1 // SPDX-License-Identifier: GPL-2.0+ 2 /* 3 * This file contains the functions which manage clocksource drivers. 4 * 5 * Copyright (C) 2004, 2005 IBM, John Stultz (johnstul@us.ibm.com) 6 */ 7 8 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 9 10 #include <linux/device.h> 11 #include <linux/clocksource.h> 12 #include <linux/init.h> 13 #include <linux/module.h> 14 #include <linux/sched.h> /* for spin_unlock_irq() using preempt_count() m68k */ 15 #include <linux/tick.h> 16 #include <linux/kthread.h> 17 #include <linux/prandom.h> 18 #include <linux/cpu.h> 19 20 #include "tick-internal.h" 21 #include "timekeeping_internal.h" 22 23 /** 24 * clocks_calc_mult_shift - calculate mult/shift factors for scaled math of clocks 25 * @mult: pointer to mult variable 26 * @shift: pointer to shift variable 27 * @from: frequency to convert from 28 * @to: frequency to convert to 29 * @maxsec: guaranteed runtime conversion range in seconds 30 * 31 * The function evaluates the shift/mult pair for the scaled math 32 * operations of clocksources and clockevents. 33 * 34 * @to and @from are frequency values in HZ. For clock sources @to is 35 * NSEC_PER_SEC == 1GHz and @from is the counter frequency. For clock 36 * event @to is the counter frequency and @from is NSEC_PER_SEC. 37 * 38 * The @maxsec conversion range argument controls the time frame in 39 * seconds which must be covered by the runtime conversion with the 40 * calculated mult and shift factors. This guarantees that no 64bit 41 * overflow happens when the input value of the conversion is 42 * multiplied with the calculated mult factor. Larger ranges may 43 * reduce the conversion accuracy by choosing smaller mult and shift 44 * factors. 45 */ 46 void 47 clocks_calc_mult_shift(u32 *mult, u32 *shift, u32 from, u32 to, u32 maxsec) 48 { 49 u64 tmp; 50 u32 sft, sftacc= 32; 51 52 /* 53 * Calculate the shift factor which is limiting the conversion 54 * range: 55 */ 56 tmp = ((u64)maxsec * from) >> 32; 57 while (tmp) { 58 tmp >>=1; 59 sftacc--; 60 } 61 62 /* 63 * Find the conversion shift/mult pair which has the best 64 * accuracy and fits the maxsec conversion range: 65 */ 66 for (sft = 32; sft > 0; sft--) { 67 tmp = (u64) to << sft; 68 tmp += from / 2; 69 do_div(tmp, from); 70 if ((tmp >> sftacc) == 0) 71 break; 72 } 73 *mult = tmp; 74 *shift = sft; 75 } 76 EXPORT_SYMBOL_GPL(clocks_calc_mult_shift); 77 78 /*[Clocksource internal variables]--------- 79 * curr_clocksource: 80 * currently selected clocksource. 81 * suspend_clocksource: 82 * used to calculate the suspend time. 83 * clocksource_list: 84 * linked list with the registered clocksources 85 * clocksource_mutex: 86 * protects manipulations to curr_clocksource and the clocksource_list 87 * override_name: 88 * Name of the user-specified clocksource. 89 */ 90 static struct clocksource *curr_clocksource; 91 static struct clocksource *suspend_clocksource; 92 static LIST_HEAD(clocksource_list); 93 static DEFINE_MUTEX(clocksource_mutex); 94 static char override_name[CS_NAME_LEN]; 95 static int finished_booting; 96 static u64 suspend_start; 97 98 /* 99 * Threshold: 0.0312s, when doubled: 0.0625s. 100 * Also a default for cs->uncertainty_margin when registering clocks. 101 */ 102 #define WATCHDOG_THRESHOLD (NSEC_PER_SEC >> 5) 103 104 /* 105 * Maximum permissible delay between two readouts of the watchdog 106 * clocksource surrounding a read of the clocksource being validated. 107 * This delay could be due to SMIs, NMIs, or to VCPU preemptions. Used as 108 * a lower bound for cs->uncertainty_margin values when registering clocks. 109 */ 110 #ifdef CONFIG_CLOCKSOURCE_WATCHDOG_MAX_SKEW_US 111 #define MAX_SKEW_USEC CONFIG_CLOCKSOURCE_WATCHDOG_MAX_SKEW_US 112 #else 113 #define MAX_SKEW_USEC 100 114 #endif 115 116 #define WATCHDOG_MAX_SKEW (MAX_SKEW_USEC * NSEC_PER_USEC) 117 118 #ifdef CONFIG_CLOCKSOURCE_WATCHDOG 119 static void clocksource_watchdog_work(struct work_struct *work); 120 static void clocksource_select(void); 121 122 static LIST_HEAD(watchdog_list); 123 static struct clocksource *watchdog; 124 static struct timer_list watchdog_timer; 125 static DECLARE_WORK(watchdog_work, clocksource_watchdog_work); 126 static DEFINE_SPINLOCK(watchdog_lock); 127 static int watchdog_running; 128 static atomic_t watchdog_reset_pending; 129 130 static inline void clocksource_watchdog_lock(unsigned long *flags) 131 { 132 spin_lock_irqsave(&watchdog_lock, *flags); 133 } 134 135 static inline void clocksource_watchdog_unlock(unsigned long *flags) 136 { 137 spin_unlock_irqrestore(&watchdog_lock, *flags); 138 } 139 140 static int clocksource_watchdog_kthread(void *data); 141 static void __clocksource_change_rating(struct clocksource *cs, int rating); 142 143 /* 144 * Interval: 0.5sec. 145 */ 146 #define WATCHDOG_INTERVAL (HZ >> 1) 147 148 static void clocksource_watchdog_work(struct work_struct *work) 149 { 150 /* 151 * We cannot directly run clocksource_watchdog_kthread() here, because 152 * clocksource_select() calls timekeeping_notify() which uses 153 * stop_machine(). One cannot use stop_machine() from a workqueue() due 154 * lock inversions wrt CPU hotplug. 155 * 156 * Also, we only ever run this work once or twice during the lifetime 157 * of the kernel, so there is no point in creating a more permanent 158 * kthread for this. 159 * 160 * If kthread_run fails the next watchdog scan over the 161 * watchdog_list will find the unstable clock again. 162 */ 163 kthread_run(clocksource_watchdog_kthread, NULL, "kwatchdog"); 164 } 165 166 static void __clocksource_unstable(struct clocksource *cs) 167 { 168 cs->flags &= ~(CLOCK_SOURCE_VALID_FOR_HRES | CLOCK_SOURCE_WATCHDOG); 169 cs->flags |= CLOCK_SOURCE_UNSTABLE; 170 171 /* 172 * If the clocksource is registered clocksource_watchdog_kthread() will 173 * re-rate and re-select. 