1 // SPDX-License-Identifier: GPL-2.0
2 // Copyright (C) 2016, Linaro Ltd - Daniel Lezcano <daniel.lezcano@linaro.org>
3 #define pr_fmt(fmt) "irq_timings: " fmt
4
5 #include <linux/kernel.h>
6 #include <linux/percpu.h>
7 #include <linux/slab.h>
8 #include <linux/static_key.h>
9 #include <linux/init.h>
10 #include <linux/interrupt.h>
11 #include <linux/idr.h>
12 #include <linux/irq.h>
13 #include <linux/math64.h>
14 #include <linux/log2.h>
15
16 #include <trace/events/irq.h>
17
18 #include "internals.h"
19
20 DEFINE_STATIC_KEY_FALSE(irq_timing_enabled);
21
22 DEFINE_PER_CPU(struct irq_timings, irq_timings);
23
24 static DEFINE_IDR(irqt_stats);
25
irq_timings_enable(void)26 void irq_timings_enable(void)
27 {
28 static_branch_enable(&irq_timing_enabled);
29 }
30
irq_timings_disable(void)31 void irq_timings_disable(void)
32 {
33 static_branch_disable(&irq_timing_enabled);
34 }
35
36 /*
37 * The main goal of this algorithm is to predict the next interrupt
38 * occurrence on the current CPU.
39 *
40 * Currently, the interrupt timings are stored in a circular array
41 * buffer every time there is an interrupt, as a tuple: the interrupt
42 * number and the associated timestamp when the event occurred <irq,
43 * timestamp>.
44 *
45 * For every interrupt occurring in a short period of time, we can
46 * measure the elapsed time between the occurrences for the same
47 * interrupt and we end up with a suite of intervals. The experience
48 * showed the interrupts are often coming following a periodic
49 * pattern.
50 *
51 * The objective of the algorithm is to find out this periodic pattern
52 * in a fastest way and use its period to predict the next irq event.
53 *
54 * When the next interrupt event is requested, we are in the situation
55 * where the interrupts are disabled and the circular buffer
56 * containing the timings is filled with the events which happened
57 * after the previous next-interrupt-event request.
58 *
59 * At this point, we read the circular buffer and we fill the irq
60 * related statistics structure. After this step, the circular array
61 * containing the timings is empty because all the values are
62 * dispatched in their corresponding buffers.
63 *
64 * Now for each interrupt, we can predict the next event by using the
65 * suffix array, log interval and exponential moving average
66 *
67 * 1. Suffix array
68 *
69 * Suffix array is an array of all the suffixes of a string. It is
70 * widely used as a data structure for compression, text search, ...
71 * For instance for the word 'banana', the suffixes will be: 'banana'
72 * 'anana' 'nana' 'ana' 'na' 'a'
73 *
74 * Usually, the suffix array is sorted but for our purpose it is
75 * not necessary and won't provide any improvement in the context of
76 * the solved problem where we clearly define the boundaries of the
77 * search by a max period and min period.
78 *
79 * The suffix array will build a suite of intervals of different
80 * length and will look for the repetition of each suite. If the suite
81 * is repeating then we have the period because it is the length of
82 * the suite whatever its position in the buffer.
83 *
84 * 2. Log interval
85 *
86 * We saw the irq timings allow to compute the interval of the
87 * occurrences for a specific interrupt. We can reasonably assume the
88 * longer is the interval, the higher is the error for the next event
89 * and we can consider storing those interval values into an array
90 * where each slot in the array correspond to an interval at the power
91 * of 2 of the index. For example, index 12 will contain values
92 * between 2^11 and 2^12.
93 *
94 * At the end we have an array of values where at each index defines a
95 * [2^index - 1, 2 ^ index] interval values allowing to store a large
96 * number of values inside a small array.
97 *
98 * For example, if we have the value 1123, then we store it at
99 * ilog2(1123) = 10 index value.
100 *
101 * Storing those value at the specific index is done by computing an
102 * exponential moving average for this specific slot. For instance,
103 * for values 1800, 1123, 1453, ... fall under the same slot (10) and
104 * the exponential moving average is computed every time a new value
105 * is stored at this slot.
