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 116*5fdade95SNicolas 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 * 125*5fdade95SNicolas 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 134*5fdade95SNicolas 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 */ 143*5fdade95SNicolas 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; 1557d2f944aSThomas Gleixner do_div(tmp, from); 1567d2f944aSThomas Gleixner if ((tmp >> sftacc) == 0) 1577d2f944aSThomas Gleixner break; 1587d2f944aSThomas Gleixner } 1597d2f944aSThomas Gleixner *mult = tmp; 1607d2f944aSThomas Gleixner *shift = sft; 1617d2f944aSThomas Gleixner } 1627d2f944aSThomas Gleixner 163734efb46Sjohn stultz /*[Clocksource internal variables]--------- 164734efb46Sjohn stultz * curr_clocksource: 165f1b82746SMartin Schwidefsky * currently selected clocksource. 166734efb46Sjohn stultz * clocksource_list: 167734efb46Sjohn stultz * linked list with the registered clocksources 16875c5158fSMartin Schwidefsky * clocksource_mutex: 16975c5158fSMartin Schwidefsky * protects manipulations to curr_clocksource and the clocksource_list 170734efb46Sjohn stultz * override_name: 171734efb46Sjohn stultz * Name of the user-specified clocksource. 172734efb46Sjohn stultz */ 173f1b82746SMartin Schwidefsky static struct clocksource *curr_clocksource; 174734efb46Sjohn stultz static LIST_HEAD(clocksource_list); 17575c5158fSMartin Schwidefsky static DEFINE_MUTEX(clocksource_mutex); 176734efb46Sjohn stultz static char override_name[32]; 17754a6bc0bSThomas Gleixner static int finished_booting; 178734efb46Sjohn stultz 1795d8b34fdSThomas Gleixner #ifdef CONFIG_CLOCKSOURCE_WATCHDOG 180f79e0258SMartin Schwidefsky static void clocksource_watchdog_work(struct work_struct *work); 181f79e0258SMartin Schwidefsky 1825d8b34fdSThomas Gleixner static LIST_HEAD(watchdog_list); 1835d8b34fdSThomas Gleixner static struct clocksource *watchdog; 1845d8b34fdSThomas Gleixner static struct timer_list watchdog_timer; 185f79e0258SMartin Schwidefsky static DECLARE_WORK(watchdog_work, clocksource_watchdog_work); 1865d8b34fdSThomas Gleixner static DEFINE_SPINLOCK(watchdog_lock); 1875d8b34fdSThomas Gleixner static cycle_t watchdog_last; 188fb63a0ebSMartin Schwidefsky static int watchdog_running; 189b52f52a0SThomas Gleixner 19001548f4dSMartin Schwidefsky static int clocksource_watchdog_kthread(void *data); 191d0981a1bSThomas Gleixner static void __clocksource_change_rating(struct clocksource *cs, int rating); 192c55c87c8SMartin Schwidefsky 1935d8b34fdSThomas Gleixner /* 19435c35d1aSDaniel Walker * Interval: 0.5sec Threshold: 0.0625s 1955d8b34fdSThomas Gleixner */ 1965d8b34fdSThomas Gleixner #define WATCHDOG_INTERVAL (HZ >> 1) 19735c35d1aSDaniel Walker #define WATCHDOG_THRESHOLD (NSEC_PER_SEC >> 4) 1985d8b34fdSThomas Gleixner 19901548f4dSMartin Schwidefsky static void clocksource_watchdog_work(struct work_struct *work) 20001548f4dSMartin Schwidefsky { 20101548f4dSMartin Schwidefsky /* 20201548f4dSMartin Schwidefsky * If kthread_run fails the next watchdog scan over the 20301548f4dSMartin Schwidefsky * watchdog_list will find the unstable clock again. 20401548f4dSMartin Schwidefsky */ 20501548f4dSMartin Schwidefsky kthread_run(clocksource_watchdog_kthread, NULL, "kwatchdog"); 20601548f4dSMartin Schwidefsky } 20701548f4dSMartin Schwidefsky 2087285dd7fSThomas Gleixner static void __clocksource_unstable(struct clocksource *cs) 2097285dd7fSThomas Gleixner { 2107285dd7fSThomas Gleixner cs->flags &= ~(CLOCK_SOURCE_VALID_FOR_HRES | CLOCK_SOURCE_WATCHDOG); 2117285dd7fSThomas Gleixner cs->flags |= CLOCK_SOURCE_UNSTABLE; 21254a6bc0bSThomas Gleixner if (finished_booting) 2137285dd7fSThomas Gleixner schedule_work(&watchdog_work); 2147285dd7fSThomas Gleixner } 2157285dd7fSThomas Gleixner 2168cf4e750SMartin Schwidefsky static void clocksource_unstable(struct clocksource *cs, int64_t delta) 2175d8b34fdSThomas Gleixner { 2185d8b34fdSThomas Gleixner printk(KERN_WARNING "Clocksource %s unstable (delta = %Ld ns)\n", 2195d8b34fdSThomas Gleixner cs->name, delta); 2207285dd7fSThomas Gleixner __clocksource_unstable(cs); 2217285dd7fSThomas Gleixner } 2227285dd7fSThomas Gleixner 2237285dd7fSThomas Gleixner /** 2247285dd7fSThomas Gleixner * clocksource_mark_unstable - mark clocksource unstable via watchdog 2257285dd7fSThomas Gleixner * @cs: clocksource to be marked unstable 2267285dd7fSThomas Gleixner * 2277285dd7fSThomas Gleixner * This function is called instead of clocksource_change_rating from 2287285dd7fSThomas Gleixner * cpu hotplug code to avoid a deadlock between the clocksource mutex 2297285dd7fSThomas Gleixner * and the cpu hotplug mutex. It defers the update of the clocksource 2307285dd7fSThomas Gleixner * to the watchdog thread. 2317285dd7fSThomas Gleixner */ 2327285dd7fSThomas Gleixner void clocksource_mark_unstable(struct clocksource *cs) 2337285dd7fSThomas Gleixner { 2347285dd7fSThomas Gleixner unsigned long flags; 2357285dd7fSThomas Gleixner 2367285dd7fSThomas Gleixner spin_lock_irqsave(&watchdog_lock, flags); 2377285dd7fSThomas Gleixner if (!