1734efb46Sjohn stultz /* 2734efb46Sjohn stultz * linux/kernel/time/clocksource.c 3734efb46Sjohn stultz * 4734efb46Sjohn stultz * This file contains the functions which manage clocksource drivers. 5734efb46Sjohn stultz * 6734efb46Sjohn stultz * Copyright (C) 2004, 2005 IBM, John Stultz (johnstul@us.ibm.com) 7734efb46Sjohn stultz * 8734efb46Sjohn stultz * This program is free software; you can redistribute it and/or modify 9734efb46Sjohn stultz * it under the terms of the GNU General Public License as published by 10734efb46Sjohn stultz * the Free Software Foundation; either version 2 of the License, or 11734efb46Sjohn stultz * (at your option) any later version. 12734efb46Sjohn stultz * 13734efb46Sjohn stultz * This program is distributed in the hope that it will be useful, 14734efb46Sjohn stultz * but WITHOUT ANY WARRANTY; without even the implied warranty of 15734efb46Sjohn stultz * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 16734efb46Sjohn stultz * GNU General Public License for more details. 17734efb46Sjohn stultz * 18734efb46Sjohn stultz * You should have received a copy of the GNU General Public License 19734efb46Sjohn stultz * along with this program; if not, write to the Free Software 20734efb46Sjohn stultz * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. 21734efb46Sjohn stultz * 22734efb46Sjohn stultz * TODO WishList: 23734efb46Sjohn stultz * o Allow clocksource drivers to be unregistered 24734efb46Sjohn stultz */ 25734efb46Sjohn stultz 26734efb46Sjohn stultz #include <linux/clocksource.h> 27734efb46Sjohn stultz #include <linux/sysdev.h> 28734efb46Sjohn stultz #include <linux/init.h> 29734efb46Sjohn stultz #include <linux/module.h> 30dc29a365SMathieu Desnoyers #include <linux/sched.h> /* for spin_unlock_irq() using preempt_count() m68k */ 3179bf2bb3SThomas Gleixner #include <linux/tick.h> 3201548f4dSMartin Schwidefsky #include <linux/kthread.h> 33734efb46Sjohn stultz 34a038a353SPatrick Ohly void timecounter_init(struct timecounter *tc, 35a038a353SPatrick Ohly const struct cyclecounter *cc, 36a038a353SPatrick Ohly u64 start_tstamp) 37a038a353SPatrick Ohly { 38a038a353SPatrick Ohly tc->cc = cc; 39a038a353SPatrick Ohly tc->cycle_last = cc->read(cc); 40a038a353SPatrick Ohly tc->nsec = start_tstamp; 41a038a353SPatrick Ohly } 423586e0a9SDavid S. Miller EXPORT_SYMBOL_GPL(timecounter_init); 43a038a353SPatrick Ohly 44a038a353SPatrick Ohly /** 45a038a353SPatrick Ohly * timecounter_read_delta - get nanoseconds since last call of this function 46a038a353SPatrick Ohly * @tc: Pointer to time counter 47a038a353SPatrick Ohly * 48a038a353SPatrick Ohly * When the underlying cycle counter runs over, this will be handled 49a038a353SPatrick Ohly * correctly as long as it does not run over more than once between 50a038a353SPatrick Ohly * calls. 51a038a353SPatrick Ohly * 52a038a353SPatrick Ohly * The first call to this function for a new time counter initializes 53a038a353SPatrick Ohly * the time tracking and returns an undefined result. 54a038a353SPatrick Ohly */ 55a038a353SPatrick Ohly static u64 timecounter_read_delta(struct timecounter *tc) 56a038a353SPatrick Ohly { 57a038a353SPatrick Ohly cycle_t cycle_now, cycle_delta; 58a038a353SPatrick Ohly u64 ns_offset; 59a038a353SPatrick Ohly 60a038a353SPatrick Ohly /* read cycle counter: */ 61a038a353SPatrick Ohly cycle_now = tc->cc->read(tc->cc); 62a038a353SPatrick Ohly 63a038a353SPatrick Ohly /* calculate the delta since the last timecounter_read_delta(): */ 64a038a353SPatrick Ohly cycle_delta = (cycle_now - tc->cycle_last) & tc->cc->mask; 65a038a353SPatrick Ohly 66a038a353SPatrick Ohly /* convert to nanoseconds: */ 67a038a353SPatrick Ohly ns_offset = cyclecounter_cyc2ns(tc->cc, cycle_delta); 68a038a353SPatrick Ohly 69a038a353SPatrick Ohly /* update time stamp of timecounter_read_delta() call: */ 70a038a353SPatrick Ohly tc->cycle_last = cycle_now; 71a038a353SPatrick Ohly 72a038a353SPatrick Ohly return ns_offset; 73a038a353SPatrick Ohly } 74a038a353SPatrick Ohly 75a038a353SPatrick Ohly u64 timecounter_read(struct timecounter *tc) 76a038a353SPatrick Ohly { 77a038a353SPatrick Ohly u64 nsec; 78a038a353SPatrick Ohly 79a038a353SPatrick Ohly /* increment time by nanoseconds since last call */ 80a038a353SPatrick Ohly nsec = timecounter_read_delta(tc); 81a038a353SPatrick Ohly nsec += tc->nsec; 82a038a353SPatrick Ohly tc->nsec = nsec; 83a038a353SPatrick Ohly 84a038a353SPatrick Ohly return nsec; 85a038a353SPatrick Ohly } 863586e0a9SDavid S. Miller EXPORT_SYMBOL_GPL(timecounter_read); 87a038a353SPatrick Ohly 88a038a353SPatrick Ohly u64 timecounter_cyc2time(struct timecounter *tc, 89a038a353SPatrick Ohly cycle_t cycle_tstamp) 90a038a353SPatrick Ohly { 91a038a353SPatrick Ohly u64 cycle_delta = (cycle_tstamp - tc->cycle_last) & tc->cc->mask; 92a038a353SPatrick Ohly u64 nsec; 93a038a353SPatrick Ohly 94a038a353SPatrick Ohly /* 95a038a353SPatrick Ohly * Instead of always treating cycle_tstamp as more recent 96a038a353SPatrick Ohly * than tc->cycle_last, detect when it is too far in the 97a038a353SPatrick Ohly * future and treat it as old time stamp instead. 98a038a353SPatrick Ohly */ 99a038a353SPatrick Ohly if (cycle_delta > tc->cc->mask / 2) { 100a038a353SPatrick Ohly cycle_delta = (tc->cycle_last - cycle_tstamp) & tc->cc->mask; 101a038a353SPatrick Ohly nsec = tc->nsec - cyclecounter_cyc2ns(tc->cc, cycle_delta); 102a038a353SPatrick Ohly } else { 103a038a353SPatrick Ohly nsec = cyclecounter_cyc2ns(tc->cc, cycle_delta) + tc->nsec; 104a038a353SPatrick Ohly } 105a038a353SPatrick Ohly 106a038a353SPatrick Ohly return nsec; 107a038a353SPatrick Ohly } 1083586e0a9SDavid S. Miller EXPORT_SYMBOL_GPL(timecounter_cyc2time); 109a038a353SPatrick Ohly 1107d2f944aSThomas Gleixner /** 1117d2f944aSThomas Gleixner * clocks_calc_mult_shift - calculate mult/shift factors for scaled math of clocks 1127d2f944aSThomas Gleixner * @mult: pointer to mult variable 1137d2f944aSThomas Gleixner * @shift: pointer to shift variable 1147d2f944aSThomas Gleixner * @from: frequency to convert from 1157d2f944aSThomas Gleixner * @to: frequency to convert to 1165fdade95SNicolas Pitre * @maxsec: guaranteed runtime conversion range in seconds 1177d2f944aSThomas Gleixner * 1187d2f944aSThomas Gleixner * The function evaluates the shift/mult pair for the scaled math 1197d2f944aSThomas Gleixner * operations of clocksources and clockevents. 