12345678910111213141516171819202122232425262728293031323334353637383940414243444546474849505152535455565758596061626364656667686970717273747576777879808182838485868788899091929394959697989910010110210310410510610710810911011111211311411511611711811912012112212312412512612712812913013113213313413513613713813914014114214314414514614714814915015115215315415515615715815916016116216316416516616716816917017117217317417517617717817918018118218318418518618718818919019119219319419519619719819920020120220320420520620720820921021121221321421521621721821922022122222322422522622722822923023123223323423523623723823924024124224324424524624724824925025125225325425525625725825926026126226326426526626726826927027127227327427527627727827928028128228328428528628728828929029129229329429529629729829930030130230330430530630730830931031131231331431531631731831932032132232332432532632732832933033133233333433533633733833934034134234334434534634734834935035135235335435535635735835936036136236336436536636736836937037137237337437537637737837938038138238338438538638738838939039139239339439539639739839940040140240340440540640740840941041141241341441541641741841942042142242342442542642742842943043143243343443543643743843944044144244344444544644744844945045145245345445545645745845946046146246346446546646746846947047147247347447547647747847948048148248348448548648748848949049149249349449549649749849950050150250350450550650750850951051151251351451551651751851952052152252352452552652752852953053153253353453553653753853954054154254354454554654754854955055155255355455555655755855956056156256356456556656756856957057157257357457557657757857958058158258358458558658758858959059159259359459559659759859960060160260360460560660760860961061161261361461561661761861962062162262362462562662762862963063163263363463563663763863964064164264364464564664764864965065165265365465565665765865966066166266366466566666766866967067167267367467567667767867968068168268368468568668768868969069169269369469569669769869970070170270370470570670770870971071171271371471571671771871972072172272372472572672772872973073173273373473573673773873974074174274374474574674774874975075175275375475575675775875976076176276376476576676776876977077177277377477577677777877978078178278378478578678778878979079179279379479579679779879980080180280380480580680780880981081181281381481581681781881982082182282382482582682782882983083183283383483583683783883984084184284384484584684784884985085185285385485585685785885986086186286386486586686786886987087187287387487587687787887988088188288388488588688788888989089189289389489589689789889990090190290390490590690790890991091191291391491591691791891992092192292392492592692792892993093193293393493593693793893994094194294394494594694794894995095195295395495595695795895996096196296396496596696796896997097197297397497597697797897998098198298398498598698798898999099199299399499599699799899910001001100210031004100510061007100810091010101110121013101410151016101710181019102010211022102310241025102610271028102910301031103210331034103510361037103810391040104110421043104410451046104710481049105010511052105310541055105610571058105910601061106210631064106510661067106810691070107110721073107410751076107710781079108010811082108310841085108610871088108910901091109210931094109510961097109810991100110111021103110411051106110711081109111011111112111311141115111611171118111911201121112211231124112511261127112811291130113111321133113411351136113711381139114011411142114311441145114611471148114911501151115211531154115511561157115811591160116111621163116411651166116711681169117011711172117311741175117611771178117911801181118211831184118511861187118811891190119111921193119411951196119711981199120012011202120312041205120612071208120912101211121212131214121512161217121812191220122112221223122412251226122712281229123012311232123312341235123612371238123912401241124212431244124512461247124812491250125112521253125412551256125712581259126012611262126312641265126612671268126912701271127212731274127512761277127812791280128112821283128412851286128712881289129012911292129312941295129612971298129913001301130213031304130513061307130813091310131113121313131413151316131713181319132013211322132313241325132613271328132913301331133213331334133513361337133813391340134113421343134413451346134713481349135013511352135313541355135613571358135913601361136213631364136513661367136813691370137113721373137413751376137713781379138013811382138313841385138613871388138913901391139213931394139513961397139813991400140114021403140414051406140714081409141014111412141314141415141614171418141914201421142214231424142514261427142814291430143114321433143414351436143714381439144014411442144314441445144614471448144914501451145214531454145514561457145814591460146114621463146414651466146714681469147014711472147314741475147614771478147914801481148214831484148514861487148814891490149114921493149414951496 |
- // SPDX-License-Identifier: GPL-2.0+
- /*
- * This file contains the functions which manage clocksource drivers.
- *
- * Copyright (C) 2004, 2005 IBM, John Stultz ([email protected])
- */
- #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
- #include <linux/device.h>
- #include <linux/clocksource.h>
- #include <linux/init.h>
- #include <linux/module.h>
- #include <linux/sched.h> /* for spin_unlock_irq() using preempt_count() m68k */
- #include <linux/tick.h>
- #include <linux/kthread.h>
- #include <linux/prandom.h>
- #include <linux/cpu.h>
- #include "tick-internal.h"
- #include "timekeeping_internal.h"
- /**
- * clocks_calc_mult_shift - calculate mult/shift factors for scaled math of clocks
- * @mult: pointer to mult variable
- * @shift: pointer to shift variable
- * @from: frequency to convert from
- * @to: frequency to convert to
- * @maxsec: guaranteed runtime conversion range in seconds
- *
- * The function evaluates the shift/mult pair for the scaled math
- * operations of clocksources and clockevents.
- *
- * @to and @from are frequency values in HZ. For clock sources @to is
- * NSEC_PER_SEC == 1GHz and @from is the counter frequency. For clock
- * event @to is the counter frequency and @from is NSEC_PER_SEC.
- *
- * The @maxsec conversion range argument controls the time frame in
- * seconds which must be covered by the runtime conversion with the
- * calculated mult and shift factors. This guarantees that no 64bit
- * overflow happens when the input value of the conversion is
- * multiplied with the calculated mult factor. Larger ranges may
- * reduce the conversion accuracy by choosing smaller mult and shift
- * factors.
- */
- void
- clocks_calc_mult_shift(u32 *mult, u32 *shift, u32 from, u32 to, u32 maxsec)
- {
- u64 tmp;
- u32 sft, sftacc= 32;
- /*
- * Calculate the shift factor which is limiting the conversion
- * range:
- */
- tmp = ((u64)maxsec * from) >> 32;
- while (tmp) {
- tmp >>=1;
- sftacc--;
- }
- /*
- * Find the conversion shift/mult pair which has the best
- * accuracy and fits the maxsec conversion range:
- */
- for (sft = 32; sft > 0; sft--) {
- tmp = (u64) to << sft;
- tmp += from / 2;
- do_div(tmp, from);
- if ((tmp >> sftacc) == 0)
- break;
- }
- *mult = tmp;
- *shift = sft;
- }
- EXPORT_SYMBOL_GPL(clocks_calc_mult_shift);
- /*[Clocksource internal variables]---------
- * curr_clocksource:
- * currently selected clocksource.
- * suspend_clocksource:
- * used to calculate the suspend time.
- * clocksource_list:
- * linked list with the registered clocksources
- * clocksource_mutex:
- * protects manipulations to curr_clocksource and the clocksource_list
- * override_name:
- * Name of the user-specified clocksource.