(cs->flags & CLOCK_SOURCE_UNSTABLE)) { 2387285dd7fSThomas Gleixner if (list_empty(&cs->wd_list)) 2397285dd7fSThomas Gleixner list_add(&cs->wd_list, &watchdog_list); 2407285dd7fSThomas Gleixner __clocksource_unstable(cs); 2417285dd7fSThomas Gleixner } 2427285dd7fSThomas Gleixner spin_unlock_irqrestore(&watchdog_lock, flags); 2435d8b34fdSThomas Gleixner } 2445d8b34fdSThomas Gleixner 2455d8b34fdSThomas Gleixner static void clocksource_watchdog(unsigned long data) 2465d8b34fdSThomas Gleixner { 247c55c87c8SMartin Schwidefsky struct clocksource *cs; 2485d8b34fdSThomas Gleixner cycle_t csnow, wdnow; 2495d8b34fdSThomas Gleixner int64_t wd_nsec, cs_nsec; 250c55c87c8SMartin Schwidefsky int next_cpu; 2515d8b34fdSThomas Gleixner 2525d8b34fdSThomas Gleixner spin_lock(&watchdog_lock); 253fb63a0ebSMartin Schwidefsky if (!watchdog_running) 254fb63a0ebSMartin Schwidefsky goto out; 2555d8b34fdSThomas Gleixner 2568e19608eSMagnus Damm wdnow = watchdog->read(watchdog); 257155ec602SMartin Schwidefsky wd_nsec = clocksource_cyc2ns((wdnow - watchdog_last) & watchdog->mask, 258155ec602SMartin Schwidefsky watchdog->mult, watchdog->shift); 2595d8b34fdSThomas Gleixner watchdog_last = wdnow; 2605d8b34fdSThomas Gleixner 261c55c87c8SMartin Schwidefsky list_for_each_entry(cs, &watchdog_list, wd_list) { 262c55c87c8SMartin Schwidefsky 263c55c87c8SMartin Schwidefsky /* Clocksource already marked unstable? */ 26401548f4dSMartin Schwidefsky if (cs->flags & CLOCK_SOURCE_UNSTABLE) { 26554a6bc0bSThomas Gleixner if (finished_booting) 26601548f4dSMartin Schwidefsky schedule_work(&watchdog_work); 267c55c87c8SMartin Schwidefsky continue; 26801548f4dSMartin Schwidefsky } 269c55c87c8SMartin Schwidefsky 2708e19608eSMagnus Damm csnow = cs->read(cs); 271b52f52a0SThomas Gleixner 2728cf4e750SMartin Schwidefsky /* Clocksource initialized ? */ 2738cf4e750SMartin Schwidefsky if (!(cs->flags & CLOCK_SOURCE_WATCHDOG)) { 2748cf4e750SMartin Schwidefsky cs->flags |= CLOCK_SOURCE_WATCHDOG; 275b52f52a0SThomas Gleixner cs->wd_last = csnow; 276b52f52a0SThomas Gleixner continue; 277b52f52a0SThomas Gleixner } 278b52f52a0SThomas Gleixner 2798cf4e750SMartin Schwidefsky /* Check the deviation from the watchdog clocksource. */ 280155ec602SMartin Schwidefsky cs_nsec = clocksource_cyc2ns((csnow - cs->wd_last) & 281155ec602SMartin Schwidefsky cs->mask, cs->mult, cs->shift); 2828cf4e750SMartin Schwidefsky cs->wd_last = csnow; 2838cf4e750SMartin Schwidefsky if (abs(cs_nsec - wd_nsec) > WATCHDOG_THRESHOLD) { 2848cf4e750SMartin Schwidefsky clocksource_unstable(cs, cs_nsec - wd_nsec); 2858cf4e750SMartin Schwidefsky continue; 2868cf4e750SMartin Schwidefsky } 2878cf4e750SMartin Schwidefsky 2888cf4e750SMartin Schwidefsky if (!(cs->flags & CLOCK_SOURCE_VALID_FOR_HRES) && 2898cf4e750SMartin Schwidefsky (cs->flags & CLOCK_SOURCE_IS_CONTINUOUS) && 2905d8b34fdSThomas Gleixner (watchdog->flags & CLOCK_SOURCE_IS_CONTINUOUS)) { 2915d8b34fdSThomas Gleixner cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES; 29279bf2bb3SThomas Gleixner /* 2938cf4e750SMartin Schwidefsky * We just marked the clocksource as highres-capable, 2948cf4e750SMartin Schwidefsky * notify the rest of the system as well so that we 2958cf4e750SMartin Schwidefsky * transition into high-res mode: 29679bf2bb3SThomas Gleixner */ 29779bf2bb3SThomas Gleixner tick_clock_notify(); 2985d8b34fdSThomas Gleixner } 2995d8b34fdSThomas Gleixner } 3005d8b34fdSThomas Gleixner 3016993fc5bSAndi Kleen /* 302c55c87c8SMartin Schwidefsky * Cycle through CPUs to check if the CPUs stay synchronized 303c55c87c8SMartin Schwidefsky * to each other. 3046993fc5bSAndi Kleen */ 305c55c87c8SMartin Schwidefsky next_cpu = cpumask_next(raw_smp_processor_id(), cpu_online_mask); 306cad0e458SMike Travis if (next_cpu >= nr_cpu_ids) 3076b954823SRusty Russell next_cpu = cpumask_first(cpu_online_mask); 3086993fc5bSAndi Kleen watchdog_timer.expires += WATCHDOG_INTERVAL; 3096993fc5bSAndi Kleen add_timer_on(&watchdog_timer, next_cpu); 310fb63a0ebSMartin Schwidefsky out: 3115d8b34fdSThomas Gleixner spin_unlock(&watchdog_lock); 3125d8b34fdSThomas Gleixner } 3130f8e8ef7SMartin Schwidefsky 314fb63a0ebSMartin Schwidefsky static inline void clocksource_start_watchdog(void) 315fb63a0ebSMartin Schwidefsky { 316fb63a0ebSMartin Schwidefsky if (watchdog_running || !watchdog || list_empty(&watchdog_list)) 317fb63a0ebSMartin Schwidefsky return; 318fb63a0ebSMartin Schwidefsky init_timer(&watchdog_timer); 319fb63a0ebSMartin Schwidefsky watchdog_timer.function = clocksource_watchdog; 320fb63a0ebSMartin Schwidefsky watchdog_last = watchdog->read(watchdog); 321fb63a0ebSMartin Schwidefsky watchdog_timer.expires = jiffies + WATCHDOG_INTERVAL; 322fb63a0ebSMartin Schwidefsky add_timer_on(&watchdog_timer, cpumask_first(cpu_online_mask)); 323fb63a0ebSMartin Schwidefsky watchdog_running = 1; 324fb63a0ebSMartin Schwidefsky } 325fb63a0ebSMartin Schwidefsky 326fb63a0ebSMartin Schwidefsky static inline void clocksource_stop_watchdog(void) 327fb63a0ebSMartin Schwidefsky { 328fb63a0ebSMartin Schwidefsky if (!watchdog_running || (watchdog && !list_empty(&watchdog_list))) 329fb63a0ebSMartin Schwidefsky return; 330fb63a0ebSMartin Schwidefsky del_timer(&watchdog_timer); 331fb63a0ebSMartin Schwidefsky watchdog_running = 0; 332fb63a0ebSMartin Schwidefsky } 333fb63a0ebSMartin Schwidefsky 