REG ( *( ( volatile uint32_t * ) 0xe000e014 ) )
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#define portNVIC_SYSTICK_CURRENT_VALUE_REG ( *( ( volatile uint32_t * ) 0xe000e018 ) )
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#define portNVIC_INT_CTRL_REG ( *( ( volatile uint32_t * ) 0xe000ed04 ) )
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#define portNVIC_SHPR3_REG ( *( ( volatile uint32_t * ) 0xe000ed20 ) )
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#define portNVIC_SYSTICK_CLK_BIT ( 1UL << 2UL )
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#define portNVIC_SYSTICK_INT_BIT ( 1UL << 1UL )
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#define portNVIC_SYSTICK_ENABLE_BIT ( 1UL << 0UL )
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#define portNVIC_SYSTICK_COUNT_FLAG_BIT ( 1UL << 16UL )
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#define portNVIC_PENDSVSET_BIT ( 1UL << 28UL )
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#define portMIN_INTERRUPT_PRIORITY ( 255UL )
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#define portNVIC_PENDSV_PRI ( portMIN_INTERRUPT_PRIORITY << 16UL )
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#define portNVIC_SYSTICK_PRI ( portMIN_INTERRUPT_PRIORITY << 24UL )
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/* Constants required to set up the initial stack. */
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#define portINITIAL_XPSR ( 0x01000000 )
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/* The systick is a 24-bit counter. */
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#define portMAX_24_BIT_NUMBER ( 0xffffffUL )
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/* A fiddle factor to estimate the number of SysTick counts that would have
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* occurred while the SysTick counter is stopped during tickless idle
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* calculations. */
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#ifndef portMISSED_COUNTS_FACTOR
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#define portMISSED_COUNTS_FACTOR ( 45UL )
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#endif
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/* Constants used with memory barrier intrinsics. */
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#define portSY_FULL_READ_WRITE ( 15 )
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/* Legacy macro for backward compatibility only. This macro used to be used to
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* replace the function that configures the clock used to generate the tick
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* interrupt (prvSetupTimerInterrupt()), but now the function is declared weak so
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* the application writer can override it by simply defining a function of the
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* same name (vApplicationSetupTickInterrupt()). */
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#ifndef configOVERRIDE_DEFAULT_TICK_CONFIGURATION
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#define configOVERRIDE_DEFAULT_TICK_CONFIGURATION 0
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#endif
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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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/* The number of SysTick increments that make up one tick period. */
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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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/* 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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#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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/* 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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static uint32_t ulStoppedTimerCompensation = 0;
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#endif /* configUSE_TICKLESS_IDLE */
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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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* generate the tick interrupt.
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*/
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void vPortSetupTimerInterrupt( void );
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/*
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* Exception handlers.
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*/
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void xPortPendSVHandler( void );
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void xPortSysTickHandler( void );
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void vPortSVCHandler( void );
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/*
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* Start first task is a separate function so it can be tested in isolation.
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*/
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static void prvPortStartFirstTask( void );
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/*
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* Used to catch tasks that attempt to return from their implementing function.
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*/
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static void prvTaskExitError( void );
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/*-----------------------------------------------------------*/
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/*
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* See header file for description.
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*/
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StackType_t * pxPortInitialiseStack( StackType_t * pxTopOfStack,
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TaskFunction_t pxCode,
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void * pvParameters )
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{
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/* Simulate the stack frame as it would be created by a context switch
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* interrupt. */
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pxTopOfStack--; /* Offset added to account for the way the MCU uses the stack on entry/exit of interrupts. */
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*pxTopOfStack = portINITIAL_XPSR; /* xPSR */
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pxTopOfStack--;
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*pxTopOfStack = ( StackType_t ) pxCode; /* PC */
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pxTopOfStack--;
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*pxTopOfStack = ( StackType_t ) prvTaskExitError; /* LR */
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pxTopOfStack -= 5; /* R12, R3, R2 and R1. */
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*pxTopOfStack = ( StackType_t ) pvParameters; /* R0 */
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pxTopOfStack -= 8; /* R11..R4. */
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return pxTopOfStack;
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}
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/*-----------------------------------------------------------*/
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static void prvTaskExitError( void )
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{
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/* A function that implements a task must not exit or attempt to return to
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* its caller as there is nothing to return to. If a task wants to exit it
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* should instead call vTaskDelete( NULL ).
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*
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* Artificially force an assert() to be triggered if configASSERT() is
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* defined, then stop here so application writers can catch the error. */
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configASSERT( uxCriticalNesting == ~0UL );
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portDISABLE_INTERRUPTS();
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for( ; ; )
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{
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}
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}
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/*-----------------------------------------------------------*/
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void vPortSVCHandler( void )
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{
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/* This function is no longer used, but retained for backward
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* compatibility. */
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}
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/*-----------------------------------------------------------*/
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__asm void prvPortStartFirstTask( void )
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{
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extern pxCurrentTCB;
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PRESERVE8
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/* The MSP stack is not reset as, unlike on M3/4 parts, there is no vector
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* table offset register that can be used to locate the initial stack value.