1207d2f944aSThomas Gleixner * 1217d2f944aSThomas Gleixner * @to and @from are frequency values in HZ. For clock sources @to is 1227d2f944aSThomas Gleixner * NSEC_PER_SEC == 1GHz and @from is the counter frequency. For clock 1237d2f944aSThomas Gleixner * event @to is the counter frequency and @from is NSEC_PER_SEC. 1247d2f944aSThomas Gleixner * 1255fdade95SNicolas Pitre * The @maxsec conversion range argument controls the time frame in 1267d2f944aSThomas Gleixner * seconds which must be covered by the runtime conversion with the 1277d2f944aSThomas Gleixner * calculated mult and shift factors. This guarantees that no 64bit 1287d2f944aSThomas Gleixner * overflow happens when the input value of the conversion is 1297d2f944aSThomas Gleixner * multiplied with the calculated mult factor. Larger ranges may 1307d2f944aSThomas Gleixner * reduce the conversion accuracy by chosing smaller mult and shift 1317d2f944aSThomas Gleixner * factors. 1327d2f944aSThomas Gleixner */ 1337d2f944aSThomas Gleixner void 1345fdade95SNicolas Pitre clocks_calc_mult_shift(u32 *mult, u32 *shift, u32 from, u32 to, u32 maxsec) 1357d2f944aSThomas Gleixner { 1367d2f944aSThomas Gleixner u64 tmp; 1377d2f944aSThomas Gleixner u32 sft, sftacc= 32; 1387d2f944aSThomas Gleixner 1397d2f944aSThomas Gleixner /* 1407d2f944aSThomas Gleixner * Calculate the shift factor which is limiting the conversion 1417d2f944aSThomas Gleixner * range: 1427d2f944aSThomas Gleixner */ 1435fdade95SNicolas Pitre tmp = ((u64)maxsec * from) >> 32; 1447d2f944aSThomas Gleixner while (tmp) { 1457d2f944aSThomas Gleixner tmp >>=1; 1467d2f944aSThomas Gleixner sftacc--; 1477d2f944aSThomas Gleixner } 1487d2f944aSThomas Gleixner 1497d2f944aSThomas Gleixner /* 1507d2f944aSThomas Gleixner * Find the conversion shift/mult pair which has the best 1517d2f944aSThomas Gleixner * accuracy and fits the maxsec conversion range: 1527d2f944aSThomas Gleixner */ 1537d2f944aSThomas Gleixner for (sft = 32; sft > 0; sft--) { 1547d2f944aSThomas Gleixner tmp = (u64) to << sft; 155b5776c4aSjohn stultz tmp += from / 2; 1567d2f944aSThomas Gleixner do_div(tmp, from); 1577d2f944aSThomas Gleixner if ((tmp >> sftacc) == 0) 1587d2f944aSThomas Gleixner break; 1597d2f944aSThomas Gleixner } 1607d2f944aSThomas Gleixner *mult = tmp; 1617d2f944aSThomas Gleixner *shift = sft; 1627d2f944aSThomas Gleixner } 1637d2f944aSThomas Gleixner 164734efb46Sjohn stultz /*[Clocksource internal variables]--------- 165734efb46Sjohn stultz * curr_clocksource: 166f1b82746SMartin Schwidefsky * currently selected clocksource. 167734efb46Sjohn stultz * clocksource_list: 168734efb46Sjohn stultz * linked list with the registered clocksources 16975c5158fSMartin Schwidefsky * clocksource_mutex: 17075c5158fSMartin Schwidefsky * protects manipulations to curr_clocksource and the clocksource_list 171734efb46Sjohn stultz * override_name: 172734efb46Sjohn stultz * Name of the user-specified clocksource. 173734efb46Sjohn stultz */ 174f1b82746SMartin Schwidefsky static struct clocksource *curr_clocksource; 175734efb46Sjohn stultz static LIST_HEAD(clocksource_list); 17675c5158fSMartin Schwidefsky static DEFINE_MUTEX(clocksource_mutex); 177734efb46Sjohn stultz static char override_name[32]; 17854a6bc0bSThomas Gleixner static int finished_booting; 179734efb46Sjohn stultz 1805d8b34fdSThomas Gleixner #ifdef CONFIG_CLOCKSOURCE_WATCHDOG 181f79e0258SMartin Schwidefsky static void clocksource_watchdog_work(struct work_struct *work); 182f79e0258SMartin Schwidefsky 1835d8b34fdSThomas Gleixner static LIST_HEAD(watchdog_list); 1845d8b34fdSThomas Gleixner static struct clocksource *watchdog; 1855d8b34fdSThomas Gleixner static struct timer_list watchdog_timer; 186f79e0258SMartin Schwidefsky static DECLARE_WORK(watchdog_work, clocksource_watchdog_work); 1875d8b34fdSThomas Gleixner static DEFINE_SPINLOCK(watchdog_lock); 188fb63a0ebSMartin Schwidefsky static int watchdog_running; 1899fb60336SThomas Gleixner static atomic_t watchdog_reset_pending; 190b52f52a0SThomas Gleixner 19101548f4dSMartin Schwidefsky static int clocksource_watchdog_kthread(void *data); 192d0981a1bSThomas Gleixner static void __clocksource_change_rating(struct clocksource *cs, int rating); 193c55c87c8SMartin Schwidefsky 1945d8b34fdSThomas Gleixner /* 19535c35d1aSDaniel Walker * Interval: 0.5sec Threshold: 0.0625s 1965d8b34fdSThomas Gleixner */ 1975d8b34fdSThomas Gleixner #define WATCHDOG_INTERVAL (HZ >> 1) 19835c35d1aSDaniel Walker #define WATCHDOG_THRESHOLD (NSEC_PER_SEC >> 4) 1995d8b34fdSThomas Gleixner 20001548f4dSMartin Schwidefsky static void clocksource_watchdog_work(struct work_struct *work) 20101548f4dSMartin Schwidefsky { 20201548f4dSMartin Schwidefsky /* 20301548f4dSMartin Schwidefsky * If kthread_run fails the next watchdog scan over the 20401548f4dSMartin Schwidefsky * watchdog_list will find the unstable clock again. 20501548f4dSMartin Schwidefsky */ 20601548f4dSMartin Schwidefsky kthread_run(clocksource_watchdog_kthread, NULL, "kwatchdog"); 20701548f4dSMartin Schwidefsky } 20801548f4dSMartin Schwidefsky 2097285dd7fSThomas Gleixner static void __clocksource_unstable(struct clocksource *cs) 2107285dd7fSThomas Gleixner { 2117285dd7fSThomas Gleixner cs->flags &= ~(CLOCK_SOURCE_VALID_FOR_HRES | CLOCK_SOURCE_WATCHDOG); 2127285dd7fSThomas Gleixner cs->flags |= CLOCK_SOURCE_UNSTABLE; 21354a6bc0bSThomas Gleixner if (finished_booting) 2147285dd7fSThomas Gleixner schedule_work(&watchdog_work); 2157285dd7fSThomas Gleixner } 2167285dd7fSThomas Gleixner 2178cf4e750SMartin Schwidefsky static void clocksource_unstable(struct clocksource *cs, int64_t delta) 2185d8b34fdSThomas Gleixner { 2195d8b34fdSThomas Gleixner printk(KERN_WARNING "Clocksource %s unstable (delta = %Ld ns)\n", 2205d8b34fdSThomas Gleixner cs->name, delta); 2217285dd7fSThomas Gleixner __clocksource_unstable(cs); 2227285dd7fSThomas Gleixner } 2237285dd7fSThomas Gleixner 2247285dd7fSThomas Gleixner /** 2257285dd7fSThomas Gleixner * clocksource_mark_unstable - mark clocksource unstable via watchdog 2267285dd7fSThomas Gleixner * @cs: clocksource to be marked unstable 2277285dd7fSThomas Gleixner * 2287285dd7fSThomas Gleixner * This function is called instead of clocksource_change_rating from 2297285dd7fSThomas Gleixner * cpu hotplug code to avoid a deadlock between the clocksource mutex 2307285dd7fSThomas Gleixner * and the cpu hotplug mutex. It defers the update of the clocksource 2317285dd7fSThomas Gleixner * to the watchdog thread. 