1/*
2 * FreeRTOS Kernel V11.1.0
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 <xc.h>
30#include <sys/asm.h>
31#include "ISR_Support.h"
32
33
34    .set    nomips16
35    .set    noreorder
36
37    .extern pxCurrentTCB
38    .extern vTaskSwitchContext
39    .extern vPortIncrementTick
40    .extern xISRStackTop
41
42    .global vPortStartFirstTask
43    .global vPortYieldISR
44    .global vPortTickInterruptHandler
45
46
47/******************************************************************/
48
49    .set        noreorder
50    .set        noat
51    .ent        vPortTickInterruptHandler
52
53vPortTickInterruptHandler:
54
55    portSAVE_CONTEXT
56
57    jal         vPortIncrementTick
58    nop
59
60    portRESTORE_CONTEXT
61
62    .end vPortTickInterruptHandler
63
64/******************************************************************/
65
66    .set        noreorder
67    .set        noat
68    .ent        vPortStartFirstTask
69
70vPortStartFirstTask:
71
72    /* Simply restore the context of the highest priority task that has been
73    created so far. */
74    portRESTORE_CONTEXT
75
76    .end vPortStartFirstTask
77
78
79
80/*******************************************************************/
81
82    .set        noreorder
83    .set        noat
84    .ent        vPortYieldISR
85
86vPortYieldISR:
87
88    /* Make room for the context. First save the current status so it can be
89    manipulated. */
90    addiu       sp, sp, -portCONTEXT_SIZE
91    mfc0        k1, _CP0_STATUS
92
93    /* Also save s6 and s5 so they can be used.  Any nesting interrupts should
94    maintain the values of these registers across the ISR. */
95    sw          s6, 44(sp)
96    sw          s5, 40(sp)
97    sw          k1, portSTATUS_STACK_LOCATION(sp)
98
99    /* Prepare to re-enabled interrupt above the kernel priority. */
100    ins         k1, zero, 10, 6
101    ori         k1, k1, ( configMAX_SYSCALL_INTERRUPT_PRIORITY << 10 )
102    ins         k1, zero, 1, 4
103
104    /* s5 is used as the frame pointer. */
105    add         s5, zero, sp
106
107    /* Swap to the system stack.  This is not conditional on the nesting
108    count as this interrupt is always the lowest priority and therefore
109    the nesting is always 0. */
110    la          sp, xISRStackTop
111    lw          sp, (sp)
112
113    /* Set the nesting count. */
114    la          k0, uxInterruptNesting
115    addiu       s6, zero, 1
116    sw          s6, 0(k0)
117
118    /* s6 holds the EPC value, this is saved with the rest of the context
119    after interrupts are enabled. */
120    mfc0        s6, _CP0_EPC
121
122    /* Re-enable interrupts above configMAX_SYSCALL_INTERRUPT_PRIORITY. */
123    mtc0        k1, _CP0_STATUS
124
125    /* Save the context into the space just created.  s6 is saved again
126    here as it now contains the EPC value. */
127    sw          ra, 120(s5)
128    sw          s8, 116(s5)
129    sw          t9, 112(s5)
130    sw          t8, 108(s5)
131    sw          t7, 104(s5)
132    sw          t6, 100(s5)
133    sw          t5, 96(s5)
134    sw          t4, 92(s5)
135    sw          t3, 88(s5)
136    sw          t2, 84(s5)
137    sw          t1, 80(s5)
138    sw          t0, 76(s5)
139    sw          a3, 72(s5)
140    sw          a2, 68(s5)
141    sw          a1, 64(s5)
142    sw          a0, 60(s5)
143    sw          v1, 56(s5)
144    sw          v0, 52(s5)
145    sw          s7, 48(s5)
146    sw          s6, portEPC_STACK_LOCATION(s5)
147    /* s5 and s6 has already been saved. */
148    sw          s4, 36(s5)
