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 * Implementation of functions defined in portable.h for the ARM CM4F port.
31 *----------------------------------------------------------*/
32
33 /* Scheduler includes. */
34 #include "FreeRTOS.h"
35 #include "task.h"
36
37 #ifndef __TARGET_FPU_VFP
38 #error This port can only be used when the project options are configured to enable hardware floating point support.
39 #endif
40
41 #if configMAX_SYSCALL_INTERRUPT_PRIORITY == 0
42 #error configMAX_SYSCALL_INTERRUPT_PRIORITY must not be set to 0. See http: /*www.FreeRTOS.org/RTOS-Cortex-M3-M4.html */
43 #endif
44
45 /* Legacy macro for backward compatibility only. This macro used to be used to
46 * replace the function that configures the clock used to generate the tick
47 * interrupt (prvSetupTimerInterrupt()), but now the function is declared weak so
48 * the application writer can override it by simply defining a function of the
49 * same name (vApplicationSetupTickInterrupt()). */
50 #ifndef configOVERRIDE_DEFAULT_TICK_CONFIGURATION
51 #define configOVERRIDE_DEFAULT_TICK_CONFIGURATION 0
52 #endif
53
54 /* Constants required to manipulate the core. Registers first... */
55 #define portNVIC_SYSTICK_CTRL_REG ( *( ( volatile uint32_t * ) 0xe000e010 ) )
56 #define portNVIC_SYSTICK_LOAD_REG ( *( ( volatile uint32_t * ) 0xe000e014 ) )
57 #define portNVIC_SYSTICK_CURRENT_VALUE_REG ( *( ( volatile uint32_t * ) 0xe000e018 ) )
58 #define portNVIC_SHPR3_REG ( *( ( volatile uint32_t * ) 0xe000ed20 ) )
59 /* ...then bits in the registers. */
60 #define portNVIC_SYSTICK_CLK_BIT ( 1UL << 2UL )
61 #define portNVIC_SYSTICK_INT_BIT ( 1UL << 1UL )
62 #define portNVIC_SYSTICK_ENABLE_BIT ( 1UL << 0UL )
63 #define portNVIC_SYSTICK_COUNT_FLAG_BIT ( 1UL << 16UL )
64 #define portNVIC_PENDSVCLEAR_BIT ( 1UL << 27UL )
65 #define portNVIC_PEND_SYSTICK_SET_BIT ( 1UL << 26UL )
66 #define portNVIC_PEND_SYSTICK_CLEAR_BIT ( 1UL << 25UL )
67
68 /* Constants used to detect a Cortex-M7 r0p1 core, which should use the ARM_CM7
69 * r0p1 port. */
70 #define portCPUID ( *( ( volatile uint32_t * ) 0xE000ed00 ) )
71 #define portCORTEX_M7_r0p1_ID ( 0x410FC271UL )
72 #define portCORTEX_M7_r0p0_ID ( 0x410FC270UL )
73
74 #define portMIN_INTERRUPT_PRIORITY ( 255UL )
75 #define portNVIC_PENDSV_PRI ( ( ( uint32_t ) portMIN_INTERRUPT_PRIORITY ) << 16UL )
76 #define portNVIC_SYSTICK_PRI ( ( ( uint32_t ) portMIN_INTERRUPT_PRIORITY ) << 24UL )
77
78 /* Constants required to check the validity of an interrupt priority. */
79 #define portFIRST_USER_INTERRUPT_NUMBER ( 16 )
80 #define portNVIC_IP_REGISTERS_OFFSET_16 ( 0xE000E3F0 )
81 #define portAIRCR_REG ( *( ( volatile uint32_t * ) 0xE000ED0C ) )
82 #define portMAX_8_BIT_VALUE ( ( uint8_t ) 0xff )
83 #define portTOP_BIT_OF_BYTE ( ( uint8_t ) 0x80 )
84 #define portMAX_PRIGROUP_BITS ( ( uint8_t ) 7 )
85 #define portPRIORITY_GROUP_MASK ( 0x07UL << 8UL )
86 #define portPRIGROUP_SHIFT ( 8UL )
87
88 /* Masks off all bits but the VECTACTIVE bits in the ICSR register. */
89 #define portVECTACTIVE_MASK ( 0xFFUL )
90
91 /* Constants required to manipulate the VFP. */
92 #define portFPCCR ( ( volatile uint32_t * ) 0xe000ef34 ) /* Floating point context control register. */
93 #define portASPEN_AND_LSPEN_BITS ( 0x3UL << 30UL )
94
95 /* Constants required to set up the initial stack. */
96 #define portINITIAL_XPSR ( 0x01000000 )
97 #define portINITIAL_EXC_RETURN ( 0xfffffffd )
98
99 /* The systick is a 24-bit counter. */
100 #define portMAX_24_BIT_NUMBER ( 0xffffffUL )
101
102 /* A fiddle factor to estimate the number of SysTick counts that would have
103 * occurred while the SysTick counter is stopped during tickless idle
104 * calculations. */
105 #define portMISSED_COUNTS_FACTOR ( 94UL )
106
107 /* For strict compliance with the Cortex-M spec the task start address should
108 * have bit-0 clear, as it is loaded into the PC on exit from an ISR. */
109 #define portSTART_ADDRESS_MASK ( ( StackType_t ) 0xfffffffeUL )
110
111 /* Let the user override the default SysTick clock rate. If defined by the
112 * user, this symbol must equal the SysTick clock rate when the CLK bit is 0 in the
113 * configuration register. */
114 #ifndef configSYSTICK_CLOCK_HZ
115 #define configSYSTICK_CLOCK_HZ ( configCPU_CLOCK_HZ )
116 /* Ensure the SysTick is clocked at the same frequency as the core. */
117 #define portNVIC_SYSTICK_CLK_BIT_CONFIG ( portNVIC_SYSTICK_CLK_BIT )
118 #else
119 /* Select the option to clock SysTick not at the same frequency as the core. */
120 #define portNVIC_SYSTICK_CLK_BIT_CONFIG ( 0 )
121 #endif
122
123 /*
124 * Setup the timer to generate the tick interrupts. The implementation in this
125 * file is weak to allow application writers to change the timer used to
126 * generate the tick interrupt.