2327285dd7fSThomas Gleixner */ 2337285dd7fSThomas Gleixner void clocksource_mark_unstable(struct clocksource *cs) 2347285dd7fSThomas Gleixner { 2357285dd7fSThomas Gleixner unsigned long flags; 2367285dd7fSThomas Gleixner 2377285dd7fSThomas Gleixner spin_lock_irqsave(&watchdog_lock, flags); 2387285dd7fSThomas Gleixner if (!(cs->flags & CLOCK_SOURCE_UNSTABLE)) { 2397285dd7fSThomas Gleixner if (list_empty(&cs->wd_list)) 2407285dd7fSThomas Gleixner list_add(&cs->wd_list, &watchdog_list); 2417285dd7fSThomas Gleixner __clocksource_unstable(cs); 2427285dd7fSThomas Gleixner } 2437285dd7fSThomas Gleixner spin_unlock_irqrestore(&watchdog_lock, flags); 2445d8b34fdSThomas Gleixner } 2455d8b34fdSThomas Gleixner 2465d8b34fdSThomas Gleixner static void clocksource_watchdog(unsigned long data) 2475d8b34fdSThomas Gleixner { 248c55c87c8SMartin Schwidefsky struct clocksource *cs; 2495d8b34fdSThomas Gleixner cycle_t csnow, wdnow; 2505d8b34fdSThomas Gleixner int64_t wd_nsec, cs_nsec; 2519fb60336SThomas Gleixner int next_cpu, reset_pending; 2525d8b34fdSThomas Gleixner 2535d8b34fdSThomas Gleixner spin_lock(&watchdog_lock); 254fb63a0ebSMartin Schwidefsky if (!watchdog_running) 255fb63a0ebSMartin Schwidefsky goto out; 2565d8b34fdSThomas Gleixner 2579fb60336SThomas Gleixner reset_pending = atomic_read(&watchdog_reset_pending); 2589fb60336SThomas Gleixner 259c55c87c8SMartin Schwidefsky list_for_each_entry(cs, &watchdog_list, wd_list) { 260c55c87c8SMartin Schwidefsky 261c55c87c8SMartin Schwidefsky /* Clocksource already marked unstable? */ 26201548f4dSMartin Schwidefsky if (cs->flags & CLOCK_SOURCE_UNSTABLE) { 26354a6bc0bSThomas Gleixner if (finished_booting) 26401548f4dSMartin Schwidefsky schedule_work(&watchdog_work); 265c55c87c8SMartin Schwidefsky continue; 26601548f4dSMartin Schwidefsky } 267c55c87c8SMartin Schwidefsky 268b5199515SThomas Gleixner local_irq_disable(); 2698e19608eSMagnus Damm csnow = cs->read(cs); 270b5199515SThomas Gleixner wdnow = watchdog->read(watchdog); 271b5199515SThomas Gleixner local_irq_enable(); 272b52f52a0SThomas Gleixner 2738cf4e750SMartin Schwidefsky /* Clocksource initialized ? */ 2749fb60336SThomas Gleixner if (!(cs->flags & CLOCK_SOURCE_WATCHDOG) || 2759fb60336SThomas Gleixner atomic_read(&watchdog_reset_pending)) { 2768cf4e750SMartin Schwidefsky cs->flags |= CLOCK_SOURCE_WATCHDOG; 277b5199515SThomas Gleixner cs->wd_last = wdnow; 278b5199515SThomas Gleixner cs->cs_last = csnow; 279b52f52a0SThomas Gleixner continue; 280b52f52a0SThomas Gleixner } 281b52f52a0SThomas Gleixner 282b5199515SThomas Gleixner wd_nsec = clocksource_cyc2ns((wdnow - cs->wd_last) & watchdog->mask, 283b5199515SThomas Gleixner watchdog->mult, watchdog->shift); 284b5199515SThomas Gleixner 285b5199515SThomas Gleixner cs_nsec = clocksource_cyc2ns((csnow - cs->cs_last) & 286155ec602SMartin Schwidefsky cs->mask, cs->mult, cs->shift); 287b5199515SThomas Gleixner cs->cs_last = csnow; 288b5199515SThomas Gleixner cs->wd_last = wdnow; 289b5199515SThomas Gleixner 2909fb60336SThomas Gleixner if (atomic_read(&watchdog_reset_pending)) 2919fb60336SThomas Gleixner continue; 2929fb60336SThomas Gleixner 293b5199515SThomas Gleixner /* Check the deviation from the watchdog clocksource. */ 2949fb60336SThomas Gleixner if ((abs(cs_nsec - wd_nsec) > WATCHDOG_THRESHOLD)) { 2958cf4e750SMartin Schwidefsky clocksource_unstable(cs, cs_nsec - wd_nsec); 2968cf4e750SMartin Schwidefsky continue; 2978cf4e750SMartin Schwidefsky } 2988cf4e750SMartin Schwidefsky 2998cf4e750SMartin Schwidefsky if (!(cs->flags & CLOCK_SOURCE_VALID_FOR_HRES) && 3008cf4e750SMartin Schwidefsky (cs->flags & CLOCK_SOURCE_IS_CONTINUOUS) && 3015d8b34fdSThomas Gleixner (watchdog->flags & CLOCK_SOURCE_IS_CONTINUOUS)) { 3025d8b34fdSThomas Gleixner cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES; 30379bf2bb3SThomas Gleixner /* 3048cf4e750SMartin Schwidefsky * We just marked the clocksource as highres-capable, 3058cf4e750SMartin Schwidefsky * notify the rest of the system as well so that we 3068cf4e750SMartin Schwidefsky * transition into high-res mode: 30779bf2bb3SThomas Gleixner */ 30879bf2bb3SThomas Gleixner tick_clock_notify(); 3095d8b34fdSThomas Gleixner } 3105d8b34fdSThomas Gleixner } 3115d8b34fdSThomas Gleixner 3126993fc5bSAndi Kleen /* 3139fb60336SThomas Gleixner * We only clear the watchdog_reset_pending, when we did a 3149fb60336SThomas Gleixner * full cycle through all clocksources. 3159fb60336SThomas Gleixner */ 3169fb60336SThomas Gleixner if (reset_pending) 3179fb60336SThomas Gleixner atomic_dec(&watchdog_reset_pending); 3189fb60336SThomas Gleixner 3199fb60336SThomas Gleixner /* 320c55c87c8SMartin Schwidefsky * Cycle through CPUs to check if the CPUs stay synchronized 321c55c87c8SMartin Schwidefsky * to each other. 3226993fc5bSAndi Kleen */ 323c55c87c8SMartin Schwidefsky next_cpu = cpumask_next(raw_smp_processor_id(), cpu_online_mask); 324cad0e458SMike Travis if (next_cpu >= nr_cpu_ids) 3256b954823SRusty Russell next_cpu = cpumask_first(cpu_online_mask); 3266993fc5bSAndi Kleen watchdog_timer.expires += WATCHDOG_INTERVAL; 3276993fc5bSAndi Kleen add_timer_on(&watchdog_timer, next_cpu); 328fb63a0ebSMartin Schwidefsky out: 3295d8b34fdSThomas Gleixner spin_unlock(&watchdog_lock); 3305d8b34fdSThomas Gleixner } 3310f8e8ef7SMartin Schwidefsky 332fb63a0ebSMartin Schwidefsky static inline void clocksource_start_watchdog(void) 333fb63a0ebSMartin Schwidefsky { 334fb63a0ebSMartin Schwidefsky if (watchdog_running || !watchdog || list_empty(&watchdog_list)) 335fb63a0ebSMartin Schwidefsky return; 336fb63a0ebSMartin Schwidefsky init_timer(&watchdog_timer); 337fb63a0ebSMartin Schwidefsky watchdog_timer.function = clocksource_watchdog; 338fb63a0ebSMartin Schwidefsky watchdog_timer.expires = jiffies + WATCHDOG_INTERVAL; 339fb63a0ebSMartin Schwidefsky add_timer_on(&watchdog_timer, cpumask_first(cpu_online_mask)); 340fb63a0ebSMartin Schwidefsky watchdog_running = 1; 341fb63a0ebSMartin Schwidefsky } 342fb63a0ebSMartin Schwidefsky 343fb63a0ebSMartin Schwidefsky static inline void clocksource_stop_watchdog(void) 344fb63a0ebSMartin Schwidefsky { 345fb63a0ebSMartin Schwidefsky if (!watchdog_running || (watchdog && !list_empty(&watchdog_list))) 346fb63a0ebSMartin Schwidefsky return; 347fb63a0ebSMartin Schwidefsky del_timer(&watchdog_timer); 348fb63a0ebSMartin Schwidefsky watchdog_running = 0; 349fb63a0ebSMartin Schwidefsky } 350fb63a0ebSMartin Schwidefsky 3510f8e8ef7SMartin Schwidefsky