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1477 lines
41 KiB
1477 lines
41 KiB
// 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 ([email protected]) |
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*/ |
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|
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#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt |
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|
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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 <linux/prandom.h> |
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#include <linux/cpu.h> |
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|
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#include "tick-internal.h" |
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#include "timekeeping_internal.h" |
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|
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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 choosing 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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/* |
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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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/* |
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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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|
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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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|
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/* |
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* Threshold: 0.0312s, when doubled: 0.0625s. |
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* Also a default for cs->uncertainty_margin when registering clocks. |
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*/ |
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#define WATCHDOG_THRESHOLD (NSEC_PER_SEC >> 5) |
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|
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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. Used as |
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* a lower bound for cs->uncertainty_margin values when registering clocks. |
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*/ |
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#ifdef CONFIG_CLOCKSOURCE_WATCHDOG_MAX_SKEW_US |
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#define MAX_SKEW_USEC CONFIG_CLOCKSOURCE_WATCHDOG_MAX_SKEW_US |
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#else |
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#define MAX_SKEW_USEC 100 |
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#endif |
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|
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#define WATCHDOG_MAX_SKEW (MAX_SKEW_USEC * NSEC_PER_USEC) |
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|
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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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|
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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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|
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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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|
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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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|
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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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/* |
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* Interval: 0.5sec. |
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*/ |
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#define WATCHDOG_INTERVAL (HZ >> 1) |
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|
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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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|
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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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/* |
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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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|
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if (cs->mark_unstable) |
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cs->mark_unstable(cs); |
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|
