/* | |
* FreeRTOS Kernel V10.3.0 | |
* 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 | |
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* 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 | |
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* | |
* http://www.FreeRTOS.org | |
* http://aws.amazon.com/freertos | |
* | |
* 1 tab == 4 spaces! | |
*/ | |
/* Standard includes. */ | |
#include "limits.h" | |
/* FreeRTOS includes. */ | |
#include "FreeRTOS.h" | |
#include "task.h" | |
/* SiLabs library includes. */ | |
#include "em_cmu.h" | |
#include "em_burtc.h" | |
#include "em_rmu.h" | |
#include "em_int.h" | |
#include "sleep.h" | |
/* SEE THE COMMENTS ABOVE THE DEFINITION OF configCREATE_LOW_POWER_DEMO IN | |
FreeRTOSConfig.h | |
This file contains functions that will override the default implementations | |
in the RTOS port layer. Therefore only build this file if the low power demo | |
is being built. */ | |
#if( configCREATE_LOW_POWER_DEMO == 1 ) | |
#define mainTIMER_FREQUENCY_HZ ( 2000UL ) | |
/* | |
* The low power demo does not use the SysTick, so override the | |
* vPortSetupTickInterrupt() function with an implementation that configures | |
* a low power clock source. NOTE: This function name must not be changed as | |
* it is called from the RTOS portable layer. | |
*/ | |
void vPortSetupTimerInterrupt( void ); | |
/* | |
* Override the default definition of vPortSuppressTicksAndSleep() that is | |
* weakly defined in the FreeRTOS Cortex-M port layer with a version that | |
* manages the BURTC clock, as the tick is generated from the low power BURTC | |
* and not the SysTick as would normally be the case on a Cortex-M. | |
*/ | |
void vPortSuppressTicksAndSleep( TickType_t xExpectedIdleTime ); | |
/*-----------------------------------------------------------*/ | |
/* Calculate how many clock increments make up a single tick period. */ | |
static const uint32_t ulReloadValueForOneTick = ( mainTIMER_FREQUENCY_HZ / configTICK_RATE_HZ ); | |
/* Will hold the maximum number of ticks that can be suppressed. */ | |
static uint32_t xMaximumPossibleSuppressedTicks = 0; | |
/* Flag set from the tick interrupt to allow the sleep processing to know if | |
sleep mode was exited because of a timer interrupt or a different interrupt. */ | |
static volatile uint32_t ulTickFlag = pdFALSE; | |
/* As the clock is only 2KHz, it is likely a value of 1 will be too much, so | |
use zero - but leave the value here to assist porting to different clock | |
speeds. */ | |
static const uint32_t ulStoppedTimerCompensation = 0UL; | |
/*-----------------------------------------------------------*/ | |
void vPortSetupTimerInterrupt( void ) | |
{ | |
BURTC_Init_TypeDef xBURTCInitStruct = BURTC_INIT_DEFAULT; | |
/* Configure the BURTC to generate the RTOS tick interrupt. */ | |
xMaximumPossibleSuppressedTicks = ULONG_MAX / ulReloadValueForOneTick; | |
/* Ensure LE modules are accessible. */ | |
CMU_ClockEnable( cmuClock_CORELE, true ); | |
/* Enable access to BURTC registers. */ | |
RMU_ResetControl( rmuResetBU, false ); | |
/* Generate the tick interrupt from BURTC. */ | |
xBURTCInitStruct.mode = burtcModeEM3; /* Operational in EM3. */ | |
xBURTCInitStruct.clkSel = burtcClkSelULFRCO;/* ULFRCO clock. */ | |
xBURTCInitStruct.clkDiv = burtcClkDiv_1; /* 2kHz ULFRCO clock. */ | |
xBURTCInitStruct.compare0Top = true; /* Wrap on COMP0. */ | |
BURTC_IntDisable( BURTC_IF_COMP0 ); | |
BURTC_Init( &xBURTCInitStruct ); | |