static inline void clocksource_reset_watchdog(void) 3520f8e8ef7SMartin Schwidefsky { 3530f8e8ef7SMartin Schwidefsky struct clocksource *cs; 3540f8e8ef7SMartin Schwidefsky 3550f8e8ef7SMartin Schwidefsky list_for_each_entry(cs, &watchdog_list, wd_list) 3560f8e8ef7SMartin Schwidefsky cs->flags &= ~CLOCK_SOURCE_WATCHDOG; 3570f8e8ef7SMartin Schwidefsky } 3580f8e8ef7SMartin Schwidefsky 359b52f52a0SThomas Gleixner static void clocksource_resume_watchdog(void) 360b52f52a0SThomas Gleixner { 3619fb60336SThomas Gleixner atomic_inc(&watchdog_reset_pending); 362b52f52a0SThomas Gleixner } 363b52f52a0SThomas Gleixner 364fb63a0ebSMartin Schwidefsky static void clocksource_enqueue_watchdog(struct clocksource *cs) 3655d8b34fdSThomas Gleixner { 3665d8b34fdSThomas Gleixner unsigned long flags; 3675d8b34fdSThomas Gleixner 3685d8b34fdSThomas Gleixner spin_lock_irqsave(&watchdog_lock, flags); 3695d8b34fdSThomas Gleixner if (cs->flags & CLOCK_SOURCE_MUST_VERIFY) { 370fb63a0ebSMartin Schwidefsky /* cs is a clocksource to be watched. */ 3715d8b34fdSThomas Gleixner list_add(&cs->wd_list, &watchdog_list); 372fb63a0ebSMartin Schwidefsky cs->flags &= ~CLOCK_SOURCE_WATCHDOG; 373948ac6d7SThomas Gleixner } else { 374fb63a0ebSMartin Schwidefsky /* cs is a watchdog. */ 375948ac6d7SThomas Gleixner if (cs->flags & CLOCK_SOURCE_IS_CONTINUOUS) 3765d8b34fdSThomas Gleixner cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES; 377fb63a0ebSMartin Schwidefsky /* Pick the best watchdog. */ 3785d8b34fdSThomas Gleixner if (!watchdog || cs->rating > watchdog->rating) { 3795d8b34fdSThomas Gleixner watchdog = cs; 3805d8b34fdSThomas Gleixner /* Reset watchdog cycles */ 3810f8e8ef7SMartin Schwidefsky clocksource_reset_watchdog(); 3825d8b34fdSThomas Gleixner } 3835d8b34fdSThomas Gleixner } 384fb63a0ebSMartin Schwidefsky /* Check if the watchdog timer needs to be started. */ 385fb63a0ebSMartin Schwidefsky clocksource_start_watchdog(); 3865d8b34fdSThomas Gleixner spin_unlock_irqrestore(&watchdog_lock, flags); 3875d8b34fdSThomas Gleixner } 388fb63a0ebSMartin Schwidefsky 389fb63a0ebSMartin Schwidefsky static void clocksource_dequeue_watchdog(struct clocksource *cs) 390fb63a0ebSMartin Schwidefsky { 391fb63a0ebSMartin Schwidefsky struct clocksource *tmp; 392fb63a0ebSMartin Schwidefsky unsigned long flags; 393fb63a0ebSMartin Schwidefsky 394fb63a0ebSMartin Schwidefsky spin_lock_irqsave(&watchdog_lock, flags); 395fb63a0ebSMartin Schwidefsky if (cs->flags & CLOCK_SOURCE_MUST_VERIFY) { 396fb63a0ebSMartin Schwidefsky /* cs is a watched clocksource. */ 397fb63a0ebSMartin Schwidefsky list_del_init(&cs->wd_list); 398fb63a0ebSMartin Schwidefsky } else if (cs == watchdog) { 399fb63a0ebSMartin Schwidefsky /* Reset watchdog cycles */ 400fb63a0ebSMartin Schwidefsky clocksource_reset_watchdog(); 401fb63a0ebSMartin Schwidefsky /* Current watchdog is removed. Find an alternative. */ 402fb63a0ebSMartin Schwidefsky watchdog = NULL; 403fb63a0ebSMartin Schwidefsky list_for_each_entry(tmp, &clocksource_list, list) { 404fb63a0ebSMartin Schwidefsky if (tmp == cs || tmp->flags & CLOCK_SOURCE_MUST_VERIFY) 405fb63a0ebSMartin Schwidefsky continue; 406fb63a0ebSMartin Schwidefsky if (!watchdog || tmp->rating > watchdog->rating) 407fb63a0ebSMartin Schwidefsky watchdog = tmp; 408fb63a0ebSMartin Schwidefsky } 409fb63a0ebSMartin Schwidefsky } 410fb63a0ebSMartin Schwidefsky cs->flags &= ~CLOCK_SOURCE_WATCHDOG; 411fb63a0ebSMartin Schwidefsky /* Check if the watchdog timer needs to be stopped. */ 412fb63a0ebSMartin Schwidefsky clocksource_stop_watchdog(); 413fb63a0ebSMartin Schwidefsky spin_unlock_irqrestore(&watchdog_lock, flags); 414fb63a0ebSMartin Schwidefsky } 415fb63a0ebSMartin Schwidefsky 41601548f4dSMartin Schwidefsky static int clocksource_watchdog_kthread(void *data) 417c55c87c8SMartin Schwidefsky { 418c55c87c8SMartin Schwidefsky struct clocksource *cs, *tmp; 419c55c87c8SMartin Schwidefsky unsigned long flags; 4206ea41d25SThomas Gleixner LIST_HEAD(unstable); 421c55c87c8SMartin Schwidefsky 422d0981a1bSThomas Gleixner mutex_lock(&clocksource_mutex); 423c55c87c8SMartin Schwidefsky spin_lock_irqsave(&watchdog_lock, flags); 424c55c87c8SMartin Schwidefsky list_for_each_entry_safe(cs, tmp, &watchdog_list, wd_list) 425c55c87c8SMartin Schwidefsky if (cs->flags & CLOCK_SOURCE_UNSTABLE) { 426c55c87c8SMartin Schwidefsky list_del_init(&cs->wd_list); 4276ea41d25SThomas Gleixner list_add(&cs->wd_list, &unstable); 428c55c87c8SMartin Schwidefsky } 429c55c87c8SMartin Schwidefsky /* Check if the watchdog timer needs to be stopped. */ 430c55c87c8SMartin Schwidefsky clocksource_stop_watchdog(); 4316ea41d25SThomas Gleixner spin_unlock_irqrestore(&watchdog_lock, flags); 4326ea41d25SThomas Gleixner 4336ea41d25SThomas Gleixner /* Needs to be done outside of watchdog lock */ 4346ea41d25SThomas Gleixner list_for_each_entry_safe(cs, tmp, &unstable, wd_list) { 4356ea41d25SThomas Gleixner list_del_init(&cs->wd_list); 436d0981a1bSThomas Gleixner __clocksource_change_rating(cs, 0); 4376ea41d25SThomas Gleixner } 438d0981a1bSThomas Gleixner mutex_unlock(&clocksource_mutex); 43901548f4dSMartin Schwidefsky return 0; 440c55c87c8SMartin Schwidefsky } 441c55c87c8SMartin Schwidefsky 442fb63a0ebSMartin Schwidefsky #else /* CONFIG_CLOCKSOURCE_WATCHDOG */ 443fb63a0ebSMartin Schwidefsky 444fb63a0ebSMartin Schwidefsky static void clocksource_enqueue_watchdog(struct clocksource *cs) 4455d8b34fdSThomas Gleixner { 4465d8b34fdSThomas Gleixner if (cs->flags & CLOCK_SOURCE_IS_CONTINUOUS) 4475d8b34fdSThomas Gleixner cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES; 4485d8b34fdSThomas Gleixner } 449b52f52a0SThomas Gleixner 450fb63a0ebSMartin Schwidefsky static inline void clocksource_dequeue_watchdog(struct clocksource *cs) { } 451b52f52a0SThomas Gleixner static inline void clocksource_resume_watchdog(void) { } 45254a6bc0bSThomas Gleixner static inline int clocksource_watchdog_kthread(void *data) { return 0; } 453fb63a0ebSMartin Schwidefsky 454fb63a0ebSMartin Schwidefsky #endif /* CONFIG_CLOCKSOURCE_WATCHDOG */ 4555d8b34fdSThomas Gleixner 456734efb46Sjohn stultz /** 457c54a42b1SMagnus Damm * clocksource_suspend - suspend the clocksource(s) 458c54a42b1SMagnus Damm */ 459c54a42b1SMagnus Damm void clocksource_suspend(void) 460c54a42b1SMagnus Damm { 461c54a42b1SMagnus Damm struct clocksource *cs; 462c54a42b1SMagnus Damm 463c54a42b1SMagnus Damm list_for_each_entry_reverse(cs, &clocksource_list, list) 