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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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/** |
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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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|
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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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ulong max_cswd_read_retries = 2; |
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module_param(max_cswd_read_retries, ulong, 0644); |
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EXPORT_SYMBOL_GPL(max_cswd_read_retries); |
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static int verify_n_cpus = 8; |
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module_param(verify_n_cpus, int, 0644); |
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|
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enum wd_read_status { |
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WD_READ_SUCCESS, |
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WD_READ_UNSTABLE, |
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WD_READ_SKIP |
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}; |
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static enum wd_read_status 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_end2, wd_delta; |
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int64_t wd_delay, wd_seq_delay; |
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|
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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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wd_end2 = watchdog->read(watchdog); |
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local_irq_enable(); |
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|
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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 WD_READ_SUCCESS; |
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} |
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|
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/* |
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* Now compute delay in consecutive watchdog read to see if |
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* there is too much external interferences that cause |
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* significant delay in reading both clocksource and watchdog. |
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* |
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* If consecutive WD read-back delay > WATCHDOG_MAX_SKEW/2, |
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* report system busy, reinit the watchdog and skip the current |
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* watchdog test. |
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*/ |
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wd_delta = clocksource_delta(wd_end2, wd_end, watchdog->mask); |
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wd_seq_delay = clocksource_cyc2ns(wd_delta, watchdog->mult, watchdog->shift); |
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if (wd_seq_delay > WATCHDOG_MAX_SKEW/2) |
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goto skip_test; |
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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 WD_READ_UNSTABLE; |
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|
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skip_test: |
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pr_info("timekeeping watchdog on CPU%d: %s wd-wd read-back delay of %lldns\n", |
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smp_processor_id(), watchdog->name, wd_seq_delay); |
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pr_info("wd-%s-wd read-back delay of %lldns, clock-skew test skipped!\n", |
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cs->name, wd_delay); |
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return WD_READ_SKIP; |
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} |
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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 cpumask_t cpus_chosen; |
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|
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static void clocksource_verify_choose_cpus(void) |
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{ |
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int cpu, i, n = verify_n_cpus; |
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|
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if (n < 0) { |
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/* Check all of the CPUs. */ |
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cpumask_copy(&cpus_chosen, cpu_online_mask); |
