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/clocksource.h> 11 #include <linux/cpu.h> 12 #include <linux/delay.h> 13 #include <linux/device.h> 14 #include <linux/init.h> 15 #include <linux/kthread.h> 16 #include <linux/module.h> 17 #include <linux/prandom.h> 18 #include <linux/sched.h> 19 #include <linux/tick.h> 20 #include <linux/topology.h> 21 22 #include "tick-internal.h" 23 #include "timekeeping_internal.h" 24 25 static void clocksource_enqueue(struct clocksource *cs); 26 27 static noinline u64 cycles_to_nsec_safe(struct clocksource *cs, u64 start, u64 end) 28 { 29 u64 delta = clocksource_delta(end, start, cs->mask, cs->max_raw_delta); 30 31 if (likely(delta < cs->max_cycles)) 32 return clocksource_cyc2ns(delta, cs->mult, cs->shift); 33 34 return mul_u64_u32_shr(delta, cs->mult, cs->shift); 35 } 36 37 /** 38 * clocks_calc_mult_shift - calculate mult/shift factors for scaled math of clocks 39 * @mult: pointer to mult variable 40 * @shift: pointer to shift variable 41 * @from: frequency to convert from 42 * @to: frequency to convert to 43 * @maxsec: guaranteed runtime conversion range in seconds 44 * 45 * The function evaluates the shift/mult pair for the scaled math 46 * operations of clocksources and clockevents. 47 * 48 * @to and @from are frequency values in HZ. For clock sources @to is 49 * NSEC_PER_SEC == 1GHz and @from is the counter frequency. For clock 50 * event @to is the counter frequency and @from is NSEC_PER_SEC. 51 * 52 * The @maxsec conversion range argument controls the time frame in 53 * seconds which must be covered by the runtime conversion with the 54 * calculated mult and shift factors. This guarantees that no 64bit 55 * overflow happens when the input value of the conversion is 56 * multiplied with the calculated mult factor. Larger ranges may 57 * reduce the conversion accuracy by choosing smaller mult and shift 58 * factors. 59 */ 60 void 61 clocks_calc_mult_shift(u32 *mult, u32 *shift, u32 from, u32 to, u32 maxsec) 62 { 63 u64 tmp; 64 u32 sft, sftacc= 32; 65 66 /* 67 * Calculate the shift factor which is limiting the conversion 68 * range: 69 */ 70 tmp = ((u64)maxsec * from) >> 32; 71 while (tmp) { 72 tmp >>=1; 73 sftacc--; 74 } 75 76 /* 77 * Find the conversion shift/mult pair which has the best 78 * accuracy and fits the maxsec conversion range: 79 */ 80 for (sft = 32; sft > 0; sft--) { 81 tmp = (u64) to << sft; 82 tmp += from / 2; 83 do_div(tmp, from); 84 if ((tmp >> sftacc) == 0) 85 break; 86 } 87 *mult = tmp; 88 *shift = sft; 89 } 90 EXPORT_SYMBOL_GPL(clocks_calc_mult_shift); 91 92 /*[Clocksource internal variables]--------- 93 * curr_clocksource: 94 * currently selected clocksource. 95 * suspend_clocksource: 96 * used to calculate the suspend time. 97 * clocksource_list: 98 * linked list with the registered clocksources 99 * clocksource_mutex: 100 * protects manipulations to curr_clocksource and the clocksource_list 101 * override_name: 102 * Name of the user-specified clocksource. 103 */ 104 static struct clocksource *curr_clocksource; 105 static struct clocksource *suspend_clocksource; 106 static LIST_HEAD(clocksource_list); 107 static DEFINE_MUTEX(clocksource_mutex); 108 static char override_name[CS_NAME_LEN]; 109 static int finished_booting; 110 static u64 suspend_start; 111 112 #ifdef CONFIG_CLOCKSOURCE_WATCHDOG 113 static void clocksource_watchdog_work(struct work_struct *work); 114 static void clocksource_select(void); 115 116 static LIST_HEAD(watchdog_list); 117 static struct clocksource *watchdog; 118 static struct timer_list watchdog_timer; 119 static DECLARE_WORK(watchdog_work, clocksource_watchdog_work); 120 static DEFINE_SPINLOCK(watchdog_lock); 121 static int watchdog_running; 122 static atomic_t watchdog_reset_pending; 123 124 /* Watchdog interval: 0.5sec. */ 125 #define WATCHDOG_INTERVAL (HZ >> 1) 126 #define WATCHDOG_INTERVAL_NS (WATCHDOG_INTERVAL * (NSEC_PER_SEC / HZ)) 127 128 /* Maximum time between two reference watchdog readouts */ 129 #define WATCHDOG_READOUT_MAX_NS (50U * NSEC_PER_USEC) 130 131 /* 132 * Maximum time between two remote readouts for NUMA=n. On NUMA enabled systems 133 * the timeout is calculated from the numa distance. 134 */ 135 #define WATCHDOG_DEFAULT_TIMEOUT_NS (50U * NSEC_PER_USEC) 136 137 /* 138 * Remote timeout NUMA distance multiplier. The local distance is 10. The 139 * default remote distance is 20. ACPI tables provide more accurate numbers 140 * which are guaranteed to be greater than the local distance. 141 * 142 * This results in a 5us base value, which is equivalent to the above !NUMA 143 * default. 144 */ 145 #define WATCHDOG_NUMA_MULTIPLIER_NS ((u64)(WATCHDOG_DEFAULT_TIMEOUT_NS / LOCAL_DISTANCE)) 146 147 /* Limit the NUMA timeout in case the distance values are insanely big */ 148 #define WATCHDOG_NUMA_MAX_TIMEOUT_NS ((u64)(500U * NSEC_PER_USEC)) 149 150 /* Shift values to calculate the approximate $N ppm of a given delta. */ 151 #define SHIFT_500PPM 11 152 #define SHIFT_4000PPM 8 153 154 /* Number of attempts to read the watchdog */ 155 #define WATCHDOG_FREQ_RETRIES 3 156 157 /* Five reads local and remote for inter CPU skew detection */ 158 #define WATCHDOG_REMOTE_MAX_SEQ 10 159 160 static inline void clocksource_watchdog_lock(unsigned long *flags) 161 { 162 spin_lock_irqsave(&watchdog_lock, *flags); 163 } 164 165 static inline void clocksource_watchdog_unlock(unsigned long *flags) 166 { 167 spin_unlock_irqrestore(&watchdog_lock, *flags); 168 } 169 170 static int clocksource_watchdog_kthread(void *data); 171 172 static void clocksource_watchdog_work(struct work_struct *work) 173 { 174 /* 175 * We cannot directly run clocksource_watchdog_kthread() here, because 176 * clocksource_select() calls timekeeping_notify() which uses 177 * stop_machine(). One cannot use stop_machine() from a workqueue() due 178 * lock inversions wrt CPU hotplug. 179 * 180 * Also, we only ever run this work once or twice during the lifetime 181 * of the kernel, so there is no point in creating a more permanent 182 * kthread for this. 183 * 184 * If kthread_run fails the next watchdog scan over the 185 * watchdog_list will find the unstable clock again. 