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 /*
30
31 Changes from V2.6.0
32
33 + AVR port - Replaced the inb() and outb() functions with direct memory
34 access. This allows the port to be built with the 20050414 build of
35 WinAVR.
36 */
37
38 #include <stdlib.h>
39 #include <avr/interrupt.h>
40
41 #include "FreeRTOS.h"
42 #include "task.h"
43
44 /*-----------------------------------------------------------
45 * Implementation of functions defined in portable.h for the AVR port.
46 *----------------------------------------------------------*/
47
48 /* Start tasks with interrupts enables. */
49 #define portFLAGS_INT_ENABLED ( ( StackType_t ) 0x80 )
50
51 /* Hardware constants for timer 1. */
52 #define portCLEAR_COUNTER_ON_MATCH ( ( uint8_t ) 0x08 )
53 #define portPRESCALE_64 ( ( uint8_t ) 0x03 )
54 #define portCLOCK_PRESCALER ( ( uint32_t ) 64 )
55 #define portCOMPARE_MATCH_A_INTERRUPT_ENABLE ( ( uint8_t ) 0x10 )
56
57 /*-----------------------------------------------------------*/
58
59 /* We require the address of the pxCurrentTCB variable, but don't want to know
60 any details of its type. */
61 typedef void TCB_t;
62 extern volatile TCB_t * volatile pxCurrentTCB;
63
64 /*-----------------------------------------------------------*/
65
66 /*
67 * Macro to save all the general purpose registers, the save the stack pointer
68 * into the TCB.
69 *
70 * The first thing we do is save the flags then disable interrupts. This is to
71 * guard our stack against having a context switch interrupt after we have already
72 * pushed the registers onto the stack - causing the 32 registers to be on the
73 * stack twice.
74 *
75 * r1 is set to zero as the compiler expects it to be thus, however some
76 * of the math routines make use of R1.
77 *
78 * The interrupts will have been disabled during the call to portSAVE_CONTEXT()
79 * so we need not worry about reading/writing to the stack pointer.
80 */
81
82 #define portSAVE_CONTEXT() \
83 asm volatile ( "push r0 \n\t" \
84 "in r0, __SREG__ \n\t" \
85 "cli \n\t" \
86 "push r0 \n\t" \
87 "push r1 \n\t" \
88 "clr r1 \n\t" \
89 "push r2 \n\t" \
90 "push r3 \n\t" \
91 "push r4 \n\t" \
92 "push r5 \n\t" \
93 "push r6 \n\t" \
94 "push r7 \n\t" \
95 "push r8 \n\t" \
96 "push r9 \n\t" \
97 "push r10 \n\t" \
98 "push r11 \n\t" \
99 "push r12 \n\t" \
100 "push r13 \n\t" \
101 "push r14 \n\t" \
102 "push r15 \n\t" \
103 "push r16 \n\t" \
104 "push r17 \n\t" \
105 "push r18 \n\t" \
106 "push r19 \n\t" \
107 "push r20 \n\t" \
108 "push r21 \n\t" \
109 "push r22 \n\t" \
110 "push r23 \n\t" \
111 "push r24 \n\t" \
112 "push r25 \n\t" \
113 "push r26 \n\t" \
114 "push r27 \n\t" \
115 "push r28 \n\t" \
116 "push r29 \n\t" \
117 "push r30 \n\t" \
118 "push r31 \n\t" \
119 "lds r26, pxCurrentTCB \n\t" \
120 "lds r27, pxCurrentTCB + 1 \n\t" \
121 "in r0, 0x3d \n\t" \
122 "st x+, r0 \n\t" \
123 "in r0, 0x3e \n\t" \
124 "st x+, r0 \n\t" \
125 );
126
127 /*
128 * Opposite to portSAVE_CONTEXT(). Interrupts will have been disabled during
129 * the context save so we can write to the stack pointer.