174 */ 175 if (list_empty(&cs->list)) { 176 cs->rating = 0; 177 return; 178 } 179 180 if (cs->mark_unstable) 181 cs->mark_unstable(cs); 182 183 /* kick clocksource_watchdog_kthread() */ 184 if (finished_booting) 185 schedule_work(&watchdog_work); 186 } 187 188 /** 189 * clocksource_mark_unstable - mark clocksource unstable via watchdog 190 * @cs: clocksource to be marked unstable 191 * 192 * This function is called by the x86 TSC code to mark clocksources as unstable; 193 * it defers demotion and re-selection to a kthread. 194 */ 195 void clocksource_mark_unstable(struct clocksource *cs) 196 { 197 unsigned long flags; 198 199 spin_lock_irqsave(&watchdog_lock, flags); 200 if (!(cs->flags & CLOCK_SOURCE_UNSTABLE)) { 201 if (!list_empty(&cs->list) && list_empty(&cs->wd_list)) 202 list_add(&cs->wd_list, &watchdog_list); 203 __clocksource_unstable(cs); 204 } 205 spin_unlock_irqrestore(&watchdog_lock, flags); 206 } 207 208 ulong max_cswd_read_retries = 2; 209 module_param(max_cswd_read_retries, ulong, 0644); 210 EXPORT_SYMBOL_GPL(max_cswd_read_retries); 211 static int verify_n_cpus = 8; 212 module_param(verify_n_cpus, int, 0644); 213 214 enum wd_read_status { 215 WD_READ_SUCCESS, 216 WD_READ_UNSTABLE, 217 WD_READ_SKIP 218 }; 219 220 static enum wd_read_status cs_watchdog_read(struct clocksource *cs, u64 *csnow, u64 *wdnow) 221 { 222 unsigned int nretries; 223 u64 wd_end, wd_end2, wd_delta; 224 int64_t wd_delay, wd_seq_delay; 225 226 for (nretries = 0; nretries <= max_cswd_read_retries; nretries++) { 227 local_irq_disable(); 228 *wdnow = watchdog->read(watchdog); 229 *csnow = cs->read(cs); 230 wd_end = watchdog->read(watchdog); 231 wd_end2 = watchdog->read(watchdog); 232 local_irq_enable(); 233 234 wd_delta = clocksource_delta(wd_end, *wdnow, watchdog->mask); 235 wd_delay = clocksource_cyc2ns(wd_delta, watchdog->mult, 236 watchdog->shift); 237 if (wd_delay <= WATCHDOG_MAX_SKEW) { 238 if (nretries > 1 || nretries >= max_cswd_read_retries) { 239 pr_warn("timekeeping watchdog on CPU%d: %s retried %d times before success\n", 240 smp_processor_id(), watchdog->name, nretries); 241 } 242 return WD_READ_SUCCESS; 243 } 244 245 /* 246 * Now compute delay in consecutive watchdog read to see if 247 * there is too much external interferences that cause 248 * significant delay in reading both clocksource and watchdog. 249 * 250 * If consecutive WD read-back delay > WATCHDOG_MAX_SKEW/2, 251 * report system busy, reinit the watchdog and skip the current 252 * watchdog test. 253 */ 254 wd_delta = clocksource_delta(wd_end2, wd_end, watchdog->mask); 255 wd_seq_delay = clocksource_cyc2ns(wd_delta, watchdog->mult, watchdog->shift); 256 if (wd_seq_delay > WATCHDOG_MAX_SKEW/2) 257 goto skip_test; 258 } 259 260 pr_warn("timekeeping watchdog on CPU%d: %s read-back delay of %lldns, attempt %d, marking unstable\n", 261 smp_processor_id(), watchdog->name, wd_delay, nretries); 262 return WD_READ_UNSTABLE; 263 264 skip_test: 265 pr_info("timekeeping watchdog on CPU%d: %s wd-wd read-back delay of %lldns\n", 266 smp_processor_id(), watchdog->name, wd_seq_delay); 267 pr_info("wd-%s-wd read-back delay of %lldns, clock-skew test skipped!\n", 268 cs->name, wd_delay); 269 return WD_READ_SKIP; 270 } 271 272 static u64 csnow_mid; 273 static cpumask_t cpus_ahead; 274 static cpumask_t cpus_behind; 275 static cpumask_t cpus_chosen; 276 277 static void clocksource_verify_choose_cpus(void) 278 { 279 int cpu, i, n = verify_n_cpus; 280 281 if (n < 0) { 282 /* Check all of the CPUs. */ 283 cpumask_copy(&cpus_chosen, cpu_online_mask); 284 cpumask_clear_cpu(smp_processor_id(), &cpus_chosen); 285 return; 286 } 287 288 /* If no checking desired, or no other CPU to check, leave. */ 289 cpumask_clear(&cpus_chosen); 290 if (n == 0 || num_online_cpus() <= 1) 291 return; 292 293 /* Make sure to select at least one CPU other than the current CPU. */ 294 cpu = cpumask_first(cpu_online_mask); 295 if (cpu == smp_processor_id()) 296 cpu = cpumask_next(cpu, cpu_online_mask); 297 if (WARN_ON_ONCE(cpu >= nr_cpu_ids)) 298 return; 299 cpumask_set_cpu(cpu, &cpus_chosen); 300 301 /* Force a sane value for the boot parameter. */ 302 if (n > nr_cpu_ids) 303 n = nr_cpu_ids; 304 305 /* 306 * Randomly select the specified number of CPUs. If the same 307 * CPU is selected multiple times, that CPU is checked only once, 308 * and no replacement CPU is selected. This gracefully handles 309 * situations where verify_n_cpus is greater than the number of 310 * CPUs that are currently online. 311 */ 312 for (i = 1; i < n; i++) { 313 cpu = prandom_u32() % nr_cpu_ids; 314 cpu = cpumask_next(cpu - 1, cpu_online_mask); 315 if (cpu >= nr_cpu_ids) 316 cpu = cpumask_first(cpu_online_mask); 317 if (!WARN_ON_ONCE(cpu >= nr_cpu_ids)) 318 cpumask_set_cpu(cpu, &cpus_chosen); 319 } 320 321 /* Don't verify ourselves. */ 322 cpumask_clear_cpu(smp_processor_id(), &cpus_chosen); 323 } 324 325 static void clocksource_verify_one_cpu(void *csin) 326 { 327 struct clocksource *cs = (struct clocksource *)csin; 328 329 csnow_mid = cs->read(cs); 330 } 331 332 void clocksource_verify_percpu(struct clocksource *cs) 333 { 334 int64_t cs_nsec, cs_nsec_max = 0, cs_nsec_min = LLONG_MAX; 335 u64 csnow_begin, csnow_end; 336 int cpu, testcpu; 337 s64 delta; 338 339 if (verify_n_cpus == 0) 340 return; 341 cpumask_clear(&cpus_ahead); 342 cpumask_clear(&cpus_behind); 343 cpus_read_lock(); 344 preempt_disable(); 345 clocksource_verify_choose_cpus(); 346 if (cpumask_empty(&cpus_chosen)) { 347 preempt_enable(); 348 cpus_read_unlock(); 349 pr_warn("Not enough CPUs to check clocksource '%s'.\n", cs->name); 350 return; 351 } 352 testcpu = smp_processor_id(); 353 pr_warn("Checking clocksource %s synchronization from CPU %d to CPUs %*pbl.