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
31 #include "FreeRTOS.h"
32 #include "task.h"
33
34 /*-----------------------------------------------------------
35 * Implementation of functions defined in portable.h for the AVR/IAR port.
36 *----------------------------------------------------------*/
37
38 /* Start tasks with interrupts enables. */
39 #define portFLAGS_INT_ENABLED ( ( StackType_t ) 0x80 )
40
41 /* Hardware constants for timer 1. */
42 #define portCLEAR_COUNTER_ON_MATCH ( ( uint8_t ) 0x08 )
43 #define portPRESCALE_64 ( ( uint8_t ) 0x03 )
44 #define portCLOCK_PRESCALER ( ( uint32_t ) 64 )
45 #define portCOMPARE_MATCH_A_INTERRUPT_ENABLE ( ( uint8_t ) 0x10 )
46
47 /* The number of bytes used on the hardware stack by the task start address. */
48 #define portBYTES_USED_BY_RETURN_ADDRESS ( 2 )
49 /*-----------------------------------------------------------*/
50
51 /* Stores the critical section nesting. This must not be initialised to 0.
52 It will be initialised when a task starts. */
53 #define portNO_CRITICAL_NESTING ( ( UBaseType_t ) 0 )
54 UBaseType_t uxCriticalNesting = 0x50;
55
56
57 /*
58 * Perform hardware setup to enable ticks from timer 1, compare match A.
59 */
60 static void prvSetupTimerInterrupt( void );
61
62 /*
63 * The IAR compiler does not have full support for inline assembler, so
64 * these are defined in the portmacro assembler file.
65 */
66 extern void vPortYieldFromTick( void );
67 extern void vPortStart( void );
68
69 /*-----------------------------------------------------------*/
70
71 /*
72 * See header file for description.
73 */
pxPortInitialiseStack(StackType_t * pxTopOfStack,TaskFunction_t pxCode,void * pvParameters)74 StackType_t *pxPortInitialiseStack( StackType_t *pxTopOfStack, TaskFunction_t pxCode, void *pvParameters )
75 {
76 uint16_t usAddress;
77 StackType_t *pxTopOfHardwareStack;
78
79 /* Place a few bytes of known values on the bottom of the stack.
80 This is just useful for debugging. */
81
82 *pxTopOfStack = 0x11;
83 pxTopOfStack--;
84 *pxTopOfStack = 0x22;
85 pxTopOfStack--;
86 *pxTopOfStack = 0x33;
87 pxTopOfStack--;
88
89 /* Remember where the top of the hardware stack is - this is required
90 below. */
91 pxTopOfHardwareStack = pxTopOfStack;
92
93
94 /* Simulate how the stack would look after a call to vPortYield(). */
95
96 /*lint -e950 -e611 -e923 Lint doesn't like this much - but nothing I can do about it. */
97
98
99
100 /* The IAR compiler requires two stacks per task. First there is the
101 hardware call stack which uses the AVR stack pointer. Second there is the
102 software stack (local variables, parameter passing, etc.) which uses the
103 AVR Y register.
104
105 This function places both stacks within the memory block passed in as the
106 first parameter. The hardware stack is placed at the bottom of the memory
107 block. A gap is then left for the hardware stack to grow. Next the software
108 stack is placed. The amount of space between the software and hardware
109 stacks is defined by configCALL_STACK_SIZE.
110
111
112
113 The first part of the stack is the hardware stack. Place the start
114 address of the task on the hardware stack. */
115 usAddress = ( uint16_t ) pxCode;
116 *pxTopOfStack = ( StackType_t ) ( usAddress & ( uint16_t ) 0x00ff );
117 pxTopOfStack--;
118
119 usAddress >>= 8;
120 *pxTopOfStack = ( StackType_t ) ( usAddress & ( uint16_t ) 0x00ff );
121 pxTopOfStack--;
122
123
124 /* Leave enough space for the hardware stack before starting the software
125 stack. The '- 2' is because we have already used two spaces for the
126 address of the start of the task. */
127 pxTopOfStack -= ( configCALL_STACK_SIZE - 2 );
128
129
130
131 /* Next simulate the stack as if after a call to portSAVE_CONTEXT().