127 */
128 void vPortSetupTimerInterrupt( void );
129
130 /*
131 * Exception handlers.
132 */
133 void xPortPendSVHandler( void );
134 void xPortSysTickHandler( void );
135 void vPortSVCHandler( void );
136
137 /*
138 * Start first task is a separate function so it can be tested in isolation.
139 */
140 static void prvStartFirstTask( void );
141
142 /*
143 * Functions defined in portasm.s to enable the VFP.
144 */
145 static void prvEnableVFP( void );
146
147 /*
148 * Used to catch tasks that attempt to return from their implementing function.
149 */
150 static void prvTaskExitError( void );
151
152 /*-----------------------------------------------------------*/
153
154 /* Each task maintains its own interrupt status in the critical nesting
155 * variable. */
156 static UBaseType_t uxCriticalNesting = 0xaaaaaaaa;
157
158 /*
159 * The number of SysTick increments that make up one tick period.
160 */
161 #if ( configUSE_TICKLESS_IDLE == 1 )
162 static uint32_t ulTimerCountsForOneTick = 0;
163 #endif /* configUSE_TICKLESS_IDLE */
164
165 /*
166 * The maximum number of tick periods that can be suppressed is limited by the
167 * 24 bit resolution of the SysTick timer.
168 */
169 #if ( configUSE_TICKLESS_IDLE == 1 )
170 static uint32_t xMaximumPossibleSuppressedTicks = 0;
171 #endif /* configUSE_TICKLESS_IDLE */
172
173 /*
174 * Compensate for the CPU cycles that pass while the SysTick is stopped (low
175 * power functionality only.
176 */
177 #if ( configUSE_TICKLESS_IDLE == 1 )
178 static uint32_t ulStoppedTimerCompensation = 0;
179 #endif /* configUSE_TICKLESS_IDLE */
180
181 /*
182 * Used by the portASSERT_IF_INTERRUPT_PRIORITY_INVALID() macro to ensure
183 * FreeRTOS API functions are not called from interrupts that have been assigned
184 * a priority above configMAX_SYSCALL_INTERRUPT_PRIORITY.
185 */
186 #if ( configASSERT_DEFINED == 1 )
187 static uint8_t ucMaxSysCallPriority = 0;
188 static uint32_t ulMaxPRIGROUPValue = 0;
189 static const volatile uint8_t * const pcInterruptPriorityRegisters = ( uint8_t * ) portNVIC_IP_REGISTERS_OFFSET_16;
190 #endif /* configASSERT_DEFINED */
191
192 /*-----------------------------------------------------------*/
193
194 /*
195 * See header file for description.
196 */
pxPortInitialiseStack(StackType_t * pxTopOfStack,TaskFunction_t pxCode,void * pvParameters)197 StackType_t * pxPortInitialiseStack( StackType_t * pxTopOfStack,
198 TaskFunction_t pxCode,
199 void * pvParameters )
200 {
201 /* Simulate the stack frame as it would be created by a context switch
202 * interrupt. */
203
204 /* Offset added to account for the way the MCU uses the stack on entry/exit
205 * of interrupts, and to ensure alignment. */
206 pxTopOfStack--;
207
208 *pxTopOfStack = portINITIAL_XPSR; /* xPSR */
209 pxTopOfStack--;
210 *pxTopOfStack = ( ( StackType_t ) pxCode ) & portSTART_ADDRESS_MASK; /* PC */
211 pxTopOfStack--;
212 *pxTopOfStack = ( StackType_t ) prvTaskExitError; /* LR */
213
214 /* Save code space by skipping register initialisation. */
215 pxTopOfStack -= 5; /* R12, R3, R2 and R1. */
216 *pxTopOfStack = ( StackType_t ) pvParameters; /* R0 */
217
218 /* A save method is being used that requires each task to maintain its
219 * own exec return value. */
220 pxTopOfStack--;
221 *pxTopOfStack = portINITIAL_EXC_RETURN;
222
223 pxTopOfStack -= 8; /* R11, R10, R9, R8, R7, R6, R5 and R4. */
224
225 return pxTopOfStack;
226 }
227 /*-----------------------------------------------------------*/
228
prvTaskExitError(void)229 static void prvTaskExitError( void )
230 {
231 /* A function that implements a task must not exit or attempt to return to
232 * its caller as there is nothing to return to. If a task wants to exit it
233 * should instead call vTaskDelete( NULL ).