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cpumask_clear_cpu(smp_processor_id(), &cpus_chosen); |
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return; |
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} |
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|
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/* If no checking desired, or no other CPU to check, leave. */ |
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cpumask_clear(&cpus_chosen); |
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if (n == 0 || num_online_cpus() <= 1) |
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return; |
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|
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/* Make sure to select at least one CPU other than the current CPU. */ |
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cpu = cpumask_first(cpu_online_mask); |
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if (cpu == smp_processor_id()) |
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cpu = cpumask_next(cpu, cpu_online_mask); |
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if (WARN_ON_ONCE(cpu >= nr_cpu_ids)) |
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return; |
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cpumask_set_cpu(cpu, &cpus_chosen); |
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|
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/* Force a sane value for the boot parameter. */ |
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if (n > nr_cpu_ids) |
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n = nr_cpu_ids; |
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|
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/* |
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* Randomly select the specified number of CPUs. If the same |
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* CPU is selected multiple times, that CPU is checked only once, |
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* and no replacement CPU is selected. This gracefully handles |
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* situations where verify_n_cpus is greater than the number of |
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* CPUs that are currently online. |
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*/ |
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for (i = 1; i < n; i++) { |
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cpu = prandom_u32_max(nr_cpu_ids); |
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cpu = cpumask_next(cpu - 1, cpu_online_mask); |
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if (cpu >= nr_cpu_ids) |
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cpu = cpumask_first(cpu_online_mask); |
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if (!WARN_ON_ONCE(cpu >= nr_cpu_ids)) |
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cpumask_set_cpu(cpu, &cpus_chosen); |
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} |
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|
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/* Don't verify ourselves. */ |
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cpumask_clear_cpu(smp_processor_id(), &cpus_chosen); |
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} |
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|
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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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|
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csnow_mid = cs->read(cs); |
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} |
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|
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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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|
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if (verify_n_cpus == 0) |
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return; |
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cpumask_clear(&cpus_ahead); |
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cpumask_clear(&cpus_behind); |
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cpus_read_lock(); |
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preempt_disable(); |
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clocksource_verify_choose_cpus(); |
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if (cpumask_empty(&cpus_chosen)) { |
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preempt_enable(); |
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cpus_read_unlock(); |
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pr_warn("Not enough CPUs to check clocksource '%s'.\n", cs->name); |
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return; |