- */
- static struct clocksource *curr_clocksource;
- static struct clocksource *suspend_clocksource;
- static LIST_HEAD(clocksource_list);
- static DEFINE_MUTEX(clocksource_mutex);
- static char override_name[CS_NAME_LEN];
- static int finished_booting;
- static u64 suspend_start;
- /*
- * Threshold: 0.0312s, when doubled: 0.0625s.
- * Also a default for cs->uncertainty_margin when registering clocks.
- */
- #define WATCHDOG_THRESHOLD (NSEC_PER_SEC >> 5)
- /*
- * Maximum permissible delay between two readouts of the watchdog
- * clocksource surrounding a read of the clocksource being validated.
- * This delay could be due to SMIs, NMIs, or to VCPU preemptions. Used as
- * a lower bound for cs->uncertainty_margin values when registering clocks.
- */
- #ifdef CONFIG_CLOCKSOURCE_WATCHDOG_MAX_SKEW_US
- #define MAX_SKEW_USEC CONFIG_CLOCKSOURCE_WATCHDOG_MAX_SKEW_US
- #else
- #define MAX_SKEW_USEC 100
- #endif
- #define WATCHDOG_MAX_SKEW (MAX_SKEW_USEC * NSEC_PER_USEC)
- #ifdef CONFIG_CLOCKSOURCE_WATCHDOG
- static void clocksource_watchdog_work(struct work_struct *work);
- static void clocksource_select(void);
- static LIST_HEAD(watchdog_list);
- static struct clocksource *watchdog;
- static struct timer_list watchdog_timer;
- static DECLARE_WORK(watchdog_work, clocksource_watchdog_work);
- static DEFINE_SPINLOCK(watchdog_lock);
- static int watchdog_running;
- static atomic_t watchdog_reset_pending;
- static inline void clocksource_watchdog_lock(unsigned long *flags)
- {
- spin_lock_irqsave(&watchdog_lock, *flags);
- }
- static inline void clocksource_watchdog_unlock(unsigned long *flags)
- {
- spin_unlock_irqrestore(&watchdog_lock, *flags);
- }
- static int clocksource_watchdog_kthread(void *data);
- static void __clocksource_change_rating(struct clocksource *cs, int rating);
- /*
- * Interval: 0.5sec.
- */
- #define WATCHDOG_INTERVAL (HZ >> 1)
- static void clocksource_watchdog_work(struct work_struct *work)
- {
- /*
- * We cannot directly run clocksource_watchdog_kthread() here, because
- * clocksource_select() calls timekeeping_notify() which uses
- * stop_machine(). One cannot use stop_machine() from a workqueue() due
- * lock inversions wrt CPU hotplug.
- *
- * Also, we only ever run this work once or twice during the lifetime
- * of the kernel, so there is no point in creating a more permanent
- * kthread for this.
- *
- * If kthread_run fails the next watchdog scan over the
- * watchdog_list will find the unstable clock again.
- */
- kthread_run(clocksource_watchdog_kthread, NULL, "kwatchdog");
- }
- static void __clocksource_unstable(struct clocksource *cs)
- {
- cs->flags &= ~(CLOCK_SOURCE_VALID_FOR_HRES | CLOCK_SOURCE_WATCHDOG);
- cs->flags |= CLOCK_SOURCE_UNSTABLE;
- /*
- * If the clocksource is registered clocksource_watchdog_kthread() will
- * re-rate and re-select.
- */
- if (list_empty(&cs->list)) {
- cs->rating = 0;
- return;
- }
- if (cs->mark_unstable)
- cs->mark_unstable(cs);
- /* kick clocksource_watchdog_kthread() */
- if (finished_booting)
- schedule_work(&watchdog_work);
- }
- /**
- * clocksource_mark_unstable - mark clocksource unstable via watchdog
- * @cs: clocksource to be marked unstable
- *
- * This function is called by the x86 TSC code to mark clocksources as unstable;
- * it defers demotion and re-selection to a kthread.
- */
- void clocksource_mark_unstable(struct clocksource *cs)
- {
- unsigned long flags;
- spin_lock_irqsave(&watchdog_lock, flags);
- if (!(cs->flags & CLOCK_SOURCE_UNSTABLE)) {
- if (!list_empty(&cs->list) && list_empty(&cs->wd_list))
- list_add(&cs->wd_list, &watchdog_list);
- __clocksource_unstable(cs);
- }
- spin_unlock_irqrestore(&watchdog_lock, flags);
- }
- ulong max_cswd_read_retries = 2;
- module_param(max_cswd_read_retries, ulong, 0644);
- EXPORT_SYMBOL_GPL(max_cswd_read_retries);
- static int verify_n_cpus = 8;
- module_param(verify_n_cpus, int, 0644);
- enum wd_read_status {
- WD_READ_SUCCESS,
- WD_READ_UNSTABLE,
- WD_READ_SKIP
- };
- static enum wd_read_status cs_watchdog_read(struct clocksource *cs, u64 *csnow, u64 *wdnow)
- {
- unsigned int nretries;
- u64 wd_end, wd_end2, wd_delta;
- int64_t wd_delay, wd_seq_delay;
- for (nretries = 0; nretries <= max_cswd_read_retries; nretries++) {
- local_irq_disable();
- *wdnow = watchdog->read(watchdog);
- *csnow = cs->read(cs);
- wd_end = watchdog->read(watchdog);
- wd_end2 = watchdog->read(watchdog);
- local_irq_enable();
- wd_delta = clocksource_delta(wd_end, *wdnow, watchdog->mask);
- wd_delay = clocksource_cyc2ns(wd_delta, watchdog->mult,
- watchdog->shift);
- if (wd_delay <= WATCHDOG_MAX_SKEW) {
- if (nretries > 1 || nretries >= max_cswd_read_retries) {
- pr_warn("timekeeping watchdog on CPU%d: %s retried %d times before success\n",
- smp_processor_id(), watchdog->name, nretries);
- }
- return WD_READ_SUCCESS;
- }
- /*
- * Now compute delay in consecutive watchdog read to see if
- * there is too much external interferences that cause
- * significant delay in reading both clocksource and watchdog.
- *
- * If consecutive WD read-back delay > WATCHDOG_MAX_SKEW/2,
- * report system busy, reinit the watchdog and skip the current
- * watchdog test.