3340f8e8ef7SMartin Schwidefsky static inline void clocksource_reset_watchdog(void) 3350f8e8ef7SMartin Schwidefsky { 3360f8e8ef7SMartin Schwidefsky struct clocksource *cs; 3370f8e8ef7SMartin Schwidefsky 3380f8e8ef7SMartin Schwidefsky list_for_each_entry(cs, &watchdog_list, wd_list) 3390f8e8ef7SMartin Schwidefsky cs->flags &= ~CLOCK_SOURCE_WATCHDOG; 3400f8e8ef7SMartin Schwidefsky } 3410f8e8ef7SMartin Schwidefsky 342b52f52a0SThomas Gleixner static void clocksource_resume_watchdog(void) 343b52f52a0SThomas Gleixner { 3440f8e8ef7SMartin Schwidefsky unsigned long flags; 3450f8e8ef7SMartin Schwidefsky 3467b7422a5SThomas Gleixner /* 3477b7422a5SThomas Gleixner * We use trylock here to avoid a potential dead lock when 3487b7422a5SThomas Gleixner * kgdb calls this code after the kernel has been stopped with 3497b7422a5SThomas Gleixner * watchdog_lock held. When watchdog_lock is held we just 3507b7422a5SThomas Gleixner * return and accept, that the watchdog might trigger and mark 3517b7422a5SThomas Gleixner * the monitored clock source (usually TSC) unstable. 3527b7422a5SThomas Gleixner * 3537b7422a5SThomas Gleixner * This does not affect the other caller clocksource_resume() 3547b7422a5SThomas Gleixner * because at this point the kernel is UP, interrupts are 3557b7422a5SThomas Gleixner * disabled and nothing can hold watchdog_lock. 3567b7422a5SThomas Gleixner */ 3577b7422a5SThomas Gleixner if (!spin_trylock_irqsave(&watchdog_lock, flags)) 3587b7422a5SThomas Gleixner return; 3590f8e8ef7SMartin Schwidefsky clocksource_reset_watchdog(); 3600f8e8ef7SMartin Schwidefsky spin_unlock_irqrestore(&watchdog_lock, flags); 361b52f52a0SThomas Gleixner } 362b52f52a0SThomas Gleixner 363fb63a0ebSMartin Schwidefsky static void clocksource_enqueue_watchdog(struct clocksource *cs) 3645d8b34fdSThomas Gleixner { 3655d8b34fdSThomas Gleixner unsigned long flags; 3665d8b34fdSThomas Gleixner 3675d8b34fdSThomas Gleixner spin_lock_irqsave(&watchdog_lock, flags); 3685d8b34fdSThomas Gleixner if (cs->flags & CLOCK_SOURCE_MUST_VERIFY) { 369fb63a0ebSMartin Schwidefsky /* cs is a clocksource to be watched. */ 3705d8b34fdSThomas Gleixner list_add(&cs->wd_list, &watchdog_list); 371fb63a0ebSMartin Schwidefsky cs->flags &= ~CLOCK_SOURCE_WATCHDOG; 372948ac6d7SThomas Gleixner } else { 373fb63a0ebSMartin Schwidefsky /* cs is a watchdog. */ 374948ac6d7SThomas Gleixner if (cs->flags & CLOCK_SOURCE_IS_CONTINUOUS) 3755d8b34fdSThomas Gleixner cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES; 376fb63a0ebSMartin Schwidefsky /* Pick the best watchdog. */ 3775d8b34fdSThomas Gleixner if (!watchdog || cs->rating > watchdog->rating) { 3785d8b34fdSThomas Gleixner watchdog = cs; 3795d8b34fdSThomas Gleixner /* Reset watchdog cycles */ 3800f8e8ef7SMartin Schwidefsky clocksource_reset_watchdog(); 3815d8b34fdSThomas Gleixner } 3825d8b34fdSThomas Gleixner } 383fb63a0ebSMartin Schwidefsky /* Check if the watchdog timer needs to be started. */ 384fb63a0ebSMartin Schwidefsky clocksource_start_watchdog(); 3855d8b34fdSThomas Gleixner spin_unlock_irqrestore(&watchdog_lock, flags); 3865d8b34fdSThomas Gleixner } 387fb63a0ebSMartin Schwidefsky 388fb63a0ebSMartin Schwidefsky static void clocksource_dequeue_watchdog(struct clocksource *cs) 389fb63a0ebSMartin Schwidefsky { 390fb63a0ebSMartin Schwidefsky struct clocksource *tmp; 391fb63a0ebSMartin Schwidefsky unsigned long flags; 392fb63a0ebSMartin Schwidefsky 393fb63a0ebSMartin Schwidefsky spin_lock_irqsave(&watchdog_lock, flags); 394fb63a0ebSMartin Schwidefsky if (cs->flags & CLOCK_SOURCE_MUST_VERIFY) { 395fb63a0ebSMartin Schwidefsky /* cs is a watched clocksource. */ 396fb63a0ebSMartin Schwidefsky list_del_init(&cs->wd_list); 397fb63a0ebSMartin Schwidefsky } else if (cs == watchdog) { 398fb63a0ebSMartin Schwidefsky /* Reset watchdog cycles */ 399fb63a0ebSMartin Schwidefsky clocksource_reset_watchdog(); 400fb63a0ebSMartin Schwidefsky /* Current watchdog is removed. Find an alternative. */ 401fb63a0ebSMartin Schwidefsky watchdog = NULL; 402fb63a0ebSMartin Schwidefsky list_for_each_entry(tmp, &clocksource_list, list) { 403fb63a0ebSMartin Schwidefsky if (tmp == cs || tmp->flags & CLOCK_SOURCE_MUST_VERIFY) 404fb63a0ebSMartin Schwidefsky continue; 405fb63a0ebSMartin Schwidefsky if (!watchdog || tmp->rating > watchdog->rating) 406fb63a0ebSMartin Schwidefsky watchdog = tmp; 407fb63a0ebSMartin Schwidefsky } 408fb63a0ebSMartin Schwidefsky } 409fb63a0ebSMartin Schwidefsky cs->flags &= ~CLOCK_SOURCE_WATCHDOG; 410fb63a0ebSMartin Schwidefsky /* Check if the watchdog timer needs to be stopped. */ 411fb63a0ebSMartin Schwidefsky clocksource_stop_watchdog(); 412fb63a0ebSMartin Schwidefsky spin_unlock_irqrestore(&watchdog_lock, flags); 413fb63a0ebSMartin Schwidefsky } 414fb63a0ebSMartin Schwidefsky 41501548f4dSMartin Schwidefsky static int clocksource_watchdog_kthread(void *data) 416c55c87c8SMartin Schwidefsky { 417c55c87c8SMartin Schwidefsky struct clocksource *cs, *tmp; 418c55c87c8SMartin Schwidefsky unsigned long flags; 4196ea41d25SThomas Gleixner LIST_HEAD(unstable); 420c55c87c8SMartin Schwidefsky 421d0981a1bSThomas Gleixner mutex_lock(&clocksource_mutex); 422c55c87c8SMartin Schwidefsky