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} |
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testcpu = smp_processor_id(); |
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pr_warn("Checking clocksource %s synchronization from CPU %d to CPUs %*pbl.\n", cs->name, testcpu, cpumask_pr_args(&cpus_chosen)); |
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for_each_cpu(cpu, &cpus_chosen) { |
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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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cpus_read_unlock(); |
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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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EXPORT_SYMBOL_GPL(clocksource_verify_percpu); |
|
|
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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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enum wd_read_status read_ret; |
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u32 md; |
|
|
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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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|
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reset_pending = atomic_read(&watchdog_reset_pending); |
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|
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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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|
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read_ret = cs_watchdog_read(cs, &csnow, &wdnow); |
|
|
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if (read_ret != WD_READ_SUCCESS) { |
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if (read_ret == WD_READ_UNSTABLE) |
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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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md = cs->uncertainty_margin + watchdog->uncertainty_margin; |
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if (abs(cs_nsec - wd_nsec) > md) { |
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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_nsec: %lld wd_now: %llx wd_last: %llx mask: %llx\n", |
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watchdog->name, wd_nsec, wdnow, wdlast, watchdog->mask); |
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pr_warn(" '%s' cs_nsec: %lld cs_now: %llx cs_last: %llx mask: %llx\n", |
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cs->name, cs_nsec, csnow, cslast, cs->mask); |
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if (curr_clocksource == cs) |
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pr_warn(" '%s' is current clocksource.\n", cs->name); |
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else if (curr_clocksource) |
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pr_warn(" '%s' (not '%s') is current clocksource.\n", curr_clocksource->name, cs->name); |
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else |
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pr_warn(" No current clocksource.\n"); |
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__clocksource_unstable(cs); |
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continue; |
|
} |
|
|
|
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. |
|
*/ |
|
if (!finished_booting) |
|
continue; |
|
|
|
/* |
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* If this is not the current clocksource let |
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* the watchdog thread reselect it. Due to the |
|
* change to high res this clocksource might |
|
* 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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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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/* |
|
* We only clear the watchdog_reset_pending, when we did a |
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* full cycle through all clocksources. |
|
*/ |
|
if (reset_pending) |
|
atomic_dec(&watchdog_reset_pending); |
|
|
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/* |
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* 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) |
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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); |
|
} |
|
|
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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; |
|
|
|
/* Do any required per-CPU skew verification. */ |
|
if (curr_clocksource && |
|
curr_clocksource->flags & CLOCK_SOURCE_UNSTABLE && |
|
curr_clocksource->flags & CLOCK_SOURCE_VERIFY_PERCPU) |
|
clocksource_verify_percpu(curr_clocksource); |
|
|
|
spin_lock_irqsave(&watchdog_lock, flags); |
