2 * FreeRTOS Kernel V10.3.0
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3 * Copyright (C) 2020 Amazon.com, Inc. or its affiliates. All Rights Reserved.
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5 * Permission is hereby granted, free of charge, to any person obtaining a copy of
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6 * this software and associated documentation files (the "Software"), to deal in
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7 * the Software without restriction, including without limitation the rights to
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8 * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
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9 * the Software, and to permit persons to whom the Software is furnished to do so,
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10 * subject to the following conditions:
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12 * The above copyright notice and this permission notice shall be included in all
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13 * copies or substantial portions of the Software.
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15 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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16 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
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17 * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
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18 * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
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19 * IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
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20 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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22 * http://www.FreeRTOS.org
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23 * http://aws.amazon.com/freertos
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25 * 1 tab == 4 spaces!
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28 /* Standard includes. */
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32 #include <intrinsics.h>
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34 /* Scheduler includes. */
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35 #include "FreeRTOS.h"
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38 #ifndef configINTERRUPT_CONTROLLER_BASE_ADDRESS
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39 #error configINTERRUPT_CONTROLLER_BASE_ADDRESS must be defined. See http://www.freertos.org/Using-FreeRTOS-on-Cortex-A-Embedded-Processors.html
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42 #ifndef configINTERRUPT_CONTROLLER_CPU_INTERFACE_OFFSET
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43 #error configINTERRUPT_CONTROLLER_CPU_INTERFACE_OFFSET must be defined. See http://www.freertos.org/Using-FreeRTOS-on-Cortex-A-Embedded-Processors.html
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46 #ifndef configUNIQUE_INTERRUPT_PRIORITIES
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47 #error configUNIQUE_INTERRUPT_PRIORITIES must be defined. See http://www.freertos.org/Using-FreeRTOS-on-Cortex-A-Embedded-Processors.html
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50 #ifndef configSETUP_TICK_INTERRUPT
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51 #error configSETUP_TICK_INTERRUPT() must be defined. See http://www.freertos.org/Using-FreeRTOS-on-Cortex-A-Embedded-Processors.html
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52 #endif /* configSETUP_TICK_INTERRUPT */
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54 #ifndef configMAX_API_CALL_INTERRUPT_PRIORITY
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55 #error configMAX_API_CALL_INTERRUPT_PRIORITY must be defined. See http://www.freertos.org/Using-FreeRTOS-on-Cortex-A-Embedded-Processors.html
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58 #if configMAX_API_CALL_INTERRUPT_PRIORITY == 0
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59 #error configMAX_API_CALL_INTERRUPT_PRIORITY must not be set to 0
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62 #if configMAX_API_CALL_INTERRUPT_PRIORITY > configUNIQUE_INTERRUPT_PRIORITIES
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63 #error configMAX_API_CALL_INTERRUPT_PRIORITY must be less than or equal to configUNIQUE_INTERRUPT_PRIORITIES as the lower the numeric priority value the higher the logical interrupt priority
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66 #if configUSE_PORT_OPTIMISED_TASK_SELECTION == 1
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67 /* Check the configuration. */
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68 #if( configMAX_PRIORITIES > 32 )
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69 #error configUSE_PORT_OPTIMISED_TASK_SELECTION can only be set to 1 when configMAX_PRIORITIES is less than or equal to 32. It is very rare that a system requires more than 10 to 15 difference priorities as tasks that share a priority will time slice.