spin_lock_irqsave(&watchdog_lock, flags); 423c55c87c8SMartin Schwidefsky list_for_each_entry_safe(cs, tmp, &watchdog_list, wd_list) 424c55c87c8SMartin Schwidefsky if (cs->flags & CLOCK_SOURCE_UNSTABLE) { 425c55c87c8SMartin Schwidefsky list_del_init(&cs->wd_list); 4266ea41d25SThomas Gleixner list_add(&cs->wd_list, &unstable); 427c55c87c8SMartin Schwidefsky } 428c55c87c8SMartin Schwidefsky /* Check if the watchdog timer needs to be stopped. */ 429c55c87c8SMartin Schwidefsky clocksource_stop_watchdog(); 4306ea41d25SThomas Gleixner spin_unlock_irqrestore(&watchdog_lock, flags); 4316ea41d25SThomas Gleixner 4326ea41d25SThomas Gleixner /* Needs to be done outside of watchdog lock */ 4336ea41d25SThomas Gleixner list_for_each_entry_safe(cs, tmp, &unstable, wd_list) { 4346ea41d25SThomas Gleixner list_del_init(&cs->wd_list); 435d0981a1bSThomas Gleixner __clocksource_change_rating(cs, 0); 4366ea41d25SThomas Gleixner } 437d0981a1bSThomas Gleixner mutex_unlock(&clocksource_mutex); 43801548f4dSMartin Schwidefsky return 0; 439c55c87c8SMartin Schwidefsky } 440c55c87c8SMartin Schwidefsky 441fb63a0ebSMartin Schwidefsky #else /* CONFIG_CLOCKSOURCE_WATCHDOG */ 442fb63a0ebSMartin Schwidefsky 443fb63a0ebSMartin Schwidefsky static void clocksource_enqueue_watchdog(struct clocksource *cs) 4445d8b34fdSThomas Gleixner { 4455d8b34fdSThomas Gleixner if (cs->flags & CLOCK_SOURCE_IS_CONTINUOUS) 4465d8b34fdSThomas Gleixner cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES; 4475d8b34fdSThomas Gleixner } 448b52f52a0SThomas Gleixner 449fb63a0ebSMartin Schwidefsky static inline void clocksource_dequeue_watchdog(struct clocksource *cs) { } 450b52f52a0SThomas Gleixner static inline void clocksource_resume_watchdog(void) { } 45154a6bc0bSThomas Gleixner static inline int clocksource_watchdog_kthread(void *data) { return 0; } 452fb63a0ebSMartin Schwidefsky 453fb63a0ebSMartin Schwidefsky #endif /* CONFIG_CLOCKSOURCE_WATCHDOG */ 4545d8b34fdSThomas Gleixner 455734efb46Sjohn stultz /** 456c54a42b1SMagnus Damm * clocksource_suspend - suspend the clocksource(s) 457c54a42b1SMagnus Damm */ 458c54a42b1SMagnus Damm void clocksource_suspend(void) 459c54a42b1SMagnus Damm { 460c54a42b1SMagnus Damm struct clocksource *cs; 461c54a42b1SMagnus Damm 462c54a42b1SMagnus Damm list_for_each_entry_reverse(cs, &clocksource_list, list) 463c54a42b1SMagnus Damm if (cs->suspend) 464c54a42b1SMagnus Damm cs->suspend(cs); 465c54a42b1SMagnus Damm } 466c54a42b1SMagnus Damm 467c54a42b1SMagnus Damm /** 468b52f52a0SThomas Gleixner * clocksource_resume - resume the clocksource(s) 469b52f52a0SThomas Gleixner */ 470b52f52a0SThomas Gleixner void clocksource_resume(void) 471b52f52a0SThomas Gleixner { 4722e197586SMatthias Kaehlcke struct clocksource *cs; 473b52f52a0SThomas Gleixner 47475c5158fSMartin Schwidefsky list_for_each_entry(cs, &clocksource_list, list) 475b52f52a0SThomas Gleixner if (cs->resume) 47617622339SMagnus Damm cs->resume(cs); 477b52f52a0SThomas Gleixner 478b52f52a0SThomas Gleixner clocksource_resume_watchdog(); 479b52f52a0SThomas Gleixner } 480b52f52a0SThomas Gleixner 481b52f52a0SThomas Gleixner /** 4827c3078b6SJason Wessel * clocksource_touch_watchdog - Update watchdog 4837c3078b6SJason Wessel * 4847c3078b6SJason Wessel * Update the watchdog after exception contexts such as kgdb so as not 4857b7422a5SThomas Gleixner * to incorrectly trip the watchdog. This might fail when the kernel 4867b7422a5SThomas Gleixner * was stopped in code which holds watchdog_lock. 4877c3078b6SJason Wessel */ 4887c3078b6SJason Wessel void clocksource_touch_watchdog(void) 4897c3078b6SJason Wessel { 4907c3078b6SJason Wessel clocksource_resume_watchdog(); 4917c3078b6SJason Wessel } 4927c3078b6SJason Wessel 493734efb46Sjohn stultz /** 49498962465SJon Hunter * clocksource_max_deferment - Returns max time the clocksource can be deferred 49598962465SJon Hunter * @cs: Pointer to clocksource 49698962465SJon Hunter * 49798962465SJon Hunter */ 49898962465SJon Hunter static u64 clocksource_max_deferment(struct clocksource *cs) 49998962465SJon Hunter { 50098962465SJon Hunter u64 max_nsecs, max_cycles; 50198962465SJon Hunter 50298962465SJon Hunter /* 50398962465SJon Hunter * Calculate the maximum number of cycles that we can pass to the 50498962465SJon Hunter * cyc2ns function without overflowing a 64-bit signed result. The 50598962465SJon Hunter * maximum number of cycles is equal to ULLONG_MAX/cs->mult which 50698962465SJon Hunter * is equivalent to the below. 50798962465SJon Hunter * max_cycles < (2^63)/cs->mult 50898962465SJon Hunter * max_cycles < 2^(log2((2^63)/cs->mult)) 50998962465SJon Hunter * max_cycles < 2^(log2(2^63) - log2(cs->mult)) 51098962465SJon Hunter * max_cycles < 2^(63 - log2(cs->mult)) 51198962465SJon Hunter * max_cycles < 1 << (63 - log2(cs->mult)) 51298962465SJon Hunter * Please note that we add 1 to the result of the log2 to account for 51398962465SJon Hunter * any rounding errors, ensure the above inequality is satisfied and 51498962465SJon Hunter * no overflow will occur. 