|
list_for_each_entry_safe(cs, tmp, &watchdog_list, wd_list) { |
|
if (cs->flags & CLOCK_SOURCE_UNSTABLE) { |
|
list_del_init(&cs->wd_list); |
|
__clocksource_change_rating(cs, 0); |
|
select = 1; |
|
} |
|
if (cs->flags & CLOCK_SOURCE_RESELECT) { |
|
cs->flags &= ~CLOCK_SOURCE_RESELECT; |
|
select = 1; |
|
} |
|
} |
|
/* Check if the watchdog timer needs to be stopped. */ |
|
clocksource_stop_watchdog(); |
|
spin_unlock_irqrestore(&watchdog_lock, flags); |
|
|
|
return select; |
|
} |
|
|
|
static int clocksource_watchdog_kthread(void *data) |
|
{ |
|
mutex_lock(&clocksource_mutex); |
|
if (__clocksource_watchdog_kthread()) |
|
clocksource_select(); |
|
mutex_unlock(&clocksource_mutex); |
|
return 0; |
|
} |
|
|
|
static bool clocksource_is_watchdog(struct clocksource *cs) |
|
{ |
|
return cs == watchdog; |
|
} |
|
|
|
#else /* CONFIG_CLOCKSOURCE_WATCHDOG */ |
|
|
|
static void clocksource_enqueue_watchdog(struct clocksource *cs) |
|
{ |
|
if (cs->flags & CLOCK_SOURCE_IS_CONTINUOUS) |
|
cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES; |
|
} |
|
|
|
static void clocksource_select_watchdog(bool fallback) { } |
|
static inline void clocksource_dequeue_watchdog(struct clocksource *cs) { } |
|
static inline void clocksource_resume_watchdog(void) { } |
|
static inline int __clocksource_watchdog_kthread(void) { return 0; } |
|
static bool clocksource_is_watchdog(struct clocksource *cs) { return false; } |
|
void clocksource_mark_unstable(struct clocksource *cs) { } |
|
|
|
static inline void clocksource_watchdog_lock(unsigned long *flags) { } |
|
static inline void clocksource_watchdog_unlock(unsigned long *flags) { } |
|
|
|
#endif /* CONFIG_CLOCKSOURCE_WATCHDOG */ |
|
|
|
static bool clocksource_is_suspend(struct clocksource *cs) |
|
{ |
|
return cs == suspend_clocksource; |
|
} |
|
|
|
static void __clocksource_suspend_select(struct clocksource *cs) |
|
{ |
|
/* |
|
* Skip the clocksource which will be stopped in suspend state. |
|
*/ |
|
if (!(cs->flags & CLOCK_SOURCE_SUSPEND_NONSTOP)) |
|
return; |
|
|
|
/* |
|
* The nonstop clocksource can be selected as the suspend clocksource to |
|
* calculate the suspend time, so it should not supply suspend/resume |
|
* interfaces to suspend the nonstop clocksource when system suspends. |
|
*/ |
|
if (cs->suspend || cs->resume) { |
|
pr_warn("Nonstop clocksource %s should not supply suspend/resume interfaces\n", |
|
cs->name); |
|
} |
|
|
|
/* Pick the best rating. */ |
|
if (!suspend_clocksource || cs->rating > suspend_clocksource->rating) |
|
suspend_clocksource = cs; |
|
} |
|
|
|
/** |
|
* clocksource_suspend_select - Select the best clocksource for suspend timing |
|
* @fallback: if select a fallback clocksource |
|
*/ |
|
static void clocksource_suspend_select(bool fallback) |
|
{ |
|
struct clocksource *cs, *old_suspend; |
|
|
|
old_suspend = suspend_clocksource; |
|
if (fallback) |
|
suspend_clocksource = NULL; |
|
|
|
list_for_each_entry(cs, &clocksource_list, list) { |
|
/* Skip current if we were requested for a fallback. */ |
|
if (fallback && cs == old_suspend) |
|
continue; |
|
|
|
__clocksource_suspend_select(cs); |
|
} |
|
} |
|
|
|
/** |
|
* clocksource_start_suspend_timing - Start measuring the suspend timing |
|
* @cs: current clocksource from timekeeping |
|
* @start_cycles: current cycles from timekeeping |
|
* |
|
* This function will save the start cycle values of suspend timer to calculate |
|
* the suspend time when resuming system. |
|
* |
|
* This function is called late in the suspend process from timekeeping_suspend(), |
|
* that means processes are frozen, non-boot cpus and interrupts are disabled |
|
* now. It is therefore possible to start the suspend timer without taking the |
|
* clocksource mutex. |
|
*/ |
|
void clocksource_start_suspend_timing(struct clocksource *cs, u64 start_cycles) |
|
{ |
|
if (!suspend_clocksource) |
|
return; |
|
|
|
/* |
|
* If current clocksource is the suspend timer, we should use the |
|
* tkr_mono.cycle_last value as suspend_start to avoid same reading |
|
* from suspend timer. |
|
*/ |
|
if (clocksource_is_suspend(cs)) { |
|
suspend_start = start_cycles; |
|
return; |
|
} |
|
|
|
if (suspend_clocksource->enable && |
|
suspend_clocksource->enable(suspend_clocksource)) { |
|
pr_warn_once("Failed to enable the non-suspend-able clocksource.\n"); |
|
return; |
|
} |
|
|
|
suspend_start = suspend_clocksource->read(suspend_clocksource); |
|
} |
|
|
|
/** |
|
* clocksource_stop_suspend_timing - Stop measuring the suspend timing |
|
* @cs: current clocksource from timekeeping |
|
* @cycle_now: current cycles from timekeeping |
|
* |
|
* This function will calculate the suspend time from suspend timer. |
|
* |
|
* Returns nanoseconds since suspend started, 0 if no usable suspend clocksource. |
|
* |
|
* This function is called early in the resume process from timekeeping_resume(), |
|