464c54a42b1SMagnus Damm if (cs->suspend) 465c54a42b1SMagnus Damm cs->suspend(cs); 466c54a42b1SMagnus Damm } 467c54a42b1SMagnus Damm 468c54a42b1SMagnus Damm /** 469b52f52a0SThomas Gleixner * clocksource_resume - resume the clocksource(s) 470b52f52a0SThomas Gleixner */ 471b52f52a0SThomas Gleixner void clocksource_resume(void) 472b52f52a0SThomas Gleixner { 4732e197586SMatthias Kaehlcke struct clocksource *cs; 474b52f52a0SThomas Gleixner 47575c5158fSMartin Schwidefsky list_for_each_entry(cs, &clocksource_list, list) 476b52f52a0SThomas Gleixner if (cs->resume) 47717622339SMagnus Damm cs->resume(cs); 478b52f52a0SThomas Gleixner 479b52f52a0SThomas Gleixner clocksource_resume_watchdog(); 480b52f52a0SThomas Gleixner } 481b52f52a0SThomas Gleixner 482b52f52a0SThomas Gleixner /** 4837c3078b6SJason Wessel * clocksource_touch_watchdog - Update watchdog 4847c3078b6SJason Wessel * 4857c3078b6SJason Wessel * Update the watchdog after exception contexts such as kgdb so as not 4867b7422a5SThomas Gleixner * to incorrectly trip the watchdog. This might fail when the kernel 4877b7422a5SThomas Gleixner * was stopped in code which holds watchdog_lock. 4887c3078b6SJason Wessel */ 4897c3078b6SJason Wessel void clocksource_touch_watchdog(void) 4907c3078b6SJason Wessel { 4917c3078b6SJason Wessel clocksource_resume_watchdog(); 4927c3078b6SJason Wessel } 4937c3078b6SJason Wessel 494734efb46Sjohn stultz /** 495*d65670a7SJohn Stultz * clocksource_max_adjustment- Returns max adjustment amount 496*d65670a7SJohn Stultz * @cs: Pointer to clocksource 497*d65670a7SJohn Stultz * 498*d65670a7SJohn Stultz */ 499*d65670a7SJohn Stultz static u32 clocksource_max_adjustment(struct clocksource *cs) 500*d65670a7SJohn Stultz { 501*d65670a7SJohn Stultz u64 ret; 502*d65670a7SJohn Stultz /* 503*d65670a7SJohn Stultz * We won't try to correct for more then 11% adjustments (110,000 ppm), 504*d65670a7SJohn Stultz */ 505*d65670a7SJohn Stultz ret = (u64)cs->mult * 11; 506*d65670a7SJohn Stultz do_div(ret,100); 507*d65670a7SJohn Stultz return (u32)ret; 508*d65670a7SJohn Stultz } 509*d65670a7SJohn Stultz 510*d65670a7SJohn Stultz /** 51198962465SJon Hunter * clocksource_max_deferment - Returns max time the clocksource can be deferred 51298962465SJon Hunter * @cs: Pointer to clocksource 51398962465SJon Hunter * 51498962465SJon Hunter */ 51598962465SJon Hunter static u64 clocksource_max_deferment(struct clocksource *cs) 51698962465SJon Hunter { 51798962465SJon Hunter u64 max_nsecs, max_cycles; 51898962465SJon Hunter 51998962465SJon Hunter /* 52098962465SJon Hunter * Calculate the maximum number of cycles that we can pass to the 52198962465SJon Hunter * cyc2ns function without overflowing a 64-bit signed result. The 522*d65670a7SJohn Stultz * maximum number of cycles is equal to ULLONG_MAX/(cs->mult+cs->maxadj) 523*d65670a7SJohn Stultz * which is equivalent to the below. 524*d65670a7SJohn Stultz * max_cycles < (2^63)/(cs->mult + cs->maxadj) 525*d65670a7SJohn Stultz * max_cycles < 2^(log2((2^63)/(cs->mult + cs->maxadj))) 526*d65670a7SJohn Stultz * max_cycles < 2^(log2(2^63) - log2(cs->mult + cs->maxadj)) 527*d65670a7SJohn Stultz * max_cycles < 2^(63 - log2(cs->mult + cs->maxadj)) 528*d65670a7SJohn Stultz * max_cycles < 1 << (63 - log2(cs->mult + cs->maxadj)) 52998962465SJon Hunter * Please note that we add 1 to the result of the log2 to account for 53098962465SJon Hunter * any rounding errors, ensure the above inequality is satisfied and 53198962465SJon Hunter * no overflow will occur. 53298962465SJon Hunter */ 533*d65670a7SJohn Stultz max_cycles = 1ULL << (63 - (ilog2(cs->mult + cs->maxadj) + 1)); 53498962465SJon Hunter 53598962465SJon Hunter /* 53698962465SJon Hunter * The actual maximum number of cycles we can defer the clocksource is 53798962465SJon Hunter * determined by the minimum of max_cycles and cs->mask. 538*d65670a7SJohn Stultz * Note: Here we subtract the maxadj to make sure we don't sleep for 539*d65670a7SJohn Stultz * too long if there's a large negative adjustment. 54098962465SJon Hunter */ 54198962465SJon Hunter max_cycles = min_t(u64, max_cycles, (u64) cs->mask); 542*d65670a7SJohn Stultz max_nsecs = clocksource_cyc2ns(max_cycles, cs->mult - cs->maxadj, 543*d65670a7SJohn Stultz cs->shift); 54498962465SJon Hunter 54598962465SJon Hunter /* 54698962465SJon Hunter * To ensure that the clocksource does not wrap whilst we are idle, 54798962465SJon Hunter * limit the time the clocksource can be deferred by 12.5%. Please 54898962465SJon Hunter * note a margin of 12.5% is used because this can be computed with 54998962465SJon Hunter * a shift, versus say 10% which would require division. 55098962465SJon Hunter */ 55198962465SJon Hunter return max_nsecs - (max_nsecs >> 5); 55298962465SJon Hunter } 55398962465SJon Hunter 554592913ecSJohn Stultz #ifndef CONFIG_ARCH_USES_GETTIMEOFFSET 555734efb46Sjohn stultz 556734efb46Sjohn stultz /** 557f1b82746SMartin Schwidefsky * clocksource_select - Select the best clocksource available 558734efb46Sjohn stultz * 55975c5158fSMartin Schwidefsky * Private function. Must hold clocksource_mutex when called. 560734efb46Sjohn stultz * 56192c7e002SThomas Gleixner * Select the clocksource with the best rating, or the clocksource, 56292c7e002SThomas Gleixner * which is selected by userspace override. 563734efb46Sjohn stultz */ 564f1b82746SMartin Schwidefsky static void clocksource_select(void) 565734efb46Sjohn stultz { 566f1b82746SMartin Schwidefsky struct clocksource *best, *cs; 5675d8b34fdSThomas Gleixner 56875c5158fSMartin Schwidefsky if (!finished_booting || list_empty(&clocksource_list)) 569f1b82746SMartin Schwidefsky return; 570f1b82746SMartin Schwidefsky /* First clocksource on the list has the best rating. */ 571f1b82746SMartin Schwidefsky best = list_first_entry(&clocksource_list, struct clocksource, list); 572f1b82746SMartin Schwidefsky /* Check for the override clocksource. */ 573f1b82746SMartin Schwidefsky list_for_each_entry(cs, &clocksource_list, list) { 574f1b82746SMartin Schwidefsky if (strcmp(cs->name, override_name) != 0) 575f1b82746SMartin Schwidefsky continue; 576f1b82746SMartin Schwidefsky /* 577f1b82746SMartin Schwidefsky * Check to make sure we don't switch to a non-highres 578f1b82746SMartin Schwidefsky * capable clocksource if the tick code is in oneshot 579f1b82746SMartin Schwidefsky * mode (highres or nohz) 580f1b82746SMartin Schwidefsky */ 581f1b82746SMartin Schwidefsky if (!