\n", cs->name, testcpu, cpumask_pr_args(&cpus_chosen)); 354 for_each_cpu(cpu, &cpus_chosen) { 355 if (cpu == testcpu) 356 continue; 357 csnow_begin = cs->read(cs); 358 smp_call_function_single(cpu, clocksource_verify_one_cpu, cs, 1); 359 csnow_end = cs->read(cs); 360 delta = (s64)((csnow_mid - csnow_begin) & cs->mask); 361 if (delta < 0) 362 cpumask_set_cpu(cpu, &cpus_behind); 363 delta = (csnow_end - csnow_mid) & cs->mask; 364 if (delta < 0) 365 cpumask_set_cpu(cpu, &cpus_ahead); 366 delta = clocksource_delta(csnow_end, csnow_begin, cs->mask); 367 cs_nsec = clocksource_cyc2ns(delta, cs->mult, cs->shift); 368 if (cs_nsec > cs_nsec_max) 369 cs_nsec_max = cs_nsec; 370 if (cs_nsec < cs_nsec_min) 371 cs_nsec_min = cs_nsec; 372 } 373 preempt_enable(); 374 cpus_read_unlock(); 375 if (!cpumask_empty(&cpus_ahead)) 376 pr_warn(" CPUs %*pbl ahead of CPU %d for clocksource %s.\n", 377 cpumask_pr_args(&cpus_ahead), testcpu, cs->name); 378 if (!cpumask_empty(&cpus_behind)) 379 pr_warn(" CPUs %*pbl behind CPU %d for clocksource %s.\n", 380 cpumask_pr_args(&cpus_behind), testcpu, cs->name); 381 if (!cpumask_empty(&cpus_ahead) || !cpumask_empty(&cpus_behind)) 382 pr_warn(" CPU %d check durations %lldns - %lldns for clocksource %s.\n", 383 testcpu, cs_nsec_min, cs_nsec_max, cs->name); 384 } 385 EXPORT_SYMBOL_GPL(clocksource_verify_percpu); 386 387 static void clocksource_watchdog(struct timer_list *unused) 388 { 389 u64 csnow, wdnow, cslast, wdlast, delta; 390 int next_cpu, reset_pending; 391 int64_t wd_nsec, cs_nsec; 392 struct clocksource *cs; 393 enum wd_read_status read_ret; 394 u32 md; 395 396 spin_lock(&watchdog_lock); 397 if (!watchdog_running) 398 goto out; 399 400 reset_pending = atomic_read(&watchdog_reset_pending); 401 402 list_for_each_entry(cs, &watchdog_list, wd_list) { 403 404 /* Clocksource already marked unstable? */ 405 if (cs->flags & CLOCK_SOURCE_UNSTABLE) { 406 if (finished_booting) 407 schedule_work(&watchdog_work); 408 continue; 409 } 410 411 read_ret = cs_watchdog_read(cs, &csnow, &wdnow); 412 413 if (read_ret != WD_READ_SUCCESS) { 414 if (read_ret == WD_READ_UNSTABLE) 415 /* Clock readout unreliable, so give it up. */ 416 __clocksource_unstable(cs); 417 continue; 418 } 419 420 /* Clocksource initialized ? */ 421 if (!(cs->flags & CLOCK_SOURCE_WATCHDOG) || 422 atomic_read(&watchdog_reset_pending)) { 423 cs->flags |= CLOCK_SOURCE_WATCHDOG; 424 cs->wd_last = wdnow; 425 cs->cs_last = csnow; 426 continue; 427 } 428 429 delta = clocksource_delta(wdnow, cs->wd_last, watchdog->mask); 430 wd_nsec = clocksource_cyc2ns(delta, watchdog->mult, 431 watchdog->shift); 432 433 delta = clocksource_delta(csnow, cs->cs_last, cs->mask); 434 cs_nsec = clocksource_cyc2ns(delta, cs->mult, cs->shift); 435 wdlast = cs->wd_last; /* save these in case we print them */ 436 cslast = cs->cs_last; 437 cs->cs_last = csnow; 438 cs->wd_last = wdnow; 439 440 if (atomic_read(&watchdog_reset_pending)) 441 continue; 442 443 /* Check the deviation from the watchdog clocksource. */ 444 md = cs->uncertainty_margin + watchdog->uncertainty_margin; 445 if (abs(cs_nsec - wd_nsec) > md) { 446 pr_warn("timekeeping watchdog on CPU%d: Marking clocksource '%s' as unstable because the skew is too large:\n", 447 smp_processor_id(), cs->name); 448 pr_warn(" '%s' wd_nsec: %lld wd_now: %llx wd_last: %llx mask: %llx\n", 449 watchdog->name, wd_nsec, wdnow, wdlast, watchdog->mask); 450 pr_warn(" '%s' cs_nsec: %lld cs_now: %llx cs_last: %llx mask: %llx\n", 451 cs->name, cs_nsec, csnow, cslast, cs->mask); 452 if (curr_clocksource == cs) 453 pr_warn(" '%s' is current clocksource.\n", cs->name); 454 else if (curr_clocksource) 455 pr_warn(" '%s' (not '%s') is current clocksource.\n", curr_clocksource->name, cs->name); 456 else 457 pr_warn(" No current clocksource.\n"); 458 __clocksource_unstable(cs); 459 continue; 460 } 461 462 if (cs == curr_clocksource && cs->tick_stable) 463 cs->tick_stable(cs); 464 465 if (!(cs->flags & CLOCK_SOURCE_VALID_FOR_HRES) && 466 (cs->flags & CLOCK_SOURCE_IS_CONTINUOUS) && 467 (watchdog->flags & CLOCK_SOURCE_IS_CONTINUOUS)) { 468 /* Mark it valid for high-res. */ 469 cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES; 470 471 /* 472 * clocksource_done_booting() will sort it if 473 * finished_booting is not set yet. 474 */ 475 if (!finished_booting) 476 continue; 477 478 /* 479 * If this is not the current clocksource let 480 * the watchdog thread reselect it. Due to the 481 * change to high res this clocksource might 482 * be preferred now. If it is the current 483 * clocksource let the tick code know about 484 * that change. 485 */ 486 if (cs != curr_clocksource) { 487 cs->flags |= CLOCK_SOURCE_RESELECT; 488 schedule_work(&watchdog_work); 489 } else { 490 tick_clock_notify(); 491 } 492 } 493 } 494 495 /* 496 * We only clear the watchdog_reset_pending, when we did a 497 * full cycle through all clocksources. 498 */ 499 if (reset_pending) 500 atomic_dec(&watchdog_reset_pending); 501 502 /* 503 * Cycle through CPUs to check if the CPUs stay synchronized 504 * to each other. 505 */ 506 next_cpu = cpumask_next(raw_smp_processor_id(), cpu_online_mask); 507 if (next_cpu >= nr_cpu_ids) 508 next_cpu = cpumask_first(cpu_online_mask); 509 510 /* 511 * Arm timer if not already pending: could race with concurrent 512 * pair clocksource_stop_watchdog() clocksource_start_watchdog(). 