// SPDX-License-Identifier: GPL-2.0+
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/*
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* This file contains the functions which manage clocksource drivers.
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*
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* Copyright (C) 2004, 2005 IBM, John Stultz (johnstul@us.ibm.com)
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*/
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#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
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#include <linux/device.h>
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#include <linux/clocksource.h>
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#include <linux/init.h>
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#include <linux/module.h>
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#include <linux/sched.h> /* for spin_unlock_irq() using preempt_count() m68k */
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#include <linux/tick.h>
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#include <linux/kthread.h>
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#include "tick-internal.h"
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#include "timekeeping_internal.h"
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/**
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* clocks_calc_mult_shift - calculate mult/shift factors for scaled math of clocks
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* @mult: pointer to mult variable
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* @shift: pointer to shift variable
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* @from: frequency to convert from
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* @to: frequency to convert to
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* @maxsec: guaranteed runtime conversion range in seconds
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*
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* The function evaluates the shift/mult pair for the scaled math
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* operations of clocksources and clockevents.
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*
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* @to and @from are frequency values in HZ. For clock sources @to is
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* NSEC_PER_SEC == 1GHz and @from is the counter frequency. For clock
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* event @to is the counter frequency and @from is NSEC_PER_SEC.
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*
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* The @maxsec conversion range argument controls the time frame in
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* seconds which must be covered by the runtime conversion with the
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* calculated mult and shift factors. This guarantees that no 64bit
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* overflow happens when the input value of the conversion is
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* multiplied with the calculated mult factor. Larger ranges may
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* reduce the conversion accuracy by chosing smaller mult and shift
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* factors.
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*/
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void
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clocks_calc_mult_shift(u32 *mult, u32 *shift, u32 from, u32 to, u32 maxsec)
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{
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u64 tmp;
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u32 sft, sftacc= 32;
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/*
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* Calculate the shift factor which is limiting the conversion
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* range:
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*/
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tmp = ((u64)maxsec * from) >> 32;
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while (tmp) {
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tmp >>=1;
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sftacc--;
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}
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/*
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* Find the conversion shift/mult pair which has the best
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* accuracy and fits the maxsec conversion range:
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*/
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for (sft = 32; sft > 0; sft--) {
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tmp = (u64) to << sft;
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tmp += from / 2;
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do_div(tmp, from);
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if ((tmp >> sftacc) == 0)
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break;
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}
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*mult = tmp;
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*shift = sft;
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}
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EXPORT_SYMBOL_GPL(clocks_calc_mult_shift);
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/*[Clocksource internal variables]---------
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* curr_clocksource:
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* currently selected clocksource.
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* suspend_clocksource:
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* used to calculate the suspend time.
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* clocksource_list:
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* linked list with the registered clocksources
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* clocksource_mutex:
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* protects manipulations to curr_clocksource and the clocksource_list
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* override_name:
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* Name of the user-specified clocksource.
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*/
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static struct clocksource *curr_clocksource;
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static struct clocksource *suspend_clocksource;
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static LIST_HEAD(clocksource_list);
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static DEFINE_MUTEX(clocksource_mutex);
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static char override_name[CS_NAME_LEN];
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static int finished_booting;
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static u64 suspend_start;
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#ifdef CONFIG_CLOCKSOURCE_WATCHDOG
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static void clocksource_watchdog_work(struct work_struct *work);
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static void clocksource_select(void);
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static LIST_HEAD(watchdog_list);
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static struct clocksource *watchdog;
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static struct timer_list watchdog_timer;
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static DECLARE_WORK(watchdog_work, clocksource_watchdog_work);
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static DEFINE_SPINLOCK(watchdog_lock);
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static int watchdog_running;
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static atomic_t watchdog_reset_pending;
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static inline void clocksource_watchdog_lock(unsigned long *flags)
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{
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spin_lock_irqsave(&watchdog_lock, *flags);
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}
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static inline void clocksource_watchdog_unlock(unsigned long *flags)
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{
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spin_unlock_irqrestore(&watchdog_lock, *flags);
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}
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static int clocksource_watchdog_kthread(void *data);
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static void __clocksource_change_rating(struct clocksource *cs, int rating);
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/*
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* Interval: 0.5sec Threshold: 0.0625s
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*/
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#define WATCHDOG_INTERVAL (HZ >> 1)
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#define WATCHDOG_THRESHOLD (NSEC_PER_SEC >> 4)
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/*
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* Maximum permissible delay between two readouts of the watchdog
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* clocksource surrounding a read of the clocksource being validated.