/* The tick interrupt must be set to the lowest priority possible. */ | |
NVIC_SetPriority( BURTC_IRQn, configLIBRARY_LOWEST_INTERRUPT_PRIORITY ); | |
NVIC_ClearPendingIRQ( BURTC_IRQn ); | |
NVIC_EnableIRQ( BURTC_IRQn ); | |
BURTC_CompareSet( 0, ulReloadValueForOneTick ); | |
BURTC_IntClear( BURTC_IF_COMP0 ); | |
BURTC_IntEnable( BURTC_IF_COMP0 ); | |
BURTC_CounterReset(); | |
} | |
/*-----------------------------------------------------------*/ | |
void vPortSuppressTicksAndSleep( TickType_t xExpectedIdleTime ) | |
{ | |
uint32_t ulReloadValue, ulCompleteTickPeriods, ulCountBeforeSleep, ulCountAfterSleep; | |
eSleepModeStatus eSleepAction; | |
TickType_t xModifiableIdleTime; | |
/* THIS FUNCTION IS CALLED WITH THE SCHEDULER SUSPENDED. */ | |
/* Make sure the BURTC reload value does not overflow the counter. */ | |
if( xExpectedIdleTime > xMaximumPossibleSuppressedTicks ) | |
{ | |
xExpectedIdleTime = xMaximumPossibleSuppressedTicks; | |
} | |
/* Calculate the reload value required to wait xExpectedIdleTime tick | |
periods. */ | |
ulReloadValue = ulReloadValueForOneTick * xExpectedIdleTime; | |
if( ulReloadValue > ulStoppedTimerCompensation ) | |
{ | |
/* Compensate for the fact that the BURTC is going to be stopped | |
momentarily. */ | |
ulReloadValue -= ulStoppedTimerCompensation; | |
} | |
/* Stop the BURTC momentarily. The time the BURTC 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. The count is latched before stopping the timer as | |
stopping the timer appears to clear the count. */ | |
ulCountBeforeSleep = BURTC_CounterGet(); | |
BURTC_Enable( false ); | |
/* If this function is re-entered before one complete tick period then the | |
reload value might be set to take into account a partial time slice, but | |
just reading the count assumes it is counting up to a full ticks worth - so | |
add in the difference if any. */ | |
ulCountBeforeSleep += ( ulReloadValueForOneTick - BURTC_CompareGet( 0 ) ); | |
/* Enter a critical section but don't use the taskENTER_CRITICAL() method as | |
that will mask interrupts that should exit sleep mode. */ | |
INT_Disable(); | |
__asm volatile( "dsb" ); | |
__asm volatile( "isb" ); | |
/* The tick flag is set to false before sleeping. If it is true when sleep | |
mode is exited then sleep mode was probably exited because the tick was | |
suppressed for the entire xExpectedIdleTime period. */ | |
ulTickFlag = pdFALSE; | |
/* If a context switch is pending then abandon the low power entry as the | |
context switch might have been pended by an external interrupt that requires | |
processing. */ | |
eSleepAction = eTaskConfirmSleepModeStatus(); | |
if( eSleepAction == eAbortSleep ) | |
{ | |
/* Restart tick and count up to whatever was left of the current time | |
slice. */ | |
BURTC_CompareSet( 0, ( ulReloadValueForOneTick - ulCountBeforeSleep ) + ulStoppedTimerCompensation ); | |
BURTC_Enable( true ); | |
/* Re-enable interrupts - see comments above the INT_Enable() call | |
above. */ | |
INT_Enable(); | |
} | |
else | |
{ | |
/* Adjust the reload value to take into account that the current time | |
slice is already partially complete. */ | |
ulReloadValue -= ulCountBeforeSleep; | |
BURTC_CompareSet( 0, ulReloadValue ); | |
/* Restart the BURTC. */ | |
BURTC_Enable( true ); | |
/* Allow the application to define some pre-sleep processing. */ | |
xModifiableIdleTime = xExpectedIdleTime; | |
configPRE_SLEEP_PROCESSING( xModifiableIdleTime ); | |
/* xExpectedIdleTime being set to 0 by configPRE_SLEEP_PROCESSING() | |