234 *
235 * Artificially force an assert() to be triggered if configASSERT() is
236 * defined, then stop here so application writers can catch the error. */
237 configASSERT( uxCriticalNesting == ~0UL );
238 portDISABLE_INTERRUPTS();
239
240 for( ; ; )
241 {
242 }
243 }
244 /*-----------------------------------------------------------*/
245
vPortSVCHandler(void)246 __asm void vPortSVCHandler( void )
247 {
248 /* *INDENT-OFF* */
249 PRESERVE8
250
251 /* Get the location of the current TCB. */
252 ldr r3, =pxCurrentTCB
253 ldr r1, [ r3 ]
254 ldr r0, [ r1 ]
255 /* Pop the core registers. */
256 ldmia r0!, {r4-r11,r14}
257 msr psp, r0
258 isb
259 mov r0, #0
260 msr basepri, r0
261 bx r14
262 /* *INDENT-ON* */
263 }
264 /*-----------------------------------------------------------*/
265
prvStartFirstTask(void)266 __asm void prvStartFirstTask( void )
267 {
268 /* *INDENT-OFF* */
269 PRESERVE8
270
271 /* Use the NVIC offset register to locate the stack. */
272 ldr r0, =0xE000ED08
273 ldr r0, [ r0 ]
274 ldr r0, [ r0 ]
275 /* Set the msp back to the start of the stack. */
276 msr msp, r0
277
278 /* Clear the bit that indicates the FPU is in use in case the FPU was used
279 * before the scheduler was started - which would otherwise result in the
280 * unnecessary leaving of space in the SVC stack for lazy saving of FPU
281 * registers. */
282 mov r0, #0
283 msr control, r0
284 /* Globally enable interrupts. */
285 cpsie i
286 cpsie f
287 dsb
288 isb
289 /* Call SVC to start the first task. */
290 svc 0
291 nop
292 nop
293 /* *INDENT-ON* */
294 }
295 /*-----------------------------------------------------------*/
296
prvEnableVFP(void)297 __asm void prvEnableVFP( void )
298 {
299 /* *INDENT-OFF* */
300 PRESERVE8
301
302 /* The FPU enable bits are in the CPACR. */
303 ldr.w r0, =0xE000ED88
304 ldr r1, [ r0 ]
305
306 /* Enable CP10 and CP11 coprocessors, then save back. */
307 orr r1, r1, #( 0xf << 20 )
308 str r1, [ r0 ]
309 bx r14
310 nop
311 /* *INDENT-ON* */
312 }
313 /*-----------------------------------------------------------*/
314
315 /*
316 * See header file for description.
317 */
xPortStartScheduler(void)318 BaseType_t xPortStartScheduler( void )
319 {
320 /* configMAX_SYSCALL_INTERRUPT_PRIORITY must not be set to 0.
321 * See https://www.FreeRTOS.org/RTOS-Cortex-M3-M4.html */
322 configASSERT( configMAX_SYSCALL_INTERRUPT_PRIORITY );
323
324 /* This port can be used on all revisions of the Cortex-M7 core other than
325 * the r0p1 parts. r0p1 parts should use the port from the
326 * /source/portable/GCC/ARM_CM7/r0p1 directory. */
327 configASSERT( portCPUID != portCORTEX_M7_r0p1_ID );
328 configASSERT( portCPUID != portCORTEX_M7_r0p0_ID );
329
330 #if ( configASSERT_DEFINED == 1 )
331 {
332 volatile uint8_t ucOriginalPriority;
333 volatile uint32_t ulImplementedPrioBits = 0;
334 volatile uint8_t * const pucFirstUserPriorityRegister = ( uint8_t * ) ( portNVIC_IP_REGISTERS_OFFSET_16 + portFIRST_USER_INTERRUPT_NUMBER );
335 volatile uint8_t ucMaxPriorityValue;
336
337 /* Determine the maximum priority from which ISR safe FreeRTOS API
338 * functions can be called. ISR safe functions are those that end in
339 * "FromISR". FreeRTOS maintains separate thread and ISR API functions to
340 * ensure interrupt entry is as fast and simple as possible.
