#include "task.h"\r
\r
/* Constants required to manipulate the NVIC. */\r
-#define portNVIC_SYSTICK_CTRL ( ( volatile uint32_t * ) 0xe000e010 )\r
-#define portNVIC_SYSTICK_LOAD ( ( volatile uint32_t * ) 0xe000e014 )\r
-#define portNVIC_SYSTICK_CURRENT_VALUE ( ( volatile uint32_t * ) 0xe000e018 )\r
-#define portNVIC_INT_CTRL ( ( volatile uint32_t *) 0xe000ed04 )\r
-#define portNVIC_SYSPRI2 ( ( volatile uint32_t *) 0xe000ed20 )\r
-#define portNVIC_SYSTICK_CLK 0x00000004\r
-#define portNVIC_SYSTICK_INT 0x00000002\r
-#define portNVIC_SYSTICK_ENABLE 0x00000001\r
-#define portNVIC_PENDSVSET 0x10000000\r
+#define portNVIC_SYSTICK_CTRL_REG ( * ( ( volatile uint32_t * ) 0xe000e010 ) )\r
+#define portNVIC_SYSTICK_LOAD_REG ( * ( ( volatile uint32_t * ) 0xe000e014 ) )\r
+#define portNVIC_SYSTICK_CURRENT_VALUE_REG ( * ( ( volatile uint32_t * ) 0xe000e018 ) )\r
+#define portNVIC_INT_CTRL_REG ( * ( ( volatile uint32_t * ) 0xe000ed04 ) )\r
+#define portNVIC_SYSPRI2_REG ( * ( ( volatile uint32_t * ) 0xe000ed20 ) )\r
+#define portNVIC_SYSTICK_CLK_BIT ( 1UL << 2UL )\r
+#define portNVIC_SYSTICK_INT_BIT ( 1UL << 1UL )\r
+#define portNVIC_SYSTICK_ENABLE_BIT ( 1UL << 0UL )\r
+#define portNVIC_SYSTICK_COUNT_FLAG_BIT ( 1UL << 16UL )\r
+#define portNVIC_PENDSVSET_BIT ( 1UL << 28UL )\r
#define portMIN_INTERRUPT_PRIORITY ( 255UL )\r
#define portNVIC_PENDSV_PRI ( portMIN_INTERRUPT_PRIORITY << 16UL )\r
#define portNVIC_SYSTICK_PRI ( portMIN_INTERRUPT_PRIORITY << 24UL )\r
/* Constants required to set up the initial stack. */\r
#define portINITIAL_XPSR ( 0x01000000 )\r
\r
+/* The systick is a 24-bit counter. */\r
+#define portMAX_24_BIT_NUMBER ( 0xffffffUL )\r
+\r
+/* A fiddle factor to estimate the number of SysTick counts that would have\r
+occurred while the SysTick counter is stopped during tickless idle\r
+calculations. */\r
+#ifndef portMISSED_COUNTS_FACTOR\r
+ #define portMISSED_COUNTS_FACTOR ( 45UL )\r
+#endif\r
+\r
/* Let the user override the pre-loading of the initial LR with the address of\r
prvTaskExitError() in case it messes up unwinding of the stack in the\r
debugger. */\r
\r
/*-----------------------------------------------------------*/\r
\r
+/*\r
+* The number of SysTick increments that make up one tick period.\r
+*/\r
+#if( configUSE_TICKLESS_IDLE == 1 )\r
+ static uint32_t ulTimerCountsForOneTick = 0;\r
+#endif /* configUSE_TICKLESS_IDLE */\r
+\r
+/*\r
+ * The maximum number of tick periods that can be suppressed is limited by the\r
+ * 24 bit resolution of the SysTick timer.\r
+ */\r
+#if( configUSE_TICKLESS_IDLE == 1 )\r
+ static uint32_t xMaximumPossibleSuppressedTicks = 0;\r
+#endif /* configUSE_TICKLESS_IDLE */\r
+\r
+/*\r
+ * Compensate for the CPU cycles that pass while the SysTick is stopped (low\r
+ * power functionality only.\r
+ */\r
+#if( configUSE_TICKLESS_IDLE == 1 )\r
+ static uint32_t ulStoppedTimerCompensation = 0;\r
+#endif /* configUSE_TICKLESS_IDLE */\r
+\r
+/*-----------------------------------------------------------*/\r
+\r
/*\r
* See header file for description.\r
*/\r