513 */ 514 if (!timer_pending(&watchdog_timer)) { 515 watchdog_timer.expires += WATCHDOG_INTERVAL; 516 add_timer_on(&watchdog_timer, next_cpu); 517 } 518 out: 519 spin_unlock(&watchdog_lock); 520 } 521 522 static inline void clocksource_start_watchdog(void) 523 { 524 if (watchdog_running || !watchdog || list_empty(&watchdog_list)) 525 return; 526 timer_setup(&watchdog_timer, clocksource_watchdog, 0); 527 watchdog_timer.expires = jiffies + WATCHDOG_INTERVAL; 528 add_timer_on(&watchdog_timer, cpumask_first(cpu_online_mask)); 529 watchdog_running = 1; 530 } 531 532 static inline void clocksource_stop_watchdog(void) 533 { 534 if (!watchdog_running || (watchdog && !list_empty(&watchdog_list))) 535 return; 536 del_timer(&watchdog_timer); 537 watchdog_running = 0; 538 } 539 540 static inline void clocksource_reset_watchdog(void) 541 { 542 struct clocksource *cs; 543 544 list_for_each_entry(cs, &watchdog_list, wd_list) 545 cs->flags &= ~CLOCK_SOURCE_WATCHDOG; 546 } 547 548 static void clocksource_resume_watchdog(void) 549 { 550 atomic_inc(&watchdog_reset_pending); 551 } 552 553 static void clocksource_enqueue_watchdog(struct clocksource *cs) 554 { 555 INIT_LIST_HEAD(&cs->wd_list); 556 557 if (cs->flags & CLOCK_SOURCE_MUST_VERIFY) { 558 /* cs is a clocksource to be watched. */ 559 list_add(&cs->wd_list, &watchdog_list); 560 cs->flags &= ~CLOCK_SOURCE_WATCHDOG; 561 } else { 562 /* cs is a watchdog. */ 563 if (cs->flags & CLOCK_SOURCE_IS_CONTINUOUS) 564 cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES; 565 } 566 } 567 568 static void clocksource_select_watchdog(bool fallback) 569 { 570 struct clocksource *cs, *old_wd; 571 unsigned long flags; 572 573 spin_lock_irqsave(&watchdog_lock, flags); 574 /* save current watchdog */ 575 old_wd = watchdog; 576 if (fallback) 577 watchdog = NULL; 578 579 list_for_each_entry(cs, &clocksource_list, list) { 580 /* cs is a clocksource to be watched. */ 581 if (cs->flags & CLOCK_SOURCE_MUST_VERIFY) 582 continue; 583 584 /* Skip current if we were requested for a fallback. */ 585 if (fallback && cs == old_wd) 586 continue; 587 588 /* Pick the best watchdog. */ 589 if (!watchdog || cs->rating > watchdog->rating) 590 watchdog = cs; 591 } 592 /* If we failed to find a fallback restore the old one. */ 593 if (!watchdog) 594 watchdog = old_wd; 595 596 /* If we changed the watchdog we need to reset cycles. */ 597 if (watchdog != old_wd) 598 clocksource_reset_watchdog(); 599 600 /* Check if the watchdog timer needs to be started. */ 601 clocksource_start_watchdog(); 602 spin_unlock_irqrestore(&watchdog_lock, flags); 603 } 604 605 static void clocksource_dequeue_watchdog(struct clocksource *cs) 606 { 607 if (cs != watchdog) { 608 if (cs->flags & CLOCK_SOURCE_MUST_VERIFY) { 609 /* cs is a watched clocksource. */ 610 list_del_init(&cs->wd_list); 611 /* Check if the watchdog timer needs to be stopped. */ 612 clocksource_stop_watchdog(); 613 } 614 } 615 } 616 617 static int __clocksource_watchdog_kthread(void) 618 { 619 struct clocksource *cs, *tmp; 620 unsigned long flags; 621 int select = 0; 622 623 /* Do any required per-CPU skew verification. */ 624 if (curr_clocksource && 625 curr_clocksource->flags & CLOCK_SOURCE_UNSTABLE && 626 curr_clocksource->flags & CLOCK_SOURCE_VERIFY_PERCPU) 627 clocksource_verify_percpu(curr_clocksource); 628 629 spin_lock_irqsave(&watchdog_lock, flags); 630 list_for_each_entry_safe(cs, tmp, &watchdog_list, wd_list) { 631 if (cs->flags & CLOCK_SOURCE_UNSTABLE) { 632 list_del_init(&cs->wd_list); 633 __clocksource_change_rating(cs, 0); 634 select = 1; 635 } 636 if (cs->flags & CLOCK_SOURCE_RESELECT) { 637 cs->flags &= ~CLOCK_SOURCE_RESELECT; 638 select = 1; 639 } 640 } 641 /* Check if the watchdog timer needs to be stopped. */ 642 clocksource_stop_watchdog(); 643 spin_unlock_irqrestore(&watchdog_lock, flags); 644 645 return select; 646 } 647 648 static int clocksource_watchdog_kthread(void *data) 649 { 650 mutex_lock(&clocksource_mutex); 651 if (__clocksource_watchdog_kthread()) 652 clocksource_select(); 653 mutex_unlock(&clocksource_mutex); 654 return 0; 655 } 656 657 static bool clocksource_is_watchdog(struct clocksource *cs) 658 { 659 return cs == watchdog; 660 } 661 662 #else /* CONFIG_CLOCKSOURCE_WATCHDOG */ 663 664 static void clocksource_enqueue_watchdog(struct clocksource *cs) 665 { 666 if (cs->flags & CLOCK_SOURCE_IS_CONTINUOUS) 667 cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES; 668 } 669 670 static void clocksource_select_watchdog(bool fallback) { } 671 static inline void clocksource_dequeue_watchdog(struct clocksource *cs) { } 672 static inline void clocksource_resume_watchdog(void) { } 673 static inline int __clocksource_watchdog_kthread(void) { return 0; } 674 static bool clocksource_is_watchdog(struct clocksource *cs) { return false; } 675 void clocksource_mark_unstable(struct clocksource *cs) { } 676 677 static inline void clocksource_watchdog_lock(unsigned long *flags) { } 678 static inline void clocksource_watchdog_unlock(unsigned long *flags) { } 679 680 #endif /* CONFIG_CLOCKSOURCE_WATCHDOG */ 681 682 static bool clocksource_is_suspend(struct clocksource *cs) 683 { 684 return cs == suspend_clocksource; 685 } 686 687 static void __clocksource_suspend_select(struct clocksource *cs) 688 { 689 /* 690 * Skip the clocksource which will be stopped in suspend state. 691 */ 692 if (!(cs->flags & CLOCK_SOURCE_SUSPEND_NONSTOP)) 693 return; 694 695 /* 696 * The nonstop clocksource can be selected as the suspend clocksource to 697 * calculate the suspend time, so it should not supply suspend/resume 698 * interfaces to suspend the nonstop clocksource when system suspends. 699 */ 700 if (cs->suspend || cs->resume) { 701 pr_warn("Nonstop clocksource %s should not supply suspend/resume interfaces\n", 702 cs->name); 703 } 704 705 /* Pick the best rating. */ 706 if (!suspend_clocksource || cs->rating > suspend_clocksource->rating) 707 suspend_clocksource = cs; 708 } 709 710 /** 711 * clocksource_suspend_select - Select the best clocksource for suspend timing 712 * @fallback: if select a fallback clocksource 713 */ 714 static void clocksource_suspend_select(bool fallback) 715 { 716 struct clocksource *cs, *old_suspend; 717 718 old_suspend = suspend_clocksource; 719 if (fallback) 720 suspend_clocksource = NULL; 721 722 list_for_each_entry(cs, &clocksource_list, list) { 723 /* Skip current if we were requested for a fallback. */ 724 if (fallback && cs == old_suspend) 725 continue; 726 727 __clocksource_suspend_select(cs); 728 } 729 } 730 731 /** 732 * clocksource_start_suspend_timing - Start measuring the suspend timing 733 * @cs: current clocksource from timekeeping 734 * @start_cycles: current cycles from timekeeping 735 * 736 * This function will save the start cycle values of suspend timer to calculate 737 * the suspend time when resuming system. 