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 <stdlib.h>
30 #include "porthardware.h"
31 #include "FreeRTOS.h"
32 #include "task.h"
33
34 /*-----------------------------------------------------------
35 * Implementation of functions defined in portable.h for the AVR port.
36 *----------------------------------------------------------*/
37
38 /* Start tasks with interrupts enables. */
39 #define portFLAGS_INT_ENABLED ( ( StackType_t ) 0x80 )
40
41 /*-----------------------------------------------------------*/
42
43
44 #define portBYTES_USED_BY_RETURN_ADDRESS 2
45 #define portNO_CRITICAL_NESTING ( ( UBaseType_t ) 0 )
46
47 /* Stores the critical section nesting. This must not be initialised to 0.
48 * It will be initialised when a task starts. */
49 UBaseType_t uxCriticalNesting = 0x50;
50
51 /*
52 * Setup timer to generate a tick interrupt.
53 */
54 static void prvSetupTimerInterrupt( void );
55
56 /*
57 * The IAR compiler does not have full support for inline assembler, so
58 * these are defined in the portmacro assembler file.
59 */
60 extern void vPortYieldFromTick( void );
61 extern void vPortStart( void );
62
63 /*-----------------------------------------------------------*/
64
65 /*
66 * See header file for description.
67 */
pxPortInitialiseStack(StackType_t * pxTopOfStack,TaskFunction_t pxCode,void * pvParameters)68 StackType_t * pxPortInitialiseStack( StackType_t * pxTopOfStack,
69 TaskFunction_t pxCode,
70 void * pvParameters )
71 {
72 uint16_t usAddress;
73 StackType_t * pxTopOfHardwareStack;
74
75 /* Simulate how the stack would look after a call to vPortYield(). */
76
77 /*lint -e950 -e611 -e923 Lint doesn't like this much - but nothing I can do about it. */
78
79 /* The IAR compiler requires two stacks per task. First there is the
80 * hardware call stack which uses the AVR stack pointer. Second there is the
81 * software stack (local variables, parameter passing, etc.) which uses the
82 * AVR Y register.
83 * This function places both stacks within the memory block passed in as the
84 * first parameter. The hardware stack is placed at the bottom of the memory
85 * block. A gap is then left for the hardware stack to grow. Next the software
86 * stack is placed. The amount of space between the software and hardware
87 * stacks is defined by configCALL_STACK_SIZE.
88 * The first part of the stack is the hardware stack. Place the start
89 * address of the task on the hardware stack. */
90
91 /* Place a few bytes of known values on the bottom of the stack.
92 * This is just useful for debugging. */
93 /**pxTopOfStack = 0x11; */
94 /*pxTopOfStack--; */
95 /**pxTopOfStack = 0x22; */
96 /*pxTopOfStack--; */
97 /**pxTopOfStack = 0x33; */
98 /*pxTopOfStack--; */
99
100 /* Remember where the top of the hardware stack is - this is required
101 * below. */
102 pxTopOfHardwareStack = pxTopOfStack;
103
104 usAddress = ( uint16_t ) pxCode;
105 *pxTopOfStack = ( StackType_t ) ( usAddress & ( uint16_t ) 0x00ff );
106 pxTopOfStack--;
107
108 usAddress >>= 8;
109 *pxTopOfStack = ( StackType_t ) ( usAddress & ( uint16_t ) 0x00ff );
110 pxTopOfStack--;
111
112 /* Leave enough space for the hardware stack before starting the software
113 * stack. The '- 2' is because we have already used two spaces for the
114 * address of the start of the task. */
115 pxTopOfStack -= ( configCALL_STACK_SIZE - 2 );
116
117 /* Next simulate the stack as if after a call to portSAVE_CONTEXT().
118 * portSAVE_CONTEXT places the flags on the stack immediately after r0
119 * to ensure the interrupts get disabled as soon as possible, and so ensuring
120 * the stack use is minimal should a context switch interrupt occur. */
121
122 *pxTopOfStack = ( StackType_t ) 0x00; /* R0 */
123 pxTopOfStack--;
124 *pxTopOfStack = portFLAGS_INT_ENABLED;
125 pxTopOfStack--;
126
127 /* Next place the address of the hardware stack. This is required so
128 * the AVR stack pointer can be restored to point to the hardware stack. */
129 pxTopOfHardwareStack -= portBYTES_USED_BY_RETURN_ADDRESS;
130 usAddress = ( uint16_t ) pxTopOfHardwareStack;
131
132 /* SPL */
133 *pxTopOfStack = ( StackType_t ) ( usAddress & ( uint16_t ) 0x00ff );
134 pxTopOfStack--;
135
136 /* SPH */
137 usAddress >>= 8;
138 *pxTopOfStack = ( StackType_t ) ( usAddress & ( uint16_t ) 0x00ff );
139 pxTopOfStack--;
140
141 /* Now the remaining registers. */
142 *pxTopOfStack = ( StackType_t ) 0x01; /* R1 */
143 pxTopOfStack--;
144 *pxTopOfStack = ( StackType_t ) 0x02; /* R2 */
145 pxTopOfStack--;
146 *pxTopOfStack = ( StackType_t ) 0x03; /* R3 */
147 pxTopOfStack--;
148 *pxTopOfStack = ( StackType_t ) 0x04; /* R4 */