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71 #endif /* configUSE_PORT_OPTIMISED_TASK_SELECTION */
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73 /* In case security extensions are implemented. */
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74 #if configMAX_API_CALL_INTERRUPT_PRIORITY <= ( configUNIQUE_INTERRUPT_PRIORITIES / 2 )
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75 #error configMAX_API_CALL_INTERRUPT_PRIORITY must be greater than ( configUNIQUE_INTERRUPT_PRIORITIES / 2 )
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78 #ifndef configCLEAR_TICK_INTERRUPT
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79 #define configCLEAR_TICK_INTERRUPT()
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82 /* A critical section is exited when the critical section nesting count reaches
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84 #define portNO_CRITICAL_NESTING ( ( uint32_t ) 0 )
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86 /* In all GICs 255 can be written to the priority mask register to unmask all
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87 (but the lowest) interrupt priority. */
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88 #define portUNMASK_VALUE ( 0xFFUL )
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90 /* Tasks are not created with a floating point context, but can be given a
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91 floating point context after they have been created. A variable is stored as
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92 part of the tasks context that holds portNO_FLOATING_POINT_CONTEXT if the task
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93 does not have an FPU context, or any other value if the task does have an FPU
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95 #define portNO_FLOATING_POINT_CONTEXT ( ( StackType_t ) 0 )
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97 /* Constants required to setup the initial task context. */
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98 #define portINITIAL_SPSR ( ( StackType_t ) 0x1f ) /* System mode, ARM mode, interrupts enabled. */
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99 #define portTHUMB_MODE_BIT ( ( StackType_t ) 0x20 )
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100 #define portTHUMB_MODE_ADDRESS ( 0x01UL )
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102 /* Used by portASSERT_IF_INTERRUPT_PRIORITY_INVALID() when ensuring the binary
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104 #define portBINARY_POINT_BITS ( ( uint8_t ) 0x03 )
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106 /* Masks all bits in the APSR other than the mode bits. */
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107 #define portAPSR_MODE_BITS_MASK ( 0x1F )
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109 /* The value of the mode bits in the APSR when the CPU is executing in user
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111 #define portAPSR_USER_MODE ( 0x10 )
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113 /* Macro to unmask all interrupt priorities. */
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114 #define portCLEAR_INTERRUPT_MASK() \
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117 portICCPMR_PRIORITY_MASK_REGISTER = portUNMASK_VALUE; \
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123 /*-----------------------------------------------------------*/
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126 * Starts the first task executing. This function is necessarily written in
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127 * assembly code so is implemented in portASM.s.
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129 extern void vPortRestoreTaskContext( void );
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132 * Used to catch tasks that attempt to return from their implementing function.
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134 static void prvTaskExitError( void );
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136 /*-----------------------------------------------------------*/
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138 /* A variable is used to keep track of the critical section nesting. This
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139 variable has to be stored as part of the task context and must be initialised to
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140 a non zero value to ensure interrupts don't inadvertently become unmasked before
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141 the scheduler starts. As it is stored as part of the task context it will
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142 automatically be set to 0 when the first task is started. */
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143 volatile uint32_t ulCriticalNesting = 9999UL;
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145 /* Saved as part of the task context. If ulPortTaskHasFPUContext is non-zero
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146 then a floating point context must be saved and restored for the task. */
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147 uint32_t ulPortTaskHasFPUContext = pdFALSE;
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149 /* Set to 1 to pend a context switch from an ISR. */
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150 uint32_t ulPortYieldRequired = pdFALSE;
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152 /* Counts the interrupt nesting depth. A context switch is only performed if
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153 if the nesting depth is 0. */
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154 uint32_t ulPortInterruptNesting = 0UL;
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157 /*-----------------------------------------------------------*/
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160 * See header file for description.
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162 StackType_t *pxPortInitialiseStack( StackType_t *pxTopOfStack, TaskFunction_t pxCode, void *pvParameters )
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164 /* Setup the initial stack of the task. The stack is set exactly as
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165 expected by the portRESTORE_CONTEXT() macro.
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167 The fist real value on the stack is the status register, which is set for
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168 system mode, with interrupts enabled. A few NULLs are added first to ensure
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169 GDB does not try decoding a non-existent return address. */
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170 *pxTopOfStack = NULL;
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172 *pxTopOfStack = NULL;
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174 *pxTopOfStack = NULL;
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176 *pxTopOfStack = ( StackType_t ) portINITIAL_SPSR;
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178 if( ( ( uint32_t ) pxCode & portTHUMB_MODE_ADDRESS ) != 0x00UL )
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180 /* The task will start in THUMB mode. */
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181 *pxTopOfStack |= portTHUMB_MODE_BIT;
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186 /* Next the return address, which in this case is the start of the task. */
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187 *pxTopOfStack = ( StackType_t ) pxCode;
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190 /* Next all the registers other than the stack pointer. */
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191 *pxTopOfStack = ( StackType_t ) prvTaskExitError; /* R14 */
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193 *pxTopOfStack = ( StackType_t ) 0x12121212; /* R12 */
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195 *pxTopOfStack = ( StackType_t ) 0x11111111; /* R11 */
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197 *pxTopOfStack = ( StackType_t ) 0x10101010; /* R10 */
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199 *pxTopOfStack = ( StackType_t ) 0x09090909; /* R9 */
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201 *pxTopOfStack = ( StackType_t ) 0x08080808; /* R8 */
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203 *pxTopOfStack = ( StackType_t ) 0x07070707; /* R7 */
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205 *pxTopOfStack = ( StackType_t ) 0x06060606; /* R6 */
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207 *pxTopOfStack = ( StackType_t ) 0x05050505; /* R5 */
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209 *pxTopOfStack = ( StackType_t ) 0x04040404; /* R4 */
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211 *pxTopOfStack = ( StackType_t ) 0x03030303; /* R3 */
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213 *pxTopOfStack = ( StackType_t ) 0x02020202; /* R2 */
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215 *pxTopOfStack = ( StackType_t ) 0x01010101; /* R1 */
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217 *pxTopOfStack = ( StackType_t ) pvParameters; /* R0 */
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220 /* The task will start with a critical nesting count of 0 as interrupts are
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222 *pxTopOfStack = portNO_CRITICAL_NESTING;
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225 /* The task will start without a floating point context. A task that uses
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226 the floating point hardware must call vPortTaskUsesFPU() before executing
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227 any floating point instructions. */
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228 *pxTopOfStack = portNO_FLOATING_POINT_CONTEXT;
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230 return pxTopOfStack;
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232 /*-----------------------------------------------------------*/
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234 static void prvTaskExitError( void )
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236 /* A function that implements a task must not exit or attempt to return to
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237 its caller as there is nothing to return to. If a task wants to exit it
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238 should instead call vTaskDelete( NULL ).