106 *
107 * 3. Exponential Moving Average
108 *
109 * The EMA is largely used to track a signal for stocks or as a low
110 * pass filter. The magic of the formula, is it is very simple and the
111 * reactivity of the average can be tuned with the factors called
112 * alpha.
113 *
114 * The higher the alphas are, the faster the average respond to the
115 * signal change. In our case, if a slot in the array is a big
116 * interval, we can have numbers with a big difference between
117 * them. The impact of those differences in the average computation
118 * can be tuned by changing the alpha value.
119 *
120 *
121 * -- The algorithm --
122 *
123 * We saw the different processing above, now let's see how they are
124 * used together.
125 *
126 * For each interrupt:
127 * For each interval:
128 * Compute the index = ilog2(interval)
129 * Compute a new_ema(buffer[index], interval)
130 * Store the index in a circular buffer
131 *
132 * Compute the suffix array of the indexes
133 *
134 * For each suffix:
135 * If the suffix is reverse-found 3 times
136 * Return suffix
137 *
138 * Return Not found
139 *
140 * However we can not have endless suffix array to be build, it won't
141 * make sense and it will add an extra overhead, so we can restrict
142 * this to a maximum suffix length of 5 and a minimum suffix length of
143 * 2. The experience showed 5 is the majority of the maximum pattern
144 * period found for different devices.
145 *
146 * The result is a pattern finding less than 1us for an interrupt.
147 *
148 * Example based on real values:
149 *
150 * Example 1 : MMC write/read interrupt interval:
151 *
152 * 223947, 1240, 1384, 1386, 1386,
153 * 217416, 1236, 1384, 1386, 1387,
154 * 214719, 1241, 1386, 1387, 1384,
155 * 213696, 1234, 1384, 1386, 1388,
156 * 219904, 1240, 1385, 1389, 1385,
157 * 212240, 1240, 1386, 1386, 1386,
158 * 214415, 1236, 1384, 1386, 1387,
159 * 214276, 1234, 1384, 1388, ?
160 *
161 * For each element, apply ilog2(value)
162 *
163 * 15, 8, 8, 8, 8,
164 * 15, 8, 8, 8, 8,
165 * 15, 8, 8, 8, 8,
166 * 15, 8, 8, 8, 8,
167 * 15, 8, 8, 8, 8,
168 * 15, 8, 8, 8, 8,
169 * 15, 8, 8, 8, 8,
170 * 15, 8, 8, 8, ?
171 *
172 * Max period of 5, we take the last (max_period * 3) 15 elements as
173 * we can be confident if the pattern repeats itself three times it is
174 * a repeating pattern.
175 *
176 * 8,
177 * 15, 8, 8, 8, 8,
178 * 15, 8, 8, 8, 8,
179 * 15, 8, 8, 8, ?
180 *
181 * Suffixes are:
182 *
183 * 1) 8, 15, 8, 8, 8 <- max period
184 * 2) 8, 15, 8, 8
185 * 3) 8, 15, 8
186 * 4) 8, 15 <- min period
187 *
188 * From there we search the repeating pattern for each suffix.
189 *
190 * buffer: 8, 15, 8, 8, 8, 8, 15, 8, 8, 8, 8, 15, 8, 8, 8
191 * | | | | | | | | | | | | | | |
192 * 8, 15, 8, 8, 8 | | | | | | | | | |
193 * 8, 15, 8, 8, 8 | | | | |
194 * 8, 15, 8, 8, 8
195 *
196 * When moving the suffix, we found exactly 3 matches.
197 *
198 * The first suffix with period 5 is repeating.