(cs->flags & CLOCK_SOURCE_VALID_FOR_HRES) && 582f1b82746SMartin Schwidefsky tick_oneshot_mode_active()) { 583f1b82746SMartin Schwidefsky /* Override clocksource cannot be used. */ 584f1b82746SMartin Schwidefsky printk(KERN_WARNING "Override clocksource %s is not " 585f1b82746SMartin Schwidefsky "HRT compatible. Cannot switch while in " 586f1b82746SMartin Schwidefsky "HRT/NOHZ mode\n", cs->name); 587f1b82746SMartin Schwidefsky override_name[0] = 0; 588f1b82746SMartin Schwidefsky } else 589f1b82746SMartin Schwidefsky /* Override clocksource can be used. */ 590f1b82746SMartin Schwidefsky best = cs; 591f1b82746SMartin Schwidefsky break; 592734efb46Sjohn stultz } 59375c5158fSMartin Schwidefsky if (curr_clocksource != best) { 59475c5158fSMartin Schwidefsky printk(KERN_INFO "Switching to clocksource %s\n", best->name); 59575c5158fSMartin Schwidefsky curr_clocksource = best; 59675c5158fSMartin Schwidefsky timekeeping_notify(curr_clocksource); 597f1b82746SMartin Schwidefsky } 59875c5158fSMartin Schwidefsky } 59975c5158fSMartin Schwidefsky 600592913ecSJohn Stultz #else /* !CONFIG_ARCH_USES_GETTIMEOFFSET */ 60154a6bc0bSThomas Gleixner 60254a6bc0bSThomas Gleixner static inline void clocksource_select(void) { } 60354a6bc0bSThomas Gleixner 60454a6bc0bSThomas Gleixner #endif 60554a6bc0bSThomas Gleixner 60675c5158fSMartin Schwidefsky /* 60775c5158fSMartin Schwidefsky * clocksource_done_booting - Called near the end of core bootup 60875c5158fSMartin Schwidefsky * 60975c5158fSMartin Schwidefsky * Hack to avoid lots of clocksource churn at boot time. 61075c5158fSMartin Schwidefsky * We use fs_initcall because we want this to start before 61175c5158fSMartin Schwidefsky * device_initcall but after subsys_initcall. 61275c5158fSMartin Schwidefsky */ 61375c5158fSMartin Schwidefsky static int __init clocksource_done_booting(void) 61475c5158fSMartin Schwidefsky { 615ad6759fbSjohn stultz mutex_lock(&clocksource_mutex); 616ad6759fbSjohn stultz curr_clocksource = clocksource_default_clock(); 617ad6759fbSjohn stultz mutex_unlock(&clocksource_mutex); 618ad6759fbSjohn stultz 61975c5158fSMartin Schwidefsky finished_booting = 1; 62054a6bc0bSThomas Gleixner 62154a6bc0bSThomas Gleixner /* 62254a6bc0bSThomas Gleixner * Run the watchdog first to eliminate unstable clock sources 62354a6bc0bSThomas Gleixner */ 62454a6bc0bSThomas Gleixner clocksource_watchdog_kthread(NULL); 62554a6bc0bSThomas Gleixner 626e6c73305SThomas Gleixner mutex_lock(&clocksource_mutex); 62775c5158fSMartin Schwidefsky clocksource_select(); 628e6c73305SThomas Gleixner mutex_unlock(&clocksource_mutex); 62975c5158fSMartin Schwidefsky return 0; 63075c5158fSMartin Schwidefsky } 63175c5158fSMartin Schwidefsky fs_initcall(clocksource_done_booting); 632f1b82746SMartin Schwidefsky 63392c7e002SThomas Gleixner /* 63492c7e002SThomas Gleixner * Enqueue the clocksource sorted by rating 635734efb46Sjohn stultz */ 636f1b82746SMartin Schwidefsky static void clocksource_enqueue(struct clocksource *cs) 637734efb46Sjohn stultz { 638f1b82746SMartin Schwidefsky struct list_head *entry = &clocksource_list; 639f1b82746SMartin Schwidefsky struct clocksource *tmp; 640734efb46Sjohn stultz 641f1b82746SMartin Schwidefsky list_for_each_entry(tmp, &clocksource_list, list) 64292c7e002SThomas Gleixner /* Keep track of the place, where to insert */ 643f1b82746SMartin Schwidefsky if (tmp->rating >= cs->rating) 644f1b82746SMartin Schwidefsky entry = &tmp->list; 645f1b82746SMartin Schwidefsky list_add(&cs->list, entry); 646734efb46Sjohn stultz } 647734efb46Sjohn stultz 648d7e81c26SJohn Stultz /** 649852db46dSJohn Stultz * __clocksource_updatefreq_scale - Used update clocksource with new freq 650852db46dSJohn Stultz * @t: clocksource to be registered 651852db46dSJohn Stultz * @scale: Scale factor multiplied against freq to get clocksource hz 652852db46dSJohn Stultz * @freq: clocksource frequency (cycles per second) divided by scale 653852db46dSJohn Stultz * 654852db46dSJohn Stultz * This should only be called from the clocksource->enable() method. 655852db46dSJohn Stultz * 656852db46dSJohn Stultz * This *SHOULD NOT* be called directly! Please use the 657852db46dSJohn Stultz * clocksource_updatefreq_hz() or clocksource_updatefreq_khz helper functions. 658852db46dSJohn Stultz */ 659852db46dSJohn Stultz void __clocksource_updatefreq_scale(struct clocksource *cs, u32 scale, u32 freq) 660852db46dSJohn Stultz { 661c0e299b1SThomas Gleixner u64 sec; 662852db46dSJohn Stultz /* 663724ed53eSThomas Gleixner * Calc the maximum number of seconds which we can run before 664724ed53eSThomas Gleixner * wrapping around. For clocksources which have a mask > 32bit 665724ed53eSThomas Gleixner * we need to limit the max sleep time to have a good 666724ed53eSThomas Gleixner * conversion precision. 10 minutes is still a reasonable 667724ed53eSThomas Gleixner * amount. That results in a shift value of 24 for a 668724ed53eSThomas Gleixner * clocksource with mask >= 40bit and f >= 4GHz. That maps to 669724ed53eSThomas Gleixner * ~ 0.06ppm granularity for NTP. We apply the same 12.5% 670724ed53eSThomas Gleixner * margin as we do in clocksource_max_deferment() 671852db46dSJohn Stultz */ 672724ed53eSThomas Gleixner sec = (cs->mask - (cs->mask >> 5)); 673724ed53eSThomas Gleixner do_div(sec, freq); 674724ed53eSThomas Gleixner do_div(sec, scale); 675724ed53eSThomas Gleixner if (!sec) 676724ed53eSThomas Gleixner sec = 1; 677724ed53eSThomas Gleixner else if (sec > 600 && cs->mask > UINT_MAX) 678724ed53eSThomas Gleixner sec = 600; 679724ed53eSThomas Gleixner 680852db46dSJohn Stultz clocks_calc_mult_shift(&cs->mult, &cs->shift, freq, 681724ed53eSThomas Gleixner NSEC_PER_SEC / scale, sec * scale); 682*d65670a7SJohn Stultz 683*d65670a7SJohn Stultz /* 684*d65670a7SJohn Stultz * for clocksources that have large mults, to avoid overflow. 