738 * 739 * This function is called late in the suspend process from timekeeping_suspend(), 740 * that means processes are frozen, non-boot cpus and interrupts are disabled 741 * now. It is therefore possible to start the suspend timer without taking the 742 * clocksource mutex. 743 */ 744 void clocksource_start_suspend_timing(struct clocksource *cs, u64 start_cycles) 745 { 746 if (!suspend_clocksource) 747 return; 748 749 /* 750 * If current clocksource is the suspend timer, we should use the 751 * tkr_mono.cycle_last value as suspend_start to avoid same reading 752 * from suspend timer. 753 */ 754 if (clocksource_is_suspend(cs)) { 755 suspend_start = start_cycles; 756 return; 757 } 758 759 if (suspend_clocksource->enable && 760 suspend_clocksource->enable(suspend_clocksource)) { 761 pr_warn_once("Failed to enable the non-suspend-able clocksource.\n"); 762 return; 763 } 764 765 suspend_start = suspend_clocksource->read(suspend_clocksource); 766 } 767 768 /** 769 * clocksource_stop_suspend_timing - Stop measuring the suspend timing 770 * @cs: current clocksource from timekeeping 771 * @cycle_now: current cycles from timekeeping 772 * 773 * This function will calculate the suspend time from suspend timer. 774 * 775 * Returns nanoseconds since suspend started, 0 if no usable suspend clocksource. 776 * 777 * This function is called early in the resume process from timekeeping_resume(), 778 * that means there is only one cpu, no processes are running and the interrupts 779 * are disabled. It is therefore possible to stop the suspend timer without 780 * taking the clocksource mutex. 781 */ 782 u64 clocksource_stop_suspend_timing(struct clocksource *cs, u64 cycle_now) 783 { 784 u64 now, delta, nsec = 0; 785 786 if (!suspend_clocksource) 787 return 0; 788 789 /* 790 * If current clocksource is the suspend timer, we should use the 791 * tkr_mono.cycle_last value from timekeeping as current cycle to 792 * avoid same reading from suspend timer. 793 */ 794 if (clocksource_is_suspend(cs)) 795 now = cycle_now; 796 else 797 now = suspend_clocksource->read(suspend_clocksource); 798 799 if (now > suspend_start) { 800 delta = clocksource_delta(now, suspend_start, 801 suspend_clocksource->mask); 802 nsec = mul_u64_u32_shr(delta, suspend_clocksource->mult, 803 suspend_clocksource->shift); 804 } 805 806 /* 807 * Disable the suspend timer to save power if current clocksource is 808 * not the suspend timer. 809 */ 810 if (!clocksource_is_suspend(cs) && suspend_clocksource->disable) 811 suspend_clocksource->disable(suspend_clocksource); 812 813 return nsec; 814 } 815 816 /** 817 * clocksource_suspend - suspend the clocksource(s) 818 */ 819 void clocksource_suspend(void) 820 { 821 struct clocksource *cs; 822 823 list_for_each_entry_reverse(cs, &clocksource_list, list) 824 if (cs->suspend) 825 cs->suspend(cs); 826 } 827 828 /** 829 * clocksource_resume - resume the clocksource(s) 830 */ 831 void clocksource_resume(void) 832 { 833 struct clocksource *cs; 834 835 list_for_each_entry(cs, &clocksource_list, list) 836 if (cs->resume) 837 cs->resume(cs); 838 839 clocksource_resume_watchdog(); 840 } 841 842 /** 843 * clocksource_touch_watchdog - Update watchdog 844 * 845 * Update the watchdog after exception contexts such as kgdb so as not 846 * to incorrectly trip the watchdog. This might fail when the kernel 847 * was stopped in code which holds watchdog_lock. 848 */ 849 void clocksource_touch_watchdog(void) 850 { 851 clocksource_resume_watchdog(); 852 } 853 854 /** 855 * clocksource_max_adjustment- Returns max adjustment amount 856 * @cs: Pointer to clocksource 857 * 858 */ 859 static u32 clocksource_max_adjustment(struct clocksource *cs) 860 { 861 u64 ret; 862 /* 863 * We won't try to correct for more than 11% adjustments (110,000 ppm), 864 */ 865 ret = (u64)cs->mult * 11; 866 do_div(ret,100); 867 return (u32)ret; 868 } 869 870 /** 871 * clocks_calc_max_nsecs - Returns maximum nanoseconds that can be converted 872 * @mult: cycle to nanosecond multiplier 873 * @shift: cycle to nanosecond divisor (power of two) 874 * @maxadj: maximum adjustment value to mult (~11%) 875 * @mask: bitmask for two's complement subtraction of non 64 bit counters 876 * @max_cyc: maximum cycle value before potential overflow (does not include 877 * any safety margin) 878 * 879 * NOTE: This function includes a safety margin of 50%, in other words, we 880 * return half the number of nanoseconds the hardware counter can technically 881 * cover. This is done so that we can potentially detect problems caused by 882 * delayed timers or bad hardware, which might result in time intervals that 883 * are larger than what the math used can handle without overflows. 884 */ 885 u64 clocks_calc_max_nsecs(u32 mult, u32 shift, u32 maxadj, u64 mask, u64 *max_cyc) 886 { 887 u64 max_nsecs, max_cycles; 888 889 /* 890 * Calculate the maximum number of cycles that we can pass to the 891 * cyc2ns() function without overflowing a 64-bit result. 892 */ 893 max_cycles = ULLONG_MAX; 894 do_div(max_cycles, mult+maxadj); 895 896 /* 897 * The actual maximum number of cycles we can defer the clocksource is 898 * determined by the minimum of max_cycles and mask. 899 * Note: Here we subtract the maxadj to make sure we don't sleep for 900 * too long if there's a large negative adjustment. 