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* This delay could be due to SMIs, NMIs, or to VCPU preemptions.
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*/
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#define WATCHDOG_MAX_SKEW (100 * NSEC_PER_USEC)
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static void clocksource_watchdog_work(struct work_struct *work)
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{
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/*
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* We cannot directly run clocksource_watchdog_kthread() here, because
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* clocksource_select() calls timekeeping_notify() which uses
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* stop_machine(). One cannot use stop_machine() from a workqueue() due
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* lock inversions wrt CPU hotplug.
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*
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* Also, we only ever run this work once or twice during the lifetime
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* of the kernel, so there is no point in creating a more permanent
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* kthread for this.
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*
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* If kthread_run fails the next watchdog scan over the
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* watchdog_list will find the unstable clock again.
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*/
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kthread_run(clocksource_watchdog_kthread, NULL, "kwatchdog");
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}
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static void __clocksource_unstable(struct clocksource *cs)
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{
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cs->flags &= ~(CLOCK_SOURCE_VALID_FOR_HRES | CLOCK_SOURCE_WATCHDOG);
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cs->flags |= CLOCK_SOURCE_UNSTABLE;
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/*
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* If the clocksource is registered clocksource_watchdog_kthread() will
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* re-rate and re-select.
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*/
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if (list_empty(&cs->list)) {
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cs->rating = 0;
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return;
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}
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if (cs->mark_unstable)
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cs->mark_unstable(cs);
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/* kick clocksource_watchdog_kthread() */
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if (finished_booting)
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schedule_work(&watchdog_work);
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}
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/**
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* clocksource_mark_unstable - mark clocksource unstable via watchdog
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* @cs: clocksource to be marked unstable
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*
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* This function is called by the x86 TSC code to mark clocksources as unstable;
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* it defers demotion and re-selection to a kthread.
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*/
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void clocksource_mark_unstable(struct clocksource *cs)
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{
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unsigned long flags;
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spin_lock_irqsave(&watchdog_lock, flags);
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if (!(cs->flags & CLOCK_SOURCE_UNSTABLE)) {
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if (!list_empty(&cs->list) && list_empty(&cs->wd_list))
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list_add(&cs->wd_list, &watchdog_list);
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__clocksource_unstable(cs);
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}
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spin_unlock_irqrestore(&watchdog_lock, flags);
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}
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static ulong max_cswd_read_retries = 3;
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module_param(max_cswd_read_retries, ulong, 0644);
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static bool cs_watchdog_read(struct clocksource *cs, u64 *csnow, u64 *wdnow)
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{
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unsigned int nretries;
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u64 wd_end, wd_delta;
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int64_t wd_delay;
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for (nretries = 0; nretries <= max_cswd_read_retries; nretries++) {
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local_irq_disable();
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*wdnow = watchdog->read(watchdog);
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*csnow = cs->read(cs);
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wd_end = watchdog->read(watchdog);
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local_irq_enable();
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wd_delta = clocksource_delta(wd_end, *wdnow, watchdog->mask);
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wd_delay = clocksource_cyc2ns(wd_delta, watchdog->mult,
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watchdog->shift);
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if (wd_delay <= WATCHDOG_MAX_SKEW) {
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if (nretries > 1 || nretries >= max_cswd_read_retries) {
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pr_warn("timekeeping watchdog on CPU%d: %s retried %d times before success\n",
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smp_processor_id(), watchdog->name, nretries);
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}
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return true;
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}
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}
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pr_warn("timekeeping watchdog on CPU%d: %s read-back delay of %lldns, attempt %d, marking unstable\n",
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smp_processor_id(), watchdog->name, wd_delay, nretries);
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return false;
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}
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static u64 csnow_mid;
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static cpumask_t cpus_ahead;
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static cpumask_t cpus_behind;
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static void clocksource_verify_one_cpu(void *csin)
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{
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struct clocksource *cs = (struct clocksource *)csin;
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csnow_mid = cs->read(cs);
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}
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static void clocksource_verify_percpu(struct clocksource *cs)
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{
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int64_t cs_nsec, cs_nsec_max = 0, cs_nsec_min = LLONG_MAX;
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u64 csnow_begin, csnow_end;
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int cpu, testcpu;
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s64 delta;
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cpumask_clear(&cpus_ahead);