* that means there is only one cpu, no processes are running and the interrupts |
|
* are disabled. It is therefore possible to stop the suspend timer without |
|
* taking the clocksource mutex. |
|
*/ |
|
u64 clocksource_stop_suspend_timing(struct clocksource *cs, u64 cycle_now) |
|
{ |
|
u64 now, delta, nsec = 0; |
|
|
|
if (!suspend_clocksource) |
|
return 0; |
|
|
|
/* |
|
* If current clocksource is the suspend timer, we should use the |
|
* tkr_mono.cycle_last value from timekeeping as current cycle to |
|
* avoid same reading from suspend timer. |
|
*/ |
|
if (clocksource_is_suspend(cs)) |
|
now = cycle_now; |
|
else |
|
now = suspend_clocksource->read(suspend_clocksource); |
|
|
|
if (now > suspend_start) { |
|
delta = clocksource_delta(now, suspend_start, |
|
suspend_clocksource->mask); |
|
nsec = mul_u64_u32_shr(delta, suspend_clocksource->mult, |
|
suspend_clocksource->shift); |
|
} |
|
|
|
/* |
|
* Disable the suspend timer to save power if current clocksource is |
|
* not the suspend timer. |
|
*/ |
|
if (!clocksource_is_suspend(cs) && suspend_clocksource->disable) |
|
suspend_clocksource->disable(suspend_clocksource); |
|
|
|
return nsec; |
|
} |
|
|
|
/** |
|
* clocksource_suspend - suspend the clocksource(s) |
|
*/ |
|
void clocksource_suspend(void) |
|
{ |
|
struct clocksource *cs; |
|
|
|
list_for_each_entry_reverse(cs, &clocksource_list, list) |
|
if (cs->suspend) |
|
cs->suspend(cs); |
|
} |
|
|
|
/** |
|
* clocksource_resume - resume the clocksource(s) |
|
*/ |
|
void clocksource_resume(void) |
|
{ |
|
struct clocksource *cs; |
|
|
|
list_for_each_entry(cs, &clocksource_list, list) |
|
if (cs->resume) |
|
cs->resume(cs); |
|
|
|
clocksource_resume_watchdog(); |
|
} |
|
|
|
/** |
|
* clocksource_touch_watchdog - Update watchdog |
|
* |
|
* Update the watchdog after exception contexts such as kgdb so as not |
|
* to incorrectly trip the watchdog. This might fail when the kernel |
|
* was stopped in code which holds watchdog_lock. |
|
*/ |
|
void clocksource_touch_watchdog(void) |
|
{ |
|
clocksource_resume_watchdog(); |
|
} |
|
|
|
/** |
|
* clocksource_max_adjustment- Returns max adjustment amount |
|
* @cs: Pointer to clocksource |
|
* |
|
*/ |
|
static u32 clocksource_max_adjustment(struct clocksource *cs) |
|
{ |
|
u64 ret; |
|
/* |
|
* We won't try to correct for more than 11% adjustments (110,000 ppm), |
|
*/ |
|
ret = (u64)cs->mult * 11; |
|
do_div(ret,100); |
|
return (u32)ret; |
|
} |
|
|
|
/** |
|
* clocks_calc_max_nsecs - Returns maximum nanoseconds that can be converted |
|
* @mult: cycle to nanosecond multiplier |
|
* @shift: cycle to nanosecond divisor (power of two) |
|
* @maxadj: maximum adjustment value to mult (~11%) |
|
* @mask: bitmask for two's complement subtraction of non 64 bit counters |
|
* @max_cyc: maximum cycle value before potential overflow (does not include |
|
* any safety margin) |
|
* |
|
* NOTE: This function includes a safety margin of 50%, in other words, we |
|
* return half the number of nanoseconds the hardware counter can technically |
|
* cover. This is done so that we can potentially detect problems caused by |
|
* delayed timers or bad hardware, which might result in time intervals that |
|
* are larger than what the math used can handle without overflows. |
|
*/ |
|
u64 clocks_calc_max_nsecs(u32 mult, u32 shift, u32 maxadj, u64 mask, u64 *max_cyc) |
|
{ |
|
u64 max_nsecs, max_cycles; |
|
|
|
/* |
|
* Calculate the maximum number of cycles that we can pass to the |
|
* cyc2ns() function without overflowing a 64-bit result. |
|
*/ |
|
max_cycles = ULLONG_MAX; |
|
do_div(max_cycles, mult+maxadj); |
|
|
|
/* |
|
* The actual maximum number of cycles we can defer the clocksource is |
|
* determined by the minimum of max_cycles and mask. |
|
* Note: Here we subtract the maxadj to make sure we don't sleep for |
|
* too long if there's a large negative adjustment. |
|
*/ |
|
max_cycles = min(max_cycles, mask); |
|
max_nsecs = clocksource_cyc2ns(max_cycles, mult - maxadj, shift); |
|
|
|
/* return the max_cycles value as well if requested */ |
|
if (max_cyc) |
|
*max_cyc = max_cycles; |
|
|
|
/* Return 50% of the actual maximum, so we can detect bad values */ |
|
max_nsecs >>= 1; |
|
|
|
return max_nsecs; |
|
} |
|
|
|
/** |
|
* clocksource_update_max_deferment - Updates the clocksource max_idle_ns & max_cycles |
|
* @cs: Pointer to clocksource to be updated |
|
* |
|
*/ |
|
static inline void clocksource_update_max_deferment(struct clocksource *cs) |
|
{ |
|
cs->max_idle_ns = clocks_calc_max_nsecs(cs->mult, cs->shift, |
|
cs->maxadj, cs->mask, |
|
&cs->max_cycles); |
|
} |
|
|
|
static struct clocksource *clocksource_find_best(bool oneshot, bool skipcur) |
|
{ |
|
struct clocksource *cs; |
|
|
|
if (!finished_booting || list_empty(&clocksource_list)) |
|
return NULL; |
|
|
|
/* |
|
* We pick the clocksource with the highest rating. If oneshot |
|
* mode is active, we pick the highres valid clocksource with |