- */
- wd_delta = clocksource_delta(wd_end2, wd_end, watchdog->mask);
- wd_seq_delay = clocksource_cyc2ns(wd_delta, watchdog->mult, watchdog->shift);
- if (wd_seq_delay > WATCHDOG_MAX_SKEW/2)
- goto skip_test;
- }
- pr_warn("timekeeping watchdog on CPU%d: %s read-back delay of %lldns, attempt %d, marking unstable\n",
- smp_processor_id(), watchdog->name, wd_delay, nretries);
- return WD_READ_UNSTABLE;
- skip_test:
- pr_info("timekeeping watchdog on CPU%d: %s wd-wd read-back delay of %lldns\n",
- smp_processor_id(), watchdog->name, wd_seq_delay);
- pr_info("wd-%s-wd read-back delay of %lldns, clock-skew test skipped!\n",
- cs->name, wd_delay);
- return WD_READ_SKIP;
- }
- static u64 csnow_mid;
- static cpumask_t cpus_ahead;
- static cpumask_t cpus_behind;
- static cpumask_t cpus_chosen;
- static void clocksource_verify_choose_cpus(void)
- {
- int cpu, i, n = verify_n_cpus;
- if (n < 0) {
- /* Check all of the CPUs. */
- cpumask_copy(&cpus_chosen, cpu_online_mask);
- cpumask_clear_cpu(smp_processor_id(), &cpus_chosen);
- return;
- }
- /* If no checking desired, or no other CPU to check, leave. */
- cpumask_clear(&cpus_chosen);
- if (n == 0 || num_online_cpus() <= 1)
- return;
- /* Make sure to select at least one CPU other than the current CPU. */
- cpu = cpumask_first(cpu_online_mask);
- if (cpu == smp_processor_id())
- cpu = cpumask_next(cpu, cpu_online_mask);
- if (WARN_ON_ONCE(cpu >= nr_cpu_ids))
- return;
- cpumask_set_cpu(cpu, &cpus_chosen);
- /* Force a sane value for the boot parameter. */
- if (n > nr_cpu_ids)
- n = nr_cpu_ids;
- /*
- * Randomly select the specified number of CPUs. If the same
- * CPU is selected multiple times, that CPU is checked only once,
- * and no replacement CPU is selected. This gracefully handles
- * situations where verify_n_cpus is greater than the number of
- * CPUs that are currently online.
- */
- for (i = 1; i < n; i++) {
- cpu = prandom_u32_max(nr_cpu_ids);
- cpu = cpumask_next(cpu - 1, cpu_online_mask);
- if (cpu >= nr_cpu_ids)
- cpu = cpumask_first(cpu_online_mask);
- if (!WARN_ON_ONCE(cpu >= nr_cpu_ids))
- cpumask_set_cpu(cpu, &cpus_chosen);
- }
- /* Don't verify ourselves. */
- cpumask_clear_cpu(smp_processor_id(), &cpus_chosen);
- }
- static void clocksource_verify_one_cpu(void *csin)
- {
- struct clocksource *cs = (struct clocksource *)csin;
- csnow_mid = cs->read(cs);
- }
- void clocksource_verify_percpu(struct clocksource *cs)
- {
- int64_t cs_nsec, cs_nsec_max = 0, cs_nsec_min = LLONG_MAX;
- u64 csnow_begin, csnow_end;
- int cpu, testcpu;
- s64 delta;
- if (verify_n_cpus == 0)
- return;
- cpumask_clear(&cpus_ahead);
- cpumask_clear(&cpus_behind);
- cpus_read_lock();
- preempt_disable();
- clocksource_verify_choose_cpus();
- if (cpumask_empty(&cpus_chosen)) {
- preempt_enable();
- cpus_read_unlock();
- pr_warn("Not enough CPUs to check clocksource '%s'.\n", cs->name);
- return;
- }
- testcpu = smp_processor_id();
- pr_warn("Checking clocksource %s synchronization from CPU %d to CPUs %*pbl.\n", cs->name, testcpu, cpumask_pr_args(&cpus_chosen));
- for_each_cpu(cpu, &cpus_chosen) {
- if (cpu == testcpu)
- continue;
- csnow_begin = cs->read(cs);
- smp_call_function_single(cpu, clocksource_verify_one_cpu, cs, 1);
- csnow_end = cs->read(cs);
- delta = (s64)((csnow_mid - csnow_begin) & cs->mask);
- if (delta < 0)
- cpumask_set_cpu(cpu, &cpus_behind);
- delta = (csnow_end - csnow_mid) & cs->mask;
- if (delta < 0)
- cpumask_set_cpu(cpu, &cpus_ahead);
- delta = clocksource_delta(csnow_end, csnow_begin, cs->mask);
- cs_nsec = clocksource_cyc2ns(delta, cs->mult, cs->shift);
- if (cs_nsec > cs_nsec_max)
- cs_nsec_max = cs_nsec;
- if (cs_nsec < cs_nsec_min)
- cs_nsec_min = cs_nsec;
- }
- preempt_enable();
- cpus_read_unlock();
- if (!cpumask_empty(&cpus_ahead))
- pr_warn(" CPUs %*pbl ahead of CPU %d for clocksource %s.\n",
- cpumask_pr_args(&cpus_ahead), testcpu, cs->name);
- if (!cpumask_empty(&cpus_behind))
- pr_warn(" CPUs %*pbl behind CPU %d for clocksource %s.\n",
- cpumask_pr_args(&cpus_behind), testcpu, cs->name);
- if (!cpumask_empty(&cpus_ahead) || !cpumask_empty(&cpus_behind))
- pr_warn(" CPU %d check durations %lldns - %lldns for clocksource %s.\n",
- testcpu, cs_nsec_min, cs_nsec_max, cs->name);
- }
- EXPORT_SYMBOL_GPL(clocksource_verify_percpu);
- static inline void clocksource_reset_watchdog(void)
- {
- struct clocksource *cs;
- list_for_each_entry(cs, &watchdog_list, wd_list)
- cs->flags &= ~CLOCK_SOURCE_WATCHDOG;
- }
- static void clocksource_watchdog(struct timer_list *unused)
- {
- u64 csnow, wdnow, cslast, wdlast, delta;
- int next_cpu, reset_pending;
- int64_t wd_nsec, cs_nsec;
- struct clocksource *cs;
- enum wd_read_status read_ret;
- unsigned long extra_wait = 0;
- u32 md;
- spin_lock(&watchdog_lock);
- if (!watchdog_running)
- goto out;
- reset_pending = atomic_read(&watchdog_reset_pending);
- list_for_each_entry(cs, &watchdog_list, wd_list) {
- /* Clocksource already marked unstable? */
- if (cs->flags & CLOCK_SOURCE_UNSTABLE) {
- if (finished_booting)
- schedule_work(&watchdog_work);
- continue;
- }
- read_ret = cs_watchdog_read(cs, &csnow, &wdnow);
- if (read_ret == WD_READ_UNSTABLE) {
- /* Clock readout unreliable, so give it up. */
- __clocksource_unstable(cs);
- continue;
- }
- /*
- * When WD_READ_SKIP is returned, it means the system is likely
- * under very heavy load, where the latency of reading
- * watchdog/clocksource is very big, and affect the accuracy of
- * watchdog check. So give system some space and suspend the
- * watchdog check for 5 minutes.
- */
- if (read_ret == WD_READ_SKIP) {
- /*
- * As the watchdog timer will be suspended, and
- * cs->last could keep unchanged for 5 minutes, reset
- * the counters.
