X-Git-Url: https://git.sur5r.net/?p=freertos;a=blobdiff_plain;f=FreeRTOS%2FSource%2Fportable%2FGCC%2FARM_CM0%2Fport.c;h=18a668b9b64c57dfa18bd2da429dd75a8300df98;hp=d0b50c3927e9747504aa895c49140933e15d064f;hb=242c5762008b65c36750bc9873ded41dce1ba223;hpb=e4a38ada86f7279d432410a61a3f36bf58a1ca88

diff --git a/FreeRTOS/Source/portable/GCC/ARM_CM0/port.c b/FreeRTOS/Source/portable/GCC/ARM_CM0/port.c
index d0b50c392..18a668b9b 100644
--- a/FreeRTOS/Source/portable/GCC/ARM_CM0/port.c
+++ b/FreeRTOS/Source/portable/GCC/ARM_CM0/port.c
@@ -34,15 +34,16 @@
 #include "task.h"
 
 /* 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_INT_CTRL_REG				( * ( ( volatile uint32_t * ) 0xe000ed04 ) )
+#define portNVIC_SYSPRI2_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 )
@@ -50,6 +51,16 @@
 /* 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. */
@@ -89,6 +100,31 @@ 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.
  */
@@ -176,8 +212,8 @@ void vPortStartFirstTask( void )
 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;
+	portNVIC_SYSPRI2_REG |= portNVIC_PENDSV_PRI;
+	portNVIC_SYSPRI2_REG |= portNVIC_SYSTICK_PRI;
 
 	/* Start the timer that generates the tick ISR.  Interrupts are disabled
 	here already. */
@@ -214,7 +250,7 @@ void vPortEndScheduler( void )
 void vPortYield( void )
 {
 	/* 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. */
@@ -323,7 +359,7 @@ 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 );
@@ -336,13 +372,187 @@ uint32_t ulPreviousMask;
  */
 void prvSetupTimerInterrupt( 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) = 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;
 }
 /*-----------------------------------------------------------*/
 
+#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 */