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 26 void irq_timings_enable(void) 27 { 28 static_branch_enable(&irq_timing_enabled); 29 } 30 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 */ 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 } 316 317 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 } 381 382 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 } 434 435 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 } 445 446 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 } 472 473 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 */ 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 } 593 594 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 } 604 605 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 }; 711 712 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 } 756 757 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 } 773 774 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 } 820 821 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 } 835 836 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 } 894 895 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 } 926 927 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