186 */ 187 kthread_run(clocksource_watchdog_kthread, NULL, "kwatchdog"); 188 } 189 190 static void clocksource_change_rating(struct clocksource *cs, int rating) 191 { 192 list_del(&cs->list); 193 cs->rating = rating; 194 clocksource_enqueue(cs); 195 } 196 197 static void __clocksource_unstable(struct clocksource *cs) 198 { 199 cs->flags &= ~(CLOCK_SOURCE_VALID_FOR_HRES | CLOCK_SOURCE_WATCHDOG); 200 cs->flags |= CLOCK_SOURCE_UNSTABLE; 201 202 /* 203 * If the clocksource is registered clocksource_watchdog_kthread() will 204 * re-rate and re-select. 205 */ 206 if (list_empty(&cs->list)) { 207 cs->rating = 0; 208 return; 209 } 210 211 if (cs->mark_unstable) 212 cs->mark_unstable(cs); 213 214 /* kick clocksource_watchdog_kthread() */ 215 if (finished_booting) 216 schedule_work(&watchdog_work); 217 } 218 219 /** 220 * clocksource_mark_unstable - mark clocksource unstable via watchdog 221 * @cs: clocksource to be marked unstable 222 * 223 * This function is called by the x86 TSC code to mark clocksources as unstable; 224 * it defers demotion and re-selection to a kthread. 225 */ 226 void clocksource_mark_unstable(struct clocksource *cs) 227 { 228 unsigned long flags; 229 230 spin_lock_irqsave(&watchdog_lock, flags); 231 if (!(cs->flags & CLOCK_SOURCE_UNSTABLE)) { 232 if (!list_empty(&cs->list) && list_empty(&cs->wd_list)) 233 list_add(&cs->wd_list, &watchdog_list); 234 __clocksource_unstable(cs); 235 } 236 spin_unlock_irqrestore(&watchdog_lock, flags); 237 } 238 239 static inline void clocksource_reset_watchdog(void) 240 { 241 struct clocksource *cs; 242 243 list_for_each_entry(cs, &watchdog_list, wd_list) 244 cs->flags &= ~CLOCK_SOURCE_WATCHDOG; 245 } 246 247 enum wd_result { 248 WD_SUCCESS, 249 WD_FREQ_NO_WATCHDOG, 250 WD_FREQ_TIMEOUT, 251 WD_FREQ_RESET, 252 WD_FREQ_SKEWED, 253 WD_CPU_TIMEOUT, 254 WD_CPU_SKEWED, 255 }; 256 257 struct watchdog_cpu_data { 258 /* Keep first as it is 32 byte aligned */ 259 call_single_data_t csd; 260 atomic_t remote_inprogress; 261 enum wd_result result; 262 u64 cpu_ts[2]; 263 struct clocksource *cs; 264 /* Ensure that the sequence is in a separate cache line */ 265 atomic_t seq ____cacheline_aligned; 266 /* Set by the control CPU according to NUMA distance */ 267 u64 timeout_ns; 268 }; 269 270 struct watchdog_data { 271 raw_spinlock_t lock; 272 enum wd_result result; 273 274 u64 wd_seq; 275 u64 wd_delta; 276 u64 cs_delta; 277 u64 cpu_ts[2]; 278 279 unsigned int curr_cpu; 280 } ____cacheline_aligned_in_smp; 281 282 static void watchdog_check_skew_remote(void *unused); 283 284 static DEFINE_PER_CPU_ALIGNED(struct watchdog_cpu_data, watchdog_cpu_data) = { 285 .csd = CSD_INIT(watchdog_check_skew_remote, NULL), 286 }; 287 288 static struct watchdog_data watchdog_data = { 289 .lock = __RAW_SPIN_LOCK_UNLOCKED(watchdog_data.lock), 290 }; 291 292 static inline void watchdog_set_result(struct watchdog_cpu_data *wd, enum wd_result result) 293 { 294 guard(raw_spinlock)(&watchdog_data.lock); 295 if (!wd->result) { 296 atomic_set(&wd->seq, WATCHDOG_REMOTE_MAX_SEQ); 297 WRITE_ONCE(wd->result, result); 298 } 299 } 300 301 /* Wait for the sequence number to hand over control. */ 302 static bool watchdog_wait_seq(struct watchdog_cpu_data *wd, u64 start, int seq) 303 { 304 for(int cnt = 0; atomic_read(&wd->seq) < seq; cnt++) { 305 /* Bail if the other side set an error result */ 306 if (READ_ONCE(wd->result) != WD_SUCCESS) 307 return false; 308 309 /* Prevent endless loops if the other CPU does not react. */ 310 if (cnt == 5000) { 311 u64 nsecs = ktime_get_raw_fast_ns(); 312 313 if (nsecs - start >=wd->timeout_ns) { 314 watchdog_set_result(wd, WD_CPU_TIMEOUT); 315 return false; 316 } 317 cnt = 0; 318 } 319 cpu_relax(); 320 } 321 return seq < WATCHDOG_REMOTE_MAX_SEQ; 322 } 323 324 static void watchdog_check_skew(struct watchdog_cpu_data *wd, int index) 325 { 326 u64 prev, now, delta, start = ktime_get_raw_fast_ns(); 327 int local = index, remote = (index + 1) & 0x1; 328 struct clocksource *cs = wd->cs; 329 330 /* Set the local timestamp so that the first iteration works correctly */ 331 wd->cpu_ts[local] = cs->read(cs); 332 333 /* Signal arrival */ 334 atomic_inc(&wd->seq); 335 336 for (int seq = local + 2; seq < WATCHDOG_REMOTE_MAX_SEQ; seq += 2) { 337 if (!watchdog_wait_seq(wd, start, seq)) 338 return; 339 340 /* Capture local timestamp before possible non-local coherency overhead */ 341 now = cs->read(cs); 342 343 /* Store local timestamp before reading remote to limit coherency stalls */ 344 wd->cpu_ts[local] = now; 345 346 prev = wd->cpu_ts[remote]; 347 delta = (now - prev) & cs->mask; 348 349 if (delta > cs->max_raw_delta) { 350 watchdog_set_result(wd, WD_CPU_SKEWED); 351 return; 352 } 353 354 /* Hand over to the remote CPU */ 355 atomic_inc(&wd->seq); 356 } 357 } 358 359 static void watchdog_check_skew_remote(void *unused) 360 { 361 struct watchdog_cpu_data *wd = this_cpu_ptr(&watchdog_cpu_data); 362 363 atomic_inc(&wd->remote_inprogress); 364 watchdog_check_skew(wd, 1); 365 atomic_dec(&wd->remote_inprogress); 366 } 367 368 static inline bool wd_csd_locked(struct watchdog_cpu_data *wd) 369 { 370 return READ_ONCE(wd->csd.node.u_flags) & CSD_FLAG_LOCK; 371 } 372 373 /* 374 * This is only invoked for remote CPUs. See watchdog_check_cpu_skew(). 