685*d65670a7SJohn Stultz * Since mult may be adjusted by ntp, add an safety extra margin 686*d65670a7SJohn Stultz * 687*d65670a7SJohn Stultz */ 688*d65670a7SJohn Stultz cs->maxadj = clocksource_max_adjustment(cs); 689*d65670a7SJohn Stultz while ((cs->mult + cs->maxadj < cs->mult) 690*d65670a7SJohn Stultz || (cs->mult - cs->maxadj > cs->mult)) { 691*d65670a7SJohn Stultz cs->mult >>= 1; 692*d65670a7SJohn Stultz cs->shift--; 693*d65670a7SJohn Stultz cs->maxadj = clocksource_max_adjustment(cs); 694*d65670a7SJohn Stultz } 695*d65670a7SJohn Stultz 696852db46dSJohn Stultz cs->max_idle_ns = clocksource_max_deferment(cs); 697852db46dSJohn Stultz } 698852db46dSJohn Stultz EXPORT_SYMBOL_GPL(__clocksource_updatefreq_scale); 699852db46dSJohn Stultz 700852db46dSJohn Stultz /** 701d7e81c26SJohn Stultz * __clocksource_register_scale - Used to install new clocksources 702d7e81c26SJohn Stultz * @t: clocksource to be registered 703d7e81c26SJohn Stultz * @scale: Scale factor multiplied against freq to get clocksource hz 704d7e81c26SJohn Stultz * @freq: clocksource frequency (cycles per second) divided by scale 705d7e81c26SJohn Stultz * 706d7e81c26SJohn Stultz * Returns -EBUSY if registration fails, zero otherwise. 707d7e81c26SJohn Stultz * 708d7e81c26SJohn Stultz * This *SHOULD NOT* be called directly! Please use the 709d7e81c26SJohn Stultz * clocksource_register_hz() or clocksource_register_khz helper functions. 710d7e81c26SJohn Stultz */ 711d7e81c26SJohn Stultz int __clocksource_register_scale(struct clocksource *cs, u32 scale, u32 freq) 712d7e81c26SJohn Stultz { 713d7e81c26SJohn Stultz 714b595076aSUwe Kleine-König /* Initialize mult/shift and max_idle_ns */ 715852db46dSJohn Stultz __clocksource_updatefreq_scale(cs, scale, freq); 716d7e81c26SJohn Stultz 717852db46dSJohn Stultz /* Add clocksource to the clcoksource list */ 718d7e81c26SJohn Stultz mutex_lock(&clocksource_mutex); 719d7e81c26SJohn Stultz clocksource_enqueue(cs); 720d7e81c26SJohn Stultz clocksource_enqueue_watchdog(cs); 721e05b2efbSjohn stultz clocksource_select(); 722d7e81c26SJohn Stultz mutex_unlock(&clocksource_mutex); 723d7e81c26SJohn Stultz return 0; 724d7e81c26SJohn Stultz } 725d7e81c26SJohn Stultz EXPORT_SYMBOL_GPL(__clocksource_register_scale); 726d7e81c26SJohn Stultz 727d7e81c26SJohn Stultz 728734efb46Sjohn stultz /** 729a2752549Sjohn stultz * clocksource_register - Used to install new clocksources 730734efb46Sjohn stultz * @t: clocksource to be registered 731734efb46Sjohn stultz * 732734efb46Sjohn stultz * Returns -EBUSY if registration fails, zero otherwise. 733734efb46Sjohn stultz */ 734f1b82746SMartin Schwidefsky int clocksource_register(struct clocksource *cs) 735734efb46Sjohn stultz { 736*d65670a7SJohn Stultz /* calculate max adjustment for given mult/shift */ 737*d65670a7SJohn Stultz cs->maxadj = clocksource_max_adjustment(cs); 738*d65670a7SJohn Stultz WARN_ONCE(cs->mult + cs->maxadj < cs->mult, 739*d65670a7SJohn Stultz "Clocksource %s might overflow on 11%% adjustment\n", 740*d65670a7SJohn Stultz cs->name); 741*d65670a7SJohn Stultz 74298962465SJon Hunter /* calculate max idle time permitted for this clocksource */ 74398962465SJon Hunter cs->max_idle_ns = clocksource_max_deferment(cs); 74498962465SJon Hunter 74575c5158fSMartin Schwidefsky mutex_lock(&clocksource_mutex); 746f1b82746SMartin Schwidefsky clocksource_enqueue(cs); 747fb63a0ebSMartin Schwidefsky clocksource_enqueue_watchdog(cs); 748e05b2efbSjohn stultz clocksource_select(); 74975c5158fSMartin Schwidefsky mutex_unlock(&clocksource_mutex); 750f1b82746SMartin Schwidefsky return 0; 751734efb46Sjohn stultz } 752a2752549Sjohn stultz EXPORT_SYMBOL(clocksource_register); 753734efb46Sjohn stultz 754d0981a1bSThomas Gleixner static void __clocksource_change_rating(struct clocksource *cs, int rating) 755d0981a1bSThomas Gleixner { 756d0981a1bSThomas Gleixner list_del(&cs->list); 757d0981a1bSThomas Gleixner cs->rating = rating; 758d0981a1bSThomas Gleixner clocksource_enqueue(cs); 759d0981a1bSThomas Gleixner clocksource_select(); 760d0981a1bSThomas Gleixner } 761d0981a1bSThomas Gleixner 762734efb46Sjohn stultz /** 76392c7e002SThomas Gleixner * clocksource_change_rating - Change the rating of a registered clocksource 764734efb46Sjohn stultz */ 76592c7e002SThomas Gleixner void clocksource_change_rating(struct clocksource *cs, int rating) 766734efb46Sjohn stultz { 76775c5158fSMartin Schwidefsky mutex_lock(&clocksource_mutex); 768d0981a1bSThomas Gleixner __clocksource_change_rating(cs, rating); 76975c5158fSMartin Schwidefsky mutex_unlock(&clocksource_mutex); 770734efb46Sjohn stultz } 771fb63a0ebSMartin Schwidefsky EXPORT_SYMBOL(clocksource_change_rating); 772734efb46Sjohn stultz 7734713e22cSThomas Gleixner /** 7744713e22cSThomas Gleixner * clocksource_unregister - remove a registered clocksource 7754713e22cSThomas Gleixner */ 7764713e22cSThomas Gleixner void clocksource_unregister(struct clocksource *cs) 7774713e22cSThomas Gleixner { 77875c5158fSMartin Schwidefsky mutex_lock(&clocksource_mutex); 779fb63a0ebSMartin Schwidefsky clocksource_dequeue_watchdog(cs); 7804713e22cSThomas Gleixner list_del(&cs->list); 781f1b82746SMartin Schwidefsky clocksource_select(); 78275c5158fSMartin Schwidefsky mutex_unlock(&clocksource_mutex); 7834713e22cSThomas Gleixner } 784fb63a0ebSMartin Schwidefsky EXPORT_SYMBOL(clocksource_unregister); 7854713e22cSThomas Gleixner 7862b013700SDaniel Walker #ifdef CONFIG_SYSFS 787734efb46Sjohn stultz /** 788734efb46Sjohn stultz * sysfs_show_current_clocksources - sysfs interface for current clocksource 789734efb46Sjohn stultz * @dev: unused 790734efb46Sjohn stultz * @buf: char buffer to be filled with clocksource list 791734efb46Sjohn stultz * 792734efb46Sjohn stultz * Provides sysfs interface for listing current clocksource. 793734efb46Sjohn stultz */ 794734efb46Sjohn stultz static ssize_t 7954a0b2b4dSAndi Kleen sysfs_show_current_clocksources(struct sys_device *dev, 7964a0b2b4dSAndi Kleen struct sysdev_attribute *attr, char *buf) 797734efb46Sjohn stultz { 7985e2cb101SMiao Xie ssize_t count = 0; 799734efb46Sjohn stultz 80075c5158fSMartin Schwidefsky mutex_lock(&clocksource_mutex); 8015e2cb101SMiao Xie count = snprintf(buf, PAGE_SIZE, "%s\n", curr_clocksource->name); 80275c5158fSMartin Schwidefsky mutex_unlock(&clocksource_mutex); 803734efb46Sjohn stultz 8045e2cb101SMiao Xie return count; 805734efb46Sjohn stultz } 806734efb46Sjohn stultz 807734efb46Sjohn stultz /** 808734efb46Sjohn stultz * sysfs_override_clocksource - interface for manually overriding clocksource 809734efb46Sjohn stultz * @dev: unused 810734efb46Sjohn stultz * @buf: name of override clocksource 811734efb46Sjohn stultz * @count: length of buffer 812734efb46Sjohn stultz * 813734efb46Sjohn stultz * Takes input from sysfs interface for manually overriding the default 814b71a8eb0SUwe Kleine-König * clocksource selection. 