341 *
342 * Save the interrupt priority value that is about to be clobbered. */
343 ucOriginalPriority = *pucFirstUserPriorityRegister;
344
345 /* Determine the number of priority bits available. First write to all
346 * possible bits. */
347 *pucFirstUserPriorityRegister = portMAX_8_BIT_VALUE;
348
349 /* Read the value back to see how many bits stuck. */
350 ucMaxPriorityValue = *pucFirstUserPriorityRegister;
351
352 /* Use the same mask on the maximum system call priority. */
353 ucMaxSysCallPriority = configMAX_SYSCALL_INTERRUPT_PRIORITY & ucMaxPriorityValue;
354
355 /* Check that the maximum system call priority is nonzero after
356 * accounting for the number of priority bits supported by the
357 * hardware. A priority of 0 is invalid because setting the BASEPRI
358 * register to 0 unmasks all interrupts, and interrupts with priority 0
359 * cannot be masked using BASEPRI.
360 * See https://www.FreeRTOS.org/RTOS-Cortex-M3-M4.html */
361 configASSERT( ucMaxSysCallPriority );
362
363 /* Check that the bits not implemented in hardware are zero in
364 * configMAX_SYSCALL_INTERRUPT_PRIORITY. */
365 configASSERT( ( configMAX_SYSCALL_INTERRUPT_PRIORITY & ( ~ucMaxPriorityValue ) ) == 0U );
366
367 /* Calculate the maximum acceptable priority group value for the number
368 * of bits read back. */
369
370 while( ( ucMaxPriorityValue & portTOP_BIT_OF_BYTE ) == portTOP_BIT_OF_BYTE )
371 {
372 ulImplementedPrioBits++;
373 ucMaxPriorityValue <<= ( uint8_t ) 0x01;
374 }
375
376 if( ulImplementedPrioBits == 8 )
377 {
378 /* When the hardware implements 8 priority bits, there is no way for
379 * the software to configure PRIGROUP to not have sub-priorities. As
380 * a result, the least significant bit is always used for sub-priority
381 * and there are 128 preemption priorities and 2 sub-priorities.
382 *
383 * This may cause some confusion in some cases - for example, if
384 * configMAX_SYSCALL_INTERRUPT_PRIORITY is set to 5, both 5 and 4
385 * priority interrupts will be masked in Critical Sections as those
386 * are at the same preemption priority. This may appear confusing as
387 * 4 is higher (numerically lower) priority than
388 * configMAX_SYSCALL_INTERRUPT_PRIORITY and therefore, should not
389 * have been masked. Instead, if we set configMAX_SYSCALL_INTERRUPT_PRIORITY
390 * to 4, this confusion does not happen and the behaviour remains the same.
391 *
392 * The following assert ensures that the sub-priority bit in the
393 * configMAX_SYSCALL_INTERRUPT_PRIORITY is clear to avoid the above mentioned
394 * confusion. */
395 configASSERT( ( configMAX_SYSCALL_INTERRUPT_PRIORITY & 0x1U ) == 0U );
396 ulMaxPRIGROUPValue = 0;
397 }
398 else
399 {
400 ulMaxPRIGROUPValue = portMAX_PRIGROUP_BITS - ulImplementedPrioBits;
401 }
402
403 /* Shift the priority group value back to its position within the AIRCR
404 * register. */
405 ulMaxPRIGROUPValue <<= portPRIGROUP_SHIFT;
406 ulMaxPRIGROUPValue &= portPRIORITY_GROUP_MASK;
407
408 /* Restore the clobbered interrupt priority register to its original
409 * value. */
410 *pucFirstUserPriorityRegister = ucOriginalPriority;
411 }
412 #endif /* configASSERT_DEFINED */
413
414 /* Make PendSV and SysTick the lowest priority interrupts. */
415 portNVIC_SHPR3_REG |= portNVIC_PENDSV_PRI;
416 portNVIC_SHPR3_REG |= portNVIC_SYSTICK_PRI;
417
418 /* Start the timer that generates the tick ISR. Interrupts are disabled
419 * here already. */
420 vPortSetupTimerInterrupt();
421
422 /* Initialise the critical nesting count ready for the first task. */
423 uxCriticalNesting = 0;
424
425 /* Ensure the VFP is enabled - it should be anyway. */
426 prvEnableVFP();
427
428 /* Lazy save always. */
429 *( portFPCCR ) |= portASPEN_AND_LSPEN_BITS;
430
431 /* Start the first task. */
432 prvStartFirstTask();
433
434 /* Should not get here! */
435 return 0;
436 }
437 /*-----------------------------------------------------------*/
438
vPortEndScheduler(void)439 void vPortEndScheduler( void )
440 {
441 /* Not implemented in ports where there is nothing to return to.
