| /* |
| * linux/kernel/time/clocksource.c |
| * |
| * This file contains the functions which manage clocksource drivers. |
| * |
| * Copyright (C) 2004, 2005 IBM, John Stultz (johnstul@us.ibm.com) |
| * |
| * This program is free software; you can redistribute it and/or modify |
| * it under the terms of the GNU General Public License as published by |
| * the Free Software Foundation; either version 2 of the License, or |
| * (at your option) any later version. |
| * |
| * This program is distributed in the hope that it will be useful, |
| * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| * GNU General Public License for more details. |
| * |
| * You should have received a copy of the GNU General Public License |
| * along with this program; if not, write to the Free Software |
| * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. |
| * |
| * TODO WishList: |
| * o Allow clocksource drivers to be unregistered |
| */ |
| |
| #include <linux/clocksource.h> |
| #include <linux/sysdev.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> |
| |
| void timecounter_init(struct timecounter *tc, |
| const struct cyclecounter *cc, |
| u64 start_tstamp) |
| { |
| tc->cc = cc; |
| tc->cycle_last = cc->read(cc); |
| tc->nsec = start_tstamp; |
| } |
| EXPORT_SYMBOL_GPL(timecounter_init); |
| |
| /** |
| * timecounter_read_delta - get nanoseconds since last call of this function |
| * @tc: Pointer to time counter |
| * |
| * When the underlying cycle counter runs over, this will be handled |
| * correctly as long as it does not run over more than once between |
| * calls. |
| * |
| * The first call to this function for a new time counter initializes |
| * the time tracking and returns an undefined result. |
| */ |
| static u64 timecounter_read_delta(struct timecounter *tc) |
| { |
| cycle_t cycle_now, cycle_delta; |
| u64 ns_offset; |
| |
| /* read cycle counter: */ |
| cycle_now = tc->cc->read(tc->cc); |
| |
| /* calculate the delta since the last timecounter_read_delta(): */ |
| cycle_delta = (cycle_now - tc->cycle_last) & tc->cc->mask; |
| |
| /* convert to nanoseconds: */ |
| ns_offset = cyclecounter_cyc2ns(tc->cc, cycle_delta); |
| |
| /* update time stamp of timecounter_read_delta() call: */ |
| tc->cycle_last = cycle_now; |
| |
| return ns_offset; |
| } |
| |
| u64 timecounter_read(struct timecounter *tc) |
| { |
| u64 nsec; |
| |
| /* increment time by nanoseconds since last call */ |
| nsec = timecounter_read_delta(tc); |
| nsec += tc->nsec; |
| tc->nsec = nsec; |
| |
| return nsec; |
| } |
| EXPORT_SYMBOL_GPL(timecounter_read); |
| |
| u64 timecounter_cyc2time(struct timecounter *tc, |
| cycle_t cycle_tstamp) |
| { |
| u64 cycle_delta = (cycle_tstamp - tc->cycle_last) & tc->cc->mask; |
| u64 nsec; |
| |
| /* |
| * Instead of always treating cycle_tstamp as more recent |
| * than tc->cycle_last, detect when it is too far in the |
| * future and treat it as old time stamp instead. |
| */ |
| if (cycle_delta > tc->cc->mask / 2) { |
| cycle_delta = (tc->cycle_last - cycle_tstamp) & tc->cc->mask; |
| nsec = tc->nsec - cyclecounter_cyc2ns(tc->cc, cycle_delta); |
| } else { |
| nsec = cyclecounter_cyc2ns(tc->cc, cycle_delta) + tc->nsec; |
| } |
| |
| return nsec; |
| } |
| EXPORT_SYMBOL_GPL(timecounter_cyc2time); |
| |
| /** |
| * 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 chosing 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; |
| } |
| |
| /*[Clocksource internal variables]--------- |
| * curr_clocksource: |
| * currently selected clocksource. |
| * 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 LIST_HEAD(clocksource_list); |
| static DEFINE_MUTEX(clocksource_mutex); |
| static char override_name[32]; |
| static int finished_booting; |
| |
| #ifdef CONFIG_CLOCKSOURCE_WATCHDOG |
| static void clocksource_watchdog_work(struct work_struct *work); |