130 */
131
132 #define portRESTORE_CONTEXT() \
133 asm volatile ( "lds r26, pxCurrentTCB \n\t" \
134 "lds r27, pxCurrentTCB + 1 \n\t" \
135 "ld r28, x+ \n\t" \
136 "out __SP_L__, r28 \n\t" \
137 "ld r29, x+ \n\t" \
138 "out __SP_H__, r29 \n\t" \
139 "pop r31 \n\t" \
140 "pop r30 \n\t" \
141 "pop r29 \n\t" \
142 "pop r28 \n\t" \
143 "pop r27 \n\t" \
144 "pop r26 \n\t" \
145 "pop r25 \n\t" \
146 "pop r24 \n\t" \
147 "pop r23 \n\t" \
148 "pop r22 \n\t" \
149 "pop r21 \n\t" \
150 "pop r20 \n\t" \
151 "pop r19 \n\t" \
152 "pop r18 \n\t" \
153 "pop r17 \n\t" \
154 "pop r16 \n\t" \
155 "pop r15 \n\t" \
156 "pop r14 \n\t" \
157 "pop r13 \n\t" \
158 "pop r12 \n\t" \
159 "pop r11 \n\t" \
160 "pop r10 \n\t" \
161 "pop r9 \n\t" \
162 "pop r8 \n\t" \
163 "pop r7 \n\t" \
164 "pop r6 \n\t" \
165 "pop r5 \n\t" \
166 "pop r4 \n\t" \
167 "pop r3 \n\t" \
168 "pop r2 \n\t" \
169 "pop r1 \n\t" \
170 "pop r0 \n\t" \
171 "out __SREG__, r0 \n\t" \
172 "pop r0 \n\t" \
173 );
174
175 /*-----------------------------------------------------------*/
176
177 /*
178 * Perform hardware setup to enable ticks from timer 1, compare match A.
179 */
180 static void prvSetupTimerInterrupt( void );
181 /*-----------------------------------------------------------*/
182
183 /*
184 * See header file for description.
185 */
pxPortInitialiseStack(StackType_t * pxTopOfStack,TaskFunction_t pxCode,void * pvParameters)186 StackType_t *pxPortInitialiseStack( StackType_t *pxTopOfStack, TaskFunction_t pxCode, void *pvParameters )
187 {
188 uint16_t usAddress;
189
190 /* Place a few bytes of known values on the bottom of the stack.
191 This is just useful for debugging. */
192
193 *pxTopOfStack = 0x11;
194 pxTopOfStack--;
195 *pxTopOfStack = 0x22;
196 pxTopOfStack--;
197 *pxTopOfStack = 0x33;
198 pxTopOfStack--;
199
200 /* Simulate how the stack would look after a call to vPortYield() generated by
201 the compiler. */
202
203 /*lint -e950 -e611 -e923 Lint doesn't like this much - but nothing I can do about it. */
204
205 /* The start of the task code will be popped off the stack last, so place
206 it on first. */
207 usAddress = ( uint16_t ) pxCode;
208 *pxTopOfStack = ( StackType_t ) ( usAddress & ( uint16_t ) 0x00ff );
209 pxTopOfStack--;
210
211 usAddress >>= 8;
212 *pxTopOfStack = ( StackType_t ) ( usAddress & ( uint16_t ) 0x00ff );
213 pxTopOfStack--;
214
215 /* Next simulate the stack as if after a call to portSAVE_CONTEXT().