- */
- clocksource_reset_watchdog();
- extra_wait = HZ * 300;
- break;
- }
- /* Clocksource initialized ? */
- if (!(cs->flags & CLOCK_SOURCE_WATCHDOG) ||
- atomic_read(&watchdog_reset_pending)) {
- cs->flags |= CLOCK_SOURCE_WATCHDOG;
- cs->wd_last = wdnow;
- cs->cs_last = csnow;
- continue;
- }
- delta = clocksource_delta(wdnow, cs->wd_last, watchdog->mask);
- wd_nsec = clocksource_cyc2ns(delta, watchdog->mult,
- watchdog->shift);
- delta = clocksource_delta(csnow, cs->cs_last, cs->mask);
- cs_nsec = clocksource_cyc2ns(delta, cs->mult, cs->shift);
- wdlast = cs->wd_last; /* save these in case we print them */
- cslast = cs->cs_last;
- cs->cs_last = csnow;
- cs->wd_last = wdnow;
- if (atomic_read(&watchdog_reset_pending))
- continue;
- /* Check the deviation from the watchdog clocksource. */
- md = cs->uncertainty_margin + watchdog->uncertainty_margin;
- if (abs(cs_nsec - wd_nsec) > md) {
- pr_warn("timekeeping watchdog on CPU%d: Marking clocksource '%s' as unstable because the skew is too large:\n",
- smp_processor_id(), cs->name);
- pr_warn(" '%s' wd_nsec: %lld wd_now: %llx wd_last: %llx mask: %llx\n",
- watchdog->name, wd_nsec, wdnow, wdlast, watchdog->mask);
- pr_warn(" '%s' cs_nsec: %lld cs_now: %llx cs_last: %llx mask: %llx\n",
- cs->name, cs_nsec, csnow, cslast, cs->mask);
- if (curr_clocksource == cs)
- pr_warn(" '%s' is current clocksource.\n", cs->name);
- else if (curr_clocksource)
- pr_warn(" '%s' (not '%s') is current clocksource.\n", curr_clocksource->name, cs->name);
- else
- pr_warn(" No current clocksource.\n");
- __clocksource_unstable(cs);
- continue;
- }
- if (cs == curr_clocksource && cs->tick_stable)
- cs->tick_stable(cs);
- if (!(cs->flags & CLOCK_SOURCE_VALID_FOR_HRES) &&
- (cs->flags & CLOCK_SOURCE_IS_CONTINUOUS) &&
- (watchdog->flags & CLOCK_SOURCE_IS_CONTINUOUS)) {
- /* Mark it valid for high-res. */
- cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES;
- /*
- * clocksource_done_booting() will sort it if
- * finished_booting is not set yet.
- */
- if (!finished_booting)
- continue;
- /*
- * If this is not the current clocksource let
- * the watchdog thread reselect it. Due to the
- * change to high res this clocksource might
- * be preferred now. If it is the current
- * clocksource let the tick code know about
- * that change.
- */
- if (cs != curr_clocksource) {
- cs->flags |= CLOCK_SOURCE_RESELECT;
- schedule_work(&watchdog_work);
- } else {
- tick_clock_notify();
- }
- }
- }
- /*
- * We only clear the watchdog_reset_pending, when we did a
- * full cycle through all clocksources.
- */
- if (reset_pending)
- atomic_dec(&watchdog_reset_pending);
- /*
- * Cycle through CPUs to check if the CPUs stay synchronized
- * to each other.
- */
- next_cpu = cpumask_next(raw_smp_processor_id(), cpu_online_mask);
- if (next_cpu >= nr_cpu_ids)
- next_cpu = cpumask_first(cpu_online_mask);
- /*
- * Arm timer if not already pending: could race with concurrent
- * pair clocksource_stop_watchdog() clocksource_start_watchdog().
- */
- if (!timer_pending(&watchdog_timer)) {
- watchdog_timer.expires += WATCHDOG_INTERVAL + extra_wait;
- add_timer_on(&watchdog_timer, next_cpu);
- }
- out:
- spin_unlock(&watchdog_lock);
- }
- static inline void clocksource_start_watchdog(void)
- {
- if (watchdog_running || !watchdog || list_empty(&watchdog_list))
- return;
- timer_setup(&watchdog_timer, clocksource_watchdog, 0);
- watchdog_timer.expires = jiffies + WATCHDOG_INTERVAL;
- add_timer_on(&watchdog_timer, cpumask_first(cpu_online_mask));
- watchdog_running = 1;
- }
- static inline void clocksource_stop_watchdog(void)
- {
- if (!watchdog_running || (watchdog && !list_empty(&watchdog_list)))
- return;
- del_timer(&watchdog_timer);
- watchdog_running = 0;
- }
- static void clocksource_resume_watchdog(void)
- {
- atomic_inc(&watchdog_reset_pending);
- }
- static void clocksource_enqueue_watchdog(struct clocksource *cs)
- {
- INIT_LIST_HEAD(&cs->wd_list);
- if (cs->flags & CLOCK_SOURCE_MUST_VERIFY) {
- /* cs is a clocksource to be watched. */
- list_add(&cs->wd_list, &watchdog_list);
- cs->flags &= ~CLOCK_SOURCE_WATCHDOG;
- } else {
- /* cs is a watchdog. */
- if (cs->flags & CLOCK_SOURCE_IS_CONTINUOUS)
- cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES;
- }
- }
- static void clocksource_select_watchdog(bool fallback)
- {
- struct clocksource *cs, *old_wd;
- unsigned long flags;
- spin_lock_irqsave(&watchdog_lock, flags);
- /* save current watchdog */
- old_wd = watchdog;
- if (fallback)
- watchdog = NULL;
- list_for_each_entry(cs, &clocksource_list, list) {
- /* cs is a clocksource to be watched. */
- if (cs->flags & CLOCK_SOURCE_MUST_VERIFY)
- continue;
- /* Skip current if we were requested for a fallback. */
- if (fallback && cs == old_wd)
- continue;
- /* Pick the best watchdog. */
- if (!watchdog || cs->rating > watchdog->rating)
- watchdog = cs;
- }
- /* If we failed to find a fallback restore the old one. */
- if (!watchdog)
- watchdog = old_wd;
- /* If we changed the watchdog we need to reset cycles. */
- if (watchdog != old_wd)
- clocksource_reset_watchdog();
- /* Check if the watchdog timer needs to be started. */
- clocksource_start_watchdog();
- spin_unlock_irqrestore(&watchdog_lock, flags);
- }
- static void clocksource_dequeue_watchdog(struct clocksource *cs)
- {
- if (cs != watchdog) {
- if (cs->flags & CLOCK_SOURCE_MUST_VERIFY) {
- /* cs is a watched clocksource. */
- list_del_init(&cs->wd_list);
- /* Check if the watchdog timer needs to be stopped. */
- clocksource_stop_watchdog();
- }
- }
- }
- static int __clocksource_watchdog_kthread(void)
- {
- struct clocksource *cs, *tmp;
- unsigned long flags;
- int select = 0;
- /* Do any required per-CPU skew verification. */