442 * Artificially force an assert. */
443 configASSERT( uxCriticalNesting == 1000UL );
444 }
445 /*-----------------------------------------------------------*/
446
vPortEnterCritical(void)447 void vPortEnterCritical( void )
448 {
449 portDISABLE_INTERRUPTS();
450 uxCriticalNesting++;
451
452 /* This is not the interrupt safe version of the enter critical function so
453 * assert() if it is being called from an interrupt context. Only API
454 * functions that end in "FromISR" can be used in an interrupt. Only assert if
455 * the critical nesting count is 1 to protect against recursive calls if the
456 * assert function also uses a critical section. */
457 if( uxCriticalNesting == 1 )
458 {
459 configASSERT( ( portNVIC_INT_CTRL_REG & portVECTACTIVE_MASK ) == 0 );
460 }
461 }
462 /*-----------------------------------------------------------*/
463
vPortExitCritical(void)464 void vPortExitCritical( void )
465 {
466 configASSERT( uxCriticalNesting );
467 uxCriticalNesting--;
468
469 if( uxCriticalNesting == 0 )
470 {
471 portENABLE_INTERRUPTS();
472 }
473 }
474 /*-----------------------------------------------------------*/
475
xPortPendSVHandler(void)476 __asm void xPortPendSVHandler( void )
477 {
478 extern uxCriticalNesting;
479 extern pxCurrentTCB;
480 extern vTaskSwitchContext;
481
482 /* *INDENT-OFF* */
483 PRESERVE8
484
485 mrs r0, psp
486 isb
487 /* Get the location of the current TCB. */
488 ldr r3, =pxCurrentTCB
489 ldr r2, [ r3 ]
490
491 /* Is the task using the FPU context? If so, push high vfp registers. */
492 tst r14, #0x10
493 it eq
494 vstmdbeq r0!, {s16-s31}
495
496 /* Save the core registers. */
497 stmdb r0!, {r4-r11, r14}
498
499 /* Save the new top of stack into the first member of the TCB. */
500 str r0, [ r2 ]
501
502 stmdb sp!, {r0, r3}
503 mov r0, #configMAX_SYSCALL_INTERRUPT_PRIORITY
504 msr basepri, r0
505 dsb
506 isb
507 bl vTaskSwitchContext
508 mov r0, #0
509 msr basepri, r0
510 ldmia sp!, {r0, r3}
511
512 /* The first item in pxCurrentTCB is the task top of stack. */
513 ldr r1, [ r3 ]
514 ldr r0, [ r1 ]
515
516 /* Pop the core registers. */
517 ldmia r0!, {r4-r11, r14}
518
519 /* Is the task using the FPU context? If so, pop the high vfp registers
520 * too. */
521 tst r14, #0x10
522 it eq
523 vldmiaeq r0!, {s16-s31}
524
525 msr psp, r0
526 isb
527 #ifdef WORKAROUND_PMU_CM001 /* XMC4000 specific errata */
528 #if WORKAROUND_PMU_CM001 == 1
529 push { r14 }
530 pop { pc }
531 nop
532 #endif
533 #endif
534
535 bx r14
536 /* *INDENT-ON* */
537 }
538 /*-----------------------------------------------------------*/
539
xPortSysTickHandler(void)540 void xPortSysTickHandler( void )
541 {
542 /* The SysTick runs at the lowest interrupt priority, so when this interrupt
543 * executes all interrupts must be unmasked. There is therefore no need to
544 * save and then restore the interrupt mask value as its value is already
545 * known - therefore the slightly faster vPortRaiseBASEPRI() function is used
546 * in place of portSET_INTERRUPT_MASK_FROM_ISR(). */
547 vPortRaiseBASEPRI();
548 {
549 /* Increment the RTOS tick. */
550 if( xTaskIncrementTick() != pdFALSE )
551 {
552 /* A context switch is required. Context switching is performed in
553 * the PendSV interrupt. Pend the PendSV interrupt. */
554 portNVIC_INT_CTRL_REG = portNVIC_PENDSVSET_BIT;
555 }
556 }
557
558 vPortClearBASEPRIFromISR();
559 }
560 /*-----------------------------------------------------------*/
561
562 #if ( configUSE_TICKLESS_IDLE == 1 )
563
vPortSuppressTicksAndSleep(TickType_t xExpectedIdleTime)564 __weak void vPortSuppressTicksAndSleep( TickType_t xExpectedIdleTime )
565 {
566 uint32_t ulReloadValue, ulCompleteTickPeriods, ulCompletedSysTickDecrements, ulSysTickDecrementsLeft;
567 TickType_t xModifiableIdleTime;
568
569 /* Make sure the SysTick reload value does not overflow the counter. */
570 if( xExpectedIdleTime > xMaximumPossibleSuppressedTicks )
571 {
572 xExpectedIdleTime = xMaximumPossibleSuppressedTicks;
573 }
574
575 /* Enter a critical section but don't use the taskENTER_CRITICAL()
576 * method as that will mask interrupts that should exit sleep mode. */
577 __disable_irq();
578 __dsb( portSY_FULL_READ_WRITE );
579 __isb( portSY_FULL_READ_WRITE );
580
581 /* If a context switch is pending or a task is waiting for the scheduler
582 * to be unsuspended then abandon the low power entry. */