199 *
200 * The next event is (3 * max_period) % suffix_period
201 *
202 * In this example, the result 0, so the next event is suffix[0] => 8
203 *
204 * However, 8 is the index in the array of exponential moving average
205 * which was calculated on the fly when storing the values, so the
206 * interval is ema[8] = 1366
207 *
208 *
209 * Example 2:
210 *
211 * 4, 3, 5, 100,
212 * 3, 3, 5, 117,
213 * 4, 4, 5, 112,
214 * 4, 3, 4, 110,
215 * 3, 5, 3, 117,
216 * 4, 4, 5, 112,
217 * 4, 3, 4, 110,
218 * 3, 4, 5, 112,
219 * 4, 3, 4, 110
220 *
221 * ilog2
222 *
223 * 0, 0, 0, 4,
224 * 0, 0, 0, 4,
225 * 0, 0, 0, 4,
226 * 0, 0, 0, 4,
227 * 0, 0, 0, 4,
228 * 0, 0, 0, 4,
229 * 0, 0, 0, 4,
230 * 0, 0, 0, 4,
231 * 0, 0, 0, 4
232 *
233 * Max period 5:
234 * 0, 0, 4,
235 * 0, 0, 0, 4,
236 * 0, 0, 0, 4,
237 * 0, 0, 0, 4
238 *
239 * Suffixes:
240 *
241 * 1) 0, 0, 4, 0, 0
242 * 2) 0, 0, 4, 0
243 * 3) 0, 0, 4
244 * 4) 0, 0
245 *
246 * buffer: 0, 0, 4, 0, 0, 0, 4, 0, 0, 0, 4, 0, 0, 0, 4
247 * | | | | | | X
248 * 0, 0, 4, 0, 0, | X
249 * 0, 0
250 *
251 * buffer: 0, 0, 4, 0, 0, 0, 4, 0, 0, 0, 4, 0, 0, 0, 4
252 * | | | | | | | | | | | | | | |
253 * 0, 0, 4, 0, | | | | | | | | | | |
254 * 0, 0, 4, 0, | | | | | | |
255 * 0, 0, 4, 0, | | |
256 * 0 0 4
257 *
258 * Pattern is found 3 times, the remaining is 1 which results from
259 * (max_period * 3) % suffix_period. This value is the index in the
260 * suffix arrays. The suffix array for a period 4 has the value 4
261 * at index 1.
262 */
263 #define EMA_ALPHA_VAL 64
264 #define EMA_ALPHA_SHIFT 7
265
266 #define PREDICTION_PERIOD_MIN 3
267 #define PREDICTION_PERIOD_MAX 5
268 #define PREDICTION_FACTOR 4
269 #define PREDICTION_MAX 10 /* 2 ^ PREDICTION_MAX useconds */
270 #define PREDICTION_BUFFER_SIZE 16 /* slots for EMAs, hardly more than 16 */
271
272 /*
273 * Number of elements in the circular buffer: If it happens it was
274 * flushed before, then the number of elements could be smaller than
275 * IRQ_TIMINGS_SIZE, so the count is used, otherwise the array size is
276 * used as we wrapped. The index begins from zero when we did not
277 * wrap. That could be done in a nicer way with the proper circular
278 * array structure type but with the cost of extra computation in the
279 * interrupt handler hot path. We choose efficiency.
280 */
281 #define for_each_irqts(i, irqts) \
282 for (i = irqts->count < IRQ_TIMINGS_SIZE ? \
283 0 : irqts->count & IRQ_TIMINGS_MASK, \
284 irqts->count = min(IRQ_TIMINGS_SIZE, \
285 irqts->count); \
286 irqts->count > 0; irqts->count--, \
287 i = (i + 1) & IRQ_TIMINGS_MASK)
288
289 struct irqt_stat {
290 u64 last_ts;
291 u64 ema_time[PREDICTION_BUFFER_SIZE];
292 int timings[IRQ_TIMINGS_SIZE];
293 int circ_timings[IRQ_TIMINGS_SIZE];
294 int count;
295 };
296
297 /*
298 * Exponential moving average computation
299 */
irq_timings_ema_new(u64 value,u64 ema_old)300 static u64 irq_timings_ema_new(u64 value, u64 ema_old)
301 {
302 s64 diff;
303
304 if (unlikely(!ema_old))
305 return value;
306
307 diff = (value - ema_old) * EMA_ALPHA_VAL;
308 /*
309 * We can use a s64 type variable to be added with the u64
310 * ema_old variable as this one will never have its topmost
311 * bit set, it will be always smaller than 2^63 nanosec
312 * interrupt interval (292 years).
313 */
314 return ema_old + (diff >> EMA_ALPHA_SHIFT);
315 }
316
irq_timings_next_event_index(int * buffer,size_t len,int period_max)317 static int irq_timings_next_event_index(int *buffer, size_t len, int period_max)
318 {
319 int period;
320
321 /*
322 * Move the beginning pointer to the end minus the max period x 3.
