;/* ; * FreeRTOS Kernel V10.5.1 ; * 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, RAMPZ st -y, r0 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+ out RAMPZ, 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