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|
;/*
; * FreeRTOS Kernel <DEVELOPMENT BRANCH>
; * Copyright (C) 2021 Amazon.com, Inc. or its affiliates. All Rights Reserved.
; *
; * SPDX-License-Identifier: MIT
; *
; * Permission is hereby granted, free of charge, to any person obtaining a copy of
; * this software and associated documentation files (the "Software"), to deal in
; * the Software without restriction, including without limitation the rights to
; * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
; * the Software, and to permit persons to whom the Software is furnished to do so,
; * subject to the following conditions:
; *
; * The above copyright notice and this permission notice shall be included in all
; * copies or substantial portions of the Software.
; *
; * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
; * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
; * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
; * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
; * IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
; * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
; *
; * https://www.FreeRTOS.org
; * https://github.com/FreeRTOS
; *
; */
#include "porthardware.h"
; Declare all extern symbols here - including any ISRs that are referenced in
; the vector table.
; ISR functions
; -------------
EXTERN TICK_INT
; Functions used by scheduler
; ---------------------------
EXTERN vTaskSwitchContext
EXTERN pxCurrentTCB
EXTERN xTaskIncrementTick
EXTERN uxCriticalNesting
; Functions implemented in this file
; ----------------------------------
PUBLIC vPortYield
PUBLIC vPortYieldFromTick
PUBLIC vPortYieldFromISR
PUBLIC vPortStart
; Interrupt vector table.
; -----------------------
;
; For simplicity the RTOS tick interrupt routine uses the __task keyword.
; As the IAR compiler does not permit a function to be declared using both
; __task and __interrupt, the use of __task necessitates that the interrupt
; vector table be setup manually.
;
; To write an ISR, implement the ISR function using the __interrupt keyword
; but do not install the interrupt using the "#pragma vector=ABC" method.
; Instead manually place the name of the ISR in the vector table using an
; ORG and jmp instruction as demonstrated below.
; You will also have to add an EXTERN statement at the top of the file.
ASEG
ORG TICK_INT_vect ; Vector address
jmp TICK_INT ; ISR
RSEG CODE
CLR_INT MACRO FLAG_REG, FLAG_MASK
st -y, r16
ldi r16, FLAG_MASK
sts FLAG_REG, r16
ld r16, y+
ENDM
; Saving and Restoring a Task Context and Task Switching
; ------------------------------------------------------
;
; The IAR compiler does not fully support inline assembler, so saving and
; restoring a task context has to be written in an asm file.
;
; vPortYield() and vPortYieldFromTick() are usually written in C. Doing
; so in this case would required calls to be made to portSAVE_CONTEXT() and
; portRESTORE_CONTEXT(). This is dis-advantageous as the context switch
; function would require two extra jump and return instructions over the
; WinAVR equivalent.
;
; To avoid this I have opted to implement both vPortYield() and
; vPortYieldFromTick() in this assembly file. For convenience
; portSAVE_CONTEXT and portRESTORE_CONTEXT are implemented as macros.
portSAVE_CONTEXT MACRO
st -y, r0 ; First save the r0 register - we need to use this.
in r0, SREG ; Obtain the SREG value so we can disable interrupts...
cli ; ... as soon as possible.
st -y, r0 ; Store the SREG as it was before we disabled interrupts.
in r0, SPL ; Next store the hardware stack pointer. The IAR...
st -y, r0 ; ... compiler uses the hardware stack as a call stack ...
in r0, SPH ; ... only.
st -y, r0
st -y, r1 ; Now store the rest of the registers. Dont store the ...
st -y, r2 ; ... the Y register here as it is used as the software
st -y, r3 ; stack pointer and will get saved into the TCB.
st -y, r4
st -y, r5
st -y, r6
st -y, r7
st -y, r8
st -y, r9
st -y, r10
st -y, r11
st -y, r12
st -y, r13
st -y, r14
st -y, r15
st -y, r16
st -y, r17
st -y, r18
st -y, r19
st -y, r20
st -y, r21
st -y, r22
st -y, r23
st -y, r24
st -y, r25
st -y, r26
st -y, r27
st -y, r30
st -y, r31
lds r0, uxCriticalNesting
st -y, r0 ; Store the critical nesting counter.
lds r26, pxCurrentTCB ; Finally save the software stack pointer (Y ...
lds r27, pxCurrentTCB + 1 ; ... register) into the TCB.
st x+, r28
st x+, r29
ENDM
portRESTORE_CONTEXT MACRO
lds r26, pxCurrentTCB
lds r27, pxCurrentTCB + 1 ; Restore the software stack pointer from ...
ld r28, x+ ; the TCB into the software stack pointer (...
ld r29, x+ ; ... the Y register).
ld r0, y+
sts uxCriticalNesting, r0
ld r31, y+ ; Restore the registers down to R0. The Y
ld r30, y+ ; register is missing from this list as it
ld r27, y+ ; has already been restored.
ld r26, y+
ld r25, y+
ld r24, y+
ld r23, y+
ld r22, y+
ld r21, y+
ld r20, y+
ld r19, y+
ld r18, y+
ld r17, y+
ld r16, y+
ld r15, y+
ld r14, y+
ld r13, y+
ld r12, y+
ld r11, y+
ld r10, y+
ld r9, y+
ld r8, y+
ld r7, y+
ld r6, y+
ld r5, y+
ld r4, y+
ld r3, y+
ld r2, y+
ld r1, y+
ld r0, y+ ; The next thing on the stack is the ...
out SPH, r0 ; ... hardware stack pointer.
ld r0, y+
out SPL, r0
ld r0, y+ ; Next there is the SREG register.
out SREG, r0
ld r0, y+ ; Finally we have finished with r0, so restore r0.
ENDM
; vPortYield(), vPortYieldFromTick() and vPortYieldFromISR()
; -------------------------------------
;
; Manual and preemptive context switch functions respectively.
; The IAR compiler does not fully support inline assembler,
; so these are implemented here rather than the more usually
; place of within port.c.
vPortYield:
portSAVE_CONTEXT ; Save the context of the current task.
call vTaskSwitchContext ; Call the scheduler.
portRESTORE_CONTEXT ; Restore the context of whichever task the ...
ret ; ... scheduler decided should run.
vPortYieldFromTick:
CLR_INT INT_FLAGS, INT_MASK ; Clear tick interrupt flag
portSAVE_CONTEXT ; Save the context of the current task.
call xTaskIncrementTick ; Call the timer tick function.
tst r16
breq SkipTaskSwitch
call vTaskSwitchContext ; Call the scheduler.
SkipTaskSwitch:
portRESTORE_CONTEXT ; Restore the context of whichever task the ...
reti ; ... scheduler decided should run.
vPortYieldFromISR:
portSAVE_CONTEXT ; Save the context of the current task.
call vTaskSwitchContext ; Call the scheduler.
portRESTORE_CONTEXT ; Restore the context of whichever task the ...
reti ; ... scheduler decided should run.
; vPortStart()
; ------------
;
; Again due to the lack of inline assembler, this is required
; to get access to the portRESTORE_CONTEXT macro.
vPortStart:
portRESTORE_CONTEXT
ret
; Just a filler for unused interrupt vectors.
vNoISR:
reti
END
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