132 portSAVE_CONTEXT places the flags on the stack immediately after r0
133 to ensure the interrupts get disabled as soon as possible, and so ensuring
134 the stack use is minimal should a context switch interrupt occur. */
135 *pxTopOfStack = ( StackType_t ) 0x00; /* R0 */
136 pxTopOfStack--;
137 *pxTopOfStack = portFLAGS_INT_ENABLED;
138 pxTopOfStack--;
139
140 /* Next place the address of the hardware stack. This is required so
141 the AVR stack pointer can be restored to point to the hardware stack. */
142 pxTopOfHardwareStack -= portBYTES_USED_BY_RETURN_ADDRESS;
143 usAddress = ( uint16_t ) pxTopOfHardwareStack;
144
145 /* SPL */
146 *pxTopOfStack = ( StackType_t ) ( usAddress & ( uint16_t ) 0x00ff );
147 pxTopOfStack--;
148
149 /* SPH */
150 usAddress >>= 8;
151 *pxTopOfStack = ( StackType_t ) ( usAddress & ( uint16_t ) 0x00ff );
152 pxTopOfStack--;
153
154
155
156
157 /* Now the remaining registers. */
158 *pxTopOfStack = ( StackType_t ) 0x01; /* R1 */
159 pxTopOfStack--;
160 *pxTopOfStack = ( StackType_t ) 0x02; /* R2 */
161 pxTopOfStack--;
162 *pxTopOfStack = ( StackType_t ) 0x03; /* R3 */
163 pxTopOfStack--;
164 *pxTopOfStack = ( StackType_t ) 0x04; /* R4 */
165 pxTopOfStack--;
166 *pxTopOfStack = ( StackType_t ) 0x05; /* R5 */
167 pxTopOfStack--;
168 *pxTopOfStack = ( StackType_t ) 0x06; /* R6 */
169 pxTopOfStack--;
170 *pxTopOfStack = ( StackType_t ) 0x07; /* R7 */
171 pxTopOfStack--;
172 *pxTopOfStack = ( StackType_t ) 0x08; /* R8 */
173 pxTopOfStack--;
174 *pxTopOfStack = ( StackType_t ) 0x09; /* R9 */
175 pxTopOfStack--;
176 *pxTopOfStack = ( StackType_t ) 0x10; /* R10 */
177 pxTopOfStack--;
178 *pxTopOfStack = ( StackType_t ) 0x11; /* R11 */
179 pxTopOfStack--;
180 *pxTopOfStack = ( StackType_t ) 0x12; /* R12 */
181 pxTopOfStack--;
182 *pxTopOfStack = ( StackType_t ) 0x13; /* R13 */
183 pxTopOfStack--;
184 *pxTopOfStack = ( StackType_t ) 0x14; /* R14 */
185 pxTopOfStack--;
186 *pxTopOfStack = ( StackType_t ) 0x15; /* R15 */
187 pxTopOfStack--;
188
189 /* Place the parameter on the stack in the expected location. */
190 usAddress = ( uint16_t ) pvParameters;
191 *pxTopOfStack = ( StackType_t ) ( usAddress & ( uint16_t ) 0x00ff );
192 pxTopOfStack--;
193
194 usAddress >>= 8;
195 *pxTopOfStack = ( StackType_t ) ( usAddress & ( uint16_t ) 0x00ff );
196 pxTopOfStack--;
197
198 *pxTopOfStack = ( StackType_t ) 0x18; /* R18 */
199 pxTopOfStack--;
200 *pxTopOfStack = ( StackType_t ) 0x19; /* R19 */
201 pxTopOfStack--;
202 *pxTopOfStack = ( StackType_t ) 0x20; /* R20 */
203 pxTopOfStack--;
204 *pxTopOfStack = ( StackType_t ) 0x21; /* R21 */
205 pxTopOfStack--;
206 *pxTopOfStack = ( StackType_t ) 0x22; /* R22 */
207 pxTopOfStack--;
208 *pxTopOfStack = ( StackType_t ) 0x23; /* R23 */
209 pxTopOfStack--;
210 *pxTopOfStack = ( StackType_t ) 0x24; /* R24 */
211 pxTopOfStack--;
212 *pxTopOfStack = ( StackType_t ) 0x25; /* R25 */
213 pxTopOfStack--;
214 *pxTopOfStack = ( StackType_t ) 0x26; /* R26 X */
215 pxTopOfStack--;
216 *pxTopOfStack = ( StackType_t ) 0x27; /* R27 */
217 pxTopOfStack--;
218
219 /* The Y register is not stored as it is used as the software stack and
220 gets saved into the task control block. */
221
222 *pxTopOfStack = ( StackType_t ) 0x30; /* R30 Z */
223 pxTopOfStack--;
224 *pxTopOfStack = ( StackType_t ) 0x031; /* R31 */
225
226 pxTopOfStack--;
227 *pxTopOfStack = portNO_CRITICAL_NESTING; /* Critical nesting is zero when the task starts. */
228
229 /*lint +e950 +e611 +e923 */
230
231 return pxTopOfStack;
232 }
233 /*-----------------------------------------------------------*/
234
xPortStartScheduler(void)235 BaseType_t xPortStartScheduler( void )
236 {
237 /* Setup the hardware to generate the tick. */
238 prvSetupTimerInterrupt();
239
240 /* Restore the context of the first task that is going to run.