51598962465SJon Hunter */ 51698962465SJon Hunter max_cycles = 1ULL << (63 - (ilog2(cs->mult) + 1)); 51798962465SJon Hunter 51898962465SJon Hunter /* 51998962465SJon Hunter * The actual maximum number of cycles we can defer the clocksource is 52098962465SJon Hunter * determined by the minimum of max_cycles and cs->mask. 52198962465SJon Hunter */ 52298962465SJon Hunter max_cycles = min_t(u64, max_cycles, (u64) cs->mask); 52398962465SJon Hunter max_nsecs = clocksource_cyc2ns(max_cycles, cs->mult, cs->shift); 52498962465SJon Hunter 52598962465SJon Hunter /* 52698962465SJon Hunter * To ensure that the clocksource does not wrap whilst we are idle, 52798962465SJon Hunter * limit the time the clocksource can be deferred by 12.5%. Please 52898962465SJon Hunter * note a margin of 12.5% is used because this can be computed with 52998962465SJon Hunter * a shift, versus say 10% which would require division. 53098962465SJon Hunter */ 53198962465SJon Hunter return max_nsecs - (max_nsecs >> 5); 53298962465SJon Hunter } 53398962465SJon Hunter 534592913ecSJohn Stultz #ifndef CONFIG_ARCH_USES_GETTIMEOFFSET 535734efb46Sjohn stultz 536734efb46Sjohn stultz /** 537f1b82746SMartin Schwidefsky * clocksource_select - Select the best clocksource available 538734efb46Sjohn stultz * 53975c5158fSMartin Schwidefsky * Private function. Must hold clocksource_mutex when called. 540734efb46Sjohn stultz * 54192c7e002SThomas Gleixner * Select the clocksource with the best rating, or the clocksource, 54292c7e002SThomas Gleixner * which is selected by userspace override. 543734efb46Sjohn stultz */ 544f1b82746SMartin Schwidefsky static void clocksource_select(void) 545734efb46Sjohn stultz { 546f1b82746SMartin Schwidefsky struct clocksource *best, *cs; 5475d8b34fdSThomas Gleixner 54875c5158fSMartin Schwidefsky if (!finished_booting || list_empty(&clocksource_list)) 549f1b82746SMartin Schwidefsky return; 550f1b82746SMartin Schwidefsky /* First clocksource on the list has the best rating. */ 551f1b82746SMartin Schwidefsky best = list_first_entry(&clocksource_list, struct clocksource, list); 552f1b82746SMartin Schwidefsky /* Check for the override clocksource. */ 553f1b82746SMartin Schwidefsky list_for_each_entry(cs, &clocksource_list, list) { 554f1b82746SMartin Schwidefsky if (strcmp(cs->name, override_name) != 0) 555f1b82746SMartin Schwidefsky continue; 556f1b82746SMartin Schwidefsky /* 557f1b82746SMartin Schwidefsky * Check to make sure we don't switch to a non-highres 558f1b82746SMartin Schwidefsky * capable clocksource if the tick code is in oneshot 559f1b82746SMartin Schwidefsky * mode (highres or nohz) 560f1b82746SMartin Schwidefsky */ 561f1b82746SMartin Schwidefsky if (!(cs->flags & CLOCK_SOURCE_VALID_FOR_HRES) && 562f1b82746SMartin Schwidefsky tick_oneshot_mode_active()) { 563f1b82746SMartin Schwidefsky /* Override clocksource cannot be used. */ 564f1b82746SMartin Schwidefsky printk(KERN_WARNING "Override clocksource %s is not " 565f1b82746SMartin Schwidefsky "HRT compatible. Cannot switch while in " 566f1b82746SMartin Schwidefsky "HRT/NOHZ mode\n", cs->name); 567f1b82746SMartin Schwidefsky override_name[0] = 0; 568f1b82746SMartin Schwidefsky } else 569f1b82746SMartin Schwidefsky /* Override clocksource can be used. */ 570f1b82746SMartin Schwidefsky best = cs; 571f1b82746SMartin Schwidefsky break; 572734efb46Sjohn stultz } 57375c5158fSMartin Schwidefsky if (curr_clocksource != best) { 57475c5158fSMartin Schwidefsky printk(KERN_INFO "Switching to clocksource %s\n", best->name); 57575c5158fSMartin Schwidefsky curr_clocksource = best; 57675c5158fSMartin Schwidefsky timekeeping_notify(curr_clocksource); 577f1b82746SMartin Schwidefsky } 57875c5158fSMartin Schwidefsky } 57975c5158fSMartin Schwidefsky 580592913ecSJohn Stultz #else /* !CONFIG_ARCH_USES_GETTIMEOFFSET */ 58154a6bc0bSThomas Gleixner 58254a6bc0bSThomas Gleixner static inline void clocksource_select(void) { } 58354a6bc0bSThomas Gleixner 58454a6bc0bSThomas Gleixner #endif 58554a6bc0bSThomas Gleixner 58675c5158fSMartin Schwidefsky /* 58775c5158fSMartin Schwidefsky * clocksource_done_booting - Called near the end of core bootup 58875c5158fSMartin Schwidefsky * 58975c5158fSMartin Schwidefsky * Hack to avoid lots of clocksource churn at boot time. 59075c5158fSMartin Schwidefsky * We use fs_initcall because we want this to start before 59175c5158fSMartin Schwidefsky * device_initcall but after subsys_initcall. 59275c5158fSMartin Schwidefsky */ 59375c5158fSMartin Schwidefsky static int __init clocksource_done_booting(void) 59475c5158fSMartin Schwidefsky { 595ad6759fbSjohn stultz mutex_lock(&clocksource_mutex); 596ad6759fbSjohn stultz curr_clocksource = clocksource_default_clock(); 597ad6759fbSjohn stultz mutex_unlock(&clocksource_mutex); 598ad6759fbSjohn stultz 59975c5158fSMartin Schwidefsky finished_booting = 1; 60054a6bc0bSThomas Gleixner 60154a6bc0bSThomas Gleixner /* 60254a6bc0bSThomas Gleixner * Run the watchdog first to eliminate unstable clock sources 60354a6bc0bSThomas Gleixner */ 60454a6bc0bSThomas Gleixner clocksource_watchdog_kthread(NULL); 60554a6bc0bSThomas Gleixner 606e6c73305SThomas Gleixner mutex_lock(&clocksource_mutex); 60775c5158fSMartin Schwidefsky clocksource_select(); 608e6c73305SThomas Gleixner mutex_unlock(&clocksource_mutex); 60975c5158fSMartin Schwidefsky return 0; 61075c5158fSMartin Schwidefsky } 61175c5158fSMartin