375 */ 376 static inline u64 wd_get_remote_timeout(unsigned int remote_cpu) 377 { 378 unsigned int n1, n2; 379 u64 ns; 380 381 if (nr_node_ids == 1) 382 return WATCHDOG_DEFAULT_TIMEOUT_NS; 383 384 n1 = cpu_to_node(smp_processor_id()); 385 n2 = cpu_to_node(remote_cpu); 386 ns = WATCHDOG_NUMA_MULTIPLIER_NS * node_distance(n1, n2); 387 return min(ns, WATCHDOG_NUMA_MAX_TIMEOUT_NS); 388 } 389 390 static void __watchdog_check_cpu_skew(struct clocksource *cs, unsigned int cpu) 391 { 392 struct watchdog_cpu_data *wd; 393 394 wd = per_cpu_ptr(&watchdog_cpu_data, cpu); 395 if (atomic_read(&wd->remote_inprogress) || wd_csd_locked(wd)) { 396 watchdog_data.result = WD_CPU_TIMEOUT; 397 return; 398 } 399 400 atomic_set(&wd->seq, 0); 401 wd->result = WD_SUCCESS; 402 wd->cs = cs; 403 /* Store the current CPU ID for the watchdog test unit */ 404 cs->wd_cpu = smp_processor_id(); 405 406 wd->timeout_ns = wd_get_remote_timeout(cpu); 407 408 /* Kick the remote CPU into the watchdog function */ 409 if (WARN_ON_ONCE(smp_call_function_single_async(cpu, &wd->csd))) { 410 watchdog_data.result = WD_CPU_TIMEOUT; 411 return; 412 } 413 414 scoped_guard(irq) 415 watchdog_check_skew(wd, 0); 416 417 scoped_guard(raw_spinlock_irq, &watchdog_data.lock) { 418 watchdog_data.result = wd->result; 419 memcpy(watchdog_data.cpu_ts, wd->cpu_ts, sizeof(wd->cpu_ts)); 420 } 421 } 422 423 static void watchdog_check_cpu_skew(struct clocksource *cs) 424 { 425 unsigned int cpu = watchdog_data.curr_cpu; 426 427 cpu = cpumask_next_wrap(cpu, cpu_online_mask); 428 watchdog_data.curr_cpu = cpu; 429 430 /* Skip the current CPU. Handles num_online_cpus() == 1 as well */ 431 if (cpu == smp_processor_id()) 432 return; 433 434 /* Don't interfere with the test mechanics */ 435 if ((cs->flags & CLOCK_SOURCE_WDTEST) && !(cs->flags & CLOCK_SOURCE_WDTEST_PERCPU)) 436 return; 437 438 __watchdog_check_cpu_skew(cs, cpu); 439 } 440 441 static bool watchdog_check_freq(struct clocksource *cs, bool reset_pending) 442 { 443 unsigned int ppm_shift = SHIFT_4000PPM; 444 u64 wd_ts0, wd_ts1, cs_ts; 445 446 watchdog_data.result = WD_SUCCESS; 447 if (!watchdog) { 448 watchdog_data.result = WD_FREQ_NO_WATCHDOG; 449 return false; 450 } 451 452 if (cs->flags & CLOCK_SOURCE_WDTEST_PERCPU) 453 return true; 454 455 /* 456 * If both the clocksource and the watchdog claim they are 457 * calibrated use 500ppm limit. Uncalibrated clocksources need a 458 * larger allowance because thefirmware supplied frequencies can be 459 * way off. 460 */ 461 if (watchdog->flags & CLOCK_SOURCE_CALIBRATED && cs->flags & CLOCK_SOURCE_CALIBRATED) 462 ppm_shift = SHIFT_500PPM; 463 464 for (int retries = 0; retries < WATCHDOG_FREQ_RETRIES; retries++) { 465 s64 wd_last, cs_last, wd_seq, wd_delta, cs_delta, max_delta; 466 467 scoped_guard(irq) { 468 wd_ts0 = watchdog->read(watchdog); 469 cs_ts = cs->read(cs); 470 wd_ts1 = watchdog->read(watchdog); 471 } 472 473 wd_last = cs->wd_last; 474 cs_last = cs->cs_last; 475 476 /* Validate the watchdog readout window */ 477 wd_seq = cycles_to_nsec_safe(watchdog, wd_ts0, wd_ts1); 478 if (wd_seq > WATCHDOG_READOUT_MAX_NS) { 479 /* Store for printout in case all retries fail */ 480 watchdog_data.wd_seq = wd_seq; 481 continue; 482 } 483 484 /* Store for subsequent processing */ 485 cs->wd_last = wd_ts0; 486 cs->cs_last = cs_ts; 487 488 /* First round or reset pending? */ 489 if (!(cs->flags & CLOCK_SOURCE_WATCHDOG) || reset_pending) 490 goto reset; 491 492 /* Calculate the nanosecond deltas from the last invocation */ 493 wd_delta = cycles_to_nsec_safe(watchdog, wd_last, wd_ts0); 494 cs_delta = cycles_to_nsec_safe(cs, cs_last, cs_ts); 495 496 watchdog_data.wd_delta = wd_delta; 497 watchdog_data.cs_delta = cs_delta; 498 499 /* 500 * Ensure that the deltas are within the readout limits of 501 * the clocksource and the watchdog. Long delays can cause 502 * clocksources to overflow. 503 */ 504 max_delta = max(wd_delta, cs_delta); 505 if (max_delta > cs->max_idle_ns || max_delta > watchdog->max_idle_ns) 506 goto reset; 507 508 /* 509 * Calculate and validate the skew against the allowed PPM 510 * value of the maximum delta plus the watchdog readout 511 * time. 512 */ 513 if (abs(wd_delta - cs_delta) < (max_delta >> ppm_shift) + wd_seq) 514 return true; 515 516 watchdog_data.result = WD_FREQ_SKEWED; 517 return false; 518 } 519 520 watchdog_data.result = WD_FREQ_TIMEOUT; 521 return false; 522 523 reset: 524 cs->flags |= CLOCK_SOURCE_WATCHDOG; 525 watchdog_data.result = WD_FREQ_RESET; 526 return false; 527 } 528 529 /* Synchronization for sched clock */ 530 static void clocksource_tick_stable(struct clocksource *cs) 531 { 532 if (cs == curr_clocksource && cs->tick_stable) 533 cs->tick_stable(cs); 534 } 535 536 /* Conditionaly enable high resolution mode */ 537 static void clocksource_enable_highres(struct clocksource *cs) 538 { 539 if ((cs->flags & CLOCK_SOURCE_VALID_FOR_HRES) || 540 !(cs->flags & CLOCK_SOURCE_IS_CONTINUOUS) || 541 !watchdog || !(watchdog->flags & CLOCK_SOURCE_IS_CONTINUOUS)) 542 return; 543 544 /* Mark it valid for high-res. */ 545 cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES; 546 547 /* 548 * Can't schedule work before finished_booting is 549 * true. clocksource_done_booting will take care of it. 550 */ 551 if (!finished_booting) 552 return; 553 554 if (cs->flags & CLOCK_SOURCE_WDTEST) 555 return; 556 557 /* 558 * If this is not the current clocksource let the watchdog thread 559 * reselect it. Due to the change to high res this clocksource 560 * might be preferred now. If it is the current clocksource let the 561 * tick code know about that change. 562 */ 563 if (cs != curr_clocksource) { 564 cs->flags |= CLOCK_SOURCE_RESELECT; 565 schedule_work(&watchdog_work); 566 } else { 567 tick_clock_notify(); 568 } 569 } 570 571 static DEFINE_RATELIMIT_STATE(ratelimit_state, 5 * HZ, 2); 572 573 static void watchdog_print_freq_timeout(struct clocksource *cs) 574 { 575 if (!__ratelimit(&ratelimit_state)) 576 return; 577 pr_info("Watchdog %s read timed out. Readout sequence took: %lluns\n", 578 watchdog->name, watchdog_data.wd_seq); 579 } 580 581 static void watchdog_print_freq_skew(struct clocksource *cs) 582 { 583 pr_warn("Marking clocksource %s unstable due to frequency skew\n", cs->name); 584 pr_warn("Watchdog %20s interval: %16lluns\n", watchdog->name, watchdog_data.wd_delta); 585 pr_warn("Clocksource %20s interval: %16lluns\n", cs->name, watchdog_data.cs_delta); 586 } 587 588 static void watchdog_handle_remote_timeout(struct clocksource *cs) 589 { 590 pr_info_once("Watchdog remote CPU %u read timed out\n", watchdog_data.curr_cpu); 591 } 592 593 static void watchdog_print_remote_skew(struct clocksource *cs) 594 { 595 pr_warn("Marking clocksource %s unstable due to inter CPU skew\n", cs->name); 596 if (watchdog_data.cpu_ts[0] < watchdog_data.cpu_ts[1]) { 597 pr_warn("CPU%u %16llu < CPU%u %16llu (cycles)\n", smp_processor_id(), 598 watchdog_data.cpu_ts[0], watchdog_data.curr_cpu, watchdog_data.cpu_ts[1]); 599 } else { 600 pr_warn("CPU%u %16llu < CPU%u %16llu (cycles)\n", watchdog_data.curr_cpu, 601 watchdog_data.cpu_ts[1], smp_processor_id(), watchdog_data.cpu_ts[0]); 602 } 603 } 604 605 static void watchdog_check_result(struct clocksource *cs) 606 { 607 switch (watchdog_data.result) { 608 case WD_SUCCESS: 609 clocksource_tick_stable(cs); 610 clocksource_enable_highres(cs); 611 return; 612 613 case WD_FREQ_TIMEOUT: 614 watchdog_print_freq_timeout(cs); 615 /* Try again later and invalidate the reference timestamps. */ 616 cs->flags &= ~CLOCK_SOURCE_WATCHDOG; 617 return; 618 619 case WD_FREQ_NO_WATCHDOG: 620 case WD_FREQ_RESET: 621 /* 622 * Nothing to do when the reference timestamps were reset 623 * or no watchdog clocksource registered. 