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cpumask_clear(&cpus_behind);
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preempt_disable();
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testcpu = smp_processor_id();
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pr_warn("Checking clocksource %s synchronization from CPU %d.\n", cs->name, testcpu);
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for_each_online_cpu(cpu) {
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if (cpu == testcpu)
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continue;
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csnow_begin = cs->read(cs);
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smp_call_function_single(cpu, clocksource_verify_one_cpu, cs, 1);
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csnow_end = cs->read(cs);
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delta = (s64)((csnow_mid - csnow_begin) & cs->mask);
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if (delta < 0)
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cpumask_set_cpu(cpu, &cpus_behind);
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delta = (csnow_end - csnow_mid) & cs->mask;
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if (delta < 0)
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cpumask_set_cpu(cpu, &cpus_ahead);
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delta = clocksource_delta(csnow_end, csnow_begin, cs->mask);
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cs_nsec = clocksource_cyc2ns(delta, cs->mult, cs->shift);
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if (cs_nsec > cs_nsec_max)
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cs_nsec_max = cs_nsec;
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if (cs_nsec < cs_nsec_min)
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cs_nsec_min = cs_nsec;
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}
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preempt_enable();
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if (!cpumask_empty(&cpus_ahead))
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pr_warn(" CPUs %*pbl ahead of CPU %d for clocksource %s.\n",
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cpumask_pr_args(&cpus_ahead), testcpu, cs->name);
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if (!cpumask_empty(&cpus_behind))
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pr_warn(" CPUs %*pbl behind CPU %d for clocksource %s.\n",
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cpumask_pr_args(&cpus_behind), testcpu, cs->name);
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if (!cpumask_empty(&cpus_ahead) || !cpumask_empty(&cpus_behind))
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pr_warn(" CPU %d check durations %lldns - %lldns for clocksource %s.\n",
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testcpu, cs_nsec_min, cs_nsec_max, cs->name);
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}
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static void clocksource_watchdog(struct timer_list *unused)
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{
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u64 csnow, wdnow, cslast, wdlast, delta;
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int next_cpu, reset_pending;
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int64_t wd_nsec, cs_nsec;
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struct clocksource *cs;
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spin_lock(&watchdog_lock);
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if (!watchdog_running)
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goto out;
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reset_pending = atomic_read(&watchdog_reset_pending);
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list_for_each_entry(cs, &watchdog_list, wd_list) {
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/* Clocksource already marked unstable? */
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if (cs->flags & CLOCK_SOURCE_UNSTABLE) {
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if (finished_booting)
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schedule_work(&watchdog_work);
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continue;
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}
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if (!cs_watchdog_read(cs, &csnow, &wdnow)) {
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/* Clock readout unreliable, so give it up. */
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__clocksource_unstable(cs);
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continue;
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}
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/* Clocksource initialized ? */
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if (!(cs->flags & CLOCK_SOURCE_WATCHDOG) ||
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atomic_read(&watchdog_reset_pending)) {
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cs->flags |= CLOCK_SOURCE_WATCHDOG;
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cs->wd_last = wdnow;
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cs->cs_last = csnow;
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continue;
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}
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delta = clocksource_delta(wdnow, cs->wd_last, watchdog->mask);
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wd_nsec = clocksource_cyc2ns(delta, watchdog->mult,
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watchdog->shift);
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delta = clocksource_delta(csnow, cs->cs_last, cs->mask);
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cs_nsec = clocksource_cyc2ns(delta, cs->mult, cs->shift);
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wdlast = cs->wd_last; /* save these in case we print them */
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cslast = cs->cs_last;
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cs->cs_last = csnow;
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cs->wd_last = wdnow;
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if (atomic_read(&watchdog_reset_pending))
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continue;
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/* Check the deviation from the watchdog clocksource. */
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if (abs(cs_nsec - wd_nsec) > WATCHDOG_THRESHOLD) {
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pr_warn("timekeeping watchdog on CPU%d: Marking clocksource '%s' as unstable because the skew is too large:\n",
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smp_processor_id(), cs->name);
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pr_warn(" '%s' wd_now: %llx wd_last: %llx mask: %llx\n",
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watchdog->name, wdnow, wdlast, watchdog->mask);
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pr_warn(" '%s' cs_now: %llx cs_last: %llx mask: %llx\n",
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cs->name, csnow, cslast, cs->mask);
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__clocksource_unstable(cs);
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continue;
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}
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if (cs == curr_clocksource && cs->tick_stable)
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cs->tick_stable(cs);
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if (!(cs->flags & CLOCK_SOURCE_VALID_FOR_HRES) &&
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(cs->flags & CLOCK_SOURCE_IS_CONTINUOUS) &&
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(watchdog->flags & CLOCK_SOURCE_IS_CONTINUOUS)) {
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/* Mark it valid for high-res. */
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cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES;
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/*
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* clocksource_done_booting() will sort it if
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* finished_booting is not set yet.
