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125 lines
4.2 KiB
ArmAsm
125 lines
4.2 KiB
ArmAsm
;/*
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; * FreeRTOS Kernel <DEVELOPMENT BRANCH>
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; * Copyright (C) 2021 Amazon.com, Inc. or its affiliates. All Rights Reserved.
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; *
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; * SPDX-License-Identifier: MIT
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; *
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; * Permission is hereby granted, free of charge, to any person obtaining a copy of
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; * this software and associated documentation files (the "Software"), to deal in
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; * the Software without restriction, including without limitation the rights to
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; * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
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; * the Software, and to permit persons to whom the Software is furnished to do so,
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; * subject to the following conditions:
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; *
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; * The above copyright notice and this permission notice shall be included in all
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; * copies or substantial portions of the Software.
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; *
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; * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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; * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
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; * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
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; * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
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; * IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
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; * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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; *
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; * https://www.FreeRTOS.org
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; * https://github.com/FreeRTOS
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; *
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; */
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INCLUDE portmacro.inc
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IMPORT vTaskSwitchContext
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IMPORT xTaskIncrementTick
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EXPORT vPortYieldProcessor
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EXPORT vPortStartFirstTask
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EXPORT vPreemptiveTick
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EXPORT vPortYield
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VICVECTADDR EQU 0xFFFFF030
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T0IR EQU 0xE0004000
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T0MATCHBIT EQU 0x00000001
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ARM
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AREA PORT_ASM, CODE, READONLY
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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; Starting the first task is done by just restoring the context
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; setup by pxPortInitialiseStack
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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vPortStartFirstTask
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PRESERVE8
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portRESTORE_CONTEXT
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vPortYield
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PRESERVE8
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SVC 0
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bx lr
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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; Interrupt service routine for the SWI interrupt. The vector table is
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; configured in the startup.s file.
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;
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; vPortYieldProcessor() is used to manually force a context switch. The
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; SWI interrupt is generated by a call to taskYIELD() or portYIELD().
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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vPortYieldProcessor
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PRESERVE8
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; Within an IRQ ISR the link register has an offset from the true return
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; address, but an SWI ISR does not. Add the offset manually so the same
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; ISR return code can be used in both cases.
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ADD LR, LR, #4
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; Perform the context switch.
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portSAVE_CONTEXT ; Save current task context
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LDR R0, =vTaskSwitchContext ; Get the address of the context switch function
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MOV LR, PC ; Store the return address
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BX R0 ; Call the contedxt switch function
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portRESTORE_CONTEXT ; restore the context of the selected task
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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; Interrupt service routine for preemptive scheduler tick timer
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; Only used if portUSE_PREEMPTION is set to 1 in portmacro.h
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;
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; Uses timer 0 of LPC21XX Family
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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vPreemptiveTick
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PRESERVE8
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portSAVE_CONTEXT ; Save the context of the current task.
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LDR R0, =xTaskIncrementTick ; Increment the tick count.
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MOV LR, PC ; This may make a delayed task ready
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BX R0 ; to run.
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CMP R0, #0
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BEQ SkipContextSwitch
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LDR R0, =vTaskSwitchContext ; Find the highest priority task that
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MOV LR, PC ; is ready to run.
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BX R0
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SkipContextSwitch
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MOV R0, #T0MATCHBIT ; Clear the timer event
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LDR R1, =T0IR
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STR R0, [R1]
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LDR R0, =VICVECTADDR ; Acknowledge the interrupt
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STR R0,[R0]
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portRESTORE_CONTEXT ; Restore the context of the highest
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; priority task that is ready to run.
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END
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