241 Normally we would just call portRESTORE_CONTEXT() here, but as the IAR
242 compiler does not fully support inline assembler we have to make a call.*/
243 vPortStart();
244
245 /* Should not get here! */
246 return pdTRUE;
247 }
248 /*-----------------------------------------------------------*/
249
vPortEndScheduler(void)250 void vPortEndScheduler( void )
251 {
252 /* It is unlikely that the AVR port will get stopped. If required simply
253 disable the tick interrupt here. */
254 }
255 /*-----------------------------------------------------------*/
256
257 /*
258 * Setup timer 1 compare match A to generate a tick interrupt.
259 */
prvSetupTimerInterrupt(void)260 static void prvSetupTimerInterrupt( void )
261 {
262 uint32_t ulCompareMatch;
263 uint8_t ucHighByte, ucLowByte;
264
265 /* Using 16bit timer 1 to generate the tick. Correct fuses must be
266 selected for the configCPU_CLOCK_HZ clock. */
267
268 ulCompareMatch = configCPU_CLOCK_HZ / configTICK_RATE_HZ;
269
270 /* We only have 16 bits so have to scale to get our required tick rate. */
271 ulCompareMatch /= portCLOCK_PRESCALER;
272
273 /* Adjust for correct value. */
274 ulCompareMatch -= ( uint32_t ) 1;
275
276 /* Setup compare match value for compare match A. Interrupts are disabled
277 before this is called so we need not worry here. */
278 ucLowByte = ( uint8_t ) ( ulCompareMatch & ( uint32_t ) 0xff );
279 ulCompareMatch >>= 8;
280 ucHighByte = ( uint8_t ) ( ulCompareMatch & ( uint32_t ) 0xff );
281 OCR1AH = ucHighByte;
282 OCR1AL = ucLowByte;
283
284 /* Setup clock source and compare match behaviour. */
285 ucLowByte = portCLEAR_COUNTER_ON_MATCH | portPRESCALE_64;
286 TCCR1B = ucLowByte;
287
288 /* Enable the interrupt - this is okay as interrupt are currently globally
289 disabled. */
290 TIMSK |= portCOMPARE_MATCH_A_INTERRUPT_ENABLE;
291 }
292 /*-----------------------------------------------------------*/
293
294 #if configUSE_PREEMPTION == 1
295
296 /*
297 * Tick ISR for preemptive scheduler. We can use a __task attribute as
298 * the context is saved at the start of vPortYieldFromTick(). The tick
299 * count is incremented after the context is saved.
300 */
SIG_OUTPUT_COMPARE1A(void)301 __task void SIG_OUTPUT_COMPARE1A( void )
302 {
303 vPortYieldFromTick();
304 asm( "reti" );
305 }
306
307 #else
308
309 /*
310 * Tick ISR for the cooperative scheduler. All this does is increment the
311 * tick count. We don't need to switch context, this can only be done by
312 * manual calls to taskYIELD();
313 *
314 * THE INTERRUPT VECTOR IS POPULATED IN portmacro.s90. DO NOT INSTALL
315 * IT HERE USING THE USUAL PRAGMA.
316 */
SIG_OUTPUT_COMPARE1A(void)317 __interrupt void SIG_OUTPUT_COMPARE1A( void )
318 {
319 xTaskIncrementTick();
320 }
321 #endif
322 /*-----------------------------------------------------------*/
323
vPortEnterCritical(void)324 void vPortEnterCritical( void )
325 {
326 portDISABLE_INTERRUPTS();
327 uxCriticalNesting++;
328 }
329 /*-----------------------------------------------------------*/
330
vPortExitCritical(void)331 void vPortExitCritical( void )
332 {
333 uxCriticalNesting--;
334 if( uxCriticalNesting == portNO_CRITICAL_NESTING )
335 {
336 portENABLE_INTERRUPTS();
337 }
338 }
339