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240 Artificially force an assert() to be triggered if configASSERT() is
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241 defined, then stop here so application writers can catch the error. */
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242 configASSERT( ulPortInterruptNesting == ~0UL );
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243 portDISABLE_INTERRUPTS();
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246 /*-----------------------------------------------------------*/
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248 BaseType_t xPortStartScheduler( void )
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252 /* Only continue if the CPU is not in User mode. The CPU must be in a
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253 Privileged mode for the scheduler to start. */
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254 __asm volatile ( "MRS %0, APSR" : "=r" ( ulAPSR ) );
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255 ulAPSR &= portAPSR_MODE_BITS_MASK;
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256 configASSERT( ulAPSR != portAPSR_USER_MODE );
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258 if( ulAPSR != portAPSR_USER_MODE )
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260 /* Only continue if the binary point value is set to its lowest possible
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261 setting. See the comments in vPortValidateInterruptPriority() below for
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262 more information. */
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263 configASSERT( ( portICCBPR_BINARY_POINT_REGISTER & portBINARY_POINT_BITS ) <= portMAX_BINARY_POINT_VALUE );
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265 if( ( portICCBPR_BINARY_POINT_REGISTER & portBINARY_POINT_BITS ) <= portMAX_BINARY_POINT_VALUE )
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267 /* Start the timer that generates the tick ISR. */
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268 configSETUP_TICK_INTERRUPT();
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271 vPortRestoreTaskContext();
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275 /* Will only get here if vTaskStartScheduler() was called with the CPU in
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276 a non-privileged mode or the binary point register was not set to its lowest
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280 /*-----------------------------------------------------------*/
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282 void vPortEndScheduler( void )
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284 /* Not implemented in ports where there is nothing to return to.
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285 Artificially force an assert. */
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286 configASSERT( ulCriticalNesting == 1000UL );
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288 /*-----------------------------------------------------------*/
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290 void vPortEnterCritical( void )
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292 /* Disable interrupts as per portDISABLE_INTERRUPTS(); */
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293 ulPortSetInterruptMask();
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295 /* Now interrupts are disabled ulCriticalNesting can be accessed
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296 directly. Increment ulCriticalNesting to keep a count of how many times
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297 portENTER_CRITICAL() has been called. */
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298 ulCriticalNesting++;
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300 /* This is not the interrupt safe version of the enter critical function so
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301 assert() if it is being called from an interrupt context. Only API
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302 functions that end in "FromISR" can be used in an interrupt. Only assert if
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303 the critical nesting count is 1 to protect against recursive calls if the
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304 assert function also uses a critical section. */
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305 if( ulCriticalNesting == 1 )
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307 configASSERT( ulPortInterruptNesting == 0 );
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310 /*-----------------------------------------------------------*/
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312 void vPortExitCritical( void )
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314 if( ulCriticalNesting > portNO_CRITICAL_NESTING )
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316 /* Decrement the nesting count as the critical section is being
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318 ulCriticalNesting--;
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320 /* If the nesting level has reached zero then all interrupt
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321 priorities must be re-enabled. */
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322 if( ulCriticalNesting == portNO_CRITICAL_NESTING )
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324 /* Critical nesting has reached zero so all interrupt priorities
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325 should be unmasked. */
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326 portCLEAR_INTERRUPT_MASK();
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330 /*-----------------------------------------------------------*/
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332 void FreeRTOS_Tick_Handler( void )
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334 /* Set interrupt mask before altering scheduler structures. The tick
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335 handler runs at the lowest priority, so interrupts cannot already be masked,
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336 so there is no need to save and restore the current mask value. */