583 if( eTaskConfirmSleepModeStatus() == eAbortSleep )
584 {
585 /* Re-enable interrupts - see comments above the __disable_irq()
586 * call above. */
587 __enable_irq();
588 }
589 else
590 {
591 /* Stop the SysTick momentarily. The time the SysTick is stopped for
592 * is accounted for as best it can be, but using the tickless mode will
593 * inevitably result in some tiny drift of the time maintained by the
594 * kernel with respect to calendar time. */
595 portNVIC_SYSTICK_CTRL_REG = ( portNVIC_SYSTICK_CLK_BIT_CONFIG | portNVIC_SYSTICK_INT_BIT );
596
597 /* Use the SysTick current-value register to determine the number of
598 * SysTick decrements remaining until the next tick interrupt. If the
599 * current-value register is zero, then there are actually
600 * ulTimerCountsForOneTick decrements remaining, not zero, because the
601 * SysTick requests the interrupt when decrementing from 1 to 0. */
602 ulSysTickDecrementsLeft = portNVIC_SYSTICK_CURRENT_VALUE_REG;
603
604 if( ulSysTickDecrementsLeft == 0 )
605 {
606 ulSysTickDecrementsLeft = ulTimerCountsForOneTick;
607 }
608
609 /* Calculate the reload value required to wait xExpectedIdleTime
610 * tick periods. -1 is used because this code normally executes part
611 * way through the first tick period. But if the SysTick IRQ is now
612 * pending, then clear the IRQ, suppressing the first tick, and correct
613 * the reload value to reflect that the second tick period is already
614 * underway. The expected idle time is always at least two ticks. */
615 ulReloadValue = ulSysTickDecrementsLeft + ( ulTimerCountsForOneTick * ( xExpectedIdleTime - 1UL ) );
616
617 if( ( portNVIC_INT_CTRL_REG & portNVIC_PEND_SYSTICK_SET_BIT ) != 0 )
618 {
619 portNVIC_INT_CTRL_REG = portNVIC_PEND_SYSTICK_CLEAR_BIT;
620 ulReloadValue -= ulTimerCountsForOneTick;
621 }
622
623 if( ulReloadValue > ulStoppedTimerCompensation )
624 {
625 ulReloadValue -= ulStoppedTimerCompensation;
626 }
627
628 /* Set the new reload value. */
629 portNVIC_SYSTICK_LOAD_REG = ulReloadValue;
630
631 /* Clear the SysTick count flag and set the count value back to
632 * zero. */
633 portNVIC_SYSTICK_CURRENT_VALUE_REG = 0UL;
634
635 /* Restart SysTick. */
636 portNVIC_SYSTICK_CTRL_REG |= portNVIC_SYSTICK_ENABLE_BIT;
637
638 /* Sleep until something happens. configPRE_SLEEP_PROCESSING() can
639 * set its parameter to 0 to indicate that its implementation contains
640 * its own wait for interrupt or wait for event instruction, and so wfi
641 * should not be executed again. However, the original expected idle
642 * time variable must remain unmodified, so a copy is taken. */
643 xModifiableIdleTime = xExpectedIdleTime;
644 configPRE_SLEEP_PROCESSING( xModifiableIdleTime );
645
646 if( xModifiableIdleTime > 0 )
647 {
648 __dsb( portSY_FULL_READ_WRITE );
649 __wfi();
650 __isb( portSY_FULL_READ_WRITE );
651 }
652
653 configPOST_SLEEP_PROCESSING( xExpectedIdleTime );
654
655 /* Re-enable interrupts to allow the interrupt that brought the MCU
656 * out of sleep mode to execute immediately. See comments above
657 * the __disable_irq() call above. */
658 __enable_irq();
659 __dsb( portSY_FULL_READ_WRITE );
660 __isb( portSY_FULL_READ_WRITE );
661
662 /* Disable interrupts again because the clock is about to be stopped
663 * and interrupts that execute while the clock is stopped will increase
664 * any slippage between the time maintained by the RTOS and calendar
665 * time. */
666 __disable_irq();
667 __dsb( portSY_FULL_READ_WRITE );
668 __isb( portSY_FULL_READ_WRITE );
669
670 /* Disable the SysTick clock without reading the
671 * portNVIC_SYSTICK_CTRL_REG register to ensure the
672 * portNVIC_SYSTICK_COUNT_FLAG_BIT is not cleared if it is set. Again,
673 * the time the SysTick is stopped for is accounted for as best it can
674 * be, but using the tickless mode will inevitably result in some tiny
675 * drift of the time maintained by the kernel with respect to calendar
676 * time*/
677 portNVIC_SYSTICK_CTRL_REG = ( portNVIC_SYSTICK_CLK_BIT_CONFIG | portNVIC_SYSTICK_INT_BIT );
678
679 /* Determine whether the SysTick has already counted to zero. */
680 if( ( portNVIC_SYSTICK_CTRL_REG & portNVIC_SYSTICK_COUNT_FLAG_BIT ) != 0 )
681 {
682 uint32_t ulCalculatedLoadValue;
683
684 /* The tick interrupt ended the sleep (or is now pending), and