901 */ 902 max_cycles = min(max_cycles, mask); 903 max_nsecs = clocksource_cyc2ns(max_cycles, mult - maxadj, shift); 904 905 /* return the max_cycles value as well if requested */ 906 if (max_cyc) 907 *max_cyc = max_cycles; 908 909 /* Return 50% of the actual maximum, so we can detect bad values */ 910 max_nsecs >>= 1; 911 912 return max_nsecs; 913 } 914 915 /** 916 * clocksource_update_max_deferment - Updates the clocksource max_idle_ns & max_cycles 917 * @cs: Pointer to clocksource to be updated 918 * 919 */ 920 static inline void clocksource_update_max_deferment(struct clocksource *cs) 921 { 922 cs->max_idle_ns = clocks_calc_max_nsecs(cs->mult, cs->shift, 923 cs->maxadj, cs->mask, 924 &cs->max_cycles); 925 } 926 927 static struct clocksource *clocksource_find_best(bool oneshot, bool skipcur) 928 { 929 struct clocksource *cs; 930 931 if (!finished_booting || list_empty(&clocksource_list)) 932 return NULL; 933 934 /* 935 * We pick the clocksource with the highest rating. If oneshot 936 * mode is active, we pick the highres valid clocksource with 937 * the best rating. 938 */ 939 list_for_each_entry(cs, &clocksource_list, list) { 940 if (skipcur && cs == curr_clocksource) 941 continue; 942 if (oneshot && !(cs->flags & CLOCK_SOURCE_VALID_FOR_HRES)) 943 continue; 944 return cs; 945 } 946 return NULL; 947 } 948 949 static void __clocksource_select(bool skipcur) 950 { 951 bool oneshot = tick_oneshot_mode_active(); 952 struct clocksource *best, *cs; 953 954 /* Find the best suitable clocksource */ 955 best = clocksource_find_best(oneshot, skipcur); 956 if (!best) 957 return; 958 959 if (!strlen(override_name)) 960 goto found; 961 962 /* Check for the override clocksource. */ 963 list_for_each_entry(cs, &clocksource_list, list) { 964 if (skipcur && cs == curr_clocksource) 965 continue; 966 if (strcmp(cs->name, override_name) != 0) 967 continue; 968 /* 969 * Check to make sure we don't switch to a non-highres 970 * capable clocksource if the tick code is in oneshot 971 * mode (highres or nohz) 972 */ 973 if (!(cs->flags & CLOCK_SOURCE_VALID_FOR_HRES) && oneshot) { 974 /* Override clocksource cannot be used. */ 975 if (cs->flags & CLOCK_SOURCE_UNSTABLE) { 976 pr_warn("Override clocksource %s is unstable and not HRT compatible - cannot switch while in HRT/NOHZ mode\n", 977 cs->name); 978 override_name[0] = 0; 979 } else { 980 /* 981 * The override cannot be currently verified. 982 * Deferring to let the watchdog check. 983 */ 984 pr_info("Override clocksource %s is not currently HRT compatible - deferring\n", 985 cs->name); 986 } 987 } else 988 /* Override clocksource can be used. */ 989 best = cs; 990 break; 991 } 992 993 found: 994 if (curr_clocksource != best && !timekeeping_notify(best)) { 995 pr_info("Switched to clocksource %s\n", best->name); 996 curr_clocksource = best; 997 } 998 } 999 1000 /** 1001 * clocksource_select - Select the best clocksource available 1002 * 1003 * Private function. Must hold clocksource_mutex when called. 1004 * 1005 * Select the clocksource with the best rating, or the clocksource, 1006 * which is selected by userspace override. 1007 */ 1008 static void clocksource_select(void) 1009 { 1010 __clocksource_select(false); 1011 } 1012 1013 static void clocksource_select_fallback(void) 1014 { 1015 __clocksource_select(true); 1016 } 1017 1018 /* 1019 * clocksource_done_booting - Called near the end of core bootup 1020 * 1021 * Hack to avoid lots of clocksource churn at boot time. 1022 * We use fs_initcall because we want this to start before 1023 * device_initcall but after subsys_initcall. 1024 */ 1025 static int __init clocksource_done_booting(void) 1026 { 1027 mutex_lock(&clocksource_mutex); 1028 curr_clocksource = clocksource_default_clock(); 1029 finished_booting = 1; 1030 /* 1031 * Run the watchdog first to eliminate unstable clock sources 1032 */ 1033 __clocksource_watchdog_kthread(); 1034 clocksource_select(); 1035 mutex_unlock(&clocksource_mutex); 1036 return 0; 1037 } 1038 fs_initcall(clocksource_done_booting); 1039 1040 /* 1041 * Enqueue the clocksource sorted by rating 1042 */ 1043 static void clocksource_enqueue(struct clocksource *cs) 1044 { 1045 struct list_head *entry = &clocksource_list; 1046 struct clocksource *tmp; 1047 1048 list_for_each_entry(tmp, &clocksource_list, list) { 1049 /* Keep track of the place, where to insert */ 1050 if (tmp->rating < cs->rating) 1051 break; 1052 entry = &tmp->list; 1053 } 1054 list_add(&cs->list, entry); 1055 } 1056 1057 /** 1058 * __clocksource_update_freq_scale - Used update clocksource with new freq 1059 * @cs: clocksource to be registered 1060 * @scale: Scale factor multiplied against freq to get clocksource hz 1061 * @freq: clocksource frequency (cycles per second) divided by scale 1062 * 1063 * This should only be called from the clocksource->enable() method. 1064 * 1065 * This *SHOULD NOT* be called directly! Please use the 1066 * __clocksource_update_freq_hz() or __clocksource_update_freq_khz() helper 1067 * functions. 1068 */ 1069 void __clocksource_update_freq_scale(struct clocksource *cs, u32 scale, u32 freq) 1070 { 1071 u64 sec; 1072 1073 /* 1074 * Default clocksources are *special* and self-define their mult/shift. 1075 * But, you're not special, so you should specify a freq value. 1076 */ 1077 if (freq) { 1078 /* 1079 * Calc the maximum number of seconds which we can run before 1080 * wrapping around. For clocksources which have a mask > 32-bit 1081 * we need to limit the max sleep time to have a good 1082 * conversion precision. 