Schwidefsky fs_initcall(clocksource_done_booting); 612f1b82746SMartin Schwidefsky 61392c7e002SThomas Gleixner /* 61492c7e002SThomas Gleixner * Enqueue the clocksource sorted by rating 615734efb46Sjohn stultz */ 616f1b82746SMartin Schwidefsky static void clocksource_enqueue(struct clocksource *cs) 617734efb46Sjohn stultz { 618f1b82746SMartin Schwidefsky struct list_head *entry = &clocksource_list; 619f1b82746SMartin Schwidefsky struct clocksource *tmp; 620734efb46Sjohn stultz 621f1b82746SMartin Schwidefsky list_for_each_entry(tmp, &clocksource_list, list) 62292c7e002SThomas Gleixner /* Keep track of the place, where to insert */ 623f1b82746SMartin Schwidefsky if (tmp->rating >= cs->rating) 624f1b82746SMartin Schwidefsky entry = &tmp->list; 625f1b82746SMartin Schwidefsky list_add(&cs->list, entry); 626734efb46Sjohn stultz } 627734efb46Sjohn stultz 628d7e81c26SJohn Stultz 629d7e81c26SJohn Stultz /* 630d7e81c26SJohn Stultz * Maximum time we expect to go between ticks. This includes idle 631d7e81c26SJohn Stultz * tickless time. It provides the trade off between selecting a 632d7e81c26SJohn Stultz * mult/shift pair that is very precise but can only handle a short 633d7e81c26SJohn Stultz * period of time, vs. a mult/shift pair that can handle long periods 634d7e81c26SJohn Stultz * of time but isn't as precise. 635d7e81c26SJohn Stultz * 636d7e81c26SJohn Stultz * This is a subsystem constant, and actual hardware limitations 637d7e81c26SJohn Stultz * may override it (ie: clocksources that wrap every 3 seconds). 638d7e81c26SJohn Stultz */ 639d7e81c26SJohn Stultz #define MAX_UPDATE_LENGTH 5 /* Seconds */ 640d7e81c26SJohn Stultz 641d7e81c26SJohn Stultz /** 642852db46dSJohn Stultz * __clocksource_updatefreq_scale - Used update clocksource with new freq 643852db46dSJohn Stultz * @t: clocksource to be registered 644852db46dSJohn Stultz * @scale: Scale factor multiplied against freq to get clocksource hz 645852db46dSJohn Stultz * @freq: clocksource frequency (cycles per second) divided by scale 646852db46dSJohn Stultz * 647852db46dSJohn Stultz * This should only be called from the clocksource->enable() method. 648852db46dSJohn Stultz * 649852db46dSJohn Stultz * This *SHOULD NOT* be called directly! Please use the 650852db46dSJohn Stultz * clocksource_updatefreq_hz() or clocksource_updatefreq_khz helper functions. 651852db46dSJohn Stultz */ 652852db46dSJohn Stultz void __clocksource_updatefreq_scale(struct clocksource *cs, u32 scale, u32 freq) 653852db46dSJohn Stultz { 654852db46dSJohn Stultz /* 655852db46dSJohn Stultz * Ideally we want to use some of the limits used in 656852db46dSJohn Stultz * clocksource_max_deferment, to provide a more informed 657852db46dSJohn Stultz * MAX_UPDATE_LENGTH. But for now this just gets the 658852db46dSJohn Stultz * register interface working properly. 659852db46dSJohn Stultz */ 660852db46dSJohn Stultz clocks_calc_mult_shift(&cs->mult, &cs->shift, freq, 661852db46dSJohn Stultz NSEC_PER_SEC/scale, 662852db46dSJohn Stultz MAX_UPDATE_LENGTH*scale); 663852db46dSJohn Stultz cs->max_idle_ns = clocksource_max_deferment(cs); 664852db46dSJohn Stultz } 665852db46dSJohn Stultz EXPORT_SYMBOL_GPL(__clocksource_updatefreq_scale); 666852db46dSJohn Stultz 667852db46dSJohn Stultz /** 668d7e81c26SJohn Stultz * __clocksource_register_scale - Used to install new clocksources 669d7e81c26SJohn Stultz * @t: clocksource to be registered 670d7e81c26SJohn Stultz * @scale: Scale factor multiplied against freq to get clocksource hz 671d7e81c26SJohn Stultz * @freq: clocksource frequency (cycles per second) divided by scale 672d7e81c26SJohn Stultz * 673d7e81c26SJohn Stultz * Returns -EBUSY if registration fails, zero otherwise. 674d7e81c26SJohn Stultz * 675d7e81c26SJohn Stultz * This *SHOULD NOT* be called directly! Please use the 676d7e81c26SJohn Stultz * clocksource_register_hz() or clocksource_register_khz helper functions. 677d7e81c26SJohn Stultz */ 678d7e81c26SJohn Stultz int __clocksource_register_scale(struct clocksource *cs, u32 scale, u32 freq) 679d7e81c26SJohn Stultz { 680d7e81c26SJohn Stultz 681852db46dSJohn Stultz /* Intialize mult/shift and max_idle_ns */ 682852db46dSJohn Stultz __clocksource_updatefreq_scale(cs, scale, freq); 683d7e81c26SJohn Stultz 684852db46dSJohn Stultz /* Add clocksource to the clcoksource list */ 685d7e81c26SJohn Stultz mutex_lock(&clocksource_mutex); 686d7e81c26SJohn Stultz clocksource_enqueue(cs); 687d7e81c26SJohn Stultz clocksource_select(); 688d7e81c26SJohn Stultz clocksource_enqueue_watchdog(cs); 689d7e81c26SJohn Stultz mutex_unlock(&clocksource_mutex); 690d7e81c26SJohn Stultz return 0; 691d7e81c26SJohn Stultz } 692d7e81c26SJohn Stultz EXPORT_SYMBOL_GPL(__clocksource_register_scale); 693d7e81c26SJohn Stultz 694d7e81c26SJohn Stultz 695734efb46Sjohn stultz /** 696a2752549Sjohn stultz * clocksource_register - Used to install new clocksources 697734efb46Sjohn stultz * @t: clocksource to be registered 698734efb46Sjohn stultz * 699734efb46Sjohn stultz * Returns -EBUSY if registration fails, zero otherwise. 