- if (curr_clocksource &&
- curr_clocksource->flags & CLOCK_SOURCE_UNSTABLE &&
- curr_clocksource->flags & CLOCK_SOURCE_VERIFY_PERCPU)
- clocksource_verify_percpu(curr_clocksource);
- spin_lock_irqsave(&watchdog_lock, flags);
- list_for_each_entry_safe(cs, tmp, &watchdog_list, wd_list) {
- if (cs->flags & CLOCK_SOURCE_UNSTABLE) {
- list_del_init(&cs->wd_list);
- __clocksource_change_rating(cs, 0);
- select = 1;
- }
- if (cs->flags & CLOCK_SOURCE_RESELECT) {
- cs->flags &= ~CLOCK_SOURCE_RESELECT;
- select = 1;
- }
- }
- /* Check if the watchdog timer needs to be stopped. */
- clocksource_stop_watchdog();
- spin_unlock_irqrestore(&watchdog_lock, flags);
- return select;
- }
- static int clocksource_watchdog_kthread(void *data)
- {
- mutex_lock(&clocksource_mutex);
- if (__clocksource_watchdog_kthread())
- clocksource_select();
- mutex_unlock(&clocksource_mutex);
- return 0;
- }
- static bool clocksource_is_watchdog(struct clocksource *cs)
- {
- return cs == watchdog;
- }
- #else /* CONFIG_CLOCKSOURCE_WATCHDOG */
- static void clocksource_enqueue_watchdog(struct clocksource *cs)
- {
- if (cs->flags & CLOCK_SOURCE_IS_CONTINUOUS)
- cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES;
- }
- static void clocksource_select_watchdog(bool fallback) { }
- static inline void clocksource_dequeue_watchdog(struct clocksource *cs) { }
- static inline void clocksource_resume_watchdog(void) { }
- static inline int __clocksource_watchdog_kthread(void) { return 0; }
- static bool clocksource_is_watchdog(struct clocksource *cs) { return false; }
- void clocksource_mark_unstable(struct clocksource *cs) { }
- static inline void clocksource_watchdog_lock(unsigned long *flags) { }
- static inline void clocksource_watchdog_unlock(unsigned long *flags) { }
- #endif /* CONFIG_CLOCKSOURCE_WATCHDOG */
- static bool clocksource_is_suspend(struct clocksource *cs)
- {
- return cs == suspend_clocksource;
- }
- static void __clocksource_suspend_select(struct clocksource *cs)
- {
- /*
- * Skip the clocksource which will be stopped in suspend state.
- */
- if (!(cs->flags & CLOCK_SOURCE_SUSPEND_NONSTOP))
- return;
- /*
- * The nonstop clocksource can be selected as the suspend clocksource to
- * calculate the suspend time, so it should not supply suspend/resume
- * interfaces to suspend the nonstop clocksource when system suspends.
- */
- if (cs->suspend || cs->resume) {
- pr_warn("Nonstop clocksource %s should not supply suspend/resume interfaces\n",
- cs->name);
- }
- /* Pick the best rating. */
- if (!suspend_clocksource || cs->rating > suspend_clocksource->rating)
- suspend_clocksource = cs;
- }
- /**
- * clocksource_suspend_select - Select the best clocksource for suspend timing
- * @fallback: if select a fallback clocksource
- */
- static void clocksource_suspend_select(bool fallback)
- {
- struct clocksource *cs, *old_suspend;
- old_suspend = suspend_clocksource;
- if (fallback)
- suspend_clocksource = NULL;
- list_for_each_entry(cs, &clocksource_list, list) {
- /* Skip current if we were requested for a fallback. */
- if (fallback && cs == old_suspend)
- continue;
- __clocksource_suspend_select(cs);
- }
- }
- /**
- * clocksource_start_suspend_timing - Start measuring the suspend timing
- * @cs: current clocksource from timekeeping
- * @start_cycles: current cycles from timekeeping
- *
- * This function will save the start cycle values of suspend timer to calculate
- * the suspend time when resuming system.
- *
- * This function is called late in the suspend process from timekeeping_suspend(),
- * that means processes are frozen, non-boot cpus and interrupts are disabled
- * now. It is therefore possible to start the suspend timer without taking the
- * clocksource mutex.
- */
- void clocksource_start_suspend_timing(struct clocksource *cs, u64 start_cycles)
- {
- if (!suspend_clocksource)
- return;
- /*
- * If current clocksource is the suspend timer, we should use the
- * tkr_mono.cycle_last value as suspend_start to avoid same reading
- * from suspend timer.
- */
- if (clocksource_is_suspend(cs)) {
- suspend_start = start_cycles;
- return;
- }
- if (suspend_clocksource->enable &&
- suspend_clocksource->enable(suspend_clocksource)) {
- pr_warn_once("Failed to enable the non-suspend-able clocksource.\n");
- return;
- }
- suspend_start = suspend_clocksource->read(suspend_clocksource);
- }
- /**
- * clocksource_stop_suspend_timing - Stop measuring the suspend timing
- * @cs: current clocksource from timekeeping
- * @cycle_now: current cycles from timekeeping
- *
- * This function will calculate the suspend time from suspend timer.
- *
- * Returns nanoseconds since suspend started, 0 if no usable suspend clocksource.
- *
- * This function is called early in the resume process from timekeeping_resume(),
- * that means there is only one cpu, no processes are running and the interrupts
- * are disabled. It is therefore possible to stop the suspend timer without
- * taking the clocksource mutex.
- */
- u64 clocksource_stop_suspend_timing(struct clocksource *cs, u64 cycle_now)
- {
- u64 now, delta, nsec = 0;
- if (!suspend_clocksource)
- return 0;
- /*
- * If current clocksource is the suspend timer, we should use the
- * tkr_mono.cycle_last value from timekeeping as current cycle to
- * avoid same reading from suspend timer.
- */
- if (clocksource_is_suspend(cs))
- now = cycle_now;
- else
- now = suspend_clocksource->read(suspend_clocksource);
- if (now > suspend_start) {
- delta = clocksource_delta(now, suspend_start,
- suspend_clocksource->mask);
- nsec = mul_u64_u32_shr(delta, suspend_clocksource->mult,
- suspend_clocksource->shift);
- }
- /*
- * Disable the suspend timer to save power if current clocksource is
- * not the suspend timer.