149    sw          s3, 32(s5)
150    sw          s2, 28(s5)
151    sw          s1, 24(s5)
152    sw          s0, 20(s5)
153    sw          $1, 16(s5)
154
155    /* s7 is used as a scratch register as this should always be saved across
156    nesting interrupts. */
157    mfhi        s7
158    sw          s7, 12(s5)
159    mflo        s7
160    sw          s7, 8(s5)
161
162    /* Save the stack pointer to the task. */
163    la          s7, pxCurrentTCB
164    lw          s7, (s7)
165    sw          s5, (s7)
166
167    /* Set the interrupt mask to the max priority that can use the API.  The
168    yield handler will only be called at configKERNEL_INTERRUPT_PRIORITY which
169    is below configMAX_SYSCALL_INTERRUPT_PRIORITY - so this can only ever
170    raise the IPL value and never lower it. */
171    di
172    ehb
173    mfc0        s7, _CP0_STATUS
174    ins         s7, zero, 10, 6
175    ori         s6, s7, ( configMAX_SYSCALL_INTERRUPT_PRIORITY << 10 ) | 1
176
177    /* This mtc0 re-enables interrupts, but only above
178    configMAX_SYSCALL_INTERRUPT_PRIORITY. */
179    mtc0        s6, _CP0_STATUS
180    ehb
181
182    /* Clear the software interrupt in the core. */
183    mfc0        s6, _CP0_CAUSE
184    ins         s6, zero, 8, 1
185    mtc0        s6, _CP0_CAUSE
186    ehb
187
188    /* Clear the interrupt in the interrupt controller. */
189    la          s6, IFS0CLR
190    addiu       s4, zero, 2
191    sw          s4, (s6)
192
193    jal         vTaskSwitchContext
194    nop
195
196    /* Clear the interrupt mask again.  The saved status value is still in s7. */
197    mtc0        s7, _CP0_STATUS
198    ehb
199
200    /* Restore the stack pointer from the TCB. */
201    la          s0, pxCurrentTCB
202    lw          s0, (s0)
203    lw          s5, (s0)
204
205    /* Restore the rest of the context. */
206    lw          s0, 8(s5)
207    mtlo        s0
208    lw          s0, 12(s5)
209    mthi        s0
210    lw          $1, 16(s5)
211    lw          s0, 20(s5)
212    lw          s1, 24(s5)
213    lw          s2, 28(s5)
214    lw          s3, 32(s5)
215    lw          s4, 36(s5)
216    /* s5 is loaded later. */
217    lw          s6, 44(s5)
218    lw          s7, 48(s5)
219    lw          v0, 52(s5)
220    lw          v1, 56(s5)
221    lw          a0, 60(s5)
222    lw          a1, 64(s5)
223    lw          a2, 68(s5)
224    lw          a3, 72(s5)
225    lw          t0, 76(s5)
226    lw          t1, 80(s5)
227    lw          t2, 84(s5)
228    lw          t3, 88(s5)
229    lw          t4, 92(s5)
230    lw          t5, 96(s5)
231    lw          t6, 100(s5)
232    lw          t7, 104(s5)
233    lw          t8, 108(s5)
234    lw          t9, 112(s5)
235    lw          s8, 116(s5)
236    lw          ra, 120(s5)
237
238    /* Protect access to the k registers, and others. */
239    di
240    ehb
241
242    /* Set nesting back to zero.  As the lowest priority interrupt this
243    interrupt cannot have nested. */
244    la          k0, uxInterruptNesting
245    sw          zero, 0(k0)
246
247    /* Switch back to use the real stack pointer. */
248    add         sp, zero, s5
249
250    /* Restore the real s5 value. */
251    lw          s5, 40(sp)
252
253    /* Pop the status and epc values. */
254    lw          k1, portSTATUS_STACK_LOCATION(sp)
255    lw          k0, portEPC_STACK_LOCATION(sp)
256
257    /* Remove stack frame. */
258    addiu       sp, sp, portCONTEXT_SIZE
259
260    mtc0        k1, _CP0_STATUS
261    mtc0        k0, _CP0_EPC
262    ehb
263    eret
264    nop
265
266    .end        vPortYieldISR
267