685 * a new tick period has started. Reset portNVIC_SYSTICK_LOAD_REG
686 * with whatever remains of the new tick period. */
687 ulCalculatedLoadValue = ( ulTimerCountsForOneTick - 1UL ) - ( ulReloadValue - portNVIC_SYSTICK_CURRENT_VALUE_REG );
688
689 /* Don't allow a tiny value, or values that have somehow
690 * underflowed because the post sleep hook did something
691 * that took too long or because the SysTick current-value register
692 * is zero. */
693 if( ( ulCalculatedLoadValue <= ulStoppedTimerCompensation ) || ( ulCalculatedLoadValue > ulTimerCountsForOneTick ) )
694 {
695 ulCalculatedLoadValue = ( ulTimerCountsForOneTick - 1UL );
696 }
697
698 portNVIC_SYSTICK_LOAD_REG = ulCalculatedLoadValue;
699
700 /* As the pending tick will be processed as soon as this
701 * function exits, the tick value maintained by the tick is stepped
702 * forward by one less than the time spent waiting. */
703 ulCompleteTickPeriods = xExpectedIdleTime - 1UL;
704 }
705 else
706 {
707 /* Something other than the tick interrupt ended the sleep. */
708
709 /* Use the SysTick current-value register to determine the
710 * number of SysTick decrements remaining until the expected idle
711 * time would have ended. */
712 ulSysTickDecrementsLeft = portNVIC_SYSTICK_CURRENT_VALUE_REG;
713 #if ( portNVIC_SYSTICK_CLK_BIT_CONFIG != portNVIC_SYSTICK_CLK_BIT )
714 {
715 /* If the SysTick is not using the core clock, the current-
716 * value register might still be zero here. In that case, the
717 * SysTick didn't load from the reload register, and there are
718 * ulReloadValue decrements remaining in the expected idle
719 * time, not zero. */
720 if( ulSysTickDecrementsLeft == 0 )
721 {
722 ulSysTickDecrementsLeft = ulReloadValue;
723 }
724 }
725 #endif /* portNVIC_SYSTICK_CLK_BIT_CONFIG */
726
727 /* Work out how long the sleep lasted rounded to complete tick
728 * periods (not the ulReload value which accounted for part
729 * ticks). */
730 ulCompletedSysTickDecrements = ( xExpectedIdleTime * ulTimerCountsForOneTick ) - ulSysTickDecrementsLeft;
731
732 /* How many complete tick periods passed while the processor
733 * was waiting? */
734 ulCompleteTickPeriods = ulCompletedSysTickDecrements / ulTimerCountsForOneTick;
735
736 /* The reload value is set to whatever fraction of a single tick
737 * period remains. */
738 portNVIC_SYSTICK_LOAD_REG = ( ( ulCompleteTickPeriods + 1UL ) * ulTimerCountsForOneTick ) - ulCompletedSysTickDecrements;
739 }
740
741 /* Restart SysTick so it runs from portNVIC_SYSTICK_LOAD_REG again,
742 * then set portNVIC_SYSTICK_LOAD_REG back to its standard value. If
743 * the SysTick is not using the core clock, temporarily configure it to
744 * use the core clock. This configuration forces the SysTick to load
745 * from portNVIC_SYSTICK_LOAD_REG immediately instead of at the next
746 * cycle of the other clock. Then portNVIC_SYSTICK_LOAD_REG is ready
747 * to receive the standard value immediately. */
748 portNVIC_SYSTICK_CURRENT_VALUE_REG = 0UL;
749 portNVIC_SYSTICK_CTRL_REG = portNVIC_SYSTICK_CLK_BIT | portNVIC_SYSTICK_INT_BIT | portNVIC_SYSTICK_ENABLE_BIT;
750 #if ( portNVIC_SYSTICK_CLK_BIT_CONFIG == portNVIC_SYSTICK_CLK_BIT )
751 {
752 portNVIC_SYSTICK_LOAD_REG = ulTimerCountsForOneTick - 1UL;
753 }
754 #else
755 {
756 /* The temporary usage of the core clock has served its purpose,
757 * as described above. Resume usage of the other clock. */
758 portNVIC_SYSTICK_CTRL_REG = portNVIC_SYSTICK_CLK_BIT | portNVIC_SYSTICK_INT_BIT;
759
760 if( ( portNVIC_SYSTICK_CTRL_REG & portNVIC_SYSTICK_COUNT_FLAG_BIT ) != 0 )
761 {
762 /* The partial tick period already ended. Be sure the SysTick
763 * counts it only once. */
764 portNVIC_SYSTICK_CURRENT_VALUE_REG = 0;
765 }
766
767 portNVIC_SYSTICK_LOAD_REG = ulTimerCountsForOneTick - 1UL;
768 portNVIC_SYSTICK_CTRL_REG = portNVIC_SYSTICK_CLK_BIT_CONFIG | portNVIC_SYSTICK_INT_BIT | portNVIC_SYSTICK_ENABLE_BIT;
769 }
770 #endif /* portNVIC_SYSTICK_CLK_BIT_CONFIG */
771
772 /* Step the tick to account for any tick periods that elapsed. */
773 vTaskStepTick( ulCompleteTickPeriods );
774
775 /* Exit with interrupts enabled. */
776 __enable_irq();
777 }
778 }
779
780 #endif /* #if configUSE_TICKLESS_IDLE */
781
782 /*-----------------------------------------------------------*/
783
784 /*
785 * Setup the SysTick timer to generate the tick interrupts at the required
786 * frequency.