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*/
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if (!finished_booting)
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continue;
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/*
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* If this is not the current clocksource let
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* the watchdog thread reselect it. Due to the
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* change to high res this clocksource might
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* be preferred now. If it is the current
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* clocksource let the tick code know about
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* that change.
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*/
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if (cs != curr_clocksource) {
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cs->flags |= CLOCK_SOURCE_RESELECT;
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schedule_work(&watchdog_work);
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} else {
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tick_clock_notify();
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}
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}
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}
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/*
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* We only clear the watchdog_reset_pending, when we did a
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* full cycle through all clocksources.
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*/
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if (reset_pending)
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atomic_dec(&watchdog_reset_pending);
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/*
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* Cycle through CPUs to check if the CPUs stay synchronized
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* to each other.
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*/
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next_cpu = cpumask_next(raw_smp_processor_id(), cpu_online_mask);
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if (next_cpu >= nr_cpu_ids)
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next_cpu = cpumask_first(cpu_online_mask);
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/*
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* Arm timer if not already pending: could race with concurrent
|
* pair clocksource_stop_watchdog() clocksource_start_watchdog().
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*/
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if (!timer_pending(&watchdog_timer)) {
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watchdog_timer.expires += WATCHDOG_INTERVAL;
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add_timer_on(&watchdog_timer, next_cpu);
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}
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out:
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spin_unlock(&watchdog_lock);
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}
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static inline void clocksource_start_watchdog(void)
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{
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if (watchdog_running || !watchdog || list_empty(&watchdog_list))
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return;
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timer_setup(&watchdog_timer, clocksource_watchdog, 0);
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watchdog_timer.expires = jiffies + WATCHDOG_INTERVAL;
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add_timer_on(&watchdog_timer, cpumask_first(cpu_online_mask));
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watchdog_running = 1;
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}
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static inline void clocksource_stop_watchdog(void)
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{
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if (!watchdog_running || (watchdog && !list_empty(&watchdog_list)))
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return;
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del_timer(&watchdog_timer);
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watchdog_running = 0;
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}
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static inline void clocksource_reset_watchdog(void)
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{
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struct clocksource *cs;
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list_for_each_entry(cs, &watchdog_list, wd_list)
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cs->flags &= ~CLOCK_SOURCE_WATCHDOG;
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}
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static void clocksource_resume_watchdog(void)
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{
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atomic_inc(&watchdog_reset_pending);
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}
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static void clocksource_enqueue_watchdog(struct clocksource *cs)
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{
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INIT_LIST_HEAD(&cs->wd_list);