|
* the best rating. |
|
*/ |
|
list_for_each_entry(cs, &clocksource_list, list) { |
|
if (skipcur && cs == curr_clocksource) |
|
continue; |
|
if (oneshot && !(cs->flags & CLOCK_SOURCE_VALID_FOR_HRES)) |
|
continue; |
|
return cs; |
|
} |
|
return NULL; |
|
} |
|
|
|
static void __clocksource_select(bool skipcur) |
|
{ |
|
bool oneshot = tick_oneshot_mode_active(); |
|
struct clocksource *best, *cs; |
|
|
|
/* Find the best suitable clocksource */ |
|
best = clocksource_find_best(oneshot, skipcur); |
|
if (!best) |
|
return; |
|
|
|
if (!strlen(override_name)) |
|
goto found; |
|
|
|
/* Check for the override clocksource. */ |
|
list_for_each_entry(cs, &clocksource_list, list) { |
|
if (skipcur && cs == curr_clocksource) |
|
continue; |
|
if (strcmp(cs->name, override_name) != 0) |
|
continue; |
|
/* |
|
* Check to make sure we don't switch to a non-highres |
|
* capable clocksource if the tick code is in oneshot |
|
* mode (highres or nohz) |
|
*/ |
|
if (!(cs->flags & CLOCK_SOURCE_VALID_FOR_HRES) && oneshot) { |
|
/* Override clocksource cannot be used. */ |
|
if (cs->flags & CLOCK_SOURCE_UNSTABLE) { |
|
pr_warn("Override clocksource %s is unstable and not HRT compatible - cannot switch while in HRT/NOHZ mode\n", |
|
cs->name); |
|
override_name[0] = 0; |
|
} else { |
|
/* |
|
* The override cannot be currently verified. |
|
* Deferring to let the watchdog check. |
|
*/ |
|
pr_info("Override clocksource %s is not currently HRT compatible - deferring\n", |
|
cs->name); |
|
} |
|
} else |
|
/* Override clocksource can be used. */ |
|
best = cs; |
|
break; |
|
} |
|
|
|
found: |
|
if (curr_clocksource != best && !timekeeping_notify(best)) { |
|
pr_info("Switched to clocksource %s\n", best->name); |
|
curr_clocksource = best; |
|
} |
|
} |
|
|
|
/** |
|
* clocksource_select - Select the best clocksource available |
|
* |
|
* Private function. Must hold clocksource_mutex when called. |
|
* |
|
* Select the clocksource with the best rating, or the clocksource, |
|
* which is selected by userspace override. |
|
*/ |
|
static void clocksource_select(void) |
|
{ |
|
__clocksource_select(false); |
|
} |
|
|
|
static void clocksource_select_fallback(void) |
|
{ |
|
__clocksource_select(true); |
|
} |
|
|
|
/* |
|
* clocksource_done_booting - Called near the end of core bootup |
|
* |
|
* Hack to avoid lots of clocksource churn at boot time. |
|
* We use fs_initcall because we want this to start before |
|
* device_initcall but after subsys_initcall. |
|
*/ |
|
static int __init clocksource_done_booting(void) |
|
{ |
|
mutex_lock(&clocksource_mutex); |
|
curr_clocksource = clocksource_default_clock(); |
|
finished_booting = 1; |
|
/* |
|
* Run the watchdog first to eliminate unstable clock sources |
|
*/ |
|
__clocksource_watchdog_kthread(); |
|
clocksource_select(); |
|
mutex_unlock(&clocksource_mutex); |
|
return 0; |
|
} |
|
fs_initcall(clocksource_done_booting); |
|
|
|
/* |
|
* Enqueue the clocksource sorted by rating |
|
*/ |
|
static void clocksource_enqueue(struct clocksource *cs) |
|
{ |
|
struct list_head *entry = &clocksource_list; |
|
struct clocksource *tmp; |
|
|
|
list_for_each_entry(tmp, &clocksource_list, list) { |
|
/* Keep track of the place, where to insert */ |
|
if (tmp->rating < cs->rating) |
|
break; |
|
entry = &tmp->list; |
|
} |
|
list_add(&cs->list, entry); |
|
} |
|
|
|
/** |
|
* __clocksource_update_freq_scale - Used update clocksource with new freq |
|
* @cs: clocksource to be registered |
|
* @scale: Scale factor multiplied against freq to get clocksource hz |
|
* @freq: clocksource frequency (cycles per second) divided by scale |
|
* |
|
* This should only be called from the clocksource->enable() method. |
|
* |
|
* This *SHOULD NOT* be called directly! Please use the |
|
* __clocksource_update_freq_hz() or __clocksource_update_freq_khz() helper |
|
* functions. |
|
*/ |
|
void __clocksource_update_freq_scale(struct clocksource *cs, u32 scale, u32 freq) |
|
{ |
|
u64 sec; |
|
|
|
/* |
|
* Default clocksources are *special* and self-define their mult/shift. |
|
* But, you're not special, so you should specify a freq value. |
|
*/ |
|
if (freq) { |
|
/* |
|
* Calc the maximum number of seconds which we can run before |
|
* wrapping around. For clocksources which have a mask > 32-bit |
|
* we need to limit the max sleep time to have a good |
|
* conversion precision. 10 minutes is still a reasonable |
|
* amount. That results in a shift value of 24 for a |
|
* clocksource with mask >= 40-bit and f >= 4GHz. That maps to |
|
* ~ 0.06ppm granularity for NTP. |
|
*/ |
|
sec = cs->mask; |
|
do_div(sec, freq); |
|
do_div(sec, scale); |
|
if (!sec) |
|
sec = 1; |
|
else if (sec > 600 && cs->mask > UINT_MAX) |
|
sec = 600; |
|
|
|
clocks_calc_mult_shift(&cs->mult, &cs->shift, freq, |
|
NSEC_PER_SEC / scale, sec * scale); |
|
} |
|
|
|
/* |
|
* If the uncertainty margin is not specified, calculate it. |