323 * We are at the point we can begin searching the pattern
324 */
325 buffer = &buffer[len - (period_max * 3)];
326
327 /* Adjust the length to the maximum allowed period x 3 */
328 len = period_max * 3;
329
330 /*
331 * The buffer contains the suite of intervals, in a ilog2
332 * basis, we are looking for a repetition. We point the
333 * beginning of the search three times the length of the
334 * period beginning at the end of the buffer. We do that for
335 * each suffix.
336 */
337 for (period = period_max; period >= PREDICTION_PERIOD_MIN; period--) {
338
339 /*
340 * The first comparison always succeed because the
341 * suffix is deduced from the first n-period bytes of
342 * the buffer and we compare the initial suffix with
343 * itself, so we can skip the first iteration.
344 */
345 int idx = period;
346 size_t size = period;
347
348 /*
349 * We look if the suite with period 'i' repeat
350 * itself. If it is truncated at the end, as it
351 * repeats we can use the period to find out the next
352 * element with the modulo.
353 */
354 while (!memcmp(buffer, &buffer[idx], size * sizeof(int))) {
355
356 /*
357 * Move the index in a period basis
358 */
359 idx += size;
360
361 /*
362 * If this condition is reached, all previous
363 * memcmp were successful, so the period is
364 * found.
365 */
366 if (idx == len)
367 return buffer[len % period];
368
369 /*
370 * If the remaining elements to compare are
371 * smaller than the period, readjust the size
372 * of the comparison for the last iteration.
373 */
374 if (len - idx < period)
375 size = len - idx;
376 }
377 }
378
379 return -1;
380 }
381
__irq_timings_next_event(struct irqt_stat * irqs,int irq,u64 now)382 static u64 __irq_timings_next_event(struct irqt_stat *irqs, int irq, u64 now)
383 {
384 int index, i, period_max, count, start, min = INT_MAX;
385
386 if ((now - irqs->last_ts) >= NSEC_PER_SEC) {
387 irqs->count = irqs->last_ts = 0;
388 return U64_MAX;
389 }
390
391 /*
392 * As we want to find three times the repetition, we need a
393 * number of intervals greater or equal to three times the
394 * maximum period, otherwise we truncate the max period.
395 */
396 period_max = irqs->count > (3 * PREDICTION_PERIOD_MAX) ?
397 PREDICTION_PERIOD_MAX : irqs->count / 3;
398
399 /*
400 * If we don't have enough irq timings for this prediction,
401 * just bail out.
402 */
403 if (period_max <= PREDICTION_PERIOD_MIN)
404 return U64_MAX;
405
406 /*
407 * 'count' will depends if the circular buffer wrapped or not
408 */
409 count = irqs->count < IRQ_TIMINGS_SIZE ?
410 irqs->count : IRQ_TIMINGS_SIZE;
411
412 start = irqs->count < IRQ_TIMINGS_SIZE ?
413 0 : (irqs->count & IRQ_TIMINGS_MASK);
414
415 /*
416 * Copy the content of the circular buffer into another buffer
417 * in order to linearize the buffer instead of dealing with
418 * wrapping indexes and shifted array which will be prone to
419 * error and extremely difficult to debug.
420 */
421 for (i = 0; i < count; i++) {
422 int index = (start + i) & IRQ_TIMINGS_MASK;
423
424 irqs->timings[i] = irqs->circ_timings[index];
425 min = min_t(int, irqs->timings[i], min);
426 }
427
428 index = irq_timings_next_event_index(irqs->timings, count, period_max);
429 if (index < 0)
430 return irqs->last_ts + irqs->ema_time[min];
431
432 return irqs->last_ts + irqs->ema_time[index];
433 }
434
irq_timings_interval_index(u64 interval)435 static __always_inline int irq_timings_interval_index(u64 interval)
436 {
437 /*
438 * The PREDICTION_FACTOR increase the interval size for the
439 * array of exponential average.
440 */
441 u64 interval_us = (interval >> 10) / PREDICTION_FACTOR;
442
443 return likely(interval_us) ? ilog2(interval_us) : 0;
444 }
445
__irq_timings_store(int irq,struct irqt_stat * irqs,u64 interval)446 static __always_inline void __irq_timings_store(int irq, struct irqt_stat *irqs,
447 u64 interval)
448 {
449 int index;
450
451 /*
452 * Get the index in the ema table for this interrupt.
