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Add "Tickless Idle" support for ARMv8M ports (FreeRTOS#29)
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Signed-off-by: Gaurav Aggarwal <aggarg@amazon.com>
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@aggarg
aggarg authored Mar 16, 2020
1 parent 459dceb commit 177e79f
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Showing 27 changed files with 2,286 additions and 200 deletions.
260 changes: 238 additions & 22 deletions portable/ARMv8M/non_secure/port.c
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Original file line number Diff line number Diff line change
Expand Up @@ -71,25 +71,32 @@
/**
* @brief 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_PENDSVSET ( 0x10000000 )
#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_SYSPRI2_REG ( * ( ( volatile uint32_t * ) 0xe000ed20 ) )
#define portNVIC_SYSTICK_ENABLE_BIT ( 1UL << 0UL )
#define portNVIC_SYSTICK_INT_BIT ( 1UL << 1UL )
#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 )
#ifndef configSYSTICK_CLOCK_HZ
#define configSYSTICK_CLOCK_HZ configCPU_CLOCK_HZ
/* Ensure the SysTick is clocked at the same frequency as the core. */
#define portNVIC_SYSTICK_CLK_BIT ( 1UL << 2UL )
#else
/* The way the SysTick is clocked is not modified in case it is not the
* same a the core. */
#define portNVIC_SYSTICK_CLK_BIT ( 0 )
#endif
/*-----------------------------------------------------------*/

/**
* @brief Constants required to manipulate the SCB.
*/
#define portSCB_SYS_HANDLER_CTRL_STATE_REG ( * ( volatile uint32_t * ) 0xe000ed24 )
#define portSCB_MEM_FAULT_ENABLE ( 1UL << 16UL )
#define portSCB_MEM_FAULT_ENABLE_BIT ( 1UL << 16UL )
/*-----------------------------------------------------------*/

/**
Expand Down Expand Up @@ -169,15 +176,30 @@
#define portMPU_RLAR_REGION_ENABLE ( 1UL )

/* Enable privileged access to unmapped region. */
#define portMPU_PRIV_BACKGROUND_ENABLE ( 1UL << 2UL )
#define portMPU_PRIV_BACKGROUND_ENABLE_BIT ( 1UL << 2UL )

/* Enable MPU. */
#define portMPU_ENABLE ( 1UL << 0UL )
#define portMPU_ENABLE_BIT ( 1UL << 0UL )

/* Expected value of the portMPU_TYPE register. */
#define portEXPECTED_MPU_TYPE_VALUE ( 8UL << 8UL ) /* 8 regions, unified. */
/*-----------------------------------------------------------*/

/**
* @brief The maximum 24-bit number.
*
* It is needed because the systick is a 24-bit counter.
*/
#define portMAX_24_BIT_NUMBER ( 0xffffffUL )

/**
* @brief 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 )
/*-----------------------------------------------------------*/

/**
* @brief Constants required to set up the initial stack.
*/
Expand Down Expand Up @@ -332,17 +354,211 @@ static volatile uint32_t ulCriticalNesting = 0xaaaaaaaaUL;
*/
portDONT_DISCARD volatile SecureContextHandle_t xSecureContext = portNO_SECURE_CONTEXT;
#endif /* configENABLE_TRUSTZONE */

#if( configUSE_TICKLESS_IDLE == 1 )
/**
* @brief The number of SysTick increments that make up one tick period.
*/
static uint32_t ulTimerCountsForOneTick = 0;

/**
* @brief The maximum number of tick periods that can be suppressed is
* limited by the 24 bit resolution of the SysTick timer.
*/
static uint32_t xMaximumPossibleSuppressedTicks = 0;

/**
* @brief Compensate for the CPU cycles that pass while the SysTick is
* stopped (low power functionality only).
*/
static uint32_t ulStoppedTimerCompensation = 0;
#endif /* configUSE_TICKLESS_IDLE */
/*-----------------------------------------------------------*/

#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 un-suspended 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
* the cpsid instruction 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 interrupts enabled. */
__asm volatile( "cpsie i" ::: "memory" );
}
}
#endif /* configUSE_TICKLESS_IDLE */
/*-----------------------------------------------------------*/

__attribute__(( weak )) void vPortSetupTimerInterrupt( void ) /* PRIVILEGED_FUNCTION */
{
/* 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;
portNVIC_SYSTICK_CTRL_REG = 0UL;
portNVIC_SYSTICK_CURRENT_VALUE_REG = 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;
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;
}
/*-----------------------------------------------------------*/

Expand Down Expand Up @@ -446,11 +662,11 @@ volatile uint32_t ulDummy = 0UL;
( portMPU_RLAR_REGION_ENABLE );

/* Enable mem fault. */
portSCB_SYS_HANDLER_CTRL_STATE_REG |= portSCB_MEM_FAULT_ENABLE;
portSCB_SYS_HANDLER_CTRL_STATE_REG |= portSCB_MEM_FAULT_ENABLE_BIT;