- */
- if (!clocksource_is_suspend(cs) && suspend_clocksource->disable)
- suspend_clocksource->disable(suspend_clocksource);
- return nsec;
- }
- /**
- * clocksource_suspend - suspend the clocksource(s)
- */
- void clocksource_suspend(void)
- {
- struct clocksource *cs;
- list_for_each_entry_reverse(cs, &clocksource_list, list)
- if (cs->suspend)
- cs->suspend(cs);
- }
- /**
- * clocksource_resume - resume the clocksource(s)
- */
- void clocksource_resume(void)
- {
- struct clocksource *cs;
- list_for_each_entry(cs, &clocksource_list, list)
- if (cs->resume)
- cs->resume(cs);
- clocksource_resume_watchdog();
- }
- /**
- * clocksource_touch_watchdog - Update watchdog
- *
- * Update the watchdog after exception contexts such as kgdb so as not
- * to incorrectly trip the watchdog. This might fail when the kernel
- * was stopped in code which holds watchdog_lock.
- */
- void clocksource_touch_watchdog(void)
- {
- clocksource_resume_watchdog();
- }
- /**
- * clocksource_max_adjustment- Returns max adjustment amount
- * @cs: Pointer to clocksource
- *
- */
- static u32 clocksource_max_adjustment(struct clocksource *cs)
- {
- u64 ret;
- /*
- * We won't try to correct for more than 11% adjustments (110,000 ppm),
- */
- ret = (u64)cs->mult * 11;
- do_div(ret,100);
- return (u32)ret;
- }
- /**
- * clocks_calc_max_nsecs - Returns maximum nanoseconds that can be converted
- * @mult: cycle to nanosecond multiplier
- * @shift: cycle to nanosecond divisor (power of two)
- * @maxadj: maximum adjustment value to mult (~11%)
- * @mask: bitmask for two's complement subtraction of non 64 bit counters
- * @max_cyc: maximum cycle value before potential overflow (does not include
- * any safety margin)
- *
- * NOTE: This function includes a safety margin of 50%, in other words, we
- * return half the number of nanoseconds the hardware counter can technically
- * cover. This is done so that we can potentially detect problems caused by
- * delayed timers or bad hardware, which might result in time intervals that
- * are larger than what the math used can handle without overflows.
- */
- u64 clocks_calc_max_nsecs(u32 mult, u32 shift, u32 maxadj, u64 mask, u64 *max_cyc)
- {
- u64 max_nsecs, max_cycles;
- /*
- * Calculate the maximum number of cycles that we can pass to the
- * cyc2ns() function without overflowing a 64-bit result.
- */
- max_cycles = ULLONG_MAX;
- do_div(max_cycles, mult+maxadj);
- /*
- * The actual maximum number of cycles we can defer the clocksource is
- * determined by the minimum of max_cycles and mask.
- * Note: Here we subtract the maxadj to make sure we don't sleep for
- * too long if there's a large negative adjustment.
- */
- max_cycles = min(max_cycles, mask);
- max_nsecs = clocksource_cyc2ns(max_cycles, mult - maxadj, shift);
- /* return the max_cycles value as well if requested */
- if (max_cyc)
- *max_cyc = max_cycles;
- /* Return 50% of the actual maximum, so we can detect bad values */
- max_nsecs >>= 1;
- return max_nsecs;
- }
- /**
- * clocksource_update_max_deferment - Updates the clocksource max_idle_ns & max_cycles
- * @cs: Pointer to clocksource to be updated
- *
- */
- static inline void clocksource_update_max_deferment(struct clocksource *cs)
- {
- cs->max_idle_ns = clocks_calc_max_nsecs(cs->mult, cs->shift,
- cs->maxadj, cs->mask,
- &cs->max_cycles);
- }
- static struct clocksource *clocksource_find_best(bool oneshot, bool skipcur)
- {
- struct clocksource *cs;
- if (!finished_booting || list_empty(&clocksource_list))
- return NULL;
- /*
- * We pick the clocksource with the highest rating. If oneshot
- * mode is active, we pick the highres valid clocksource with
- * the best rating.
- */
- list_for_each_entry(cs, &clocksource_list, list) {
- if (skipcur && cs == curr_clocksource)
- continue;
- if (oneshot && !(cs->flags & CLOCK_SOURCE_VALID_FOR_HRES))
- continue;
- return cs;
- }
- return NULL;
- }
- static void __clocksource_select(bool skipcur)
- {
- bool oneshot = tick_oneshot_mode_active();
- struct clocksource *best, *cs;
- /* Find the best suitable clocksource */
- best = clocksource_find_best(oneshot, skipcur);
- if (!best)
- return;
- if (!strlen(override_name))
- goto found;
- /* Check for the override clocksource. */
- list_for_each_entry(cs, &clocksource_list, list) {
- if (skipcur && cs == curr_clocksource)
- continue;
- if (strcmp(cs->name, override_name) != 0)
- continue;
- /*
- * Check to make sure we don't switch to a non-highres
- * capable clocksource if the tick code is in oneshot
- * mode (highres or nohz)
- */
- if (!(cs->flags & CLOCK_SOURCE_VALID_FOR_HRES) && oneshot) {
- /* Override clocksource cannot be used. */
- if (cs->flags & CLOCK_SOURCE_UNSTABLE) {
- pr_warn("Override clocksource %s is unstable and not HRT compatible - cannot switch while in HRT/NOHZ mode\n",
- cs->name);
- override_name[0] = 0;
- } else {
- /*
- * The override cannot be currently verified.
- * Deferring to let the watchdog check.
- */
- pr_info("Override clocksource %s is not currently HRT compatible - deferring\n",
- cs->name);
- }
- } else
- /* Override clocksource can be used. */
- best = cs;
- break;
- }
- found:
- if (curr_clocksource != best && !timekeeping_notify(best)) {
- pr_info("Switched to clocksource %s\n", best->name);
- curr_clocksource = best;
- }
- }
- /**
- * clocksource_select - Select the best clocksource available
- *
- * Private function. Must hold clocksource_mutex when called.
- *
- * Select the clocksource with the best rating, or the clocksource,
- * which is selected by userspace override.
- */
- static void clocksource_select(void)
- {
- __clocksource_select(false);
- }
- static void clocksource_select_fallback(void)
- {
- __clocksource_select(true);
- }
- /*
- * clocksource_done_booting - Called near the end of core bootup
- *
- * Hack to avoid lots of clocksource churn at boot time.
- * We use fs_initcall because we want this to start before
- * device_initcall but after subsys_initcall.
- */
- static int __init clocksource_done_booting(void)
- {
- mutex_lock(&clocksource_mutex);
- curr_clocksource = clocksource_default_clock();
- finished_booting = 1;
- /*
- * Run the watchdog first to eliminate unstable clock sources
- */
- __clocksource_watchdog_kthread();
- clocksource_select();
- mutex_unlock(&clocksource_mutex);
- return 0;
- }
- fs_initcall(clocksource_done_booting);
- /*
- * Enqueue the clocksource sorted by rating
- */
- static void clocksource_enqueue(struct clocksource *cs)
- {
- struct list_head *entry = &clocksource_list;
- struct clocksource *tmp;
- list_for_each_entry(tmp, &clocksource_list, list) {
- /* Keep track of the place, where to insert */
- if (tmp->rating < cs->rating)
- break;
- entry = &tmp->list;
- }
- list_add(&cs->list, entry);
- }
- /**
- * __clocksource_update_freq_scale - Used update clocksource with new freq
- * @cs: clocksource to be registered
- * @scale: Scale factor multiplied against freq to get clocksource hz
- * @freq: clocksource frequency (cycles per second) divided by scale
- *
- * This should only be called from the clocksource->enable() method.