453 */
454 index = irq_timings_interval_index(interval);
455
456 if (index > PREDICTION_BUFFER_SIZE - 1) {
457 irqs->count = 0;
458 return;
459 }
460
461 /*
462 * Store the index as an element of the pattern in another
463 * circular array.
464 */
465 irqs->circ_timings[irqs->count & IRQ_TIMINGS_MASK] = index;
466
467 irqs->ema_time[index] = irq_timings_ema_new(interval,
468 irqs->ema_time[index]);
469
470 irqs->count++;
471 }
472
irq_timings_store(int irq,struct irqt_stat * irqs,u64 ts)473 static inline void irq_timings_store(int irq, struct irqt_stat *irqs, u64 ts)
474 {
475 u64 old_ts = irqs->last_ts;
476 u64 interval;
477
478 /*
479 * The timestamps are absolute time values, we need to compute
480 * the timing interval between two interrupts.
481 */
482 irqs->last_ts = ts;
483
484 /*
485 * The interval type is u64 in order to deal with the same
486 * type in our computation, that prevent mindfuck issues with
487 * overflow, sign and division.
488 */
489 interval = ts - old_ts;
490
491 /*
492 * The interrupt triggered more than one second apart, that
493 * ends the sequence as predictable for our purpose. In this
494 * case, assume we have the beginning of a sequence and the
495 * timestamp is the first value. As it is impossible to
496 * predict anything at this point, return.
497 *
498 * Note the first timestamp of the sequence will always fall
499 * in this test because the old_ts is zero. That is what we
500 * want as we need another timestamp to compute an interval.
501 */
502 if (interval >= NSEC_PER_SEC) {
503 irqs->count = 0;
504 return;
505 }
506
507 __irq_timings_store(irq, irqs, interval);
508 }
509
510 /**
511 * irq_timings_next_event - Return when the next event is supposed to arrive
512 *
513 * During the last busy cycle, the number of interrupts is incremented
514 * and stored in the irq_timings structure. This information is
515 * necessary to:
516 *
517 * - know if the index in the table wrapped up:
518 *
519 * If more than the array size interrupts happened during the
520 * last busy/idle cycle, the index wrapped up and we have to
521 * begin with the next element in the array which is the last one
522 * in the sequence, otherwise it is at the index 0.
523 *
524 * - have an indication of the interrupts activity on this CPU
525 * (eg. irq/sec)
526 *
527 * The values are 'consumed' after inserting in the statistical model,
528 * thus the count is reinitialized.
529 *
530 * The array of values **must** be browsed in the time direction, the
531 * timestamp must increase between an element and the next one.
532 *
533 * Returns a nanosec time based estimation of the earliest interrupt,
534 * U64_MAX otherwise.
535 */
irq_timings_next_event(u64 now)536 u64 irq_timings_next_event(u64 now)
537 {
538 struct irq_timings *irqts = this_cpu_ptr(&irq_timings);
539 struct irqt_stat *irqs;
540 struct irqt_stat __percpu *s;
541 u64 ts, next_evt = U64_MAX;
542 int i, irq = 0;
543
544 /*
545 * This function must be called with the local irq disabled in
546 * order to prevent the timings circular buffer to be updated
547 * while we are reading it.
548 */
549 lockdep_assert_irqs_disabled();
550
551 if (!irqts->count)
552 return next_evt;
553
554 /*
555 * Number of elements in the circular buffer: If it happens it
556 * was flushed before, then the number of elements could be
557 * smaller than IRQ_TIMINGS_SIZE, so the count is used,
558 * otherwise the array size is used as we wrapped. The index
559 * begins from zero when we did not wrap. That could be done
560 * in a nicer way with the proper circular array structure
561 * type but with the cost of extra computation in the
562 * interrupt handler hot path. We choose efficiency.
563 *
564 * Inject measured irq/timestamp to the pattern prediction
565 * model while decrementing the counter because we consume the
566 * data from our circular buffer.
567 */
568 for_each_irqts(i, irqts) {
569 irq = irq_timing_decode(irqts->values[i], &ts);
570 s = idr_find(&irqt_stats, irq);
571 if (s)
572 irq_timings_store(irq, this_cpu_ptr(s), ts);
573 }
574
575 /*
576 * Look in the list of interrupts' statistics, the earliest
577 * next event.