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338 portICCPMR_PRIORITY_MASK_REGISTER = ( uint32_t ) ( configMAX_API_CALL_INTERRUPT_PRIORITY << portPRIORITY_SHIFT );
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343 /* Increment the RTOS tick. */
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344 if( xTaskIncrementTick() != pdFALSE )
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346 ulPortYieldRequired = pdTRUE;
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349 /* Ensure all interrupt priorities are active again. */
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350 portCLEAR_INTERRUPT_MASK();
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351 configCLEAR_TICK_INTERRUPT();
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353 /*-----------------------------------------------------------*/
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355 void vPortTaskUsesFPU( void )
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357 uint32_t ulInitialFPSCR = 0;
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359 /* A task is registering the fact that it needs an FPU context. Set the
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360 FPU flag (which is saved as part of the task context). */
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361 ulPortTaskHasFPUContext = pdTRUE;
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363 /* Initialise the floating point status register. */
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364 __asm( "FMXR FPSCR, %0" :: "r" (ulInitialFPSCR) );
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366 /*-----------------------------------------------------------*/
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368 void vPortClearInterruptMask( uint32_t ulNewMaskValue )
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370 if( ulNewMaskValue == pdFALSE )
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372 portCLEAR_INTERRUPT_MASK();
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375 /*-----------------------------------------------------------*/
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377 uint32_t ulPortSetInterruptMask( void )
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382 if( portICCPMR_PRIORITY_MASK_REGISTER == ( uint32_t ) ( configMAX_API_CALL_INTERRUPT_PRIORITY << portPRIORITY_SHIFT ) )
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384 /* Interrupts were already masked. */
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389 ulReturn = pdFALSE;
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390 portICCPMR_PRIORITY_MASK_REGISTER = ( uint32_t ) ( configMAX_API_CALL_INTERRUPT_PRIORITY << portPRIORITY_SHIFT );
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398 /*-----------------------------------------------------------*/
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400 #if( configASSERT_DEFINED == 1 )
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402 void vPortValidateInterruptPriority( void )
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404 /* The following assertion will fail if a service routine (ISR) for
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405 an interrupt that has been assigned a priority above
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406 configMAX_SYSCALL_INTERRUPT_PRIORITY calls an ISR safe FreeRTOS API
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407 function. ISR safe FreeRTOS API functions must *only* be called
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408 from interrupts that have been assigned a priority at or below
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409 configMAX_SYSCALL_INTERRUPT_PRIORITY.
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411 Numerically low interrupt priority numbers represent logically high
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412 interrupt priorities, therefore the priority of the interrupt must
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413 be set to a value equal to or numerically *higher* than
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414 configMAX_SYSCALL_INTERRUPT_PRIORITY.
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416 FreeRTOS maintains separate thread and ISR API functions to ensure
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417 interrupt entry is as fast and simple as possible.
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419 The following links provide detailed information:
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420 http://www.freertos.org/RTOS-Cortex-M3-M4.html
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421 http://www.freertos.org/FAQHelp.html */
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422 configASSERT( portICCRPR_RUNNING_PRIORITY_REGISTER >= ( uint32_t ) ( configMAX_API_CALL_INTERRUPT_PRIORITY << portPRIORITY_SHIFT ) );
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424 /* Priority grouping: The interrupt controller (GIC) allows the bits
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425 that define each interrupt's priority to be split between bits that
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426 define the interrupt's pre-emption priority bits and bits that define
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427 the interrupt's sub-priority. For simplicity all bits must be defined
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428 to be pre-emption priority bits. The following assertion will fail if
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429 this is not the case (if some bits represent a sub-priority).
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431 The priority grouping is configured by the GIC's binary point register
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432 (ICCBPR). Writting 0 to ICCBPR will ensure it is set to its lowest
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433 possible value (which may be above 0). */
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434 configASSERT( ( portICCBPR_BINARY_POINT_REGISTER & portBINARY_POINT_BITS ) <= portMAX_BINARY_POINT_VALUE );
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437 #endif /* configASSERT_DEFINED */
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