BaseType_t xPortStartScheduler( void )\r
{\r
/* Make PendSV, CallSV and SysTick the same priority as the kernel. */\r
- *(portNVIC_SYSPRI2) |= portNVIC_PENDSV_PRI;\r
- *(portNVIC_SYSPRI2) |= portNVIC_SYSTICK_PRI;\r
+ portNVIC_SYSPRI2_REG |= portNVIC_PENDSV_PRI;\r
+ portNVIC_SYSPRI2_REG |= portNVIC_SYSTICK_PRI;\r
\r
/* Start the timer that generates the tick ISR. Interrupts are disabled\r
here already. */\r
void vPortYield( void )\r
{\r
/* Set a PendSV to request a context switch. */\r
- *( portNVIC_INT_CTRL ) = portNVIC_PENDSVSET;\r
+ portNVIC_INT_CTRL_REG = portNVIC_PENDSVSET_BIT;\r
\r
/* Barriers are normally not required but do ensure the code is completely\r
within the specified behaviour for the architecture. */\r
if( xTaskIncrementTick() != pdFALSE )\r
{\r
/* Pend a context switch. */\r
- *(portNVIC_INT_CTRL) = portNVIC_PENDSVSET;\r
+ portNVIC_INT_CTRL_REG = portNVIC_PENDSVSET_BIT;\r
}\r
}\r
portCLEAR_INTERRUPT_MASK_FROM_ISR( ulPreviousMask );\r
*/\r
void prvSetupTimerInterrupt( void )\r
{\r
+ /* Calculate the constants required to configure the tick interrupt. */\r
+ #if( configUSE_TICKLESS_IDLE == 1 )\r
+ {\r
+ ulTimerCountsForOneTick = ( configCPU_CLOCK_HZ / configTICK_RATE_HZ );\r
+ xMaximumPossibleSuppressedTicks = portMAX_24_BIT_NUMBER / ulTimerCountsForOneTick;\r
+ ulStoppedTimerCompensation = portMISSED_COUNTS_FACTOR;\r
+ }\r
+ #endif /* configUSE_TICKLESS_IDLE */\r
+\r
/* Stop and reset the SysTick. */\r
- *(portNVIC_SYSTICK_CTRL) = 0UL;\r
- *(portNVIC_SYSTICK_CURRENT_VALUE) = 0UL;\r
+ portNVIC_SYSTICK_CTRL_REG = 0UL;\r
+ portNVIC_SYSTICK_CURRENT_VALUE_REG = 0UL;\r
\r
/* Configure SysTick to interrupt at the requested rate. */\r
- *(portNVIC_SYSTICK_LOAD) = ( configCPU_CLOCK_HZ / configTICK_RATE_HZ ) - 1UL;\r
- *(portNVIC_SYSTICK_CTRL) = portNVIC_SYSTICK_CLK | portNVIC_SYSTICK_INT | portNVIC_SYSTICK_ENABLE;\r
+ portNVIC_SYSTICK_LOAD_REG = ( configCPU_CLOCK_HZ / configTICK_RATE_HZ ) - 1UL;\r
+ portNVIC_SYSTICK_CTRL_REG = portNVIC_SYSTICK_CLK_BIT | portNVIC_SYSTICK_INT_BIT | portNVIC_SYSTICK_ENABLE_BIT;\r
}\r
/*-----------------------------------------------------------*/\r
\r
+#if( configUSE_TICKLESS_IDLE == 1 )\r
+\r
+ __attribute__((weak)) void vPortSuppressTicksAndSleep( TickType_t xExpectedIdleTime )\r
+ {\r
+ uint32_t ulReloadValue, ulCompleteTickPeriods, ulCompletedSysTickDecrements;\r
+ TickType_t xModifiableIdleTime;\r
+\r
+ /* Make sure the SysTick reload value does not overflow the counter. */\r
+ if( xExpectedIdleTime > xMaximumPossibleSuppressedTicks )\r
+ {\r
+ xExpectedIdleTime = xMaximumPossibleSuppressedTicks;\r
+ }\r
+\r
+ /* Stop the SysTick momentarily. The time the SysTick is stopped for\r
+ is accounted for as best it can be, but using the tickless mode will\r
+ inevitably result in some tiny drift of the time maintained by the\r
+ kernel with respect to calendar time. */\r
+ portNVIC_SYSTICK_CTRL_REG &= ~portNVIC_SYSTICK_ENABLE_BIT;\r
+\r
+ /* Calculate the reload value required to wait xExpectedIdleTime\r
+ tick periods. -1 is used because this code will execute part way\r