| |
| 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 int clocksource_watchdog_kthread(void *data); |
| static void __clocksource_change_rating(struct clocksource *cs, int rating); |
| |
| /* |
| * Interval: 0.5sec Threshold: 0.0625s |
| */ |
| #define WATCHDOG_INTERVAL (HZ >> 1) |
| #define WATCHDOG_THRESHOLD (NSEC_PER_SEC >> 4) |
| |
| static void clocksource_watchdog_work(struct work_struct *work) |
| { |
| /* |
| * 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 (finished_booting) |
| schedule_work(&watchdog_work); |
| } |
| |
| static void clocksource_unstable(struct clocksource *cs, int64_t delta) |
| { |
| printk(KERN_WARNING "Clocksource %s unstable (delta = %Ld ns)\n", |
| cs->name, delta); |
| __clocksource_unstable(cs); |
| } |
| |
| /** |
| * clocksource_mark_unstable - mark clocksource unstable via watchdog |
| * @cs: clocksource to be marked unstable |
| * |
| * This function is called instead of clocksource_change_rating from |
| * cpu hotplug code to avoid a deadlock between the clocksource mutex |
| * and the cpu hotplug mutex. It defers the update of the clocksource |
| * to the watchdog thread. |
| */ |
| 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->wd_list)) |
| list_add(&cs->wd_list, &watchdog_list); |
| __clocksource_unstable(cs); |
| } |
| spin_unlock_irqrestore(&watchdog_lock, flags); |
| } |
| |
| static void clocksource_watchdog(unsigned long data) |
| { |
| struct clocksource *cs; |
| cycle_t csnow, wdnow; |
| int64_t wd_nsec, cs_nsec; |
| int next_cpu, reset_pending; |
| |
| 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; |
| } |
| |
| local_irq_disable(); |
| csnow = cs->read(cs); |
| wdnow = watchdog->read(watchdog); |
| local_irq_enable(); |
| |
| /* 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; |
| } |
| |
| wd_nsec = clocksource_cyc2ns((wdnow - cs->wd_last) & watchdog->mask, |
| watchdog->mult, watchdog->shift); |
| |
| cs_nsec = clocksource_cyc2ns((csnow - cs->cs_last) & |
| cs->mask, cs->mult, cs->shift); |
| cs->cs_last = csnow; |
| cs->wd_last = wdnow; |
| |
| if (atomic_read(&watchdog_reset_pending)) |
| continue; |
| |
| /* Check the deviation from the watchdog clocksource. */ |
| if ((abs(cs_nsec - wd_nsec) > WATCHDOG_THRESHOLD)) { |
| clocksource_unstable(cs, cs_nsec - wd_nsec); |
| continue; |
| } |
| |
| if (!(cs->flags & CLOCK_SOURCE_VALID_FOR_HRES) && |
| (cs->flags & CLOCK_SOURCE_IS_CONTINUOUS) && |
| (watchdog->flags & CLOCK_SOURCE_IS_CONTINUOUS)) { |
| cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES; |
| /* |
| * We just marked the clocksource as highres-capable, |
| * notify the rest of the system as well so that we |
| * transition into high-res mode: |
| */ |
| 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); |
| watchdog_timer.expires += WATCHDOG_INTERVAL; |
| 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; |
| init_timer(&watchdog_timer); |
| watchdog_timer.function = clocksource_watchdog; |
| 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 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_resume_watchdog(void) |
| { |
| atomic_inc(&watchdog_reset_pending); |
| } |
| |
| static void clocksource_enqueue_watchdog(struct clocksource *cs) |
| { |
| unsigned long flags; |
| |
| spin_lock_irqsave(&watchdog_lock, flags); |
| 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; |
| /* Pick the best watchdog. */ |
| if (!watchdog || cs->rating > watchdog->rating) { |
| watchdog = cs; |
| /* Reset watchdog cycles */ |
| 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) |
| { |
| struct clocksource *tmp; |
| unsigned long flags; |
| |
| spin_lock_irqsave(&watchdog_lock, flags); |
| if (cs->flags & CLOCK_SOURCE_MUST_VERIFY) { |
| /* cs is a watched clocksource. */ |
| list_del_init(&cs->wd_list); |