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if (cs->flags & CLOCK_SOURCE_MUST_VERIFY) {
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/* cs is a clocksource to be watched. */
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list_add(&cs->wd_list, &watchdog_list);
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cs->flags &= ~CLOCK_SOURCE_WATCHDOG;
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} else {
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/* cs is a watchdog. */
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if (cs->flags & CLOCK_SOURCE_IS_CONTINUOUS)
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cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES;
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}
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}
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static void clocksource_select_watchdog(bool fallback)
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{
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struct clocksource *cs, *old_wd;
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unsigned long flags;
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spin_lock_irqsave(&watchdog_lock, flags);
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/* save current watchdog */
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old_wd = watchdog;
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if (fallback)
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watchdog = NULL;
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list_for_each_entry(cs, &clocksource_list, list) {
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/* cs is a clocksource to be watched. */
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if (cs->flags & CLOCK_SOURCE_MUST_VERIFY)
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continue;
|
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/* Skip current if we were requested for a fallback. */
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if (fallback && cs == old_wd)
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continue;
|
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/* Pick the best watchdog. */
|
if (!watchdog || cs->rating > watchdog->rating)
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watchdog = cs;
|
}
|
/* If we failed to find a fallback restore the old one. */
|
if (!watchdog)
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watchdog = old_wd;
|
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/* If we changed the watchdog we need to reset cycles. */
|
if (watchdog != old_wd)
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clocksource_reset_watchdog();
|
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/* Check if the watchdog timer needs to be started. */
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clocksource_start_watchdog();
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spin_unlock_irqrestore(&watchdog_lock, flags);
|
}
|
|
static void clocksource_dequeue_watchdog(struct clocksource *cs)
|
{
|
if (cs != watchdog) {
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if (cs->flags & CLOCK_SOURCE_MUST_VERIFY) {
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/* cs is a watched clocksource. */
|
list_del_init(&cs->wd_list);
|
/* Check if the watchdog timer needs to be stopped. */
|
clocksource_stop_watchdog();
|
}
|
}
|
}
|
|
static int __clocksource_watchdog_kthread(void)
|
{
|
struct clocksource *cs, *tmp;
|
unsigned long flags;
|
int select = 0;
|
|
/* Do any required per-CPU skew verification. */
|
if (curr_clocksource &&
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curr_clocksource->flags & CLOCK_SOURCE_UNSTABLE &&
|
curr_clocksource->flags & CLOCK_SOURCE_VERIFY_PERCPU)
|
clocksource_verify_percpu(curr_clocksource);
|
|
spin_lock_irqsave(&watchdog_lock, flags);
|
list_for_each_entry_safe(cs, tmp, &watchdog_list, wd_list) {
|
if (cs->flags & CLOCK_SOURCE_UNSTABLE) {
|
list_del_init(&cs->wd_list);
|
__clocksource_change_rating(cs, 0);
|
select = 1;
|
}
|
if (cs->flags & CLOCK_SOURCE_RESELECT) {
|
cs->flags &= ~CLOCK_SOURCE_RESELECT;
|
select = 1;
|
}
|
}
|
/* Check if the watchdog timer needs to be stopped. */
|
clocksource_stop_watchdog();
|
spin_unlock_irqrestore(&watchdog_lock, flags);
|
|
return select;
|
}
|
|
static int clocksource_watchdog_kthread(void *data)
|
{
|
mutex_lock(&clocksource_mutex);
|
if (__clocksource_watchdog_kthread())
|
clocksource_select();
|
mutex_unlock(&clocksource_mutex);
|
return 0;
|
}
|
|
static bool clocksource_is_watchdog(struct clocksource *cs)
|
{
|
return cs == watchdog;
|
}
|
|
#else /* CONFIG_CLOCKSOURCE_WATCHDOG */
|
|
static void clocksource_enqueue_watchdog(struct clocksource *cs)
|
{
|
if (cs->flags & CLOCK_SOURCE_IS_CONTINUOUS)
|
cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES;
|
}
|
|
static void clocksource_select_watchdog(bool fallback) { }
|
static inline void clocksource_dequeue_watchdog(struct clocksource *cs) { }
|
static inline void clocksource_resume_watchdog(void) { }
|
static inline int __clocksource_watchdog_kthread(void) { return 0; }
|
static bool clocksource_is_watchdog(struct clocksource *cs) { return false; }
|
void clocksource_mark_unstable(struct clocksource *cs) { }
|
|
static inline void clocksource_watchdog_lock(unsigned long *flags) { }
|
static inline void clocksource_watchdog_unlock(unsigned long *flags) { }
|
|
#endif /* CONFIG_CLOCKSOURCE_WATCHDOG */
|
|
static bool clocksource_is_suspend(struct clocksource *cs)
|
{
|
return cs == suspend_clocksource;
|
}
|
|
static void __clocksource_suspend_select(struct clocksource *cs)
|
{
|
/*
|
* Skip the clocksource which will be stopped in suspend state.
