blob: 33bf3eb44ac06e48a8868ffe63bd530795dbc314 [file] [log] [blame]
/*
* FreeRTOS Kernel V10.2.1
* Copyright (C) 2019 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.
*----------------------------------------------------------*/
/* Scheduler includes. */
#include "FreeRTOS.h"
#include "task.h"
#ifndef configSYSTICK_CLOCK_HZ
#define configSYSTICK_CLOCK_HZ configCPU_CLOCK_HZ
#endif
/* Constants required to manipulate the NVIC. */
#define portNVIC_SYSTICK_CTRL ( *( ( volatile uint32_t *) 0xe000e010 ))
#define portNVIC_SYSTICK_LOAD ( *( ( volatile uint32_t *) 0xe000e014 ))
#define portNVIC_SYSTICK_CURRENT_VALUE ( * ( ( volatile uint32_t * ) 0xe000e018 ) )
#define portNVIC_INT_CTRL ( ( volatile uint32_t *) 0xe000ed04 )
#define portNVIC_SYSPRI2 ( ( volatile uint32_t *) 0xe000ed20 )
#define portNVIC_SYSTICK_CLK 0x00000004
#define portNVIC_SYSTICK_INT 0x00000002
#define portNVIC_SYSTICK_ENABLE 0x00000001
#define portNVIC_SYSTICK_COUNT_FLAG ( 1UL << 16UL )
#define portNVIC_PENDSVSET 0x10000000
#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 )
/* Constants used with memory barrier intrinsics. */
#define portSY_FULL_READ_WRITE ( 15 )
/* 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. */
#define portMISSED_COUNTS_FACTOR ( 45UL )
/* Each task maintains its own interrupt status in the critical nesting
variable. */
static UBaseType_t uxCriticalNesting = 0xaaaaaaaa;
/*
* Setup the timer to generate the tick interrupts.
*/
static void prvSetupTimerInterrupt( void );
/*
* Exception handlers.
*/
void xPortPendSVHandler( void );
void xPortSysTickHandler( void );
void vPortSVCHandler( void );
/*
* Start first task is a separate function so it can be tested in isolation.
*/
static void prvPortStartFirstTask( void );
/*
* Used to catch tasks that attempt to return from their implementing function.
*/
static void prvTaskExitError( void );
/*-----------------------------------------------------------*/
/*
* The number of SysTick increments that make up one tick period.
*/
#if configUSE_TICKLESS_IDLE == 1
static unsigned long 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 unsigned long 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 unsigned long 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 ) 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( ;; );
}
/*-----------------------------------------------------------*/
void vPortSVCHandler( void )
{
/* This function is no longer used, but retained for backward
compatibility. */
}
/*-----------------------------------------------------------*/
__asm void prvPortStartFirstTask( void )
{
extern pxCurrentTCB;
PRESERVE8
/* 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. */
ldr r3, =pxCurrentTCB /* Obtain location of pxCurrentTCB. */
ldr r1, [r3]
ldr r0, [r1] /* The first item in pxCurrentTCB is the task top of stack. */
adds r0, #32 /* Discard everything up to r0. */
msr psp, r0 /* This is now the new top of stack to use in the task. */
movs r0, #2 /* Switch to the psp stack. */
msr CONTROL, r0
isb
pop {r0-r5} /* Pop the registers that are saved automatically. */
mov lr, r5 /* lr is now in r5. */
pop {r3} /* The return address is now in r3. */
pop {r2} /* Pop and discard the XPSR. */
cpsie i /* The first task has its context and interrupts can be enabled. */
bx r3 /* Finally, jump to the user defined task code. */
ALIGN
}
/*-----------------------------------------------------------*/
/*
* See header file for description.
*/
BaseType_t xPortStartScheduler( void )
{
/* Make PendSV, CallSV and SysTick the same priority as the kernel. */
*(portNVIC_SYSPRI2) |= portNVIC_PENDSV_PRI;
*(portNVIC_SYSPRI2) |= portNVIC_SYSTICK_PRI;
/* Start the timer that generates the tick ISR. Interrupts are disabled
here already. */
prvSetupTimerInterrupt();
/* Initialise the critical nesting count ready for the first task. */
uxCriticalNesting = 0;
/* Start the first task. */
prvPortStartFirstTask();
/* 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 ) = portNVIC_PENDSVSET;
/* Barriers are normally not required but do ensure the code is completely
within the specified behaviour for the architecture. */
__dsb( portSY_FULL_READ_WRITE );
__isb( portSY_FULL_READ_WRITE );
}
/*-----------------------------------------------------------*/
void vPortEnterCritical( void )
{
portDISABLE_INTERRUPTS();
uxCriticalNesting++;
__dsb( portSY_FULL_READ_WRITE );
__isb( portSY_FULL_READ_WRITE );
}
/*-----------------------------------------------------------*/
void vPortExitCritical( void )
{
configASSERT( uxCriticalNesting );
uxCriticalNesting--;
if( uxCriticalNesting == 0 )
{
portENABLE_INTERRUPTS();
}
}
/*-----------------------------------------------------------*/
__asm uint32_t ulSetInterruptMaskFromISR( void )
{
mrs r0, PRIMASK
cpsid i
bx lr
}
/*-----------------------------------------------------------*/
__asm void vClearInterruptMaskFromISR( uint32_t ulMask )
{
msr PRIMASK, r0
bx lr
}