578 */
579 idr_for_each_entry(&irqt_stats, s, i) {
580
581 irqs = this_cpu_ptr(s);
582
583 ts = __irq_timings_next_event(irqs, i, now);
584 if (ts <= now)
585 return now;
586
587 if (ts < next_evt)
588 next_evt = ts;
589 }
590
591 return next_evt;
592 }
593
irq_timings_free(int irq)594 void irq_timings_free(int irq)
595 {
596 struct irqt_stat __percpu *s;
597
598 s = idr_find(&irqt_stats, irq);
599 if (s) {
600 free_percpu(s);
601 idr_remove(&irqt_stats, irq);
602 }
603 }
604
irq_timings_alloc(int irq)605 int irq_timings_alloc(int irq)
606 {
607 struct irqt_stat __percpu *s;
608 int id;
609
610 /*
611 * Some platforms can have the same private interrupt per cpu,
612 * so this function may be called several times with the
613 * same interrupt number. Just bail out in case the per cpu
614 * stat structure is already allocated.
615 */
616 s = idr_find(&irqt_stats, irq);
617 if (s)
618 return 0;
619
620 s = alloc_percpu(*s);
621 if (!s)
622 return -ENOMEM;
623
624 idr_preload(GFP_KERNEL);
625 id = idr_alloc(&irqt_stats, s, irq, irq + 1, GFP_NOWAIT);
626 idr_preload_end();
627
628 if (id < 0) {
629 free_percpu(s);
630 return id;
631 }
632
633 return 0;
634 }
635
636 #ifdef CONFIG_TEST_IRQ_TIMINGS
637 struct timings_intervals {
638 u64 *intervals;
639 size_t count;
640 };
641
642 /*
643 * Intervals are given in nanosecond base
644 */
645 static u64 intervals0[] __initdata = {
646 10000, 50000, 200000, 500000,
647 10000, 50000, 200000, 500000,
648 10000, 50000, 200000, 500000,
649 10000, 50000, 200000, 500000,
650 10000, 50000, 200000, 500000,
651 10000, 50000, 200000, 500000,
652 10000, 50000, 200000, 500000,
653 10000, 50000, 200000, 500000,
654 10000, 50000, 200000,
655 };
656
657 static u64 intervals1[] __initdata = {
658 223947000, 1240000, 1384000, 1386000, 1386000,
659 217416000, 1236000, 1384000, 1386000, 1387000,
660 214719000, 1241000, 1386000, 1387000, 1384000,
661 213696000, 1234000, 1384000, 1386000, 1388000,
662 219904000, 1240000, 1385000, 1389000, 1385000,
663 212240000, 1240000, 1386000, 1386000, 1386000,
664 214415000, 1236000, 1384000, 1386000, 1387000,
665 214276000, 1234000,
666 };
667
668 static u64 intervals2[] __initdata = {
669 4000, 3000, 5000, 100000,
670 3000, 3000, 5000, 117000,
671 4000, 4000, 5000, 112000,
672 4000, 3000, 4000, 110000,
673 3000, 5000, 3000, 117000,
674 4000, 4000, 5000, 112000,
675 4000, 3000, 4000, 110000,
676 3000, 4000, 5000, 112000,
677 4000,
678 };
679
680 static u64 intervals3[] __initdata = {
681 1385000, 212240000, 1240000,
682 1386000, 214415000, 1236000,
683 1384000, 214276000, 1234000,
684 1386000, 214415000, 1236000,
685 1385000, 212240000, 1240000,
686 1386000, 214415000, 1236000,
687 1384000, 214276000, 1234000,
688 1386000, 214415000, 1236000,
689 1385000, 212240000, 1240000,
690 };
691
692 static u64 intervals4[] __initdata = {
693 10000, 50000, 10000, 50000,
694 10000, 50000, 10000, 50000,
695 10000, 50000, 10000, 50000,
696 10000, 50000, 10000, 50000,
697 10000, 50000, 10000, 50000,
698 10000, 50000, 10000, 50000,
699 10000, 50000, 10000, 50000,
700 10000, 50000, 10000, 50000,
701 10000,
702 };
703
704 static struct timings_intervals tis[] __initdata = {
705 { intervals0, ARRAY_SIZE(intervals0) },
706 { intervals1, ARRAY_SIZE(intervals1) },
707 { intervals2, ARRAY_SIZE(intervals2) },
708 { intervals3, ARRAY_SIZE(intervals3) },
709 { intervals4, ARRAY_SIZE(intervals4) },
710 };
711
irq_timings_test_next_index(struct timings_intervals * ti)712 static int __init irq_timings_test_next_index(struct timings_intervals *ti)
713 {
714 int _buffer[IRQ_TIMINGS_SIZE];
715 int buffer[IRQ_TIMINGS_SIZE];
716 int index, start, i, count, period_max;
717
718 count = ti->count - 1;
719
720 period_max = count > (3 * PREDICTION_PERIOD_MAX) ?