|
*/
|
if (!(cs->flags & CLOCK_SOURCE_SUSPEND_NONSTOP))
|
return;
|
|
/*
|
* The nonstop clocksource can be selected as the suspend clocksource to
|
* calculate the suspend time, so it should not supply suspend/resume
|
* interfaces to suspend the nonstop clocksource when system suspends.
|
*/
|
if (cs->suspend || cs->resume) {
|
pr_warn("Nonstop clocksource %s should not supply suspend/resume interfaces\n",
|
cs->name);
|
}
|
|
/* Pick the best rating. */
|
if (!suspend_clocksource || cs->rating > suspend_clocksource->rating)
|
suspend_clocksource = cs;
|
}
|
|
/**
|
* clocksource_suspend_select - Select the best clocksource for suspend timing
|
* @fallback: if select a fallback clocksource
|
*/
|
static void clocksource_suspend_select(bool fallback)
|
{
|
struct clocksource *cs, *old_suspend;
|
|
old_suspend = suspend_clocksource;
|
if (fallback)
|
suspend_clocksource = NULL;
|
|
list_for_each_entry(cs, &clocksource_list, list) {
|
/* Skip current if we were requested for a fallback. */
|
if (fallback && cs == old_suspend)
|
continue;
|
|
__clocksource_suspend_select(cs);
|
}
|
}
|
|
/**
|
* clocksource_start_suspend_timing - Start measuring the suspend timing
|
* @cs: current clocksource from timekeeping
|
* @start_cycles: current cycles from timekeeping
|
*
|
* This function will save the start cycle values of suspend timer to calculate
|
* the suspend time when resuming system.
|
*
|
* This function is called late in the suspend process from timekeeping_suspend(),
|
* that means processes are 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;
|
|
clocksource_arch_init(cs);
|
|
if (cs->vdso_clock_mode < 0 ||
|
cs->vdso_clock_mode >= VDSO_CLOCKMODE_MAX) {
|
pr_warn("clocksource %s registered with invalid VDSO mode %d. Disabling VDSO support.\n",
|
cs->name, cs->vdso_clock_mode);
|
cs->vdso_clock_mode = VDSO_CLOCKMODE_NONE;
|
}
|
|
/* Initialize mult/shift and max_idle_ns */
|
__clocksource_update_freq_scale(cs, scale, freq);
|
|
/* Add clocksource to the clocksource list */
|
mutex_lock(&clocksource_mutex);
|
|
clocksource_watchdog_lock(&flags);
|
clocksource_enqueue(cs);
|
clocksource_enqueue_watchdog(cs);
|
clocksource_watchdog_unlock(&flags);
|
|
clocksource_select();
|
clocksource_select_watchdog(false);
|
__clocksource_suspend_select(cs);
|
mutex_unlock(&clocksource_mutex);
|
return 0;
|
}
|
EXPORT_SYMBOL_GPL(__clocksource_register_scale);
|
|
static void __clocksource_change_rating(struct clocksource *cs, int rating)
|
{
|
list_del(&cs->list);
|
cs->rating = rating;
|
clocksource_enqueue(cs);
|
}
|
|
/**
|
* clocksource_change_rating - Change the rating of a registered clocksource
|
* @cs: clocksource to be changed
|
* @rating: new rating
|
*/
|
void clocksource_change_rating(struct clocksource *cs, int rating)
|
{
|
unsigned long flags;
|
|
mutex_lock(&clocksource_mutex);
|
clocksource_watchdog_lock(&flags);
|
__clocksource_change_rating(cs, rating);
|
clocksource_watchdog_unlock(&flags);
|
|
clocksource_select();
|
clocksource_select_watchdog(false);
|
clocksource_suspend_select(false);
|
mutex_unlock(&clocksource_mutex);
|
}
|
EXPORT_SYMBOL(clocksource_change_rating);
|
|
/*
|
* Unbind clocksource @cs. Called with clocksource_mutex held
|
*/
|
static int clocksource_unbind(struct clocksource *cs)
|
{
|
unsigned long flags;
|
|
if (clocksource_is_watchdog(cs)) {
|
/* Select and try to install a replacement watchdog. */
|
clocksource_select_watchdog(true);
|
if (clocksource_is_watchdog(cs))
|
return -EBUSY;
|
}
|
|
if (cs == curr_clocksource) {
|
/* Select and try to install a replacement clock source */
|
clocksource_select_fallback();
|
if (curr_clocksource == cs)
|
return -EBUSY;
|
}
|
|
if (clocksource_is_suspend(cs)) {
|
/*
|
* Select and try to install a replacement suspend clocksource.