| } else if (cs == watchdog) { |
| /* Reset watchdog cycles */ |
| clocksource_reset_watchdog(); |
| /* Current watchdog is removed. Find an alternative. */ |
| watchdog = NULL; |
| list_for_each_entry(tmp, &clocksource_list, list) { |
| if (tmp == cs || tmp->flags & CLOCK_SOURCE_MUST_VERIFY) |
| continue; |
| if (!watchdog || tmp->rating > watchdog->rating) |
| watchdog = tmp; |
| } |
| } |
| cs->flags &= ~CLOCK_SOURCE_WATCHDOG; |
| /* Check if the watchdog timer needs to be stopped. */ |
| clocksource_stop_watchdog(); |
| spin_unlock_irqrestore(&watchdog_lock, flags); |
| } |
| |
| static int clocksource_watchdog_kthread(void *data) |
| { |
| struct clocksource *cs, *tmp; |
| unsigned long flags; |
| LIST_HEAD(unstable); |
| |
| mutex_lock(&clocksource_mutex); |
| 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); |
| list_add(&cs->wd_list, &unstable); |
| } |
| /* Check if the watchdog timer needs to be stopped. */ |
| clocksource_stop_watchdog(); |
| spin_unlock_irqrestore(&watchdog_lock, flags); |
| |
| /* Needs to be done outside of watchdog lock */ |
| list_for_each_entry_safe(cs, tmp, &unstable, wd_list) { |
| list_del_init(&cs->wd_list); |
| __clocksource_change_rating(cs, 0); |
| } |
| mutex_unlock(&clocksource_mutex); |
| return 0; |
| } |
| |
| #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 inline void clocksource_dequeue_watchdog(struct clocksource *cs) { } |
| static inline void clocksource_resume_watchdog(void) { } |
| static inline int clocksource_watchdog_kthread(void *data) { return 0; } |
| |
| #endif /* CONFIG_CLOCKSOURCE_WATCHDOG */ |
| |
| /** |
| * 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 then 11% adjustments (110,000 ppm), |
| */ |
| ret = (u64)cs->mult * 11; |
| do_div(ret,100); |
| return (u32)ret; |
| } |
| |
| /** |
| * clocksource_max_deferment - Returns max time the clocksource can be deferred |
| * @cs: Pointer to clocksource |
| * |
| */ |
| static u64 clocksource_max_deferment(struct clocksource *cs) |
| { |
| u64 max_nsecs, max_cycles; |
| |
| /* |
| * Calculate the maximum number of cycles that we can pass to the |
| * cyc2ns function without overflowing a 64-bit signed result. The |
| * maximum number of cycles is equal to ULLONG_MAX/(cs->mult+cs->maxadj) |
| * which is equivalent to the below. |
| * max_cycles < (2^63)/(cs->mult + cs->maxadj) |
| * max_cycles < 2^(log2((2^63)/(cs->mult + cs->maxadj))) |
| * max_cycles < 2^(log2(2^63) - log2(cs->mult + cs->maxadj)) |
| * max_cycles < 2^(63 - log2(cs->mult + cs->maxadj)) |
| * max_cycles < 1 << (63 - log2(cs->mult + cs->maxadj)) |
| * Please note that we add 1 to the result of the log2 to account for |
| * any rounding errors, ensure the above inequality is satisfied and |
| * no overflow will occur. |
| */ |
| max_cycles = 1ULL << (63 - (ilog2(cs->mult + cs->maxadj) + 1)); |
| |
| /* |
| * The actual maximum number of cycles we can defer the clocksource is |
| * determined by the minimum of max_cycles and cs->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_t(u64, max_cycles, (u64) cs->mask); |
| max_nsecs = clocksource_cyc2ns(max_cycles, cs->mult - cs->maxadj, |
| cs->shift); |
| |
| /* |
| * To ensure that the clocksource does not wrap whilst we are idle, |
| * limit the time the clocksource can be deferred by 12.5%. Please |
| * note a margin of 12.5% is used because this can be computed with |
| * a shift, versus say 10% which would require division. |
| */ |
| return max_nsecs - (max_nsecs >> 5); |
| } |
| |
| #ifndef CONFIG_ARCH_USES_GETTIMEOFFSET |
| |
| /** |
| * 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) |
| { |
| struct clocksource *best, *cs; |
| |
| if (!finished_booting || list_empty(&clocksource_list)) |
| return; |
| /* First clocksource on the list has the best rating. */ |
| best = list_first_entry(&clocksource_list, struct clocksource, list); |
