xref: /Kernel-v10.6.2/portable/RVDS/ARM7_LPC21xx/portASM.s (revision ef7b253b56c9788077f5ecd6c9deb4021923d646) 
1;/*
2; * FreeRTOS Kernel V10.6.2
3; * Copyright (C) 2021 Amazon.com, Inc. or its affiliates.  All Rights Reserved.
4; *
5; * SPDX-License-Identifier: MIT
6; *
7; * Permission is hereby granted, free of charge, to any person obtaining a copy of
8; * this software and associated documentation files (the "Software"), to deal in
9; * the Software without restriction, including without limitation the rights to
10; * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
11; * the Software, and to permit persons to whom the Software is furnished to do so,
12; * subject to the following conditions:
13; *
14; * The above copyright notice and this permission notice shall be included in all
15; * copies or substantial portions of the Software.
16; *
17; * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
18; * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
19; * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
20; * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
21; * IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
22; * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
23; *
24; * https://www.FreeRTOS.org
25; * https://github.com/FreeRTOS
26; *
27; */
28
29    INCLUDE portmacro.inc
30
31    IMPORT  vTaskSwitchContext
32    IMPORT  xTaskIncrementTick
33
34    EXPORT  vPortYieldProcessor
35    EXPORT  vPortStartFirstTask
36    EXPORT  vPreemptiveTick
37    EXPORT  vPortYield
38
39
40VICVECTADDR EQU 0xFFFFF030
41T0IR        EQU 0xE0004000
42T0MATCHBIT  EQU 0x00000001
43
44    ARM
45    AREA    PORT_ASM, CODE, READONLY
46
47
48
49;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
50; Starting the first task is done by just restoring the context
51; setup by pxPortInitialiseStack
52;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
53vPortStartFirstTask
54
55    PRESERVE8
56
57    portRESTORE_CONTEXT
58
59vPortYield
60
61    PRESERVE8
62
63    SVC 0
64    bx lr
65
66;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
67; Interrupt service routine for the SWI interrupt.  The vector table is
68; configured in the startup.s file.
69;
70; vPortYieldProcessor() is used to manually force a context switch.  The
71; SWI interrupt is generated by a call to taskYIELD() or portYIELD().
72;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
73
74vPortYieldProcessor
75
76    PRESERVE8
77
78    ; Within an IRQ ISR the link register has an offset from the true return
79    ; address, but an SWI ISR does not.  Add the offset manually so the same
80    ; ISR return code can be used in both cases.
81    ADD LR, LR, #4
82
83    ; Perform the context switch.
84    portSAVE_CONTEXT                    ; Save current task context
85    LDR R0, =vTaskSwitchContext         ; Get the address of the context switch function
86    MOV LR, PC                          ; Store the return address
87    BX  R0                              ; Call the contedxt switch function
88    portRESTORE_CONTEXT                 ; restore the context of the selected task
89
90
91
92;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
93; Interrupt service routine for preemptive scheduler tick timer
94; Only used if portUSE_PREEMPTION is set to 1 in portmacro.h
95;
96; Uses timer 0 of LPC21XX Family
97;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
98
99vPreemptiveTick
100
101    PRESERVE8
102
103    portSAVE_CONTEXT                    ; Save the context of the current task.
104
105    LDR R0, =xTaskIncrementTick         ; Increment the tick count.
106    MOV LR, PC                          ; This may make a delayed task ready
107    BX R0                               ; to run.
108
109    CMP R0, #0
110    BEQ SkipContextSwitch
111    LDR R0, =vTaskSwitchContext         ; Find the highest priority task that
112    MOV LR, PC                          ; is ready to run.
113    BX R0
114SkipContextSwitch
115    MOV R0, #T0MATCHBIT                 ; Clear the timer event
116    LDR R1, =T0IR
117    STR R0, [R1]
118
119    LDR R0, =VICVECTADDR                ; Acknowledge the interrupt
120    STR R0,[R0]
121
122    portRESTORE_CONTEXT                 ; Restore the context of the highest
123                                        ; priority task that is ready to run.
124    END
125