|
* If no replacement suspend clocksource, we will just let the
|
* clocksource go and have no suspend clocksource.
|
*/
|
clocksource_suspend_select(true);
|
}
|
|
clocksource_watchdog_lock(&flags);
|
clocksource_dequeue_watchdog(cs);
|
list_del_init(&cs->list);
|
clocksource_watchdog_unlock(&flags);
|
|
return 0;
|
}
|
|
/**
|
* clocksource_unregister - remove a registered clocksource
|
* @cs: clocksource to be unregistered
|
*/
|
int clocksource_unregister(struct clocksource *cs)
|
{
|
int ret = 0;
|
|
mutex_lock(&clocksource_mutex);
|
if (!list_empty(&cs->list))
|
ret = clocksource_unbind(cs);
|
mutex_unlock(&clocksource_mutex);
|
return ret;
|
}
|
EXPORT_SYMBOL(clocksource_unregister);
|
|
#ifdef CONFIG_SYSFS
|
/**
|
* current_clocksource_show - sysfs interface for current clocksource
|
* @dev: unused
|
* @attr: unused
|
* @buf: char buffer to be filled with clocksource list
|
*
|
* Provides sysfs interface for listing current clocksource.
|
*/
|
static ssize_t current_clocksource_show(struct device *dev,
|
struct device_attribute *attr,
|
char *buf)
|
{
|
ssize_t count = 0;
|
|
mutex_lock(&clocksource_mutex);
|
count = snprintf(buf, PAGE_SIZE, "%s\n", curr_clocksource->name);
|
mutex_unlock(&clocksource_mutex);
|
|
return count;
|
}
|
|
ssize_t sysfs_get_uname(const char *buf, char *dst, size_t cnt)
|
{
|
size_t ret = cnt;
|
|
/* strings from sysfs write are not 0 terminated! */
|
if (!cnt || cnt >= CS_NAME_LEN)
|
return -EINVAL;
|
|
/* strip of \n: */
|
if (buf[cnt-1] == '\n')
|
cnt--;
|
if (cnt > 0)
|
memcpy(dst, buf, cnt);
|
dst[cnt] = 0;
|
return ret;
|
}
|
|
/**
|
* current_clocksource_store - interface for manually overriding clocksource
|
* @dev: unused
|
* @attr: unused
|
* @buf: name of override clocksource
|
* @count: length of buffer
|
*
|
* Takes input from sysfs interface for manually overriding the default
|
* clocksource selection.
|
*/
|
static ssize_t current_clocksource_store(struct device *dev,
|
struct device_attribute *attr,
|
const char *buf, size_t count)
|
{
|
ssize_t ret;
|
|
mutex_lock(&clocksource_mutex);
|
|
ret = sysfs_get_uname(buf, override_name, count);
|
if (ret >= 0)
|
clocksource_select();
|
|
mutex_unlock(&clocksource_mutex);
|
|
return ret;
|
}
|
static DEVICE_ATTR_RW(current_clocksource);
|
|
/**
|
* unbind_clocksource_store - interface for manually unbinding clocksource
|
* @dev: unused
|
* @attr: unused
|
* @buf: unused
|
* @count: length of buffer
|
*
|
* Takes input from sysfs interface for manually unbinding a clocksource.