624 */ 625 return; 626 627 case WD_FREQ_SKEWED: 628 watchdog_print_freq_skew(cs); 629 break; 630 631 case WD_CPU_TIMEOUT: 632 /* Remote check timed out. Try again next cycle. */ 633 watchdog_handle_remote_timeout(cs); 634 return; 635 636 case WD_CPU_SKEWED: 637 watchdog_print_remote_skew(cs); 638 break; 639 } 640 __clocksource_unstable(cs); 641 } 642 643 static void clocksource_watchdog(struct timer_list *unused) 644 { 645 struct clocksource *cs; 646 bool reset_pending; 647 648 guard(spinlock)(&watchdog_lock); 649 if (!watchdog_running) 650 return; 651 652 reset_pending = atomic_read(&watchdog_reset_pending); 653 654 list_for_each_entry(cs, &watchdog_list, wd_list) { 655 /* Clocksource already marked unstable? */ 656 if (cs->flags & CLOCK_SOURCE_UNSTABLE) { 657 if (finished_booting) 658 schedule_work(&watchdog_work); 659 continue; 660 } 661 662 /* Compare against watchdog clocksource if available */ 663 if (watchdog_check_freq(cs, reset_pending)) { 664 /* Check for inter CPU skew */ 665 watchdog_check_cpu_skew(cs); 666 } 667 668 watchdog_check_result(cs); 669 } 670 671 /* Clear after the full clocksource walk */ 672 if (reset_pending) 673 atomic_dec(&watchdog_reset_pending); 674 675 /* Could have been rearmed by a stop/start cycle */ 676 if (!timer_pending(&watchdog_timer)) { 677 watchdog_timer.expires += WATCHDOG_INTERVAL; 678 add_timer_local(&watchdog_timer); 679 } 680 } 681 682 static inline void clocksource_start_watchdog(void) 683 { 684 if (watchdog_running || list_empty(&watchdog_list)) 685 return; 686 timer_setup(&watchdog_timer, clocksource_watchdog, TIMER_PINNED); 687 watchdog_timer.expires = jiffies + WATCHDOG_INTERVAL; 688 689 add_timer_on(&watchdog_timer, get_boot_cpu_id()); 690 watchdog_running = 1; 691 } 692 693 static inline void clocksource_stop_watchdog(void) 694 { 695 if (!watchdog_running || !list_empty(&watchdog_list)) 696 return; 697 timer_delete(&watchdog_timer); 698 watchdog_running = 0; 699 } 700 701 static void clocksource_resume_watchdog(void) 702 { 703 atomic_inc(&watchdog_reset_pending); 704 } 705 706 static void clocksource_enqueue_watchdog(struct clocksource *cs) 707 { 708 INIT_LIST_HEAD(&cs->wd_list); 709 710 if (cs->flags & CLOCK_SOURCE_MUST_VERIFY) { 711 /* cs is a clocksource to be watched. */ 712 list_add(&cs->wd_list, &watchdog_list); 713 cs->flags &= ~CLOCK_SOURCE_WATCHDOG; 714 } else { 715 /* cs is a watchdog. */ 716 if (cs->flags & CLOCK_SOURCE_IS_CONTINUOUS) 717 cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES; 718 } 719 } 720 721 static void clocksource_select_watchdog(bool fallback) 722 { 723 struct clocksource *cs, *old_wd; 724 unsigned long flags; 725 726 spin_lock_irqsave(&watchdog_lock, flags); 727 /* save current watchdog */ 728 old_wd = watchdog; 729 if (fallback) 730 watchdog = NULL; 731 732 list_for_each_entry(cs, &clocksource_list, list) { 733 /* cs is a clocksource to be watched. */ 734 if (cs->flags & CLOCK_SOURCE_MUST_VERIFY) 735 continue; 736 737 /* 738 * If it's not continuous, don't put the fox in charge of 739 * the henhouse. 740 */ 741 if (!(cs->flags & CLOCK_SOURCE_IS_CONTINUOUS)) 742 continue; 743 744 /* Skip current if we were requested for a fallback. */ 745 if (fallback && cs == old_wd) 746 continue; 747 748 /* Pick the best watchdog. */ 749 if (!watchdog || cs->rating > watchdog->rating) 750 watchdog = cs; 751 } 752 /* If we failed to find a fallback restore the old one. */ 753 if (!watchdog) 754 watchdog = old_wd; 755 756 /* If we changed the watchdog we need to reset cycles. */ 757 if (watchdog != old_wd) 758 clocksource_reset_watchdog(); 759 760 /* Check if the watchdog timer needs to be started. */ 761 clocksource_start_watchdog(); 762 spin_unlock_irqrestore(&watchdog_lock, flags); 763 } 764 765 static void clocksource_dequeue_watchdog(struct clocksource *cs) 766 { 767 if (cs != watchdog) { 768 if (cs->flags & CLOCK_SOURCE_MUST_VERIFY) { 769 /* cs is a watched clocksource. */ 770 list_del_init(&cs->wd_list); 771 /* Check if the watchdog timer needs to be stopped. */ 772 clocksource_stop_watchdog(); 773 } 774 } 775 } 776 777 static int __clocksource_watchdog_kthread(void) 778 { 779 struct clocksource *cs, *tmp; 780 unsigned long flags; 781 int select = 0; 782 783 spin_lock_irqsave(&watchdog_lock, flags); 784 list_for_each_entry_safe(cs, tmp, &watchdog_list, wd_list) { 785 if (cs->flags & CLOCK_SOURCE_UNSTABLE) { 786 list_del_init(&cs->wd_list); 787 clocksource_change_rating(cs, 0); 788 select = 1; 789 } 790 if (cs->flags & CLOCK_SOURCE_RESELECT) { 791 cs->flags &= ~CLOCK_SOURCE_RESELECT; 792 select = 1; 793 } 794 } 795 /* Check if the watchdog timer needs to be stopped. */ 796 clocksource_stop_watchdog(); 797 spin_unlock_irqrestore(&watchdog_lock, flags); 798 799 return select; 800 } 801 802 static int clocksource_watchdog_kthread(void *data) 803 { 804 mutex_lock(&clocksource_mutex); 805 if (__clocksource_watchdog_kthread()) 806 clocksource_select(); 807 mutex_unlock(&clocksource_mutex); 808 return 0; 809 } 810 811 static bool clocksource_is_watchdog(struct clocksource *cs) 812 { 813 return cs == watchdog; 814 } 815 816 #else /* CONFIG_CLOCKSOURCE_WATCHDOG */ 817 818 static void clocksource_enqueue_watchdog(struct clocksource *cs) 819 { 820 if (cs->flags & CLOCK_SOURCE_IS_CONTINUOUS) 821 cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES; 