700734efb46Sjohn stultz */ 701f1b82746SMartin Schwidefsky int clocksource_register(struct clocksource *cs) 702734efb46Sjohn stultz { 70398962465SJon Hunter /* calculate max idle time permitted for this clocksource */ 70498962465SJon Hunter cs->max_idle_ns = clocksource_max_deferment(cs); 70598962465SJon Hunter 70675c5158fSMartin Schwidefsky mutex_lock(&clocksource_mutex); 707f1b82746SMartin Schwidefsky clocksource_enqueue(cs); 708f1b82746SMartin Schwidefsky clocksource_select(); 709fb63a0ebSMartin Schwidefsky clocksource_enqueue_watchdog(cs); 71075c5158fSMartin Schwidefsky mutex_unlock(&clocksource_mutex); 711f1b82746SMartin Schwidefsky return 0; 712734efb46Sjohn stultz } 713a2752549Sjohn stultz EXPORT_SYMBOL(clocksource_register); 714734efb46Sjohn stultz 715d0981a1bSThomas Gleixner static void __clocksource_change_rating(struct clocksource *cs, int rating) 716d0981a1bSThomas Gleixner { 717d0981a1bSThomas Gleixner list_del(&cs->list); 718d0981a1bSThomas Gleixner cs->rating = rating; 719d0981a1bSThomas Gleixner clocksource_enqueue(cs); 720d0981a1bSThomas Gleixner clocksource_select(); 721d0981a1bSThomas Gleixner } 722d0981a1bSThomas Gleixner 723734efb46Sjohn stultz /** 72492c7e002SThomas Gleixner * clocksource_change_rating - Change the rating of a registered clocksource 725734efb46Sjohn stultz */ 72692c7e002SThomas Gleixner void clocksource_change_rating(struct clocksource *cs, int rating) 727734efb46Sjohn stultz { 72875c5158fSMartin Schwidefsky mutex_lock(&clocksource_mutex); 729d0981a1bSThomas Gleixner __clocksource_change_rating(cs, rating); 73075c5158fSMartin Schwidefsky mutex_unlock(&clocksource_mutex); 731734efb46Sjohn stultz } 732fb63a0ebSMartin Schwidefsky EXPORT_SYMBOL(clocksource_change_rating); 733734efb46Sjohn stultz 7344713e22cSThomas Gleixner /** 7354713e22cSThomas Gleixner * clocksource_unregister - remove a registered clocksource 7364713e22cSThomas Gleixner */ 7374713e22cSThomas Gleixner void clocksource_unregister(struct clocksource *cs) 7384713e22cSThomas Gleixner { 73975c5158fSMartin Schwidefsky mutex_lock(&clocksource_mutex); 740fb63a0ebSMartin Schwidefsky clocksource_dequeue_watchdog(cs); 7414713e22cSThomas Gleixner list_del(&cs->list); 742f1b82746SMartin Schwidefsky clocksource_select(); 74375c5158fSMartin Schwidefsky mutex_unlock(&clocksource_mutex); 7444713e22cSThomas Gleixner } 745fb63a0ebSMartin Schwidefsky EXPORT_SYMBOL(clocksource_unregister); 7464713e22cSThomas Gleixner 7472b013700SDaniel Walker #ifdef CONFIG_SYSFS 748734efb46Sjohn stultz /** 749734efb46Sjohn stultz * sysfs_show_current_clocksources - sysfs interface for current clocksource 750734efb46Sjohn stultz * @dev: unused 751734efb46Sjohn stultz * @buf: char buffer to be filled with clocksource list 752734efb46Sjohn stultz * 753734efb46Sjohn stultz * Provides sysfs interface for listing current clocksource. 754734efb46Sjohn stultz */ 755734efb46Sjohn stultz static ssize_t 7564a0b2b4dSAndi Kleen sysfs_show_current_clocksources(struct sys_device *dev, 7574a0b2b4dSAndi Kleen struct sysdev_attribute *attr, char *buf) 758734efb46Sjohn stultz { 7595e2cb101SMiao Xie ssize_t count = 0; 760734efb46Sjohn stultz 76175c5158fSMartin Schwidefsky mutex_lock(&clocksource_mutex); 7625e2cb101SMiao Xie count = snprintf(buf, PAGE_SIZE, "%s\n", curr_clocksource->name); 76375c5158fSMartin Schwidefsky mutex_unlock(&clocksource_mutex); 764734efb46Sjohn stultz 7655e2cb101SMiao Xie return count; 766734efb46Sjohn stultz } 767734efb46Sjohn stultz 768734efb46Sjohn stultz /** 769734efb46Sjohn stultz * sysfs_override_clocksource - interface for manually overriding clocksource 770734efb46Sjohn stultz * @dev: unused 771734efb46Sjohn stultz * @buf: name of override clocksource 772734efb46Sjohn stultz * @count: length of buffer 773734efb46Sjohn stultz * 774734efb46Sjohn stultz * Takes input from sysfs interface for manually overriding the default 775b71a8eb0SUwe Kleine-König * clocksource selection. 776734efb46Sjohn stultz */ 777734efb46Sjohn stultz static ssize_t sysfs_override_clocksource(struct sys_device *dev, 7784a0b2b4dSAndi Kleen struct sysdev_attribute *attr, 779734efb46Sjohn stultz const char *buf, size_t count) 780734efb46Sjohn stultz { 781734efb46Sjohn stultz size_t ret = count; 78292c7e002SThomas Gleixner 783734efb46Sjohn stultz /* strings from sysfs write are not 0 terminated! */ 784734efb46Sjohn stultz if (count >= sizeof(override_name)) 785734efb46Sjohn stultz return -EINVAL; 786734efb46Sjohn stultz 787734efb46Sjohn stultz /* strip of \n: */ 788734efb46Sjohn stultz if (buf[count-1] == '\n') 789734efb46Sjohn stultz count--; 790734efb46Sjohn stultz 79175c5158fSMartin Schwidefsky mutex_lock(&clocksource_mutex); 792734efb46Sjohn stultz 79392c7e002SThomas Gleixner if (count > 0) 794734efb46Sjohn stultz memcpy(override_name, buf, count); 795734efb46Sjohn stultz override_name[count] = 0; 796f1b82746SMartin Schwidefsky clocksource_select(); 797734efb46Sjohn stultz 79875c5158fSMartin Schwidefsky mutex_unlock(&clocksource_mutex); 799734efb46Sjohn stultz 800734efb46Sjohn stultz return ret; 801734efb46Sjohn stultz } 802734efb46Sjohn stultz 803734efb46Sjohn stultz /** 804734efb46Sjohn stultz * sysfs_show_available_clocksources - sysfs interface for listing clocksource 805734efb46Sjohn stultz * @dev: unused 806734efb46Sjohn stultz * @buf: char buffer