|
*/
|
static ssize_t unbind_clocksource_store(struct device *dev,
|
struct device_attribute *attr,
|
const char *buf, size_t count)
|
{
|
struct clocksource *cs;
|
char name[CS_NAME_LEN];
|
ssize_t ret;
|
|
ret = sysfs_get_uname(buf, name, count);
|
if (ret < 0)
|
return ret;
|
|
ret = -ENODEV;
|
mutex_lock(&clocksource_mutex);
|
list_for_each_entry(cs, &clocksource_list, list) {
|
if (strcmp(cs->name, name))
|
continue;
|
ret = clocksource_unbind(cs);
|
break;
|
}
|
mutex_unlock(&clocksource_mutex);
|
|
return ret ? ret : count;
|
}
|
static DEVICE_ATTR_WO(unbind_clocksource);
|
|
/**
|
* available_clocksource_show - sysfs interface for listing clocksource
|
* @dev: unused
|
* @attr: unused
|
* @buf: char buffer to be filled with clocksource list
|
*
|
* Provides sysfs interface for listing registered clocksources
|
*/
|
static ssize_t available_clocksource_show(struct device *dev,
|
struct device_attribute *attr,
|
char *buf)
|
{
|
struct clocksource *src;
|
ssize_t count = 0;
|
|
mutex_lock(&clocksource_mutex);
|
list_for_each_entry(src, &clocksource_list, list) {
|
/*
|
* Don't show non-HRES clocksource if the tick code is
|
* in one shot mode (highres=on or nohz=on)
|
*/
|
if (!tick_oneshot_mode_active() ||
|
(src->flags & CLOCK_SOURCE_VALID_FOR_HRES))
|
count += snprintf(buf + count,
|
max((ssize_t)PAGE_SIZE - count, (ssize_t)0),
|
"%s ", src->name);
|
}
|
mutex_unlock(&clocksource_mutex);
|
|
count += snprintf(buf + count,
|
max((ssize_t)PAGE_SIZE - count, (ssize_t)0), "\n");
|
|
return count;
|
}
|
static DEVICE_ATTR_RO(available_clocksource);
|
|
static struct attribute *clocksource_attrs[] = {
|
&dev_attr_current_clocksource.attr,
|
&dev_attr_unbind_clocksource.attr,
|
&dev_attr_available_clocksource.attr,
|
NULL
|
};
|
ATTRIBUTE_GROUPS(clocksource);
|
|
static struct bus_type clocksource_subsys = {
|
.name = "clocksource",
|
.dev_name = "clocksource",
|
};
|
|
static struct device device_clocksource = {
|
.id = 0,
|
.bus = &clocksource_subsys,
|
.groups = clocksource_groups,
|
};
|
|
static int __init init_clocksource_sysfs(void)
|
{
|
int error = subsys_system_register(&clocksource_subsys, NULL);
|
|
if (!error)
|
error = device_register(&device_clocksource);
|
|
return error;
|
}
|
|
device_initcall(init_clocksource_sysfs);
|
#endif /* CONFIG_SYSFS */
|
|
/**
|
* boot_override_clocksource - boot clock override
|
* @str: override name
|
*
|
* Takes a clocksource= boot argument and uses it
|
* as the clocksource override name.
|
*/
|
static int __init boot_override_clocksource(char* str)
|
{
|
mutex_lock(&clocksource_mutex);
|
if (str)
|
strlcpy(override_name, str, sizeof(override_name));
|
mutex_unlock(&clocksource_mutex);
|
return 1;
|
}
|
|
__setup("clocksource=", boot_override_clocksource);
|
|
/**
|
* boot_override_clock - Compatibility layer for deprecated boot option
|
* @str: override name
|
*
|
* DEPRECATED! Takes a clock= boot argument and uses it
|
* as the clocksource override name
|
*/
|
static int __init boot_override_clock(char* str)
|
{
|
if (!strcmp(str, "pmtmr")) {
|
pr_warn("clock=pmtmr is deprecated - use clocksource=acpi_pm\n");
|
return boot_override_clocksource("acpi_pm");
|
}
|
pr_warn("clock= boot option is deprecated - use clocksource=xyz\n");
|
return boot_override_clocksource(str);
|
}
|
|
__setup("clock=", boot_override_clock);
|