means the application defined code has already executed the WAIT | |
instruction. */ | |
if( xModifiableIdleTime > 0 ) | |
{ | |
__asm volatile( "dsb" ); | |
SLEEP_Sleep(); | |
__asm volatile( "isb" ); | |
} | |
/* Allow the application to define some post sleep processing. */ | |
configPOST_SLEEP_PROCESSING( xModifiableIdleTime ); | |
/* Stop BURTC. 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. The count value is latched before stopping | |
the timer as stopping the timer appears to clear the count. */ | |
ulCountAfterSleep = BURTC_CounterGet(); | |
BURTC_Enable( false ); | |
/* Re-enable interrupts - see comments above the INT_Enable() call | |
above. */ | |
INT_Enable(); | |
__asm volatile( "dsb" ); | |
__asm volatile( "isb" ); | |
if( ulTickFlag != pdFALSE ) | |
{ | |
/* The tick interrupt has already executed, although because this | |
function is called with the scheduler suspended the actual tick | |
processing will not occur until after this function has exited. | |
Reset the reload value with whatever remains of this tick period. */ | |
ulReloadValue = ulReloadValueForOneTick - ulCountAfterSleep; | |
BURTC_CompareSet( 0, ulReloadValue ); | |
/* The tick interrupt handler will already have pended the tick | |
processing in the kernel. 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 sleeping. The | |
actual stepping of the tick appears later in this function. */ | |
ulCompleteTickPeriods = xExpectedIdleTime - 1UL; | |
} | |
else | |
{ | |
/* Something other than the tick interrupt ended the sleep. How | |
many complete tick periods passed while the processor was | |
sleeping? Add back in the adjustment that was made to the reload | |
value to account for the fact that a time slice was part way through | |
when this function was called. */ | |
ulCountAfterSleep += ulCountBeforeSleep; | |
ulCompleteTickPeriods = ulCountAfterSleep / ulReloadValueForOneTick; | |
/* The reload value is set to whatever fraction of a single tick | |
period remains. */ | |
ulCountAfterSleep -= ( ulCompleteTickPeriods * ulReloadValueForOneTick ); | |
ulReloadValue = ulReloadValueForOneTick - ulCountAfterSleep; | |
if( ulReloadValue == 0 ) | |
{ | |
/* There is no fraction remaining. */ | |
ulReloadValue = ulReloadValueForOneTick; | |
ulCompleteTickPeriods++; | |
} | |
BURTC_CompareSet( 0, ulReloadValue ); | |
} | |
/* Restart the BURTC so it runs up to the alarm value. The alarm value | |
will get set to the value required to generate exactly one tick period | |
the next time the BURTC interrupt executes. */ | |
BURTC_Enable( true ); | |
/* Wind the tick forward by the number of tick periods that the CPU | |
remained in a low power state. */ | |
vTaskStepTick( ulCompleteTickPeriods ); | |
} | |
} | |
/*-----------------------------------------------------------*/ | |
void BURTC_IRQHandler( void ) | |
{ | |
ulTickFlag = pdTRUE; | |
if( BURTC_CompareGet( 0 ) != ulReloadValueForOneTick ) | |
{ | |
/* Set BURTC interrupt to one RTOS tick period. */ | |
BURTC_Enable( false ); | |
BURTC_CompareSet( 0, ulReloadValueForOneTick ); | |
BURTC_Enable( true ); | |
} | |
BURTC_IntClear( _BURTC_IFC_MASK ); | |
/* Critical section which protect incrementing the tick. */ | |
portDISABLE_INTERRUPTS(); | |
{ | |
if( xTaskIncrementTick() != pdFALSE ) | |
{ | |
/* Pend a context switch. */ | |
portNVIC_INT_CTRL_REG = portNVIC_PENDSVSET_BIT; | |
} | |
} | |
portENABLE_INTERRUPTS(); | |
} | |
#endif /* ( configCREATE_LOW_POWER_DEMO == 1 ) */ | |