822 } 823 824 static void clocksource_select_watchdog(bool fallback) { } 825 static inline void clocksource_dequeue_watchdog(struct clocksource *cs) { } 826 static inline void clocksource_resume_watchdog(void) { } 827 static inline int __clocksource_watchdog_kthread(void) { return 0; } 828 static bool clocksource_is_watchdog(struct clocksource *cs) { return false; } 829 void clocksource_mark_unstable(struct clocksource *cs) { } 830 831 static inline void clocksource_watchdog_lock(unsigned long *flags) { } 832 static inline void clocksource_watchdog_unlock(unsigned long *flags) { } 833 834 #endif /* CONFIG_CLOCKSOURCE_WATCHDOG */ 835 836 static bool clocksource_is_suspend(struct clocksource *cs) 837 { 838 return cs == suspend_clocksource; 839 } 840 841 static void __clocksource_suspend_select(struct clocksource *cs) 842 { 843 /* 844 * Skip the clocksource which will be stopped in suspend state. 845 */ 846 if (!(cs->flags & CLOCK_SOURCE_SUSPEND_NONSTOP)) 847 return; 848 849 /* 850 * The nonstop clocksource can be selected as the suspend clocksource to 851 * calculate the suspend time, so it should not supply suspend/resume 852 * interfaces to suspend the nonstop clocksource when system suspends. 853 */ 854 if (cs->suspend || cs->resume) { 855 pr_warn("Nonstop clocksource %s should not supply suspend/resume interfaces\n", 856 cs->name); 857 } 858 859 /* Pick the best rating. */ 860 if (!suspend_clocksource || cs->rating > suspend_clocksource->rating) 861 suspend_clocksource = cs; 862 } 863 864 /** 865 * clocksource_suspend_select - Select the best clocksource for suspend timing 866 * @fallback: if select a fallback clocksource 867 */ 868 static void clocksource_suspend_select(bool fallback) 869 { 870 struct clocksource *cs, *old_suspend; 871 872 old_suspend = suspend_clocksource; 873 if (fallback) 874 suspend_clocksource = NULL; 875 876 list_for_each_entry(cs, &clocksource_list, list) { 877 /* Skip current if we were requested for a fallback. */ 878 if (fallback && cs == old_suspend) 879 continue; 880 881 __clocksource_suspend_select(cs); 882 } 883 } 884 885 /** 886 * clocksource_start_suspend_timing - Start measuring the suspend timing 887 * @cs: current clocksource from timekeeping 888 * @start_cycles: current cycles from timekeeping 889 * 890 * This function will save the start cycle values of suspend timer to calculate 891 * the suspend time when resuming system. 892 * 893 * This function is called late in the suspend process from timekeeping_suspend(), 894 * that means processes are frozen, non-boot cpus and interrupts are disabled 895 * now. It is therefore possible to start the suspend timer without taking the 896 * clocksource mutex. 897 */ 898 void clocksource_start_suspend_timing(struct clocksource *cs, u64 start_cycles) 899 { 900 if (!suspend_clocksource) 901 return; 902 903 /* 904 * If current clocksource is the suspend timer, we should use the 905 * tkr_mono.cycle_last value as suspend_start to avoid same reading 906 * from suspend timer. 907 */ 908 if (clocksource_is_suspend(cs)) { 909 suspend_start = start_cycles; 910 return; 911 } 912 913 if (suspend_clocksource->enable && 914 suspend_clocksource->enable(suspend_clocksource)) { 915 pr_warn_once("Failed to enable the non-suspend-able clocksource.\n"); 916 return; 917 } 918 919 suspend_start = suspend_clocksource->read(suspend_clocksource); 920 } 921 922 /** 923 * clocksource_stop_suspend_timing - Stop measuring the suspend timing 924 * @cs: current clocksource from timekeeping 925 * @cycle_now: current cycles from timekeeping 926 * 927 * This function will calculate the suspend time from suspend timer. 928 * 929 * Returns nanoseconds since suspend started, 0 if no usable suspend clocksource. 930 * 931 * This function is called early in the resume process from timekeeping_resume(), 932 * that means there is only one cpu, no processes are running and the interrupts 933 * are disabled. It is therefore possible to stop the suspend timer without 934 * taking the clocksource mutex. 935 */ 936 u64 clocksource_stop_suspend_timing(struct clocksource *cs, u64 cycle_now) 937 { 938 u64 now, nsec = 0; 939 940 if (!suspend_clocksource) 941 return 0; 942 943 /* 944 * If current clocksource is the suspend timer, we should use the 945 * tkr_mono.cycle_last value from timekeeping as current cycle to 946 * avoid same reading from suspend timer. 947 */ 948 if (clocksource_is_suspend(cs)) 949 now = cycle_now; 950 else 951 now = suspend_clocksource->read(suspend_clocksource); 952 953 if (now > suspend_start) 954 nsec = cycles_to_nsec_safe(suspend_clocksource, suspend_start, now); 955 956 /* 957 * Disable the suspend timer to save power if current clocksource is 958 * not the suspend timer. 959 */ 960 if (!clocksource_is_suspend(cs) && suspend_clocksource->disable) 961 suspend_clocksource->disable(suspend_clocksource); 962 963 return nsec; 964 } 965 966 /** 967 * clocksource_suspend - suspend the clocksource(s) 968 */ 969 void clocksource_suspend(void) 970 { 971 struct clocksource *cs; 972 973 list_for_each_entry_reverse(cs, &clocksource_list, list) 974 if (cs->suspend) 975 cs->suspend(cs); 976 } 977 978 /** 979 * clocksource_resume - resume the clocksource(s) 980 */ 981 void clocksource_resume(void) 982 { 983 struct clocksource *cs; 984 985 list_for_each_entry(cs, &clocksource_list, list) 986 if (cs->resume) 987 cs->resume(cs); 988 989 clocksource_resume_watchdog(); 990 } 991 992 /** 993 * clocksource_touch_watchdog - Update watchdog 994 * 995 * Update the watchdog after exception contexts such as kgdb so as not 996 * to incorrectly trip the watchdog. This might fail when the kernel 997 * was stopped in code which holds watchdog_lock. 998 */ 999 void clocksource_touch_watchdog(void) 1000 { 1001 clocksource_resume_watchdog(); 1002 } 1003 1004 /** 1005 * clocksource_max_adjustment- Returns max adjustment amount 1006 * @cs: Pointer to clocksource 1007 * 1008 */ 1009 static u32 clocksource_max_adjustment(struct clocksource *cs) 1010 { 1011 u64 ret; 1012 /* 1013 * We won't try to correct for more than 11% adjustments (110,000 ppm), 1014 */ 1015 ret = (u64)cs->mult * 11; 1016 do_div(ret,100); 1017 return (u32)ret; 1018 } 1019 1020 /** 1021 * clocks_calc_max_nsecs - Returns maximum nanoseconds that can be converted 1022 * @mult: cycle to nanosecond multiplier 1023 * @shift: cycle to nanosecond divisor (power of two) 1024 * @maxadj: maximum adjustment value to mult (~11%) 1025 * @mask: bitmask for two's complement subtraction of non 64 bit counters 1026 * @max_cyc: maximum cycle value before potential overflow (does not include 1027 * any safety margin) 1028 * 1029 * NOTE: This function includes a safety margin of 50%, in other words, we 1030 * return half the number of nanoseconds the hardware counter can technically 1031 * cover. This is done so that we can potentially detect problems caused by 1032 * delayed timers or bad hardware, which might result in time intervals that 1033 * are larger than what the math used can handle without overflows. 1034 */ 1035 u64 clocks_calc_max_nsecs(u32 mult, u32 shift, u32 maxadj, u64 mask, u64 *max_cyc) 1036 { 1037 u64 max_nsecs, max_cycles; 1038 1039 /* 1040 * Calculate the maximum number of cycles that we can pass to the 1041 * cyc2ns() function without overflowing a 64-bit result. 1042 */ 1043 max_cycles = ULLONG_MAX; 1044 do_div(max_cycles, mult+maxadj); 1045 1046 /* 1047 * The actual maximum number of cycles we can defer the clocksource is 1048 * determined by the minimum of max_cycles and mask. 1049 * Note: Here we subtract the maxadj to make sure we don't sleep for 1050 * too long if there's a large negative adjustment. 1051 */ 1052 max_cycles = min(max_cycles, mask); 1053 max_nsecs = clocksource_cyc2ns(max_cycles, mult - maxadj, shift); 1054 1055 /* return the max_cycles value as well if requested */ 1056 if (max_cyc) 1057 *max_cyc = max_cycles; 1058 1059 /* Return 50% of the actual maximum, so we can detect bad values */ 1060 max_nsecs >>= 1; 1061 1062 return max_nsecs; 1063 } 1064 1065 /** 1066 * clocksource_update_max_deferment - Updates the clocksource max_idle_ns & max_cycles 1067 * @cs: Pointer to clocksource to be updated 1068 * 1069 */ 1070 static inline void clocksource_update_max_deferment(struct clocksource *cs) 1071 { 1072 cs->max_idle_ns = clocks_calc_max_nsecs(cs->mult, cs->shift, 1073 cs->maxadj, cs->mask, 1074 &cs->max_cycles); 1075 1076 /* 1077 * Threshold for detecting negative motion in clocksource_delta(). 1078 * 1079 * Allow for 0.875 of the counter width so that overly long idle 1080 * sleeps, which go slightly over mask/2, do not trigger the 1081 * negative motion detection. 1082 */ 1083 cs->max_raw_delta = (cs->mask >> 1) + (cs->mask >> 2) + (cs->mask >> 3); 1084 } 1085 1086 static struct clocksource *clocksource_find_best(bool oneshot, bool skipcur) 1087 { 1088 struct clocksource *cs; 1089 1090 if (!finished_booting || list_empty(&clocksource_list)) 1091 return NULL; 1092 1093 /* 1094 * We pick the clocksource with the highest rating. If oneshot 1095 * mode is active, we pick the highres valid clocksource with 1096 * the best rating. 1097 */ 1098 list_for_each_entry(cs, &clocksource_list, list) { 1099 if (skipcur && cs == curr_clocksource) 1100 continue; 1101 if (oneshot && !(cs->flags & CLOCK_SOURCE_VALID_FOR_HRES)) 1102 continue; 1103 if (cs->flags & CLOCK_SOURCE_WDTEST) 1104 continue; 1105 return cs; 1106 } 1107 return NULL; 1108 } 1109 1110 static void __clocksource_select(bool skipcur) 1111 { 1112 bool oneshot = tick_oneshot_mode_active(); 1113 struct clocksource *best, *cs; 1114 1115 /* Find the best suitable clocksource */ 1116 best = clocksource_find_best(oneshot, skipcur); 1117 if (!best) 1118 return; 1119 1120 if (!strlen(override_name)) 1121 goto found; 1122 1123 /* Check for the override clocksource. */ 1124 list_for_each_entry(cs, &clocksource_list, list) { 1125 if (skipcur && cs == curr_clocksource) 1126 continue; 1127 if (strcmp(cs->name, override_name) != 0) 1128 continue; 1129 if (cs->flags & CLOCK_SOURCE_WDTEST) 1130 continue; 1131 /* 1132 * Check to make sure we don't switch to a non-highres 1133 * capable clocksource if the tick code is in oneshot 1134 * mode (highres or nohz) 1135 */ 1136 if (!(cs->flags & CLOCK_SOURCE_VALID_FOR_HRES) && oneshot) { 1137 /* Override clocksource cannot be used. */ 1138 if (cs->flags & CLOCK_SOURCE_UNSTABLE) { 1139 pr_warn("Override clocksource %s is unstable and not HRT compatible - cannot switch while in HRT/NOHZ mode\n", 1140 cs->name); 1141 override_name[0] = 0; 1142 } else { 1143 /* 1144 * The override cannot be currently verified. 1145 * Deferring to let the watchdog check. 1146 */ 1147 pr_info("Override clocksource %s is not currently HRT compatible - deferring\n", 1148 cs->name); 1149 } 1150 } else 1151 /* Override clocksource can be used. */ 1152 best = cs; 1153 break; 1154 } 1155 1156 found: 1157 if (curr_clocksource != best && !timekeeping_notify(best)) { 1158 pr_info("Switched to clocksource %s\n", best->name); 1159 curr_clocksource = best; 1160 } 1161 } 1162 1163 /** 1164 * clocksource_select - Select the best clocksource available 1165 * 1166 * Private function. Must hold clocksource_mutex when called. 1167 * 1168 * Select the clocksource with the best rating, or the clocksource, 1169 * which is selected by userspace override. 1170 */ 1171 static void clocksource_select(void) 1172 { 1173 __clocksource_select(false); 1174 } 1175 1176 static void clocksource_select_fallback(void) 1177 { 1178 __clocksource_select(true); 1179 } 1180 1181 /* 1182 * clocksource_done_booting - Called near the end of core bootup 1183 * 1184 * Hack to avoid lots of clocksource churn at boot time. 1185 * We use fs_initcall because we want this to start before 1186 * device_initcall but after subsys_initcall. 