/* * 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 #include #include #include #include /* for spin_unlock_irq() using preempt_count() m68k */ #include #include #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. * 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[CS_NAME_LEN]; static int finished_booting; #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 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); } /** * 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; u64 csnow, wdnow, cslast, wdlast, delta; 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; } 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->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); 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; } spin_unlock_irqrestore(&watchdog_lock, flags); } 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) { unsigned long flags; spin_lock_irqsave(&watchdog_lock, flags); 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(); } } spin_unlock_irqrestore(&watchdog_lock, flags); } static int __clocksource_watchdog_kthread(void) { struct clocksource *cs, *tmp; unsigned long flags; LIST_HEAD(unstable); 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); list_add(&cs->wd_list, &unstable); 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); /* 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); } 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) { } #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 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; /* 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; } 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) { /* 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_enqueue(cs); clocksource_enqueue_watchdog(cs); clocksource_select(); clocksource_select_watchdog(false); 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) { mutex_lock(&clocksource_mutex); __clocksource_change_rating(cs, rating); clocksource_select(); clocksource_select_watchdog(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) { 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; } clocksource_dequeue_watchdog(cs); list_del_init(&cs->list); 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 /** * sysfs_show_current_clocksources - 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 sysfs_show_current_clocksources(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; } /** * sysfs_override_clocksource - 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 sysfs_override_clocksource(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; } /** * sysfs_unbind_current_clocksource - 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 sysfs_unbind_clocksource(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; } /** * sysfs_show_available_clocksources - 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 sysfs_show_available_clocksources(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; } /* * Sysfs setup bits: */ static DEVICE_ATTR(current_clocksource, 0644, sysfs_show_current_clocksources, sysfs_override_clocksource); static DEVICE_ATTR(unbind_clocksource, 0200, NULL, sysfs_unbind_clocksource); static DEVICE_ATTR(available_clocksource, 0444, sysfs_show_available_clocksources, NULL); static struct bus_type clocksource_subsys = { .name = "clocksource", .dev_name = "clocksource", }; static struct device device_clocksource = { .id = 0, .bus = &clocksource_subsys, }; static int __init init_clocksource_sysfs(void) { int error = subsys_system_register(&clocksource_subsys, NULL); if (!error) error = device_register(&device_clocksource); if (!error) error = device_create_file( &device_clocksource, &dev_attr_current_clocksource); if (!error) error = device_create_file(&device_clocksource, &dev_attr_unbind_clocksource); if (!error) error = device_create_file( &device_clocksource, &dev_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")) { 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);