10 minutes is still a reasonable 1083 * amount. That results in a shift value of 24 for a 1084 * clocksource with mask >= 40-bit and f >= 4GHz. That maps to 1085 * ~ 0.06ppm granularity for NTP. 1086 */ 1087 sec = cs->mask; 1088 do_div(sec, freq); 1089 do_div(sec, scale); 1090 if (!sec) 1091 sec = 1; 1092 else if (sec > 600 && cs->mask > UINT_MAX) 1093 sec = 600; 1094 1095 clocks_calc_mult_shift(&cs->mult, &cs->shift, freq, 1096 NSEC_PER_SEC / scale, sec * scale); 1097 } 1098 1099 /* 1100 * If the uncertainty margin is not specified, calculate it. 1101 * If both scale and freq are non-zero, calculate the clock 1102 * period, but bound below at 2*WATCHDOG_MAX_SKEW. However, 1103 * if either of scale or freq is zero, be very conservative and 1104 * take the tens-of-milliseconds WATCHDOG_THRESHOLD value for the 1105 * uncertainty margin. Allow stupidly small uncertainty margins 1106 * to be specified by the caller for testing purposes, but warn 1107 * to discourage production use of this capability. 1108 */ 1109 if (scale && freq && !cs->uncertainty_margin) { 1110 cs->uncertainty_margin = NSEC_PER_SEC / (scale * freq); 1111 if (cs->uncertainty_margin < 2 * WATCHDOG_MAX_SKEW) 1112 cs->uncertainty_margin = 2 * WATCHDOG_MAX_SKEW; 1113 } else if (!cs->uncertainty_margin) { 1114 cs->uncertainty_margin = WATCHDOG_THRESHOLD; 1115 } 1116 WARN_ON_ONCE(cs->uncertainty_margin < 2 * WATCHDOG_MAX_SKEW); 1117 1118 /* 1119 * Ensure clocksources that have large 'mult' values don't overflow 1120 * when adjusted. 1121 */ 1122 cs->maxadj = clocksource_max_adjustment(cs); 1123 while (freq && ((cs->mult + cs->maxadj < cs->mult) 1124 || (cs->mult - cs->maxadj > cs->mult))) { 1125 cs->mult >>= 1; 1126 cs->shift--; 1127 cs->maxadj = clocksource_max_adjustment(cs); 1128 } 1129 1130 /* 1131 * Only warn for *special* clocksources that self-define 1132 * their mult/shift values and don't specify a freq. 1133 */ 1134 WARN_ONCE(cs->mult + cs->maxadj < cs->mult, 1135 "timekeeping: Clocksource %s might overflow on 11%% adjustment\n", 1136 cs->name); 1137 1138 clocksource_update_max_deferment(cs); 1139 1140 pr_info("%s: mask: 0x%llx max_cycles: 0x%llx, max_idle_ns: %lld ns\n", 1141 cs->name, cs->mask, cs->max_cycles, cs->max_idle_ns); 1142 } 1143 EXPORT_SYMBOL_GPL(__clocksource_update_freq_scale); 1144 1145 /** 1146 * __clocksource_register_scale - Used to install new clocksources 1147 * @cs: clocksource to be registered 1148 * @scale: Scale factor multiplied against freq to get clocksource hz 1149 * @freq: clocksource frequency (cycles per second) divided by scale 1150 * 1151 * Returns -EBUSY if registration fails, zero otherwise. 1152 * 1153 * This *SHOULD NOT* be called directly! Please use the 1154 * clocksource_register_hz() or clocksource_register_khz helper functions. 1155 */ 1156 int __clocksource_register_scale(struct clocksource *cs, u32 scale, u32 freq) 1157 { 1158 unsigned long flags; 1159 1160 clocksource_arch_init(cs); 1161 1162 if (WARN_ON_ONCE((unsigned int)cs->id >= CSID_MAX)) 1163 cs->id = CSID_GENERIC; 1164 if (cs->vdso_clock_mode < 0 || 1165 cs->vdso_clock_mode >= VDSO_CLOCKMODE_MAX) { 1166 pr_warn("clocksource %s registered with invalid VDSO mode %d. Disabling VDSO support.\n", 1167 cs->name, cs->vdso_clock_mode); 1168 cs->vdso_clock_mode = VDSO_CLOCKMODE_NONE; 1169 } 1170 1171 /* Initialize mult/shift and max_idle_ns */ 1172 __clocksource_update_freq_scale(cs, scale, freq); 1173 1174 /* Add clocksource to the clocksource list */ 1175 mutex_lock(&clocksource_mutex); 1176 1177 clocksource_watchdog_lock(&flags); 1178 clocksource_enqueue(cs); 1179 clocksource_enqueue_watchdog(cs); 1180 clocksource_watchdog_unlock(&flags); 1181 1182 clocksource_select(); 1183 clocksource_select_watchdog(false); 1184 __clocksource_suspend_select(cs); 1185 mutex_unlock(&clocksource_mutex); 1186 return 0; 1187 } 1188 EXPORT_SYMBOL_GPL(__clocksource_register_scale); 1189 1190 static void __clocksource_change_rating(struct clocksource *cs, int rating) 1191 { 1192 list_del(&cs->list); 1193 cs->rating = rating; 1194 clocksource_enqueue(cs); 1195 } 1196 1197 /** 1198 * clocksource_change_rating - Change the rating of a registered clocksource 1199 * @cs: clocksource to be changed 1200 * @rating: new rating 1201 */ 1202 void clocksource_change_rating(struct clocksource *cs, int rating) 1203 { 1204 unsigned long flags; 1205 1206 mutex_lock(&clocksource_mutex); 1207 clocksource_watchdog_lock(&flags); 1208 __clocksource_change_rating(cs, rating); 1209 clocksource_watchdog_unlock(&flags); 1210 1211 clocksource_select(); 1212 clocksource_select_watchdog(false); 1213 clocksource_suspend_select(false); 1214 mutex_unlock(&clocksource_mutex); 1215 } 1216 EXPORT_SYMBOL(clocksource_change_rating); 1217 1218 /* 1219 * Unbind clocksource @cs. Called with clocksource_mutex held 1220 */ 1221 static int clocksource_unbind(struct clocksource *cs) 1222 { 1223 unsigned long flags; 1224 1225 if (clocksource_is_watchdog(cs)) { 1226 /* Select and try to install a replacement watchdog. */ 1227 clocksource_select_watchdog(true); 1228 if (clocksource_is_watchdog(cs)) 1229 return -EBUSY; 1230 } 1231 1232 if (cs == curr_clocksource) { 1233 /* Select and try to install a replacement clock source */ 1234 clocksource_select_fallback(); 1235 if (curr_clocksource == cs) 1236 return -EBUSY; 1237 } 1238 1239 if (clocksource_is_suspend(cs)) { 1240 /* 1241 * Select and try to install a replacement suspend clocksource. 1242 * If no replacement suspend clocksource, we will just let the 1243 * clocksource go and have no suspend clocksource. 1244 */ 1245 clocksource_suspend_select(true); 1246 } 1247 1248 clocksource_watchdog_lock(&flags); 1249 clocksource_dequeue_watchdog(cs); 1250 list_del_init(&cs->list); 1251 clocksource_watchdog_unlock(&flags); 1252 1253 return 0; 1254 } 1255 1256 /** 1257 * clocksource_unregister - remove a registered clocksource 1258 * @cs: clocksource to be unregistered 1259 */ 1260 int clocksource_unregister(struct clocksource *cs) 1261 { 1262 int ret = 0; 1263 1264 mutex_lock(&clocksource_mutex); 1265 if (!list_empty(&cs->list)) 1266 ret = clocksource_unbind(cs); 1267 mutex_unlock(&clocksource_mutex); 1268 return ret; 1269 } 1270 EXPORT_SYMBOL(clocksource_unregister); 1271 1272 #ifdef CONFIG_SYSFS 1273 /** 1274 * current_clocksource_show - sysfs interface for current clocksource 1275 * @dev: unused 1276 * @attr: unused 1277 * @buf: char buffer to be filled with clocksource list 1278 * 1279 * Provides sysfs interface for listing current clocksource. 