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* Not all M0 parts have the application vector table at address 0. */
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/* *INDENT-OFF* */
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ldr r3, = pxCurrentTCB /* Obtain location of pxCurrentTCB. */
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ldr r1, [ r3 ]
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ldr r0, [ r1 ] /* The first item in pxCurrentTCB is the task top of stack. */
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adds r0, # 32 /* Discard everything up to r0. */
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msr psp, r0 /* This is now the new top of stack to use in the task. */
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movs r0, # 2 /* Switch to the psp stack. */
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msr CONTROL, r0
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isb
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pop {
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r0 - r5
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} /* Pop the registers that are saved automatically. */
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mov lr, r5 /* lr is now in r5. */
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pop {
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r3
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} /* The return address is now in r3. */
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pop {
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r2
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} /* Pop and discard the XPSR. */
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cpsie i /* The first task has its context and interrupts can be enabled. */
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bx r3 /* Finally, jump to the user defined task code. */
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ALIGN
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/* *INDENT-ON* */
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}
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/*-----------------------------------------------------------*/
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/*
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* See header file for description.
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*/
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BaseType_t xPortStartScheduler( void )
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{
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/* Make PendSV, CallSV and SysTick the same priority as the kernel. */
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portNVIC_SHPR3_REG |= portNVIC_PENDSV_PRI;
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portNVIC_SHPR3_REG |= portNVIC_SYSTICK_PRI;
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/* Start the timer that generates the tick ISR. Interrupts are disabled
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* here already. */
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vPortSetupTimerInterrupt();
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/* Initialise the critical nesting count ready for the first task. */
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uxCriticalNesting = 0;
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/* Start the first task. */
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prvPortStartFirstTask();
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/* Should not get here! */
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return 0;
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}
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/*-----------------------------------------------------------*/
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void vPortEndScheduler( void )
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{
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/* Not implemented in ports where there is nothing to return to.
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* Artificially force an assert. */
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configASSERT( uxCriticalNesting == 1000UL );
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}
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/*-----------------------------------------------------------*/
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void vPortYield( void )
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{
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/* Set a PendSV to request a context switch. */
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portNVIC_INT_CTRL_REG = portNVIC_PENDSVSET_BIT;
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/* Barriers are normally not required but do ensure the code is completely
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* within the specified behaviour for the architecture. */
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__dsb( portSY_FULL_READ_WRITE );
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__isb( portSY_FULL_READ_WRITE );
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}
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/*-----------------------------------------------------------*/
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void vPortEnterCritical( void )
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{
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portDISABLE_INTERRUPTS();
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uxCriticalNesting++;
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__dsb( portSY_FULL_READ_WRITE );
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__isb( portSY_FULL_READ_WRITE );
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}
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/*-----------------------------------------------------------*/
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void vPortExitCritical( void )
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{
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configASSERT( uxCriticalNesting );
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uxCriticalNesting--;
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if( uxCriticalNesting == 0 )
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{
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portENABLE_INTERRUPTS();
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}
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}
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/*-----------------------------------------------------------*/
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__asm uint32_t ulSetInterruptMaskFromISR( void )
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{
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mrs r0, PRIMASK
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cpsid i
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bx lr
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}
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/*-----------------------------------------------------------*/
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__asm void vClearInterruptMaskFromISR( uint32_t ulMask )
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{
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msr PRIMASK, r0
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bx lr
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}
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/*-----------------------------------------------------------*/
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__asm void xPortPendSVHandler( void )
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{
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extern vTaskSwitchContext
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extern pxCurrentTCB
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/* *INDENT-OFF* */
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PRESERVE8
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mrs r0, psp
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ldr r3, = pxCurrentTCB /* Get the location of the current TCB. */
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ldr r2, [ r3 ]
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subs r0, # 32 /* Make space for the remaining low registers. */
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str r0, [ r2 ] /* Save the new top of stack. */
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stmia r0 !, {
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r4 - r7
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} /* Store the low registers that are not saved automatically. */
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mov r4, r8 /* Store the high registers. */
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mov r5, r9
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mov r6, r10
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mov r7, r11
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stmia r0 !, {
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r4 - r7
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}
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push {
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r3, r14
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}
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cpsid i
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bl vTaskSwitchContext
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cpsie i
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pop {
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r2, r3
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} /* lr goes in r3. r2 now holds tcb pointer. */
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ldr r1, [ r2 ]
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ldr r0, [ r1 ] /* The first item in pxCurrentTCB is the task top of stack. */
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adds r0, # 16 /* Move to the high registers. */
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ldmia r0 !, {