| /* Check for the override clocksource. */ |
| list_for_each_entry(cs, &clocksource_list, list) { |
| 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) && |
| tick_oneshot_mode_active()) { |
| /* Override clocksource cannot be used. */ |
| printk(KERN_WARNING "Override clocksource %s is not " |
| "HRT compatible. Cannot switch while in " |
| "HRT/NOHZ mode\n", cs->name); |
| override_name[0] = 0; |
| } else |
| /* Override clocksource can be used. */ |
| best = cs; |
| break; |
| } |
| if (curr_clocksource != best) { |
| printk(KERN_INFO "Switching to clocksource %s\n", best->name); |
| curr_clocksource = best; |
| timekeeping_notify(curr_clocksource); |
| } |
| } |
| |
| #else /* !CONFIG_ARCH_USES_GETTIMEOFFSET */ |
| |
| static inline void clocksource_select(void) { } |
| |
| #endif |
| |
| /* |
| * 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(); |
| mutex_unlock(&clocksource_mutex); |
| |
| finished_booting = 1; |
| |
| /* |
| * Run the watchdog first to eliminate unstable clock sources |
| */ |
| clocksource_watchdog_kthread(NULL); |
| |
| mutex_lock(&clocksource_mutex); |
| 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) |
| entry = &tmp->list; |
| list_add(&cs->list, entry); |
| } |
| |
| /** |
| * __clocksource_updatefreq_scale - Used update clocksource with new freq |
| * @t: 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_updatefreq_hz() or clocksource_updatefreq_khz helper functions. |
| */ |
| void __clocksource_updatefreq_scale(struct clocksource *cs, u32 scale, u32 freq) |
| { |
| u64 sec; |
| /* |
| * Calc the maximum number of seconds which we can run before |
| * wrapping around. For clocksources which have a mask > 32bit |
| * 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 >= 40bit and f >= 4GHz. That maps to |
| * ~ 0.06ppm granularity for NTP. We apply the same 12.5% |
| * margin as we do in clocksource_max_deferment() |
| */ |
| sec = (cs->mask - (cs->mask >> 5)); |
| 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); |
| |
| /* |
| * for clocksources that have large mults, to avoid overflow. |
| * Since mult may be adjusted by ntp, add an safety extra margin |
| * |
| */ |
| cs->maxadj = clocksource_max_adjustment(cs); |
| while ((cs->mult + cs->maxadj < cs->mult) |
| || (cs->mult - cs->maxadj > cs->mult)) { |
| cs->mult >>= 1; |
| cs->shift--; |
| cs->maxadj = clocksource_max_adjustment(cs); |
| } |
| |
| cs->max_idle_ns = clocksource_max_deferment(cs); |
| } |
| EXPORT_SYMBOL_GPL(__clocksource_updatefreq_scale); |
| |
| /** |
| * __clocksource_register_scale - Used to install new clocksources |
| * @t: 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) |
| { |
| |
| /* Initialize mult/shift and max_idle_ns */ |
| __clocksource_updatefreq_scale(cs, scale, freq); |
| |
| /* Add clocksource to the clcoksource list */ |
| mutex_lock(&clocksource_mutex); |
| clocksource_enqueue(cs); |
| clocksource_enqueue_watchdog(cs); |
| clocksource_select(); |
| mutex_unlock(&clocksource_mutex); |
| return 0; |
| } |
| EXPORT_SYMBOL_GPL(__clocksource_register_scale); |
| |
| |
| /** |
| * clocksource_register - Used to install new clocksources |
| * @t: clocksource to be registered |
| * |
| * Returns -EBUSY if registration fails, zero otherwise. |
| */ |
| int clocksource_register(struct clocksource *cs) |
| { |
| /* calculate max adjustment for given mult/shift */ |
| cs->maxadj = clocksource_max_adjustment(cs); |
| WARN_ONCE(cs->mult + cs->maxadj < cs->mult, |
| "Clocksource %s might overflow on 11%% adjustment\n", |
| cs->name); |
| |
| /* calculate max idle time permitted for this clocksource */ |
| cs->max_idle_ns = clocksource_max_deferment(cs); |
| |
| mutex_lock(&clocksource_mutex); |
| clocksource_enqueue(cs); |
| clocksource_enqueue_watchdog(cs); |
| clocksource_select(); |