+ through one of the tick periods. */\r
+ ulReloadValue = portNVIC_SYSTICK_CURRENT_VALUE_REG + ( ulTimerCountsForOneTick * ( xExpectedIdleTime - 1UL ) );\r
+ if( ulReloadValue > ulStoppedTimerCompensation )\r
+ {\r
+ ulReloadValue -= ulStoppedTimerCompensation;\r
+ }\r
+\r
+ /* Enter a critical section but don't use the taskENTER_CRITICAL()\r
+ method as that will mask interrupts that should exit sleep mode. */\r
+ __asm volatile( "cpsid i" ::: "memory" );\r
+ __asm volatile( "dsb" );\r
+ __asm volatile( "isb" );\r
+\r
+ /* If a context switch is pending or a task is waiting for the scheduler\r
+ to be unsuspended then abandon the low power entry. */\r
+ if( eTaskConfirmSleepModeStatus() == eAbortSleep )\r
+ {\r
+ /* Restart from whatever is left in the count register to complete\r
+ this tick period. */\r
+ portNVIC_SYSTICK_LOAD_REG = portNVIC_SYSTICK_CURRENT_VALUE_REG;\r
+\r
+ /* Restart SysTick. */\r
+ portNVIC_SYSTICK_CTRL_REG |= portNVIC_SYSTICK_ENABLE_BIT;\r
+\r
+ /* Reset the reload register to the value required for normal tick\r
+ periods. */\r
+ portNVIC_SYSTICK_LOAD_REG = ulTimerCountsForOneTick - 1UL;\r
+\r
+ /* Re-enable interrupts - see comments above the cpsid instruction()\r
+ above. */\r
+ __asm volatile( "cpsie i" ::: "memory" );\r
+ }\r
+ else\r
+ {\r
+ /* Set the new reload value. */\r
+ portNVIC_SYSTICK_LOAD_REG = ulReloadValue;\r
+\r
+ /* Clear the SysTick count flag and set the count value back to\r
+ zero. */\r
+ portNVIC_SYSTICK_CURRENT_VALUE_REG = 0UL;\r
+\r
+ /* Restart SysTick. */\r
+ portNVIC_SYSTICK_CTRL_REG |= portNVIC_SYSTICK_ENABLE_BIT;\r
+\r
+ /* Sleep until something happens. configPRE_SLEEP_PROCESSING() can\r
+ set its parameter to 0 to indicate that its implementation contains\r
+ its own wait for interrupt or wait for event instruction, and so wfi\r
+ should not be executed again. However, the original expected idle\r
+ time variable must remain unmodified, so a copy is taken. */\r
+ xModifiableIdleTime = xExpectedIdleTime;\r
+ configPRE_SLEEP_PROCESSING( xModifiableIdleTime );\r
+ if( xModifiableIdleTime > 0 )\r
+ {\r
+ __asm volatile( "dsb" ::: "memory" );\r
+ __asm volatile( "wfi" );\r
+ __asm volatile( "isb" );\r
+ }\r
+ configPOST_SLEEP_PROCESSING( xExpectedIdleTime );\r
+\r
+ /* Re-enable interrupts to allow the interrupt that brought the MCU\r
+ out of sleep mode to execute immediately. see comments above\r
+ __disable_interrupt() call above. */\r
+ __asm volatile( "cpsie i" ::: "memory" );\r
+ __asm volatile( "dsb" );\r
+ __asm volatile( "isb" );\r
+\r
+ /* Disable interrupts again because the clock is about to be stopped\r
+ and interrupts that execute while the clock is stopped will increase\r
+ any slippage between the time maintained by the RTOS and calendar\r
+ time. */\r
+ __asm volatile( "cpsid i" ::: "memory" );\r
+ __asm volatile( "dsb" );\r
+ __asm volatile( "isb" );\r
+\r
+ /* Disable the SysTick clock without reading the\r
+ portNVIC_SYSTICK_CTRL_REG register to ensure the\r
+ portNVIC_SYSTICK_COUNT_FLAG_BIT is not cleared if it is set. Again,\r