- *
- * This *SHOULD NOT* be called directly! Please use the
- * __clocksource_update_freq_hz() or __clocksource_update_freq_khz() helper
- * functions.
- */
- void __clocksource_update_freq_scale(struct clocksource *cs, u32 scale, u32 freq)
- {
- u64 sec;
- /*
- * Default clocksources are *special* and self-define their mult/shift.
- * But, you're not special, so you should specify a freq value.
- */
- if (freq) {
- /*
- * Calc the maximum number of seconds which we can run before
- * wrapping around. For clocksources which have a mask > 32-bit
- * we need to limit the max sleep time to have a good
- * conversion precision. 10 minutes is still a reasonable
- * amount. That results in a shift value of 24 for a
- * clocksource with mask >= 40-bit and f >= 4GHz. That maps to
- * ~ 0.06ppm granularity for NTP.
- */
- sec = cs->mask;
- do_div(sec, freq);
- do_div(sec, scale);
- if (!sec)
- sec = 1;
- else if (sec > 600 && cs->mask > UINT_MAX)
- sec = 600;
- clocks_calc_mult_shift(&cs->mult, &cs->shift, freq,
- NSEC_PER_SEC / scale, sec * scale);
- }
- /*
- * If the uncertainty margin is not specified, calculate it.
- * If both scale and freq are non-zero, calculate the clock
- * period, but bound below at 2*WATCHDOG_MAX_SKEW. However,
- * if either of scale or freq is zero, be very conservative and
- * take the tens-of-milliseconds WATCHDOG_THRESHOLD value for the
- * uncertainty margin. Allow stupidly small uncertainty margins
- * to be specified by the caller for testing purposes, but warn
- * to discourage production use of this capability.
- */
- if (scale && freq && !cs->uncertainty_margin) {
- cs->uncertainty_margin = NSEC_PER_SEC / (scale * freq);
- if (cs->uncertainty_margin < 2 * WATCHDOG_MAX_SKEW)
- cs->uncertainty_margin = 2 * WATCHDOG_MAX_SKEW;
- } else if (!cs->uncertainty_margin) {
- cs->uncertainty_margin = WATCHDOG_THRESHOLD;
- }
- WARN_ON_ONCE(cs->uncertainty_margin < 2 * WATCHDOG_MAX_SKEW);
- /*
- * Ensure clocksources that have large 'mult' values don't overflow
- * when adjusted.
- */
- cs->maxadj = clocksource_max_adjustment(cs);
- while (freq && ((cs->mult + cs->maxadj < cs->mult)
- || (cs->mult - cs->maxadj > cs->mult))) {
- cs->mult >>= 1;
- cs->shift--;
- cs->maxadj = clocksource_max_adjustment(cs);
- }
- /*
- * Only warn for *special* clocksources that self-define
- * their mult/shift values and don't specify a freq.
- */
- WARN_ONCE(cs->mult + cs->maxadj < cs->mult,
- "timekeeping: Clocksource %s might overflow on 11%% adjustment\n",
- cs->name);
- clocksource_update_max_deferment(cs);
- pr_info("%s: mask: 0x%llx max_cycles: 0x%llx, max_idle_ns: %lld ns\n",
- cs->name, cs->mask, cs->max_cycles, cs->max_idle_ns);
- }
- EXPORT_SYMBOL_GPL(__clocksource_update_freq_scale);
- /**
- * __clocksource_register_scale - Used to install new clocksources
- * @cs: clocksource to be registered
- * @scale: Scale factor multiplied against freq to get clocksource hz
- * @freq: clocksource frequency (cycles per second) divided by scale
- *
- * Returns -EBUSY if registration fails, zero otherwise.
- *
- * This *SHOULD NOT* be called directly! Please use the
- * clocksource_register_hz() or clocksource_register_khz helper functions.
- */
- int __clocksource_register_scale(struct clocksource *cs, u32 scale, u32 freq)
- {
- unsigned long flags;
- clocksource_arch_init(cs);
- if (WARN_ON_ONCE((unsigned int)cs->id >= CSID_MAX))
- cs->id = CSID_GENERIC;
- if (cs->vdso_clock_mode < 0 ||
- cs->vdso_clock_mode >= VDSO_CLOCKMODE_MAX) {
- pr_warn("clocksource %s registered with invalid VDSO mode %d. Disabling VDSO support.\n",
- cs->name, cs->vdso_clock_mode);
- cs->vdso_clock_mode = VDSO_CLOCKMODE_NONE;
- }
- /* Initialize mult/shift and max_idle_ns */
- __clocksource_update_freq_scale(cs, scale, freq);
- /* Add clocksource to the clocksource list */
- mutex_lock(&clocksource_mutex);
- clocksource_watchdog_lock(&flags);
- clocksource_enqueue(cs);
- clocksource_enqueue_watchdog(cs);
- clocksource_watchdog_unlock(&flags);
- clocksource_select();
- clocksource_select_watchdog(false);
- __clocksource_suspend_select(cs);
- mutex_unlock(&clocksource_mutex);
- return 0;
- }
- EXPORT_SYMBOL_GPL(__clocksource_register_scale);
- static void __clocksource_change_rating(struct clocksource *cs, int rating)
- {
- list_del(&cs->list);
- cs->rating = rating;
- clocksource_enqueue(cs);
- }
- /**
- * clocksource_change_rating - Change the rating of a registered clocksource
- * @cs: clocksource to be changed
- * @rating: new rating
- */
- void clocksource_change_rating(struct clocksource *cs, int rating)
- {
- unsigned long flags;
- mutex_lock(&clocksource_mutex);
- clocksource_watchdog_lock(&flags);
- __clocksource_change_rating(cs, rating);
- clocksource_watchdog_unlock(&flags);
- clocksource_select();
- clocksource_select_watchdog(false);
- clocksource_suspend_select(false);
- mutex_unlock(&clocksource_mutex);
- }
- EXPORT_SYMBOL(clocksource_change_rating);
- /*
- * Unbind clocksource @cs. Called with clocksource_mutex held
- */
- static int clocksource_unbind(struct clocksource *cs)
- {
- unsigned long flags;
- if (clocksource_is_watchdog(cs)) {
- /* Select and try to install a replacement watchdog. */
- clocksource_select_watchdog(true);
- if (clocksource_is_watchdog(cs))
- return -EBUSY;
- }
- if (cs == curr_clocksource) {
- /* Select and try to install a replacement clock source */
- clocksource_select_fallback();
- if (curr_clocksource == cs)
- return -EBUSY;
- }
- if (clocksource_is_suspend(cs)) {
- /*
- * Select and try to install a replacement suspend clocksource.