149 pxTopOfStack--;
150 *pxTopOfStack = ( StackType_t ) 0x05; /* R5 */
151 pxTopOfStack--;
152 *pxTopOfStack = ( StackType_t ) 0x06; /* R6 */
153 pxTopOfStack--;
154 *pxTopOfStack = ( StackType_t ) 0x07; /* R7 */
155 pxTopOfStack--;
156 *pxTopOfStack = ( StackType_t ) 0x08; /* R8 */
157 pxTopOfStack--;
158 *pxTopOfStack = ( StackType_t ) 0x09; /* R9 */
159 pxTopOfStack--;
160 *pxTopOfStack = ( StackType_t ) 0x10; /* R10 */
161 pxTopOfStack--;
162 *pxTopOfStack = ( StackType_t ) 0x11; /* R11 */
163 pxTopOfStack--;
164 *pxTopOfStack = ( StackType_t ) 0x12; /* R12 */
165 pxTopOfStack--;
166 *pxTopOfStack = ( StackType_t ) 0x13; /* R13 */
167 pxTopOfStack--;
168 *pxTopOfStack = ( StackType_t ) 0x14; /* R14 */
169 pxTopOfStack--;
170 *pxTopOfStack = ( StackType_t ) 0x15; /* R15 */
171 pxTopOfStack--;
172
173 /* Place the parameter on the stack in the expected location. */
174 usAddress = ( uint16_t ) pvParameters;
175 *pxTopOfStack = ( StackType_t ) ( usAddress & ( uint16_t ) 0x00ff );
176 pxTopOfStack--;
177
178 usAddress >>= 8;
179 *pxTopOfStack = ( StackType_t ) ( usAddress & ( uint16_t ) 0x00ff );
180 pxTopOfStack--;
181
182 *pxTopOfStack = ( StackType_t ) 0x18; /* R18 */
183 pxTopOfStack--;
184 *pxTopOfStack = ( StackType_t ) 0x19; /* R19 */
185 pxTopOfStack--;
186 *pxTopOfStack = ( StackType_t ) 0x20; /* R20 */
187 pxTopOfStack--;
188 *pxTopOfStack = ( StackType_t ) 0x21; /* R21 */
189 pxTopOfStack--;
190 *pxTopOfStack = ( StackType_t ) 0x22; /* R22 */
191 pxTopOfStack--;
192 *pxTopOfStack = ( StackType_t ) 0x23; /* R23 */
193 pxTopOfStack--;
194 *pxTopOfStack = ( StackType_t ) 0x24; /* R24 */
195 pxTopOfStack--;
196 *pxTopOfStack = ( StackType_t ) 0x25; /* R25 */
197 pxTopOfStack--;
198 *pxTopOfStack = ( StackType_t ) 0x26; /* R26 X */
199 pxTopOfStack--;
200 *pxTopOfStack = ( StackType_t ) 0x27; /* R27 */
201 pxTopOfStack--;
202
203 /* The Y register is not stored as it is used as the software stack and
204 * gets saved into the task control block. */
205
206 *pxTopOfStack = ( StackType_t ) 0x30; /* R30 Z */
207 pxTopOfStack--;
208 *pxTopOfStack = ( StackType_t ) 0x031; /* R31 */
209
210 pxTopOfStack--;
211 *pxTopOfStack = portNO_CRITICAL_NESTING; /* Critical nesting is zero when the task starts. */
212
213 /*lint +e950 +e611 +e923 */
214
215 return pxTopOfStack;
216 }
217 /*-----------------------------------------------------------*/
218
xPortStartScheduler(void)219 BaseType_t xPortStartScheduler( void )
220 {
221 /* Setup the hardware to generate the tick. */
222 prvSetupTimerInterrupt();
223
224 /* Restore the context of the first task that is going to run.
225 * Normally we would just call portRESTORE_CONTEXT() here, but as the IAR
226 * compiler does not fully support inline assembler we have to make a call.*/
227 vPortStart();
228
229 /* Should not get here. */
230 return pdTRUE;
231 }
232 /*-----------------------------------------------------------*/
233
vPortEndScheduler(void)234 void vPortEndScheduler( void )
235 {
236 /* vPortEndScheduler is not implemented in this port. */
237 }
238
239 /*-----------------------------------------------------------*/
240
241 /*
242 * Setup timer to generate a tick interrupt.
243 */
prvSetupTimerInterrupt(void)244 static void prvSetupTimerInterrupt( void )
245 {
246 TICK_init();
247 }
248
249 /*-----------------------------------------------------------*/
250
251 #if configUSE_PREEMPTION == 1
252
253 /*
254 * Tick ISR for preemptive scheduler. We can use a naked attribute as
255 * the context is saved at the start of vPortYieldFromTick(). The tick
256 * count is incremented after the context is saved.
257 */
258
TICK_INT(void)259 __task void TICK_INT( void )
260 {
261 vPortYieldFromTick();
262 asm ( "reti" );
263 }
264 #else
265
266 /*
267 * Tick ISR for the cooperative scheduler. All this does is increment the
268 * tick count. We don't need to switch context, this can only be done by
269 * manual calls to taskYIELD();
270 */
271
TICK_INT(void)272 __interrupt void TICK_INT( void )
273 {
274 /* Clear tick interrupt flag. */
275 INT_FLAGS = INT_MASK;
276
277 xTaskIncrementTick();
278 }
279 #endif /* if configUSE_PREEMPTION == 1 */
280
281 /*-----------------------------------------------------------*/
282
vPortEnterCritical(void)283 void vPortEnterCritical( void )
284 {
285 portDISABLE_INTERRUPTS();
286 uxCriticalNesting++;
287 }
288
289 /*-----------------------------------------------------------*/
290
vPortExitCritical(void)291 void vPortExitCritical( void )
292 {
293 uxCriticalNesting--;
294
295 if( uxCriticalNesting == portNO_CRITICAL_NESTING )
296 {
297 portENABLE_INTERRUPTS();
298 }
299 }
300