1280 */ 1281 static ssize_t current_clocksource_show(struct device *dev, 1282 struct device_attribute *attr, 1283 char *buf) 1284 { 1285 ssize_t count = 0; 1286 1287 mutex_lock(&clocksource_mutex); 1288 count = snprintf(buf, PAGE_SIZE, "%s\n", curr_clocksource->name); 1289 mutex_unlock(&clocksource_mutex); 1290 1291 return count; 1292 } 1293 1294 ssize_t sysfs_get_uname(const char *buf, char *dst, size_t cnt) 1295 { 1296 size_t ret = cnt; 1297 1298 /* strings from sysfs write are not 0 terminated! */ 1299 if (!cnt || cnt >= CS_NAME_LEN) 1300 return -EINVAL; 1301 1302 /* strip of \n: */ 1303 if (buf[cnt-1] == '\n') 1304 cnt--; 1305 if (cnt > 0) 1306 memcpy(dst, buf, cnt); 1307 dst[cnt] = 0; 1308 return ret; 1309 } 1310 1311 /** 1312 * current_clocksource_store - interface for manually overriding clocksource 1313 * @dev: unused 1314 * @attr: unused 1315 * @buf: name of override clocksource 1316 * @count: length of buffer 1317 * 1318 * Takes input from sysfs interface for manually overriding the default 1319 * clocksource selection. 1320 */ 1321 static ssize_t current_clocksource_store(struct device *dev, 1322 struct device_attribute *attr, 1323 const char *buf, size_t count) 1324 { 1325 ssize_t ret; 1326 1327 mutex_lock(&clocksource_mutex); 1328 1329 ret = sysfs_get_uname(buf, override_name, count); 1330 if (ret >= 0) 1331 clocksource_select(); 1332 1333 mutex_unlock(&clocksource_mutex); 1334 1335 return ret; 1336 } 1337 static DEVICE_ATTR_RW(current_clocksource); 1338 1339 /** 1340 * unbind_clocksource_store - interface for manually unbinding clocksource 1341 * @dev: unused 1342 * @attr: unused 1343 * @buf: unused 1344 * @count: length of buffer 1345 * 1346 * Takes input from sysfs interface for manually unbinding a clocksource. 1347 */ 1348 static ssize_t unbind_clocksource_store(struct device *dev, 1349 struct device_attribute *attr, 1350 const char *buf, size_t count) 1351 { 1352 struct clocksource *cs; 1353 char name[CS_NAME_LEN]; 1354 ssize_t ret; 1355 1356 ret = sysfs_get_uname(buf, name, count); 1357 if (ret < 0) 1358 return ret; 1359 1360 ret = -ENODEV; 1361 mutex_lock(&clocksource_mutex); 1362 list_for_each_entry(cs, &clocksource_list, list) { 1363 if (strcmp(cs->name, name)) 1364 continue; 1365 ret = clocksource_unbind(cs); 1366 break; 1367 } 1368 mutex_unlock(&clocksource_mutex); 1369 1370 return ret ? ret : count; 1371 } 1372 static DEVICE_ATTR_WO(unbind_clocksource); 1373 1374 /** 1375 * available_clocksource_show - sysfs interface for listing clocksource 1376 * @dev: unused 1377 * @attr: unused 1378 * @buf: char buffer to be filled with clocksource list 1379 * 1380 * Provides sysfs interface for listing registered clocksources 1381 */ 1382 static ssize_t available_clocksource_show(struct device *dev, 1383 struct device_attribute *attr, 1384 char *buf) 1385 { 1386 struct clocksource *src; 1387 ssize_t count = 0; 1388 1389 mutex_lock(&clocksource_mutex); 1390 list_for_each_entry(src, &clocksource_list, list) { 1391 /* 1392 * Don't show non-HRES clocksource if the tick code is 1393 * in one shot mode (highres=on or nohz=on) 1394 */ 1395 if (!tick_oneshot_mode_active() || 1396 (src->flags & CLOCK_SOURCE_VALID_FOR_HRES)) 1397 count += snprintf(buf + count, 1398 max((ssize_t)PAGE_SIZE - count, (ssize_t)0), 1399 "%s ", src->name); 1400 } 1401 mutex_unlock(&clocksource_mutex); 1402 1403 count += snprintf(buf + count, 1404 max((ssize_t)PAGE_SIZE - count, (ssize_t)0), "\n"); 1405 1406 return count; 1407 } 1408 static DEVICE_ATTR_RO(available_clocksource); 1409 1410 static struct attribute *clocksource_attrs[] = { 1411 &dev_attr_current_clocksource.attr, 1412 &dev_attr_unbind_clocksource.attr, 1413 &dev_attr_available_clocksource.attr, 1414 NULL 1415 }; 1416 ATTRIBUTE_GROUPS(clocksource); 1417 1418 static struct bus_type clocksource_subsys = { 1419 .name = "clocksource", 1420 .dev_name = "clocksource", 1421 }; 1422 1423 static struct device device_clocksource = { 1424 .id = 0, 1425 .bus = &clocksource_subsys, 1426 .groups = clocksource_groups, 1427 }; 1428 1429 static int __init init_clocksource_sysfs(void) 1430 { 1431 int error = subsys_system_register(&clocksource_subsys, NULL); 1432 1433 if (!error) 1434 error = device_register(&device_clocksource); 1435 1436 return error; 1437 } 1438 1439 device_initcall(init_clocksource_sysfs); 1440 #endif /* CONFIG_SYSFS */ 1441 1442 /** 1443 * boot_override_clocksource - boot clock override 1444 * @str: override name 1445 * 1446 * Takes a clocksource= boot argument and uses it 1447 * as the clocksource override name. 1448 */ 1449 static int __init boot_override_clocksource(char* str) 1450 { 1451 mutex_lock(&clocksource_mutex); 1452 if (str) 1453 strlcpy(override_name, str, sizeof(override_name)); 1454 mutex_unlock(&clocksource_mutex); 1455 return 1; 1456 } 1457 1458 __setup("clocksource=", boot_override_clocksource); 1459 1460 /** 1461 * boot_override_clock - Compatibility layer for deprecated boot option 1462 * @str: override name 1463 * 1464 * DEPRECATED! Takes a clock= boot argument and uses it 1465 * as the clocksource override name 1466 */ 1467 static int __init boot_override_clock(char* str) 1468 { 1469 if (!strcmp(str, "pmtmr")) { 1470 pr_warn("clock=pmtmr is deprecated - use clocksource=acpi_pm\n"); 1471 return boot_override_clocksource("acpi_pm"); 1472 } 1473 pr_warn("clock= boot option is deprecated - use clocksource=xyz\n"); 1474 return boot_override_clocksource(str); 1475 } 1476 1477 __setup("clock=", boot_override_clock); 1478