216 portSAVE_CONTEXT places the flags on the stack immediately after r0
217 to ensure the interrupts get disabled as soon as possible, and so ensuring
218 the stack use is minimal should a context switch interrupt occur. */
219 *pxTopOfStack = ( StackType_t ) 0x00; /* R0 */
220 pxTopOfStack--;
221 *pxTopOfStack = portFLAGS_INT_ENABLED;
222 pxTopOfStack--;
223
224
225 /* Now the remaining registers. The compiler expects R1 to be 0. */
226 *pxTopOfStack = ( StackType_t ) 0x00; /* R1 */
227 pxTopOfStack--;
228 *pxTopOfStack = ( StackType_t ) 0x02; /* R2 */
229 pxTopOfStack--;
230 *pxTopOfStack = ( StackType_t ) 0x03; /* R3 */
231 pxTopOfStack--;
232 *pxTopOfStack = ( StackType_t ) 0x04; /* R4 */
233 pxTopOfStack--;
234 *pxTopOfStack = ( StackType_t ) 0x05; /* R5 */
235 pxTopOfStack--;
236 *pxTopOfStack = ( StackType_t ) 0x06; /* R6 */
237 pxTopOfStack--;
238 *pxTopOfStack = ( StackType_t ) 0x07; /* R7 */
239 pxTopOfStack--;
240 *pxTopOfStack = ( StackType_t ) 0x08; /* R8 */
241 pxTopOfStack--;
242 *pxTopOfStack = ( StackType_t ) 0x09; /* R9 */
243 pxTopOfStack--;
244 *pxTopOfStack = ( StackType_t ) 0x10; /* R10 */
245 pxTopOfStack--;
246 *pxTopOfStack = ( StackType_t ) 0x11; /* R11 */
247 pxTopOfStack--;
248 *pxTopOfStack = ( StackType_t ) 0x12; /* R12 */
249 pxTopOfStack--;
250 *pxTopOfStack = ( StackType_t ) 0x13; /* R13 */
251 pxTopOfStack--;
252 *pxTopOfStack = ( StackType_t ) 0x14; /* R14 */
253 pxTopOfStack--;
254 *pxTopOfStack = ( StackType_t ) 0x15; /* R15 */
255 pxTopOfStack--;
256 *pxTopOfStack = ( StackType_t ) 0x16; /* R16 */
257 pxTopOfStack--;
258 *pxTopOfStack = ( StackType_t ) 0x17; /* R17 */
259 pxTopOfStack--;
260 *pxTopOfStack = ( StackType_t ) 0x18; /* R18 */
261 pxTopOfStack--;
262 *pxTopOfStack = ( StackType_t ) 0x19; /* R19 */
263 pxTopOfStack--;
264 *pxTopOfStack = ( StackType_t ) 0x20; /* R20 */
265 pxTopOfStack--;
266 *pxTopOfStack = ( StackType_t ) 0x21; /* R21 */
267 pxTopOfStack--;
268 *pxTopOfStack = ( StackType_t ) 0x22; /* R22 */
269 pxTopOfStack--;
270 *pxTopOfStack = ( StackType_t ) 0x23; /* R23 */
271 pxTopOfStack--;
272
273 /* Place the parameter on the stack in the expected location. */
274 usAddress = ( uint16_t ) pvParameters;
275 *pxTopOfStack = ( StackType_t ) ( usAddress & ( uint16_t ) 0x00ff );
276 pxTopOfStack--;
277
278 usAddress >>= 8;
279 *pxTopOfStack = ( StackType_t ) ( usAddress & ( uint16_t ) 0x00ff );
280 pxTopOfStack--;
281
282 *pxTopOfStack = ( StackType_t ) 0x26; /* R26 X */
283 pxTopOfStack--;
284 *pxTopOfStack = ( StackType_t ) 0x27; /* R27 */
285 pxTopOfStack--;
286 *pxTopOfStack = ( StackType_t ) 0x28; /* R28 Y */
287 pxTopOfStack--;
288 *pxTopOfStack = ( StackType_t ) 0x29; /* R29 */
289 pxTopOfStack--;
290 *pxTopOfStack = ( StackType_t ) 0x30; /* R30 Z */
291 pxTopOfStack--;
292 *pxTopOfStack = ( StackType_t ) 0x031; /* R31 */
293 pxTopOfStack--;
294
295 /*lint +e950 +e611 +e923 */
296
297 return pxTopOfStack;
298 }
299 /*-----------------------------------------------------------*/
300
xPortStartScheduler(void)301 BaseType_t xPortStartScheduler( void )
302 {
303 /* Setup the hardware to generate the tick. */
304 prvSetupTimerInterrupt();
305
306 /* Restore the context of the first task that is going to run. */
307 portRESTORE_CONTEXT();
308
309 /* Simulate a function call end as generated by the compiler. We will now
310 jump to the start of the task the context of which we have just restored. */
311 asm volatile ( "ret" );
312
313 /* Should not get here. */
314 return pdTRUE;
315 }
316 /*-----------------------------------------------------------*/
317
vPortEndScheduler(void)318 void vPortEndScheduler( void )
319 {
320 /* It is unlikely that the AVR port will get stopped. If required simply
321 disable the tick interrupt here. */
322 }
323 /*-----------------------------------------------------------*/
324
325 /*
326 * Manual context switch. The first thing we do is save the registers so we
327 * can use a naked attribute.