1187 */ 1188 static int __init clocksource_done_booting(void) 1189 { 1190 mutex_lock(&clocksource_mutex); 1191 curr_clocksource = clocksource_default_clock(); 1192 finished_booting = 1; 1193 /* 1194 * Run the watchdog first to eliminate unstable clock sources 1195 */ 1196 __clocksource_watchdog_kthread(); 1197 clocksource_select(); 1198 mutex_unlock(&clocksource_mutex); 1199 return 0; 1200 } 1201 fs_initcall(clocksource_done_booting); 1202 1203 /* 1204 * Enqueue the clocksource sorted by rating 1205 */ 1206 static void clocksource_enqueue(struct clocksource *cs) 1207 { 1208 struct list_head *entry = &clocksource_list; 1209 struct clocksource *tmp; 1210 1211 list_for_each_entry(tmp, &clocksource_list, list) { 1212 /* Keep track of the place, where to insert */ 1213 if (tmp->rating < cs->rating) 1214 break; 1215 entry = &tmp->list; 1216 } 1217 list_add(&cs->list, entry); 1218 } 1219 1220 /** 1221 * __clocksource_update_freq_scale - Used update clocksource with new freq 1222 * @cs: clocksource to be registered 1223 * @scale: Scale factor multiplied against freq to get clocksource hz 1224 * @freq: clocksource frequency (cycles per second) divided by scale 1225 */ 1226 static void __clocksource_update_freq_scale(struct clocksource *cs, u32 scale, u32 freq) 1227 { 1228 u64 sec; 1229 1230 /* 1231 * Default clocksources are *special* and self-define their mult/shift. 1232 * But, you're not special, so you should specify a freq value. 1233 */ 1234 if (freq) { 1235 /* 1236 * Calc the maximum number of seconds which we can run before 1237 * wrapping around. For clocksources which have a mask > 32-bit 1238 * we need to limit the max sleep time to have a good 1239 * conversion precision. 10 minutes is still a reasonable 1240 * amount. That results in a shift value of 24 for a 1241 * clocksource with mask >= 40-bit and f >= 4GHz. That maps to 1242 * ~ 0.06ppm granularity for NTP. 1243 */ 1244 sec = cs->mask; 1245 do_div(sec, freq); 1246 do_div(sec, scale); 1247 if (!sec) 1248 sec = 1; 1249 else if (sec > 600 && cs->mask > UINT_MAX) 1250 sec = 600; 1251 1252 clocks_calc_mult_shift(&cs->mult, &cs->shift, freq, 1253 NSEC_PER_SEC / scale, sec * scale); 1254 1255 /* Update cs::freq_khz */ 1256 cs->freq_khz = div_u64((u64)freq * scale, 1000); 1257 } 1258 1259 /* 1260 * Ensure clocksources that have large 'mult' values don't overflow 1261 * when adjusted. 1262 */ 1263 cs->maxadj = clocksource_max_adjustment(cs); 1264 while (freq && ((cs->mult + cs->maxadj < cs->mult) 1265 || (cs->mult - cs->maxadj > cs->mult))) { 1266 cs->mult >>= 1; 1267 cs->shift--; 1268 cs->maxadj = clocksource_max_adjustment(cs); 1269 } 1270 1271 /* 1272 * Only warn for *special* clocksources that self-define 1273 * their mult/shift values and don't specify a freq. 1274 */ 1275 WARN_ONCE(cs->mult + cs->maxadj < cs->mult, 1276 "timekeeping: Clocksource %s might overflow on 11%% adjustment\n", 1277 cs->name); 1278 1279 clocksource_update_max_deferment(cs); 1280 1281 pr_info("%s: mask: 0x%llx max_cycles: 0x%llx, max_idle_ns: %lld ns\n", 1282 cs->name, cs->mask, cs->max_cycles, cs->max_idle_ns); 1283 } 1284 1285 /** 1286 * __clocksource_register_scale - Used to install new clocksources 1287 * @cs: clocksource to be registered 1288 * @scale: Scale factor multiplied against freq to get clocksource hz 1289 * @freq: clocksource frequency (cycles per second) divided by scale 1290 * 1291 * Returns -EBUSY if registration fails, zero otherwise. 1292 * 1293 * This *SHOULD NOT* be called directly! Please use the 1294 * clocksource_register_hz() or clocksource_register_khz helper functions. 1295 */ 1296 int __clocksource_register_scale(struct clocksource *cs, u32 scale, u32 freq) 1297 { 1298 unsigned long flags; 1299 1300 clocksource_arch_init(cs); 1301 1302 if (WARN_ON_ONCE((unsigned int)cs->id >= CSID_MAX)) 1303 cs->id = CSID_GENERIC; 1304 1305 if (WARN_ON_ONCE(!freq && cs->flags & CLOCK_SOURCE_HAS_COUPLED_CLOCK_EVENT)) 1306 cs->flags &= ~CLOCK_SOURCE_HAS_COUPLED_CLOCK_EVENT; 1307 1308 if (cs->vdso_clock_mode < 0 || 1309 cs->vdso_clock_mode >= VDSO_CLOCKMODE_MAX) { 1310 pr_warn("clocksource %s registered with invalid VDSO mode %d. Disabling VDSO support.\n", 1311 cs->name, cs->vdso_clock_mode); 1312 cs->vdso_clock_mode = VDSO_CLOCKMODE_NONE; 1313 } 1314 1315 /* Initialize mult/shift and max_idle_ns */ 1316 __clocksource_update_freq_scale(cs, scale, freq); 1317 1318 /* Add clocksource to the clocksource list */ 1319 mutex_lock(&clocksource_mutex); 1320 1321 clocksource_watchdog_lock(&flags); 1322 clocksource_enqueue(cs); 1323 clocksource_enqueue_watchdog(cs); 1324 clocksource_watchdog_unlock(&flags); 1325 1326 clocksource_select(); 1327 clocksource_select_watchdog(false); 1328 __clocksource_suspend_select(cs); 1329 mutex_unlock(&clocksource_mutex); 1330 return 0; 1331 } 1332 EXPORT_SYMBOL_GPL(__clocksource_register_scale); 1333 1334 static void __devm_clocksource_unregister(void *data) 1335 { 1336 struct clocksource *cs = data; 1337 1338 clocksource_unregister(cs); 1339 } 1340 1341 int __devm_clocksource_register_scale(struct device *dev, struct clocksource *cs, 1342 u32 scale, u32 freq) 1343 { 1344 int ret; 1345 1346 ret = __clocksource_register_scale(cs, scale, freq); 1347 if (ret) 1348 return ret; 1349 1350 return devm_add_action_or_reset(dev, __devm_clocksource_unregister, cs); 1351 } 1352 EXPORT_SYMBOL_GPL(__devm_clocksource_register_scale); 1353 1354 /* 1355 * Unbind clocksource @cs. Called with clocksource_mutex held 1356 */ 1357 static int clocksource_unbind(struct clocksource *cs) 1358 { 1359 unsigned long flags; 1360 1361 if (clocksource_is_watchdog(cs)) { 1362 /* Select and try to install a replacement watchdog. */ 1363 clocksource_select_watchdog(true); 1364 if (clocksource_is_watchdog(cs)) 1365 return -EBUSY; 1366 } 1367 1368 if (cs == curr_clocksource) { 1369 /* Select and try to install a replacement clock source */ 1370 clocksource_select_fallback(); 1371 if (curr_clocksource == cs) 1372 return -EBUSY; 1373 } 1374 1375 if (clocksource_is_suspend(cs)) { 1376 /* 1377 * Select and try to install a replacement suspend clocksource. 1378 * If no replacement suspend clocksource, we will just let the 1379 * clocksource go and have no suspend clocksource. 