815734efb46Sjohn stultz */ 816734efb46Sjohn stultz static ssize_t sysfs_override_clocksource(struct sys_device *dev, 8174a0b2b4dSAndi Kleen struct sysdev_attribute *attr, 818734efb46Sjohn stultz const char *buf, size_t count) 819734efb46Sjohn stultz { 820734efb46Sjohn stultz size_t ret = count; 82192c7e002SThomas Gleixner 822734efb46Sjohn stultz /* strings from sysfs write are not 0 terminated! */ 823734efb46Sjohn stultz if (count >= sizeof(override_name)) 824734efb46Sjohn stultz return -EINVAL; 825734efb46Sjohn stultz 826734efb46Sjohn stultz /* strip of \n: */ 827734efb46Sjohn stultz if (buf[count-1] == '\n') 828734efb46Sjohn stultz count--; 829734efb46Sjohn stultz 83075c5158fSMartin Schwidefsky mutex_lock(&clocksource_mutex); 831734efb46Sjohn stultz 83292c7e002SThomas Gleixner if (count > 0) 833734efb46Sjohn stultz memcpy(override_name, buf, count); 834734efb46Sjohn stultz override_name[count] = 0; 835f1b82746SMartin Schwidefsky clocksource_select(); 836734efb46Sjohn stultz 83775c5158fSMartin Schwidefsky mutex_unlock(&clocksource_mutex); 838734efb46Sjohn stultz 839734efb46Sjohn stultz return ret; 840734efb46Sjohn stultz } 841734efb46Sjohn stultz 842734efb46Sjohn stultz /** 843734efb46Sjohn stultz * sysfs_show_available_clocksources - sysfs interface for listing clocksource 844734efb46Sjohn stultz * @dev: unused 845734efb46Sjohn stultz * @buf: char buffer to be filled with clocksource list 846734efb46Sjohn stultz * 847734efb46Sjohn stultz * Provides sysfs interface for listing registered clocksources 848734efb46Sjohn stultz */ 849734efb46Sjohn stultz static ssize_t 8504a0b2b4dSAndi Kleen sysfs_show_available_clocksources(struct sys_device *dev, 8514a0b2b4dSAndi Kleen struct sysdev_attribute *attr, 8524a0b2b4dSAndi Kleen char *buf) 853734efb46Sjohn stultz { 8542e197586SMatthias Kaehlcke struct clocksource *src; 8555e2cb101SMiao Xie ssize_t count = 0; 856734efb46Sjohn stultz 85775c5158fSMartin Schwidefsky mutex_lock(&clocksource_mutex); 8582e197586SMatthias Kaehlcke list_for_each_entry(src, &clocksource_list, list) { 859cd6d95d8SThomas Gleixner /* 860cd6d95d8SThomas Gleixner * Don't show non-HRES clocksource if the tick code is 861cd6d95d8SThomas Gleixner * in one shot mode (highres=on or nohz=on) 862cd6d95d8SThomas Gleixner */ 863cd6d95d8SThomas Gleixner if (!tick_oneshot_mode_active() || 8643f68535aSjohn stultz (src->flags & CLOCK_SOURCE_VALID_FOR_HRES)) 8655e2cb101SMiao Xie count += snprintf(buf + count, 8665e2cb101SMiao Xie max((ssize_t)PAGE_SIZE - count, (ssize_t)0), 8675e2cb101SMiao Xie "%s ", src->name); 868734efb46Sjohn stultz } 86975c5158fSMartin Schwidefsky mutex_unlock(&clocksource_mutex); 870734efb46Sjohn stultz 8715e2cb101SMiao Xie count += snprintf(buf + count, 8725e2cb101SMiao Xie max((ssize_t)PAGE_SIZE - count, (ssize_t)0), "\n"); 873734efb46Sjohn stultz 8745e2cb101SMiao Xie return count; 875734efb46Sjohn stultz } 876734efb46Sjohn stultz 877734efb46Sjohn stultz /* 878734efb46Sjohn stultz * Sysfs setup bits: 879734efb46Sjohn stultz */ 8804f95f81aSHeiko Carstens static SYSDEV_ATTR(current_clocksource, 0644, sysfs_show_current_clocksources, 881734efb46Sjohn stultz sysfs_override_clocksource); 882734efb46Sjohn stultz 8834f95f81aSHeiko Carstens static SYSDEV_ATTR(available_clocksource, 0444, 884734efb46Sjohn stultz sysfs_show_available_clocksources, NULL); 885734efb46Sjohn stultz 886734efb46Sjohn stultz static struct sysdev_class clocksource_sysclass = { 887af5ca3f4SKay Sievers .name = "clocksource", 888734efb46Sjohn stultz }; 889734efb46Sjohn stultz 890734efb46Sjohn stultz static struct sys_device device_clocksource = { 891734efb46Sjohn stultz .id = 0, 892734efb46Sjohn stultz .cls = &clocksource_sysclass, 893734efb46Sjohn stultz }; 894734efb46Sjohn stultz 895ad596171Sjohn stultz static int __init init_clocksource_sysfs(void) 896734efb46Sjohn stultz { 897734efb46Sjohn stultz int error = sysdev_class_register(&clocksource_sysclass); 898734efb46Sjohn stultz 899734efb46Sjohn stultz if (!error) 900734efb46Sjohn stultz error = sysdev_register(&device_clocksource); 901734efb46Sjohn stultz if (!error) 902734efb46Sjohn stultz error = sysdev_create_file( 903734efb46Sjohn stultz &device_clocksource, 904734efb46Sjohn stultz &attr_current_clocksource); 905734efb46Sjohn stultz if (!error) 906734efb46Sjohn stultz error = sysdev_create_file( 907734efb46Sjohn stultz &device_clocksource, 908734efb46Sjohn stultz &attr_available_clocksource); 909734efb46Sjohn stultz return error; 910734efb46Sjohn stultz } 911734efb46Sjohn stultz 912734efb46Sjohn stultz device_initcall(init_clocksource_sysfs); 9132b013700SDaniel Walker #endif /* CONFIG_SYSFS */ 914734efb46Sjohn stultz 915734efb46Sjohn stultz /** 916734efb46Sjohn stultz * boot_override_clocksource - boot clock override 917734efb46Sjohn stultz * @str: override name 918734efb46Sjohn stultz * 919734efb46Sjohn stultz * Takes a clocksource= boot argument and uses it 920734efb46Sjohn stultz * as the clocksource override name. 921734efb46Sjohn stultz */ 922734efb46Sjohn stultz static int __init boot_override_clocksource(char* str) 923734efb46Sjohn stultz { 92475c5158fSMartin Schwidefsky mutex_lock(&clocksource_mutex); 925734efb46Sjohn stultz if (str) 926734efb46Sjohn stultz strlcpy(override_name, str, sizeof(override_name)); 92775c5158fSMartin Schwidefsky mutex_unlock(&clocksource_mutex); 928734efb46Sjohn stultz return 1; 929734efb46Sjohn stultz } 930734efb46Sjohn stultz 931734efb46Sjohn stultz __setup("clocksource=", boot_override_clocksource); 932734efb46Sjohn stultz 933734efb46Sjohn stultz /** 934734efb46Sjohn stultz * boot_override_clock - Compatibility layer for deprecated boot option 935734efb46Sjohn stultz * @str: override name 936734efb46Sjohn stultz * 937734efb46Sjohn stultz * DEPRECATED! Takes a clock= boot argument and uses it 938734efb46Sjohn stultz * as the clocksource override name 939734efb46Sjohn stultz */ 940734efb46Sjohn stultz static int __init boot_override_clock(char* str) 941734efb46Sjohn stultz { 9425d0cf410Sjohn stultz if (!strcmp(str, "pmtmr")) { 9435d0cf410Sjohn stultz printk("Warning: clock=pmtmr is deprecated. " 9445d0cf410Sjohn stultz "Use clocksource=acpi_pm.\n"); 9455d0cf410Sjohn stultz return boot_override_clocksource("acpi_pm"); 9465d0cf410Sjohn stultz } 9475d0cf410Sjohn stultz printk("Warning! clock= boot option is deprecated. " 9485d0cf410Sjohn stultz "Use clocksource=xyz\n"); 949734efb46Sjohn stultz return boot_override_clocksource(str); 950734efb46Sjohn stultz } 951734efb46Sjohn stultz 952734efb46Sjohn stultz __setup("clock=", boot_override_clock); 953