/*-----------------------------------------------------------*/
__asm void xPortPendSVHandler( void )
{
extern vTaskSwitchContext
extern pxCurrentTCB
PRESERVE8
mrs r0, psp
ldr r3, =pxCurrentTCB /* Get the location of the current TCB. */
ldr r2, [r3]
subs r0, #32 /* Make space for the remaining low registers. */
str r0, [r2] /* Save the new top of stack. */
stmia r0!, {r4-r7} /* Store the low registers that are not saved automatically. */
mov r4, r8 /* Store the high registers. */
mov r5, r9
mov r6, r10
mov r7, r11
stmia r0!, {r4-r7}
push {r3, r14}
cpsid i
bl vTaskSwitchContext
cpsie i
pop {r2, r3} /* lr goes in r3. r2 now holds tcb pointer. */
ldr r1, [r2]
ldr r0, [r1] /* The first item in pxCurrentTCB is the task top of stack. */
adds r0, #16 /* Move to the high registers. */
ldmia r0!, {r4-r7} /* Pop the high registers. */
mov r8, r4
mov r9, r5
mov r10, r6
mov r11, r7
msr psp, r0 /* Remember the new top of stack for the task. */
subs r0, #32 /* Go back for the low registers that are not automatically restored. */
ldmia r0!, {r4-r7} /* Pop low registers. */
bx r3
ALIGN
}
/*-----------------------------------------------------------*/
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) = portNVIC_PENDSVSET;
}
}
portCLEAR_INTERRUPT_MASK_FROM_ISR( ulPreviousMask );
}
/*-----------------------------------------------------------*/
#if configUSE_TICKLESS_IDLE == 1
__weak void vPortSuppressTicksAndSleep( TickType_t xExpectedIdleTime )
{
uint32_t ulReloadValue, ulCompleteTickPeriods, ulCompletedSysTickDecrements, ulSysTickCTRL;
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 &= ~portNVIC_SYSTICK_ENABLE;
/* 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 + ( 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_irq();
/* 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 = portNVIC_SYSTICK_CURRENT_VALUE;
/* Restart SysTick. */
portNVIC_SYSTICK_CTRL |= portNVIC_SYSTICK_ENABLE;
/* Reset the reload register to the value required for normal tick
periods. */
portNVIC_SYSTICK_LOAD = ulTimerCountsForOneTick - 1UL;
/* Re-enable interrupts - see comments above __disable_irq() call
above. */
__enable_irq();
}
else
{
/* Set the new reload value. */
portNVIC_SYSTICK_LOAD = ulReloadValue;
/* Clear the SysTick count flag and set the count value back to
zero. */
portNVIC_SYSTICK_CURRENT_VALUE = 0UL;
/* Restart SysTick. */
portNVIC_SYSTICK_CTRL |= portNVIC_SYSTICK_ENABLE;
/* 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( portSY_FULL_READ_WRITE );
__wfi();
__isb( portSY_FULL_READ_WRITE );
}
configPOST_SLEEP_PROCESSING( &xExpectedIdleTime );
/* Stop SysTick. 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. */
ulSysTickCTRL = portNVIC_SYSTICK_CTRL;
portNVIC_SYSTICK_CTRL = ( ulSysTickCTRL & ~portNVIC_SYSTICK_ENABLE );
/* Re-enable interrupts - see comments above __disable_irq() call
above. */
__enable_irq();
if( ( ulSysTickCTRL & portNVIC_SYSTICK_COUNT_FLAG ) != 0 )
{
uint32_t ulCalculatedLoadValue;
/* The tick interrupt has already executed, 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 );
/* 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 = ulCalculatedLoadValue;
/* 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 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;
/* 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 = ( ( ulCompleteTickPeriods + 1 ) * ulTimerCountsForOneTick ) - ulCompletedSysTickDecrements;
}
/* Restart SysTick so it runs from portNVIC_SYSTICK_LOAD
again, then set portNVIC_SYSTICK_LOAD back to its standard
value. The critical section is used to ensure the tick interrupt
can only execute once in the case that the reload register is near
zero. */
portNVIC_SYSTICK_CURRENT_VALUE = 0UL;
portENTER_CRITICAL();
{
portNVIC_SYSTICK_CTRL |= portNVIC_SYSTICK_ENABLE;
vTaskStepTick( ulCompleteTickPeriods );
portNVIC_SYSTICK_LOAD = ulTimerCountsForOneTick - 1UL;
}
portEXIT_CRITICAL();
}
}
#endif /* #if configUSE_TICKLESS_IDLE */
/*-----------------------------------------------------------*/
/*
* Setup the systick timer to generate the tick interrupts at the required
* frequency.
*/
void prvSetupTimerInterrupt( void )
{
/* Calculate the constants required to configure the tick interrupt. */
#if configUSE_TICKLESS_IDLE == 1
{
ulTimerCountsForOneTick = ( configSYSTICK_CLOCK_HZ / configTICK_RATE_HZ );
xMaximumPossibleSuppressedTicks = portMAX_24_BIT_NUMBER / ulTimerCountsForOneTick;
ulStoppedTimerCompensation = portMISSED_COUNTS_FACTOR / ( configCPU_CLOCK_HZ / configSYSTICK_CLOCK_HZ );
}
#endif /* configUSE_TICKLESS_IDLE */
/* Stop and reset the SysTick. */
portNVIC_SYSTICK_CTRL = 0UL;
portNVIC_SYSTICK_CURRENT_VALUE = 0UL;
/* Configure SysTick to interrupt at the requested rate. */
portNVIC_SYSTICK_LOAD = ( configCPU_CLOCK_HZ / configTICK_RATE_HZ ) - 1UL;
portNVIC_SYSTICK_CTRL = portNVIC_SYSTICK_CLK | portNVIC_SYSTICK_INT | portNVIC_SYSTICK_ENABLE;
}
/*-----------------------------------------------------------*/