to be filled with clocksource list 807734efb46Sjohn stultz * 808734efb46Sjohn stultz * Provides sysfs interface for listing registered clocksources 809734efb46Sjohn stultz */ 810734efb46Sjohn stultz static ssize_t 8114a0b2b4dSAndi Kleen sysfs_show_available_clocksources(struct sys_device *dev, 8124a0b2b4dSAndi Kleen struct sysdev_attribute *attr, 8134a0b2b4dSAndi Kleen char *buf) 814734efb46Sjohn stultz { 8152e197586SMatthias Kaehlcke struct clocksource *src; 8165e2cb101SMiao Xie ssize_t count = 0; 817734efb46Sjohn stultz 81875c5158fSMartin Schwidefsky mutex_lock(&clocksource_mutex); 8192e197586SMatthias Kaehlcke list_for_each_entry(src, &clocksource_list, list) { 820cd6d95d8SThomas Gleixner /* 821cd6d95d8SThomas Gleixner * Don't show non-HRES clocksource if the tick code is 822cd6d95d8SThomas Gleixner * in one shot mode (highres=on or nohz=on) 823cd6d95d8SThomas Gleixner */ 824cd6d95d8SThomas Gleixner if (!tick_oneshot_mode_active() || 8253f68535aSjohn stultz (src->flags & CLOCK_SOURCE_VALID_FOR_HRES)) 8265e2cb101SMiao Xie count += snprintf(buf + count, 8275e2cb101SMiao Xie max((ssize_t)PAGE_SIZE - count, (ssize_t)0), 8285e2cb101SMiao Xie "%s ", src->name); 829734efb46Sjohn stultz } 83075c5158fSMartin Schwidefsky mutex_unlock(&clocksource_mutex); 831734efb46Sjohn stultz 8325e2cb101SMiao Xie count += snprintf(buf + count, 8335e2cb101SMiao Xie max((ssize_t)PAGE_SIZE - count, (ssize_t)0), "\n"); 834734efb46Sjohn stultz 8355e2cb101SMiao Xie return count; 836734efb46Sjohn stultz } 837734efb46Sjohn stultz 838734efb46Sjohn stultz /* 839734efb46Sjohn stultz * Sysfs setup bits: 840734efb46Sjohn stultz */ 8414f95f81aSHeiko Carstens static SYSDEV_ATTR(current_clocksource, 0644, sysfs_show_current_clocksources, 842734efb46Sjohn stultz sysfs_override_clocksource); 843734efb46Sjohn stultz 8444f95f81aSHeiko Carstens static SYSDEV_ATTR(available_clocksource, 0444, 845734efb46Sjohn stultz sysfs_show_available_clocksources, NULL); 846734efb46Sjohn stultz 847734efb46Sjohn stultz static struct sysdev_class clocksource_sysclass = { 848af5ca3f4SKay Sievers .name = "clocksource", 849734efb46Sjohn stultz }; 850734efb46Sjohn stultz 851734efb46Sjohn stultz static struct sys_device device_clocksource = { 852734efb46Sjohn stultz .id = 0, 853734efb46Sjohn stultz .cls = &clocksource_sysclass, 854734efb46Sjohn stultz }; 855734efb46Sjohn stultz 856ad596171Sjohn stultz static int __init init_clocksource_sysfs(void) 857734efb46Sjohn stultz { 858734efb46Sjohn stultz int error = sysdev_class_register(&clocksource_sysclass); 859734efb46Sjohn stultz 860734efb46Sjohn stultz if (!error) 861734efb46Sjohn stultz error = sysdev_register(&device_clocksource); 862734efb46Sjohn stultz if (!error) 863734efb46Sjohn stultz error = sysdev_create_file( 864734efb46Sjohn stultz &device_clocksource, 865734efb46Sjohn stultz &attr_current_clocksource); 866734efb46Sjohn stultz if (!error) 867734efb46Sjohn stultz error = sysdev_create_file( 868734efb46Sjohn stultz &device_clocksource, 869734efb46Sjohn stultz &attr_available_clocksource); 870734efb46Sjohn stultz return error; 871734efb46Sjohn stultz } 872734efb46Sjohn stultz 873734efb46Sjohn stultz device_initcall(init_clocksource_sysfs); 8742b013700SDaniel Walker #endif /* CONFIG_SYSFS */ 875734efb46Sjohn stultz 876734efb46Sjohn stultz /** 877734efb46Sjohn stultz * boot_override_clocksource - boot clock override 878734efb46Sjohn stultz * @str: override name 879734efb46Sjohn stultz * 880734efb46Sjohn stultz * Takes a clocksource= boot argument and uses it 881734efb46Sjohn stultz * as the clocksource override name. 882734efb46Sjohn stultz */ 883734efb46Sjohn stultz static int __init boot_override_clocksource(char* str) 884734efb46Sjohn stultz { 88575c5158fSMartin Schwidefsky mutex_lock(&clocksource_mutex); 886734efb46Sjohn stultz if (str) 887734efb46Sjohn stultz strlcpy(override_name, str, sizeof(override_name)); 88875c5158fSMartin Schwidefsky mutex_unlock(&clocksource_mutex); 889734efb46Sjohn stultz return 1; 890734efb46Sjohn stultz } 891734efb46Sjohn stultz 892734efb46Sjohn stultz __setup("clocksource=", boot_override_clocksource); 893734efb46Sjohn stultz 894734efb46Sjohn stultz /** 895734efb46Sjohn stultz * boot_override_clock - Compatibility layer for deprecated boot option 896734efb46Sjohn stultz * @str: override name 897734efb46Sjohn stultz * 898734efb46Sjohn stultz * DEPRECATED! Takes a clock= boot argument and uses it 899734efb46Sjohn stultz * as the clocksource override name 900734efb46Sjohn stultz */ 901734efb46Sjohn stultz static int __init boot_override_clock(char* str) 902734efb46Sjohn stultz { 9035d0cf410Sjohn stultz if (!strcmp(str, "pmtmr")) { 9045d0cf410Sjohn stultz printk("Warning: clock=pmtmr is deprecated. " 9055d0cf410Sjohn stultz "Use clocksource=acpi_pm.\n"); 9065d0cf410Sjohn stultz return boot_override_clocksource("acpi_pm"); 9075d0cf410Sjohn stultz } 9085d0cf410Sjohn stultz printk("Warning! clock= boot option is deprecated. " 9095d0cf410Sjohn stultz "Use clocksource=xyz\n"); 910734efb46Sjohn stultz return boot_override_clocksource(str); 911734efb46Sjohn stultz } 912734efb46Sjohn stultz 913734efb46Sjohn stultz __setup("clock=", boot_override_clock); 914