1380 */ 1381 clocksource_suspend_select(true); 1382 } 1383 1384 clocksource_watchdog_lock(&flags); 1385 clocksource_dequeue_watchdog(cs); 1386 list_del_init(&cs->list); 1387 clocksource_watchdog_unlock(&flags); 1388 1389 return 0; 1390 } 1391 1392 /** 1393 * clocksource_unregister - remove a registered clocksource 1394 * @cs: clocksource to be unregistered 1395 */ 1396 int clocksource_unregister(struct clocksource *cs) 1397 { 1398 int ret = 0; 1399 1400 mutex_lock(&clocksource_mutex); 1401 if (!list_empty(&cs->list)) 1402 ret = clocksource_unbind(cs); 1403 mutex_unlock(&clocksource_mutex); 1404 return ret; 1405 } 1406 EXPORT_SYMBOL(clocksource_unregister); 1407 1408 #ifdef CONFIG_SYSFS 1409 /** 1410 * current_clocksource_show - sysfs interface for current clocksource 1411 * @dev: unused 1412 * @attr: unused 1413 * @buf: char buffer to be filled with clocksource list 1414 * 1415 * Provides sysfs interface for listing current clocksource. 1416 */ 1417 static ssize_t current_clocksource_show(struct device *dev, 1418 struct device_attribute *attr, 1419 char *buf) 1420 { 1421 ssize_t count = 0; 1422 1423 mutex_lock(&clocksource_mutex); 1424 count = sysfs_emit(buf, "%s\n", curr_clocksource->name); 1425 mutex_unlock(&clocksource_mutex); 1426 1427 return count; 1428 } 1429 1430 ssize_t sysfs_get_uname(const char *buf, char *dst, size_t cnt) 1431 { 1432 size_t ret = cnt; 1433 1434 /* strings from sysfs write are not 0 terminated! */ 1435 if (!cnt || cnt >= CS_NAME_LEN) 1436 return -EINVAL; 1437 1438 /* strip of \n: */ 1439 if (buf[cnt-1] == '\n') 1440 cnt--; 1441 if (cnt > 0) 1442 memcpy(dst, buf, cnt); 1443 dst[cnt] = 0; 1444 return ret; 1445 } 1446 1447 /** 1448 * current_clocksource_store - interface for manually overriding clocksource 1449 * @dev: unused 1450 * @attr: unused 1451 * @buf: name of override clocksource 1452 * @count: length of buffer 1453 * 1454 * Takes input from sysfs interface for manually overriding the default 1455 * clocksource selection. 1456 */ 1457 static ssize_t current_clocksource_store(struct device *dev, 1458 struct device_attribute *attr, 1459 const char *buf, size_t count) 1460 { 1461 ssize_t ret; 1462 1463 mutex_lock(&clocksource_mutex); 1464 1465 ret = sysfs_get_uname(buf, override_name, count); 1466 if (ret >= 0) 1467 clocksource_select(); 1468 1469 mutex_unlock(&clocksource_mutex); 1470 1471 return ret; 1472 } 1473 static DEVICE_ATTR_RW(current_clocksource); 1474 1475 /** 1476 * unbind_clocksource_store - interface for manually unbinding clocksource 1477 * @dev: unused 1478 * @attr: unused 1479 * @buf: unused 1480 * @count: length of buffer 1481 * 1482 * Takes input from sysfs interface for manually unbinding a clocksource. 1483 */ 1484 static ssize_t unbind_clocksource_store(struct device *dev, 1485 struct device_attribute *attr, 1486 const char *buf, size_t count) 1487 { 1488 struct clocksource *cs; 1489 char name[CS_NAME_LEN]; 1490 ssize_t ret; 1491 1492 ret = sysfs_get_uname(buf, name, count); 1493 if (ret < 0) 1494 return ret; 1495 1496 ret = -ENODEV; 1497 mutex_lock(&clocksource_mutex); 1498 list_for_each_entry(cs, &clocksource_list, list) { 1499 if (strcmp(cs->name, name)) 1500 continue; 1501 ret = clocksource_unbind(cs); 1502 break; 1503 } 1504 mutex_unlock(&clocksource_mutex); 1505 1506 return ret ? ret : count; 1507 } 1508 static DEVICE_ATTR_WO(unbind_clocksource); 1509 1510 /** 1511 * available_clocksource_show - sysfs interface for listing clocksource 1512 * @dev: unused 1513 * @attr: unused 1514 * @buf: char buffer to be filled with clocksource list 1515 * 1516 * Provides sysfs interface for listing registered clocksources 1517 */ 1518 static ssize_t available_clocksource_show(struct device *dev, 1519 struct device_attribute *attr, 1520 char *buf) 1521 { 1522 struct clocksource *src; 1523 ssize_t count = 0; 1524 1525 mutex_lock(&clocksource_mutex); 1526 list_for_each_entry(src, &clocksource_list, list) { 1527 /* 1528 * Don't show non-HRES clocksource if the tick code is 1529 * in one shot mode (highres=on or nohz=on) 1530 */ 1531 if (!tick_oneshot_mode_active() || 1532 (src->flags & CLOCK_SOURCE_VALID_FOR_HRES)) 1533 count += snprintf(buf + count, 1534 max((ssize_t)PAGE_SIZE - count, (ssize_t)0), 1535 "%s ", src->name); 1536 } 1537 mutex_unlock(&clocksource_mutex); 1538 1539 count += snprintf(buf + count, 1540 max((ssize_t)PAGE_SIZE - count, (ssize_t)0), "\n"); 1541 1542 return count; 1543 } 1544 static DEVICE_ATTR_RO(available_clocksource); 1545 1546 static struct attribute *clocksource_attrs[] = { 1547 &dev_attr_current_clocksource.attr, 1548 &dev_attr_unbind_clocksource.attr, 1549 &dev_attr_available_clocksource.attr, 1550 NULL 1551 }; 1552 ATTRIBUTE_GROUPS(clocksource); 1553 1554 static const struct bus_type clocksource_subsys = { 1555 .name = "clocksource", 1556 .dev_name = "clocksource", 1557 }; 1558 1559 static struct device device_clocksource = { 1560 .id = 0, 1561 .bus = &clocksource_subsys, 1562 .groups = clocksource_groups, 1563 }; 1564 1565 static int __init init_clocksource_sysfs(void) 1566 { 1567 int error = subsys_system_register(&clocksource_subsys, NULL); 1568 1569 if (!error) 1570 error = device_register(&device_clocksource); 1571 1572 return error; 1573 } 1574 1575 device_initcall(init_clocksource_sysfs); 1576 #endif /* CONFIG_SYSFS */ 1577 1578 /** 1579 * boot_override_clocksource - boot clock override 1580 * @str: override name 1581 * 1582 * Takes a clocksource= boot argument and uses it 1583 * as the clocksource override name. 1584 */ 1585 static int __init boot_override_clocksource(char* str) 1586 { 1587 mutex_lock(&clocksource_mutex); 1588 if (str) 1589 strscpy(override_name, str); 1590 mutex_unlock(&clocksource_mutex); 1591 return 1; 1592 } 1593 1594 __setup("clocksource=", boot_override_clocksource); 1595 1596 /** 1597 * boot_override_clock - Compatibility layer for deprecated boot option 1598 * @str: override name 1599 * 1600 * DEPRECATED! Takes a clock= boot argument and uses it 1601 * as the clocksource override name 1602 */ 1603 static int __init boot_override_clock(char* str) 1604 { 1605 if (!strcmp(str, "pmtmr")) { 1606 pr_warn("clock=pmtmr is deprecated - use clocksource=acpi_pm\n"); 1607 return boot_override_clocksource("acpi_pm"); 1608 } 1609 pr_warn("clock= boot option is deprecated - use clocksource=xyz\n"); 1610 return boot_override_clocksource(str); 1611 } 1612 1613 __setup("clock=", boot_override_clock); 1614