721 PREDICTION_PERIOD_MAX : count / 3;
722
723 /*
724 * Inject all values except the last one which will be used
725 * to compare with the next index result.
726 */
727 pr_debug("index suite: ");
728
729 for (i = 0; i < count; i++) {
730 index = irq_timings_interval_index(ti->intervals[i]);
731 _buffer[i & IRQ_TIMINGS_MASK] = index;
732 pr_cont("%d ", index);
733 }
734
735 start = count < IRQ_TIMINGS_SIZE ? 0 :
736 count & IRQ_TIMINGS_MASK;
737
738 count = min_t(int, count, IRQ_TIMINGS_SIZE);
739
740 for (i = 0; i < count; i++) {
741 int index = (start + i) & IRQ_TIMINGS_MASK;
742 buffer[i] = _buffer[index];
743 }
744
745 index = irq_timings_next_event_index(buffer, count, period_max);
746 i = irq_timings_interval_index(ti->intervals[ti->count - 1]);
747
748 if (index != i) {
749 pr_err("Expected (%d) and computed (%d) next indexes differ\n",
750 i, index);
751 return -EINVAL;
752 }
753
754 return 0;
755 }
756
irq_timings_next_index_selftest(void)757 static int __init irq_timings_next_index_selftest(void)
758 {
759 int i, ret;
760
761 for (i = 0; i < ARRAY_SIZE(tis); i++) {
762
763 pr_info("---> Injecting intervals number #%d (count=%zd)\n",
764 i, tis[i].count);
765
766 ret = irq_timings_test_next_index(&tis[i]);
767 if (ret)
768 break;
769 }
770
771 return ret;
772 }
773
irq_timings_test_irqs(struct timings_intervals * ti)774 static int __init irq_timings_test_irqs(struct timings_intervals *ti)
775 {
776 struct irqt_stat __percpu *s;
777 struct irqt_stat *irqs;
778 int i, index, ret, irq = 0xACE5;
779
780 ret = irq_timings_alloc(irq);
781 if (ret) {
782 pr_err("Failed to allocate irq timings\n");
783 return ret;
784 }
785
786 s = idr_find(&irqt_stats, irq);
787 if (!s) {
788 ret = -EIDRM;
789 goto out;
790 }
791
792 irqs = this_cpu_ptr(s);
793
794 for (i = 0; i < ti->count; i++) {
795
796 index = irq_timings_interval_index(ti->intervals[i]);
797 pr_debug("%d: interval=%llu ema_index=%d\n",
798 i, ti->intervals[i], index);
799
800 __irq_timings_store(irq, irqs, ti->intervals[i]);
801 if (irqs->circ_timings[i & IRQ_TIMINGS_MASK] != index) {
802 ret = -EBADSLT;
803 pr_err("Failed to store in the circular buffer\n");
804 goto out;
805 }
806 }
807
808 if (irqs->count != ti->count) {
809 ret = -ERANGE;
810 pr_err("Count differs\n");
811 goto out;
812 }
813
814 ret = 0;
815 out:
816 irq_timings_free(irq);
817
818 return ret;
819 }
820
irq_timings_irqs_selftest(void)821 static int __init irq_timings_irqs_selftest(void)
822 {
823 int i, ret;
824
825 for (i = 0; i < ARRAY_SIZE(tis); i++) {
826 pr_info("---> Injecting intervals number #%d (count=%zd)\n",
827 i, tis[i].count);
828 ret = irq_timings_test_irqs(&tis[i]);
829 if (ret)
830 break;
831 }
832
833 return ret;
834 }
835
irq_timings_test_irqts(struct irq_timings * irqts,unsigned count)836 static int __init irq_timings_test_irqts(struct irq_timings *irqts,
837 unsigned count)
838 {
839 int start = count >= IRQ_TIMINGS_SIZE ? count - IRQ_TIMINGS_SIZE : 0;
840 int i, irq, oirq = 0xBEEF;
841 u64 ots = 0xDEAD, ts;
842
843 /*
844 * Fill the circular buffer by using the dedicated function.