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r4 - r7
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} /* Pop the high registers. */
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mov r8, r4
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mov r9, r5
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mov r10, r6
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mov r11, r7
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msr psp, r0 /* Remember the new top of stack for the task. */
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subs r0, # 32 /* Go back for the low registers that are not automatically restored. */
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ldmia r0 !, {
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r4 - r7
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} /* Pop low registers. */
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bx r3
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ALIGN
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/* *INDENT-ON* */
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}
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/*-----------------------------------------------------------*/
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void xPortSysTickHandler( void )
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{
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uint32_t ulPreviousMask;
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ulPreviousMask = portSET_INTERRUPT_MASK_FROM_ISR();
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{
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/* Increment the RTOS tick. */
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if( xTaskIncrementTick() != pdFALSE )
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{
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/* Pend a context switch. */
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portNVIC_INT_CTRL_REG = portNVIC_PENDSVSET_BIT;
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}
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}
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portCLEAR_INTERRUPT_MASK_FROM_ISR( ulPreviousMask );
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}
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/*-----------------------------------------------------------*/
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/*
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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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__weak 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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ulTimerCountsForOneTick = ( configCPU_CLOCK_HZ / configTICK_RATE_HZ );
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xMaximumPossibleSuppressedTicks = portMAX_24_BIT_NUMBER / ulTimerCountsForOneTick;
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ulStoppedTimerCompensation = portMISSED_COUNTS_FACTOR;
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#endif /* configUSE_TICKLESS_IDLE */
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/* Stop and reset the SysTick. */
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portNVIC_SYSTICK_CTRL_REG = 0UL;
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portNVIC_SYSTICK_CURRENT_VALUE_REG = 0UL;
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/* Configure SysTick to interrupt at the requested rate. */
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portNVIC_SYSTICK_LOAD_REG = ( configCPU_CLOCK_HZ / configTICK_RATE_HZ ) - 1UL;
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portNVIC_SYSTICK_CTRL_REG = portNVIC_SYSTICK_CLK_BIT | portNVIC_SYSTICK_INT_BIT | portNVIC_SYSTICK_ENABLE_BIT;
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}
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#endif /* configOVERRIDE_DEFAULT_TICK_CONFIGURATION */
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/*-----------------------------------------------------------*/
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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;
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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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if( xExpectedIdleTime > xMaximumPossibleSuppressedTicks )
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{
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xExpectedIdleTime = xMaximumPossibleSuppressedTicks;
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}
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/* Stop the SysTick momentarily. The time the SysTick is stopped for
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* is 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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portNVIC_SYSTICK_CTRL_REG &= ~portNVIC_SYSTICK_ENABLE_BIT;
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/* Calculate the reload value required to wait xExpectedIdleTime
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* tick periods. -1 is used because this code will execute part way
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* through one of the tick periods. */
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ulReloadValue = portNVIC_SYSTICK_CURRENT_VALUE_REG + ( ulTimerCountsForOneTick * ( xExpectedIdleTime - 1UL ) );
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if( ulReloadValue > ulStoppedTimerCompensation )
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{
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ulReloadValue -= ulStoppedTimerCompensation;
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}
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/* Enter a critical section but don't use the taskENTER_CRITICAL()
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* method as that will mask interrupts that should exit sleep mode. */
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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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/* If a context switch is pending or a task is waiting for the scheduler
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* to be unsuspended then abandon the low power entry. */
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if( eTaskConfirmSleepModeStatus() == eAbortSleep )
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{
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/* Restart from whatever is left in the count register to complete
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* this tick period. */
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portNVIC_SYSTICK_LOAD_REG = portNVIC_SYSTICK_CURRENT_VALUE_REG;
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/* Restart SysTick. */
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portNVIC_SYSTICK_CTRL_REG |= portNVIC_SYSTICK_ENABLE_BIT;
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/* Reset the reload register to the value required for normal tick
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* periods. */
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portNVIC_SYSTICK_LOAD_REG = ulTimerCountsForOneTick - 1UL;
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/* Re-enable interrupts - see comments above __disable_irq() call
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* above. */
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__enable_irq();
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}
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else
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{
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/* Set the new reload value. */
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portNVIC_SYSTICK_LOAD_REG = ulReloadValue;
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/* Clear the SysTick count flag and set the count value back to
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* zero. */
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portNVIC_SYSTICK_CURRENT_VALUE_REG = 0UL;
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/* Restart SysTick. */
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portNVIC_SYSTICK_CTRL_REG |= portNVIC_SYSTICK_ENABLE_BIT;
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/* Sleep until something happens. configPRE_SLEEP_PROCESSING() can
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* set its parameter to 0 to indicate that its implementation contains
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* its own wait for interrupt or wait for event instruction, and so wfi
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* should not be executed again. However, the original expected idle
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* time variable must remain unmodified, so a copy is taken. */
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xModifiableIdleTime = xExpectedIdleTime;
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configPRE_SLEEP_PROCESSING( xModifiableIdleTime );
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if( xModifiableIdleTime > 0 )
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{
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__dsb( portSY_FULL_READ_WRITE );
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__wfi();
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__isb( portSY_FULL_READ_WRITE );
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}
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configPOST_SLEEP_PROCESSING( xExpectedIdleTime );
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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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/* 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 );
|
|
|
|
/* 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 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
|
|
* again, then set portNVIC_SYSTICK_LOAD 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_irq();
|
|
}
|
|
}
|
|
|
|
#endif /* #if configUSE_TICKLESS_IDLE */
|
|
|
|
/*-----------------------------------------------------------*/
|