787 */
788 #if ( configOVERRIDE_DEFAULT_TICK_CONFIGURATION == 0 )
789
vPortSetupTimerInterrupt(void)790 __weak void vPortSetupTimerInterrupt( void )
791 {
792 /* Calculate the constants required to configure the tick interrupt. */
793 #if ( configUSE_TICKLESS_IDLE == 1 )
794 {
795 ulTimerCountsForOneTick = ( configSYSTICK_CLOCK_HZ / configTICK_RATE_HZ );
796 xMaximumPossibleSuppressedTicks = portMAX_24_BIT_NUMBER / ulTimerCountsForOneTick;
797 ulStoppedTimerCompensation = portMISSED_COUNTS_FACTOR / ( configCPU_CLOCK_HZ / configSYSTICK_CLOCK_HZ );
798 }
799 #endif /* configUSE_TICKLESS_IDLE */
800
801 /* Stop and clear the SysTick. */
802 portNVIC_SYSTICK_CTRL_REG = 0UL;
803 portNVIC_SYSTICK_CURRENT_VALUE_REG = 0UL;
804
805 /* Configure SysTick to interrupt at the requested rate. */
806 portNVIC_SYSTICK_LOAD_REG = ( configSYSTICK_CLOCK_HZ / configTICK_RATE_HZ ) - 1UL;
807 portNVIC_SYSTICK_CTRL_REG = ( portNVIC_SYSTICK_CLK_BIT_CONFIG | portNVIC_SYSTICK_INT_BIT | portNVIC_SYSTICK_ENABLE_BIT );
808 }
809
810 #endif /* configOVERRIDE_DEFAULT_TICK_CONFIGURATION */
811 /*-----------------------------------------------------------*/
812
vPortGetIPSR(void)813 __asm uint32_t vPortGetIPSR( void )
814 {
815 /* *INDENT-OFF* */
816 PRESERVE8
817
818 mrs r0, ipsr
819 bx r14
820 /* *INDENT-ON* */
821 }
822 /*-----------------------------------------------------------*/
823
824 #if ( configASSERT_DEFINED == 1 )
825
vPortValidateInterruptPriority(void)826 void vPortValidateInterruptPriority( void )
827 {
828 uint32_t ulCurrentInterrupt;
829 uint8_t ucCurrentPriority;
830
831 /* Obtain the number of the currently executing interrupt. */
832 ulCurrentInterrupt = vPortGetIPSR();
833
834 /* Is the interrupt number a user defined interrupt? */
835 if( ulCurrentInterrupt >= portFIRST_USER_INTERRUPT_NUMBER )
836 {
837 /* Look up the interrupt's priority. */
838 ucCurrentPriority = pcInterruptPriorityRegisters[ ulCurrentInterrupt ];
839
840 /* The following assertion will fail if a service routine (ISR) for
841 * an interrupt that has been assigned a priority above
842 * configMAX_SYSCALL_INTERRUPT_PRIORITY calls an ISR safe FreeRTOS API
843 * function. ISR safe FreeRTOS API functions must *only* be called
844 * from interrupts that have been assigned a priority at or below
845 * configMAX_SYSCALL_INTERRUPT_PRIORITY.
846 *
847 * Numerically low interrupt priority numbers represent logically high
848 * interrupt priorities, therefore the priority of the interrupt must
849 * be set to a value equal to or numerically *higher* than
850 * configMAX_SYSCALL_INTERRUPT_PRIORITY.
851 *
852 * Interrupts that use the FreeRTOS API must not be left at their
853 * default priority of zero as that is the highest possible priority,
854 * which is guaranteed to be above configMAX_SYSCALL_INTERRUPT_PRIORITY,
855 * and therefore also guaranteed to be invalid.
856 *
857 * FreeRTOS maintains separate thread and ISR API functions to ensure
858 * interrupt entry is as fast and simple as possible.
859 *
860 * The following links provide detailed information:
861 * https://www.FreeRTOS.org/RTOS-Cortex-M3-M4.html
862 * https://www.FreeRTOS.org/FAQHelp.html */
863 configASSERT( ucCurrentPriority >= ucMaxSysCallPriority );
864 }
865
866 /* Priority grouping: The interrupt controller (NVIC) allows the bits
867 * that define each interrupt's priority to be split between bits that
868 * define the interrupt's pre-emption priority bits and bits that define
869 * the interrupt's sub-priority. For simplicity all bits must be defined
870 * to be pre-emption priority bits. The following assertion will fail if
871 * this is not the case (if some bits represent a sub-priority).
872 *
873 * If the application only uses CMSIS libraries for interrupt
874 * configuration then the correct setting can be achieved on all Cortex-M
875 * devices by calling NVIC_SetPriorityGrouping( 0 ); before starting the
876 * scheduler. Note however that some vendor specific peripheral libraries
877 * assume a non-zero priority group setting, in which cases using a value
878 * of zero will result in unpredictable behaviour. */
879 configASSERT( ( portAIRCR_REG & portPRIORITY_GROUP_MASK ) <= ulMaxPRIGROUPValue );
880 }
881
882 #endif /* configASSERT_DEFINED */
883