- * If no replacement suspend clocksource, we will just let the
- * clocksource go and have no suspend clocksource.
- */
- clocksource_suspend_select(true);
- }
- clocksource_watchdog_lock(&flags);
- clocksource_dequeue_watchdog(cs);
- list_del_init(&cs->list);
- clocksource_watchdog_unlock(&flags);
- return 0;
- }
- /**
- * clocksource_unregister - remove a registered clocksource
- * @cs: clocksource to be unregistered
- */
- int clocksource_unregister(struct clocksource *cs)
- {
- int ret = 0;
- mutex_lock(&clocksource_mutex);
- if (!list_empty(&cs->list))
- ret = clocksource_unbind(cs);
- mutex_unlock(&clocksource_mutex);
- return ret;
- }
- EXPORT_SYMBOL(clocksource_unregister);
- #ifdef CONFIG_SYSFS
- /**
- * current_clocksource_show - sysfs interface for current clocksource
- * @dev: unused
- * @attr: unused
- * @buf: char buffer to be filled with clocksource list
- *
- * Provides sysfs interface for listing current clocksource.
- */
- static ssize_t current_clocksource_show(struct device *dev,
- struct device_attribute *attr,
- char *buf)
- {
- ssize_t count = 0;
- mutex_lock(&clocksource_mutex);
- count = snprintf(buf, PAGE_SIZE, "%s\n", curr_clocksource->name);
- mutex_unlock(&clocksource_mutex);
- return count;
- }
- ssize_t sysfs_get_uname(const char *buf, char *dst, size_t cnt)
- {
- size_t ret = cnt;
- /* strings from sysfs write are not 0 terminated! */
- if (!cnt || cnt >= CS_NAME_LEN)
- return -EINVAL;
- /* strip of \n: */
- if (buf[cnt-1] == '\n')
- cnt--;
- if (cnt > 0)
- memcpy(dst, buf, cnt);
- dst[cnt] = 0;
- return ret;
- }
- /**
- * current_clocksource_store - interface for manually overriding clocksource
- * @dev: unused
- * @attr: unused
- * @buf: name of override clocksource
- * @count: length of buffer
- *
- * Takes input from sysfs interface for manually overriding the default
- * clocksource selection.
- */
- static ssize_t current_clocksource_store(struct device *dev,
- struct device_attribute *attr,
- const char *buf, size_t count)
- {
- ssize_t ret;
- mutex_lock(&clocksource_mutex);
- ret = sysfs_get_uname(buf, override_name, count);
- if (ret >= 0)
- clocksource_select();
- mutex_unlock(&clocksource_mutex);
- return ret;
- }
- static DEVICE_ATTR_RW(current_clocksource);
- /**
- * unbind_clocksource_store - interface for manually unbinding clocksource
- * @dev: unused
- * @attr: unused
- * @buf: unused
- * @count: length of buffer
- *
- * Takes input from sysfs interface for manually unbinding a clocksource.
- */
- static ssize_t unbind_clocksource_store(struct device *dev,
- struct device_attribute *attr,
- const char *buf, size_t count)
- {
- struct clocksource *cs;
- char name[CS_NAME_LEN];
- ssize_t ret;
- ret = sysfs_get_uname(buf, name, count);
- if (ret < 0)
- return ret;
- ret = -ENODEV;
- mutex_lock(&clocksource_mutex);
- list_for_each_entry(cs, &clocksource_list, list) {
- if (strcmp(cs->name, name))
- continue;
- ret = clocksource_unbind(cs);
- break;
- }
- mutex_unlock(&clocksource_mutex);
- return ret ? ret : count;
- }
- static DEVICE_ATTR_WO(unbind_clocksource);
- /**
- * available_clocksource_show - sysfs interface for listing clocksource
- * @dev: unused
- * @attr: unused
- * @buf: char buffer to be filled with clocksource list
- *
- * Provides sysfs interface for listing registered clocksources
- */
- static ssize_t available_clocksource_show(struct device *dev,
- struct device_attribute *attr,
- char *buf)
- {
- struct clocksource *src;
- ssize_t count = 0;
- mutex_lock(&clocksource_mutex);
- list_for_each_entry(src, &clocksource_list, list) {
- /*
- * Don't show non-HRES clocksource if the tick code is
- * in one shot mode (highres=on or nohz=on)
- */
- if (!tick_oneshot_mode_active() ||
- (src->flags & CLOCK_SOURCE_VALID_FOR_HRES))
- count += snprintf(buf + count,
- max((ssize_t)PAGE_SIZE - count, (ssize_t)0),
- "%s ", src->name);
- }
- mutex_unlock(&clocksource_mutex);
- count += snprintf(buf + count,
- max((ssize_t)PAGE_SIZE - count, (ssize_t)0), "\n");
- return count;
- }
- static DEVICE_ATTR_RO(available_clocksource);
- static struct attribute *clocksource_attrs[] = {
- &dev_attr_current_clocksource.attr,
- &dev_attr_unbind_clocksource.attr,
- &dev_attr_available_clocksource.attr,
- NULL
- };
- ATTRIBUTE_GROUPS(clocksource);
- static struct bus_type clocksource_subsys = {
- .name = "clocksource",
- .dev_name = "clocksource",
- };
- static struct device device_clocksource = {
- .id = 0,
- .bus = &clocksource_subsys,
- .groups = clocksource_groups,
- };
- static int __init init_clocksource_sysfs(void)
- {
- int error = subsys_system_register(&clocksource_subsys, NULL);
- if (!error)
- error = device_register(&device_clocksource);
- return error;
- }
- device_initcall(init_clocksource_sysfs);
- #endif /* CONFIG_SYSFS */
- /**
- * boot_override_clocksource - boot clock override
- * @str: override name
- *
- * Takes a clocksource= boot argument and uses it
- * as the clocksource override name.
- */
- static int __init boot_override_clocksource(char* str)
- {
- mutex_lock(&clocksource_mutex);
- if (str)
- strlcpy(override_name, str, sizeof(override_name));
- mutex_unlock(&clocksource_mutex);
- return 1;
- }
- __setup("clocksource=", boot_override_clocksource);
- /**
- * boot_override_clock - Compatibility layer for deprecated boot option
- * @str: override name
- *
- * DEPRECATED! Takes a clock= boot argument and uses it
- * as the clocksource override name
- */
- static int __init boot_override_clock(char* str)
- {
- if (!strcmp(str, "pmtmr")) {
- pr_warn("clock=pmtmr is deprecated - use clocksource=acpi_pm\n");
- return boot_override_clocksource("acpi_pm");
- }
- pr_warn("clock= boot option is deprecated - use clocksource=xyz\n");
- return boot_override_clocksource(str);
- }
- __setup("clock=", boot_override_clock);
|