328 */
329 void vPortYield( void ) __attribute__ ( ( naked ) );
vPortYield(void)330 void vPortYield( void )
331 {
332 portSAVE_CONTEXT();
333 vTaskSwitchContext();
334 portRESTORE_CONTEXT();
335
336 asm volatile ( "ret" );
337 }
338 /*-----------------------------------------------------------*/
339
340 /*
341 * Context switch function used by the tick. This must be identical to
342 * vPortYield() from the call to vTaskSwitchContext() onwards. The only
343 * difference from vPortYield() is the tick count is incremented as the
344 * call comes from the tick ISR.
345 */
346 void vPortYieldFromTick( void ) __attribute__ ( ( naked ) );
vPortYieldFromTick(void)347 void vPortYieldFromTick( void )
348 {
349 portSAVE_CONTEXT();
350 if( xTaskIncrementTick() != pdFALSE )
351 {
352 vTaskSwitchContext();
353 }
354 portRESTORE_CONTEXT();
355
356 asm volatile ( "ret" );
357 }
358 /*-----------------------------------------------------------*/
359
360 /*
361 * Setup timer 1 compare match A to generate a tick interrupt.
362 */
prvSetupTimerInterrupt(void)363 static void prvSetupTimerInterrupt( void )
364 {
365 uint32_t ulCompareMatch;
366 uint8_t ucHighByte, ucLowByte;
367
368 /* Using 16bit timer 1 to generate the tick. Correct fuses must be
369 selected for the configCPU_CLOCK_HZ clock. */
370
371 ulCompareMatch = configCPU_CLOCK_HZ / configTICK_RATE_HZ;
372
373 /* We only have 16 bits so have to scale to get our required tick rate. */
374 ulCompareMatch /= portCLOCK_PRESCALER;
375
376 /* Adjust for correct value. */
377 ulCompareMatch -= ( uint32_t ) 1;
378
379 /* Setup compare match value for compare match A. Interrupts are disabled
380 before this is called so we need not worry here. */
381 ucLowByte = ( uint8_t ) ( ulCompareMatch & ( uint32_t ) 0xff );
382 ulCompareMatch >>= 8;
383 ucHighByte = ( uint8_t ) ( ulCompareMatch & ( uint32_t ) 0xff );
384 OCR1AH = ucHighByte;
385 OCR1AL = ucLowByte;
386
387 /* Setup clock source and compare match behaviour. */
388 ucLowByte = portCLEAR_COUNTER_ON_MATCH | portPRESCALE_64;
389 TCCR1B = ucLowByte;
390
391 /* Enable the interrupt - this is okay as interrupt are currently globally
392 disabled. */
393 ucLowByte = TIMSK;
394 ucLowByte |= portCOMPARE_MATCH_A_INTERRUPT_ENABLE;
395 TIMSK = ucLowByte;
396 }
397 /*-----------------------------------------------------------*/
398
399 #if configUSE_PREEMPTION == 1
400
401 /*
402 * Tick ISR for preemptive scheduler. We can use a naked attribute as
403 * the context is saved at the start of vPortYieldFromTick(). The tick
404 * count is incremented after the context is saved.
405 */
406 void TIMER1_COMPA_vect( void ) __attribute__ ( ( signal, naked ) );
TIMER1_COMPA_vect(void)407 void TIMER1_COMPA_vect( void )
408 {
409 vPortYieldFromTick();
410 asm volatile ( "reti" );
411 }
412 #else
413
414 /*
415 * Tick ISR for the cooperative scheduler. All this does is increment the
416 * tick count. We don't need to switch context, this can only be done by
417 * manual calls to taskYIELD();
418 */
419 void TIMER1_COMPA_vect( void ) __attribute__ ( ( signal ) );
TIMER1_COMPA_vect(void)420 void TIMER1_COMPA_vect( void )
421 {
422 xTaskIncrementTick();
423 }
424 #endif
425
426
427
428
