2 FreeRTOS V8.2.2 - Copyright (C) 2015 Real Time Engineers Ltd.
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6 ***************************************************************************
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8 * FreeRTOS tutorial books are available in pdf and paperback. *
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9 * Complete, revised, and edited pdf reference manuals are also *
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12 * Purchasing FreeRTOS documentation will not only help you, by *
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13 * ensuring you get running as quickly as possible and with an *
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14 * in-depth knowledge of how to use FreeRTOS, it will also help *
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15 * the FreeRTOS project to continue with its mission of providing *
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16 * professional grade, cross platform, de facto standard solutions *
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17 * for microcontrollers - completely free of charge! *
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19 * >>> See http://www.FreeRTOS.org/Documentation for details. <<< *
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21 * Thank you for using FreeRTOS, and thank you for your support! *
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23 ***************************************************************************
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26 This file is part of the FreeRTOS distribution.
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28 FreeRTOS is free software; you can redistribute it and/or modify it under
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29 the terms of the GNU General Public License (version 2) as published by the
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30 Free Software Foundation AND MODIFIED BY the FreeRTOS exception.
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31 >>>NOTE<<< The modification to the GPL is included to allow you to
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32 distribute a combined work that includes FreeRTOS without being obliged to
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33 provide the source code for proprietary components outside of the FreeRTOS
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34 kernel. FreeRTOS is distributed in the hope that it will be useful, but
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35 WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
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36 or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
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37 more details. You should have received a copy of the GNU General Public
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38 License and the FreeRTOS license exception along with FreeRTOS; if not it
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39 can be viewed here: http://www.freertos.org/a00114.html and also obtained
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40 by writing to Richard Barry, contact details for whom are available on the
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45 http://www.FreeRTOS.org - Documentation, latest information, license and
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48 http://www.SafeRTOS.com - A version that is certified for use in safety
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51 http://www.OpenRTOS.com - Commercial support, development, porting,
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52 licensing and training services.
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62 /* Hardware registers. */
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67 /* Variables and functions. */
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68 .extern ulMaxAPIPriorityMask
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69 .extern _freertos_vector_table
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70 .extern pxCurrentTCB
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71 .extern vTaskSwitchContext
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72 .extern vApplicationIRQHandler
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73 .extern ulPortInterruptNesting
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74 .extern ulPortTaskHasFPUContext
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76 .global FreeRTOS_IRQ_Handler
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77 .global FreeRTOS_SWI_Handler
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78 .global vPortRestoreTaskContext
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83 .macro portSAVE_CONTEXT
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85 /* Save the LR and SPSR onto the system mode stack before switching to
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86 system mode to save the remaining system mode registers. */
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87 SRSDB sp!, #SYS_MODE
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91 /* Push the critical nesting count. */
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92 LDR R2, ulCriticalNestingConst
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96 /* Does the task have a floating point context that needs saving? If
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97 ulPortTaskHasFPUContext is 0 then no. */
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98 LDR R2, ulPortTaskHasFPUContextConst
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102 /* Save the floating point context, if any. */
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108 /* Save ulPortTaskHasFPUContext itself. */
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111 /* Save the stack pointer in the TCB. */
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112 LDR R0, pxCurrentTCBConst
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118 ; /**********************************************************************/
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120 .macro portRESTORE_CONTEXT
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122 /* Set the SP to point to the stack of the task being restored. */
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123 LDR R0, pxCurrentTCBConst
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127 /* Is there a floating point context to restore? If the restored
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128 ulPortTaskHasFPUContext is zero then no. */
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129 LDR R0, ulPortTaskHasFPUContextConst
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134 /* Restore the floating point context, if any. */
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140 /* Restore the critical section nesting depth. */
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141 LDR R0, ulCriticalNestingConst
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145 /* Ensure the priority mask is correct for the critical nesting depth. */
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146 LDR R2, ulICCPMRConst
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150 LDRNE R4, ulMaxAPIPriorityMaskConst
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154 /* Restore all system mode registers other than the SP (which is already
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158 /* Return to the task code, loading CPSR on the way. */
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166 /******************************************************************************
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167 * SVC handler is used to start the scheduler.
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168 *****************************************************************************/
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170 .type FreeRTOS_SWI_Handler, %function
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171 FreeRTOS_SWI_Handler:
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172 /* Save the context of the current task and select a new task to run. */
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174 LDR R0, vTaskSwitchContextConst
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176 portRESTORE_CONTEXT
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179 /******************************************************************************
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180 * vPortRestoreTaskContext is used to start the scheduler.
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181 *****************************************************************************/
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182 .type vPortRestoreTaskContext, %function
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183 vPortRestoreTaskContext:
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184 /* Switch to system mode. */
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186 portRESTORE_CONTEXT
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189 .type FreeRTOS_IRQ_Handler, %function
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190 FreeRTOS_IRQ_Handler:
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191 /* Return to the interrupted instruction. */
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194 /* Push the return address and SPSR. */
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199 /* Change to supervisor mode to allow reentry. */
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202 /* Push used registers. */
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205 /* Increment nesting count. r3 holds the address of ulPortInterruptNesting
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206 for future use. r1 holds the original ulPortInterruptNesting value for
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208 LDR r3, ulPortInterruptNestingConst
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213 /* Read value from the interrupt acknowledge register, which is stored in r0
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214 for future parameter and interrupt clearing use. */
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215 LDR r2, ulICCIARConst
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219 /* Ensure bit 2 of the stack pointer is clear. r2 holds the bit 2 value for
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225 /* Call the interrupt handler. */
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227 LDR r1, vApplicationIRQHandlerConst
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236 /* Write the value read from ICCIAR to ICCEOIR. */
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237 LDR r4, ulICCEOIRConst
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241 /* Restore the old nesting count. */
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244 /* A context switch is never performed if the nesting count is not 0. */
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246 BNE exit_without_switch
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248 /* Did the interrupt request a context switch? r1 holds the address of
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249 ulPortYieldRequired and r0 the value of ulPortYieldRequired for future
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251 LDR r1, =ulPortYieldRequired
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254 BNE switch_before_exit
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256 exit_without_switch:
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257 /* No context switch. Restore used registers, LR_irq and SPSR before
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266 switch_before_exit:
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267 /* A context swtich is to be performed. Clear the context switch pending
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272 /* Restore used registers, LR-irq and SPSR before saving the context
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273 to the task stack. */
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281 /* Call the function that selects the new task to execute.
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282 vTaskSwitchContext() if vTaskSwitchContext() uses LDRD or STRD
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283 instructions, or 8 byte aligned stack allocated data. LR does not need
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284 saving as a new LR will be loaded by portRESTORE_CONTEXT anyway. */
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285 LDR R0, vTaskSwitchContextConst
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288 /* Restore the context of, and branch to, the task selected to execute
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290 portRESTORE_CONTEXT
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292 ulICCIARConst: .word ulICCIAR
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293 ulICCEOIRConst: .word ulICCEOIR
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294 ulICCPMRConst: .word ulICCPMR
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295 pxCurrentTCBConst: .word pxCurrentTCB
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296 ulCriticalNestingConst: .word ulCriticalNesting
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297 ulPortTaskHasFPUContextConst: .word ulPortTaskHasFPUContext
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298 ulMaxAPIPriorityMaskConst: .word ulMaxAPIPriorityMask
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299 vTaskSwitchContextConst: .word vTaskSwitchContext
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300 vApplicationIRQHandlerConst: .word vApplicationIRQHandler
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301 ulPortInterruptNestingConst: .word ulPortInterruptNesting
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