/* Enable MPU with privileged background access i.e. unmapped
* regions have privileged access. */
portMPU_CTRL_REG |= ( portMPU_PRIV_BACKGROUND_ENABLE | portMPU_ENABLE );
portMPU_CTRL_REG |= ( portMPU_PRIV_BACKGROUND_ENABLE_BIT | portMPU_ENABLE_BIT );
}
}
#endif /* configENABLE_MPU */
Expand Down Expand Up @@ -484,7 +700,7 @@ volatile uint32_t ulDummy = 0UL;
void vPortYield( void ) /* PRIVILEGED_FUNCTION */
{
/* Set a PendSV to request a context switch. */
*( portNVIC_INT_CTRL ) = portNVIC_PENDSVSET;
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. */
Expand Down Expand Up @@ -527,7 +743,7 @@ uint32_t ulPreviousMask;
if( xTaskIncrementTick() != pdFALSE )
{
/* Pend a context switch. */
*( portNVIC_INT_CTRL ) = portNVIC_PENDSVSET;
portNVIC_INT_CTRL_REG = portNVIC_PENDSVSET_BIT;
}
}
portCLEAR_INTERRUPT_MASK_FROM_ISR( ulPreviousMask );
Expand Down Expand Up @@ -772,8 +988,8 @@ uint8_t ucSVCNumber;
BaseType_t xPortStartScheduler( void ) /* PRIVILEGED_FUNCTION */
{
/* Make PendSV, CallSV and SysTick the same priority as the kernel. */
*( portNVIC_SYSPRI2 ) |= portNVIC_PENDSV_PRI;
*( portNVIC_SYSPRI2 ) |= portNVIC_SYSTICK_PRI;
portNVIC_SYSPRI2_REG |= portNVIC_PENDSV_PRI;
portNVIC_SYSPRI2_REG |= portNVIC_SYSTICK_PRI;

#if( configENABLE_MPU == 1 )
{
Expand Down
9 changes: 9 additions & 0 deletions portable/ARMv8M/non_secure/portable/GCC/ARM_CM23/portmacro.h
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Original file line number Diff line number Diff line change
Expand Up @@ -227,6 +227,15 @@ typedef struct MPU_SETTINGS
#define portEXIT_CRITICAL() vPortExitCritical()
/*-----------------------------------------------------------*/

/**
* @brief Tickless idle/low power functionality.
*/
#ifndef portSUPPRESS_TICKS_AND_SLEEP
extern void vPortSuppressTicksAndSleep( TickType_t xExpectedIdleTime );
#define portSUPPRESS_TICKS_AND_SLEEP( xExpectedIdleTime ) vPortSuppressTicksAndSleep( xExpectedIdleTime )
#endif
/*-----------------------------------------------------------*/

/**
* @brief Task function macros as described on the FreeRTOS.org WEB site.
*/
Expand Down
9 changes: 9 additions & 0 deletions portable/ARMv8M/non_secure/portable/GCC/ARM_CM23_NTZ/portmacro.h
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Original file line number Diff line number Diff line change
Expand Up @@ -227,6 +227,15 @@ typedef struct MPU_SETTINGS
#define portEXIT_CRITICAL() vPortExitCritical()
/*-----------------------------------------------------------*/

/**
* @brief Tickless idle/low power functionality.
*/
#ifndef portSUPPRESS_TICKS_AND_SLEEP
extern void vPortSuppressTicksAndSleep( TickType_t xExpectedIdleTime );
#define portSUPPRESS_TICKS_AND_SLEEP( xExpectedIdleTime ) vPortSuppressTicksAndSleep( xExpectedIdleTime )
#endif
/*-----------------------------------------------------------*/

/**
* @brief Task function macros as described on the FreeRTOS.org WEB site.
*/
Expand Down
9 changes: 9 additions & 0 deletions portable/ARMv8M/non_secure/portable/GCC/ARM_CM33/portmacro.h
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Original file line number Diff line number Diff line change
Expand Up @@ -227,6 +227,15 @@ typedef struct MPU_SETTINGS
#define portEXIT_CRITICAL() vPortExitCritical()
/*-----------------------------------------------------------*/

/**
* @brief Tickless idle/low power functionality.
*/
#ifndef portSUPPRESS_TICKS_AND_SLEEP
extern void vPortSuppressTicksAndSleep( TickType_t xExpectedIdleTime );
#define portSUPPRESS_TICKS_AND_SLEEP( xExpectedIdleTime ) vPortSuppressTicksAndSleep( xExpectedIdleTime )
#endif
/*-----------------------------------------------------------*/

/**
* @brief Task function macros as described on the FreeRTOS.org WEB site.
*/
Expand Down
9 changes: 9 additions & 0 deletions portable/ARMv8M/non_secure/portable/GCC/ARM_CM33_NTZ/portmacro.h
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Original file line number Diff line number Diff line change
Expand Up @@ -227,6 +227,15 @@ typedef struct MPU_SETTINGS
#define portEXIT_CRITICAL() vPortExitCritical()
/*-----------------------------------------------------------*/

/**
* @brief Tickless idle/low power functionality.
*/
#ifndef portSUPPRESS_TICKS_AND_SLEEP
extern void vPortSuppressTicksAndSleep( TickType_t xExpectedIdleTime );
#define portSUPPRESS_TICKS_AND_SLEEP( xExpectedIdleTime ) vPortSuppressTicksAndSleep( xExpectedIdleTime )
#endif
/*-----------------------------------------------------------*/

/**
* @brief Task function macros as described on the FreeRTOS.org WEB site.
*/
Expand Down
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