+ the time the SysTick is stopped for is accounted for as best it can\r
+ be, but using the tickless mode will inevitably result in some tiny\r
+ drift of the time maintained by the kernel with respect to calendar\r
+ time*/\r
+ portNVIC_SYSTICK_CTRL_REG = ( portNVIC_SYSTICK_CLK_BIT | portNVIC_SYSTICK_INT_BIT );\r
+\r
+ /* Determine if the SysTick clock has already counted to zero and\r
+ been set back to the current reload value (the reload back being\r
+ correct for the entire expected idle time) or if the SysTick is yet\r
+ to count to zero (in which case an interrupt other than the SysTick\r
+ must have brought the system out of sleep mode). */\r
+ if( ( portNVIC_SYSTICK_CTRL_REG & portNVIC_SYSTICK_COUNT_FLAG_BIT ) != 0 )\r
+ {\r
+ uint32_t ulCalculatedLoadValue;\r
+\r
+ /* The tick interrupt is already pending, and the SysTick count\r
+ reloaded with ulReloadValue. Reset the\r
+ portNVIC_SYSTICK_LOAD_REG with whatever remains of this tick\r
+ period. */\r
+ ulCalculatedLoadValue = ( ulTimerCountsForOneTick - 1UL ) - ( ulReloadValue - portNVIC_SYSTICK_CURRENT_VALUE_REG );\r
+\r
+ /* Don't allow a tiny value, or values that have somehow\r
+ underflowed because the post sleep hook did something\r
+ that took too long. */\r
+ if( ( ulCalculatedLoadValue < ulStoppedTimerCompensation ) || ( ulCalculatedLoadValue > ulTimerCountsForOneTick ) )\r
+ {\r
+ ulCalculatedLoadValue = ( ulTimerCountsForOneTick - 1UL );\r
+ }\r
+\r
+ portNVIC_SYSTICK_LOAD_REG = ulCalculatedLoadValue;\r
+\r
+ /* As the pending tick will be processed as soon as this\r
+ function exits, the tick value maintained by the tick is stepped\r
+ forward by one less than the time spent waiting. */\r
+ ulCompleteTickPeriods = xExpectedIdleTime - 1UL;\r
+ }\r
+ else\r
+ {\r
+ /* Something other than the tick interrupt ended the sleep.\r
+ Work out how long the sleep lasted rounded to complete tick\r
+ periods (not the ulReload value which accounted for part\r
+ ticks). */\r
+ ulCompletedSysTickDecrements = ( xExpectedIdleTime * ulTimerCountsForOneTick ) - portNVIC_SYSTICK_CURRENT_VALUE_REG;\r
+\r
+ /* How many complete tick periods passed while the processor\r
+ was waiting? */\r
+ ulCompleteTickPeriods = ulCompletedSysTickDecrements / ulTimerCountsForOneTick;\r
+\r
+ /* The reload value is set to whatever fraction of a single tick\r
+ period remains. */\r
+ portNVIC_SYSTICK_LOAD_REG = ( ( ulCompleteTickPeriods + 1UL ) * ulTimerCountsForOneTick ) - ulCompletedSysTickDecrements;\r
+ }\r
+\r
+ /* Restart SysTick so it runs from portNVIC_SYSTICK_LOAD_REG\r
+ again, then set portNVIC_SYSTICK_LOAD_REG back to its standard\r
+ value. */\r
+ portNVIC_SYSTICK_CURRENT_VALUE_REG = 0UL;\r
+ portNVIC_SYSTICK_CTRL_REG |= portNVIC_SYSTICK_ENABLE_BIT;\r
+ vTaskStepTick( ulCompleteTickPeriods );\r
+ portNVIC_SYSTICK_LOAD_REG = ulTimerCountsForOneTick - 1UL;\r
+\r
+ /* Exit with interrpts enabled. */\r
+ __asm volatile( "cpsie i" ::: "memory" );\r
+ }\r
+ }\r
+\r
+#endif /* configUSE_TICKLESS_IDLE */\r
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