| mutex_unlock(&clocksource_mutex); |
| return 0; |
| } |
| EXPORT_SYMBOL(clocksource_register); |
| |
| static void __clocksource_change_rating(struct clocksource *cs, int rating) |
| { |
| list_del(&cs->list); |
| cs->rating = rating; |
| clocksource_enqueue(cs); |
| clocksource_select(); |
| } |
| |
| /** |
| * clocksource_change_rating - Change the rating of a registered clocksource |
| */ |
| void clocksource_change_rating(struct clocksource *cs, int rating) |
| { |
| mutex_lock(&clocksource_mutex); |
| __clocksource_change_rating(cs, rating); |
| mutex_unlock(&clocksource_mutex); |
| } |
| EXPORT_SYMBOL(clocksource_change_rating); |
| |
| /** |
| * clocksource_unregister - remove a registered clocksource |
| */ |
| void clocksource_unregister(struct clocksource *cs) |
| { |
| mutex_lock(&clocksource_mutex); |
| clocksource_dequeue_watchdog(cs); |
| list_del(&cs->list); |
| clocksource_select(); |
| mutex_unlock(&clocksource_mutex); |
| } |
| EXPORT_SYMBOL(clocksource_unregister); |
| |
| #ifdef CONFIG_SYSFS |
| /** |
| * sysfs_show_current_clocksources - sysfs interface for current clocksource |
| * @dev: unused |
| * @buf: char buffer to be filled with clocksource list |
| * |
| * Provides sysfs interface for listing current clocksource. |
| */ |
| static ssize_t |
| sysfs_show_current_clocksources(struct sys_device *dev, |
| struct sysdev_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; |
| } |
| |
| /** |
| * sysfs_override_clocksource - interface for manually overriding clocksource |
| * @dev: 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 sysfs_override_clocksource(struct sys_device *dev, |
| struct sysdev_attribute *attr, |
| const char *buf, size_t count) |
| { |
| size_t ret = count; |
| |
| /* strings from sysfs write are not 0 terminated! */ |
| if (count >= sizeof(override_name)) |
| return -EINVAL; |
| |
| /* strip of \n: */ |
| if (buf[count-1] == '\n') |
| count--; |
| |
| mutex_lock(&clocksource_mutex); |
| |
| if (count > 0) |
| memcpy(override_name, buf, count); |
| override_name[count] = 0; |
| clocksource_select(); |
| |
| mutex_unlock(&clocksource_mutex); |
| |
| return ret; |
| } |
| |
| /** |
| * sysfs_show_available_clocksources - sysfs interface for listing clocksource |
| * @dev: unused |
| * @buf: char buffer to be filled with clocksource list |
| * |
| * Provides sysfs interface for listing registered clocksources |
| */ |
| static ssize_t |
| sysfs_show_available_clocksources(struct sys_device *dev, |
| struct sysdev_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; |
| } |
| |
| /* |
| * Sysfs setup bits: |
| */ |
| static SYSDEV_ATTR(current_clocksource, 0644, sysfs_show_current_clocksources, |
| sysfs_override_clocksource); |
| |
| static SYSDEV_ATTR(available_clocksource, 0444, |
| sysfs_show_available_clocksources, NULL); |
| |
| static struct sysdev_class clocksource_sysclass = { |
| .name = "clocksource", |
| }; |
| |
| static struct sys_device device_clocksource = { |
| .id = 0, |
| .cls = &clocksource_sysclass, |
| }; |
| |
| static int __init init_clocksource_sysfs(void) |
| { |
| int error = sysdev_class_register(&clocksource_sysclass); |
| |
| if (!error) |
| error = sysdev_register(&device_clocksource); |
| if (!error) |
| error = sysdev_create_file( |
| &device_clocksource, |
| &attr_current_clocksource); |
| if (!error) |
| error = sysdev_create_file( |
| &device_clocksource, |
| &attr_available_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")) { |
| printk("Warning: clock=pmtmr is deprecated. " |
| "Use clocksource=acpi_pm.\n"); |
| return boot_override_clocksource("acpi_pm"); |
| } |
| printk("Warning! clock= boot option is deprecated. " |
| "Use clocksource=xyz\n"); |
| return boot_override_clocksource(str); |
| } |
| |
| __setup("clock=", boot_override_clock); |