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Diffstat (limited to 'kernel/time/clocksource.c')
| -rw-r--r-- | kernel/time/clocksource.c | 1294 |
1 files changed, 1294 insertions, 0 deletions
diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c new file mode 100644 index 000000000..221f8e746 --- /dev/null +++ b/kernel/time/clocksource.c @@ -0,0 +1,1294 @@ +/* + * 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 + */ + +#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 "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 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; +} +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; + +#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 void inline clocksource_watchdog_lock(unsigned long *flags) +{ + spin_lock_irqsave(&watchdog_lock, *flags); +} + +static void inline 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 Threshold: 0.0625s + */ +#define WATCHDOG_INTERVAL (HZ >> 1) +#define WATCHDOG_THRESHOLD (NSEC_PER_SEC >> 4) + +/* + * 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. + */ +#define WATCHDOG_MAX_SKEW (100 * NSEC_PER_USEC) + +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); +} + +static ulong max_cswd_read_retries = 3; +module_param(max_cswd_read_retries, ulong, 0644); + +static bool cs_watchdog_read(struct clocksource *cs, u64 *csnow, u64 *wdnow) +{ + unsigned int nretries; + u64 wd_end, wd_delta; + int64_t wd_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); + 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 true; + } + } + + 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 false; +} + +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; + + 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; + } + + if (!cs_watchdog_read(cs, &csnow, &wdnow)) { + /* Clock readout unreliable, so give it up. */ + __clocksource_unstable(cs); + continue; + } + + /* 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. */ + if (abs(cs_nsec - wd_nsec) > WATCHDOG_THRESHOLD) { + 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_now: %llx wd_last: %llx mask: %llx\n", + watchdog->name, wdnow, wdlast, watchdog->mask); + pr_warn(" '%s' cs_now: %llx cs_last: %llx mask: %llx\n", + cs->name, csnow, cslast, cs->mask); + __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; + 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 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) +{ + 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; + + 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 freezed, 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); +} + +#ifndef CONFIG_ARCH_USES_GETTIMEOFFSET + +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); +} + +#else /* !CONFIG_ARCH_USES_GETTIMEOFFSET */ +static inline void clocksource_select(void) { } +static inline void clocksource_select_fallback(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(); + 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); + } + /* + * 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; + + /* 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); |