845 */
846 for (i = 0; i < count; i++) {
847 pr_debug("%d: index=%d, ts=%llX irq=%X\n",
848 i, i & IRQ_TIMINGS_MASK, ots + i, oirq + i);
849
850 irq_timings_push(ots + i, oirq + i);
851 }
852
853 /*
854 * Compute the first elements values after the index wrapped
855 * up or not.
856 */
857 ots += start;
858 oirq += start;
859
860 /*
861 * Test the circular buffer count is correct.
862 */
863 pr_debug("---> Checking timings array count (%d) is right\n", count);
864 if (WARN_ON(irqts->count != count))
865 return -EINVAL;
866
867 /*
868 * Test the macro allowing to browse all the irqts.
869 */
870 pr_debug("---> Checking the for_each_irqts() macro\n");
871 for_each_irqts(i, irqts) {
872
873 irq = irq_timing_decode(irqts->values[i], &ts);
874
875 pr_debug("index=%d, ts=%llX / %llX, irq=%X / %X\n",
876 i, ts, ots, irq, oirq);
877
878 if (WARN_ON(ts != ots || irq != oirq))
879 return -EINVAL;
880
881 ots++; oirq++;
882 }
883
884 /*
885 * The circular buffer should have be flushed when browsed
886 * with for_each_irqts
887 */
888 pr_debug("---> Checking timings array is empty after browsing it\n");
889 if (WARN_ON(irqts->count))
890 return -EINVAL;
891
892 return 0;
893 }
894
irq_timings_irqts_selftest(void)895 static int __init irq_timings_irqts_selftest(void)
896 {
897 struct irq_timings *irqts = this_cpu_ptr(&irq_timings);
898 int i, ret;
899
900 /*
901 * Test the circular buffer with different number of
902 * elements. The purpose is to test at the limits (empty, half
903 * full, full, wrapped with the cursor at the boundaries,
904 * wrapped several times, etc ...
905 */
906 int count[] = { 0,
907 IRQ_TIMINGS_SIZE >> 1,
908 IRQ_TIMINGS_SIZE,
909 IRQ_TIMINGS_SIZE + (IRQ_TIMINGS_SIZE >> 1),
910 2 * IRQ_TIMINGS_SIZE,
911 (2 * IRQ_TIMINGS_SIZE) + 3,
912 };
913
914 for (i = 0; i < ARRAY_SIZE(count); i++) {
915
916 pr_info("---> Checking the timings with %d/%d values\n",
917 count[i], IRQ_TIMINGS_SIZE);
918
919 ret = irq_timings_test_irqts(irqts, count[i]);
920 if (ret)
921 break;
922 }
923
924 return ret;
925 }
926
irq_timings_selftest(void)927 static int __init irq_timings_selftest(void)
928 {
929 int ret;
930
931 pr_info("------------------- selftest start -----------------\n");
932
933 /*
934 * At this point, we don't except any subsystem to use the irq
935 * timings but us, so it should not be enabled.
936 */
937 if (static_branch_unlikely(&irq_timing_enabled)) {
938 pr_warn("irq timings already initialized, skipping selftest\n");
939 return 0;
940 }
941
942 ret = irq_timings_irqts_selftest();
943 if (ret)
944 goto out;
945
946 ret = irq_timings_irqs_selftest();
947 if (ret)
948 goto out;
949
950 ret = irq_timings_next_index_selftest();
951 out:
952 pr_info("---------- selftest end with %s -----------\n",
953 ret ? "failure" : "success");
954
955 return ret;
956 }
957 early_initcall(irq_timings_selftest);
958 #endif
959