|
* If both scale and freq are non-zero, calculate the clock |
|
* period, but bound below at 2*WATCHDOG_MAX_SKEW. However, |
|
* if either of scale or freq is zero, be very conservative and |
|
* take the tens-of-milliseconds WATCHDOG_THRESHOLD value for the |
|
* uncertainty margin. Allow stupidly small uncertainty margins |
|
* to be specified by the caller for testing purposes, but warn |
|
* to discourage production use of this capability. |
|
*/ |
|
if (scale && freq && !cs->uncertainty_margin) { |
|
cs->uncertainty_margin = NSEC_PER_SEC / (scale * freq); |
|
if (cs->uncertainty_margin < 2 * WATCHDOG_MAX_SKEW) |
|
cs->uncertainty_margin = 2 * WATCHDOG_MAX_SKEW; |
|
} else if (!cs->uncertainty_margin) { |
|
cs->uncertainty_margin = WATCHDOG_THRESHOLD; |
|
} |
|
WARN_ON_ONCE(cs->uncertainty_margin < 2 * WATCHDOG_MAX_SKEW); |
|
|
|
/* |
|
* Ensure clocksources that have large 'mult' values don't overflow |
|
* when adjusted. |
|
*/ |
|
cs->maxadj = clocksource_max_adjustment(cs); |
|
while (freq && ((cs->mult + cs->maxadj < cs->mult) |
|
|| (cs->mult - cs->maxadj > cs->mult))) { |
|
cs->mult >>= 1; |
|
cs->shift--; |
|
cs->maxadj = clocksource_max_adjustment(cs); |
|
} |
|
|
|
/* |
|
* Only warn for *special* clocksources that self-define |
|
* their mult/shift values and don't specify a freq. |
|
*/ |
|
WARN_ONCE(cs->mult + cs->maxadj < cs->mult, |
|
"timekeeping: Clocksource %s might overflow on 11%% adjustment\n", |
|
cs->name); |
|
|
|
clocksource_update_max_deferment(cs); |
|
|
|
pr_info("%s: mask: 0x%llx max_cycles: 0x%llx, max_idle_ns: %lld ns\n", |
|
cs->name, cs->mask, cs->max_cycles, cs->max_idle_ns); |
|
} |
|
EXPORT_SYMBOL_GPL(__clocksource_update_freq_scale); |
|
|
|
/** |
|
* __clocksource_register_scale - Used to install new clocksources |
|
* @cs: clocksource to be registered |
|
* @scale: Scale factor multiplied against freq to get clocksource hz |
|
* @freq: clocksource frequency (cycles per second) divided by scale |
|
* |
|
* Returns -EBUSY if registration fails, zero otherwise. |
|
* |
|
* This *SHOULD NOT* be called directly! Please use the |
|
* clocksource_register_hz() or clocksource_register_khz helper functions. |
|
*/ |
|
int __clocksource_register_scale(struct clocksource *cs, u32 scale, u32 freq) |
|
{ |
|
unsigned long flags; |
|
|
|
clocksource_arch_init(cs); |
|
|
|
if (WARN_ON_ONCE((unsigned int)cs->id >= CSID_MAX)) |
|
cs->id = CSID_GENERIC; |
|
if (cs->vdso_clock_mode < 0 || |
|
cs->vdso_clock_mode >= VDSO_CLOCKMODE_MAX) { |
|
pr_warn("clocksource %s registered with invalid VDSO mode %d. Disabling VDSO support.\n", |
|
cs->name, cs->vdso_clock_mode); |
|
cs->vdso_clock_mode = VDSO_CLOCKMODE_NONE; |
|
} |
|
|
|
/* Initialize mult/shift and max_idle_ns */ |
|
__clocksource_update_freq_scale(cs, scale, freq); |
|
|
|
/* Add clocksource to the clocksource list */ |
|
mutex_lock(&clocksource_mutex); |
|
|
|
clocksource_watchdog_lock(&flags); |
|
clocksource_enqueue(cs); |
|
clocksource_enqueue_watchdog(cs); |
|
clocksource_watchdog_unlock(&flags); |
|
|
|
clocksource_select(); |
|
clocksource_select_watchdog(false); |
|
__clocksource_suspend_select(cs); |
|
mutex_unlock(&clocksource_mutex); |
|
return 0; |
|
} |
|
EXPORT_SYMBOL_GPL(__clocksource_register_scale); |
|
|
|
static void __clocksource_change_rating(struct clocksource *cs, int rating) |
|
{ |
|
list_del(&cs->list); |
|
cs->rating = rating; |
|
clocksource_enqueue(cs); |
|
} |
|
|
|
/** |
|
* clocksource_change_rating - Change the rating of a registered clocksource |
|
* @cs: clocksource to be changed |
|
* @rating: new rating |
|
*/ |
|
void clocksource_change_rating(struct clocksource *cs, int rating) |
|
{ |
|
unsigned long flags; |
|
|
|
mutex_lock(&clocksource_mutex); |
|
clocksource_watchdog_lock(&flags); |
|
__clocksource_change_rating(cs, rating); |
|
clocksource_watchdog_unlock(&flags); |
|
|
|
clocksource_select(); |
|
clocksource_select_watchdog(false); |
|
clocksource_suspend_select(false); |
|
mutex_unlock(&clocksource_mutex); |
|
} |
|
EXPORT_SYMBOL(clocksource_change_rating); |
|
|
|
/* |
|
* Unbind clocksource @cs. Called with clocksource_mutex held |
|
*/ |
|
static int clocksource_unbind(struct clocksource *cs) |
|
{ |
|
unsigned long flags; |
|
|
|
if (clocksource_is_watchdog(cs)) { |
|
/* Select and try to install a replacement watchdog. */ |
|
clocksource_select_watchdog(true); |
|
if (clocksource_is_watchdog(cs)) |
|
return -EBUSY; |
|
} |
|
|
|
if (cs == curr_clocksource) { |
|
/* Select and try to install a replacement clock source */ |
|
clocksource_select_fallback(); |
|
if (curr_clocksource == cs) |
|
return -EBUSY; |
|
} |
|
|
|
if (clocksource_is_suspend(cs)) { |
|
/* |
|
* Select and try to install a replacement suspend clocksource. |
|
* If no replacement suspend clocksource, we will just let the |
|
* clocksource go and have no suspend clocksource. |
|
*/ |
|
clocksource_suspend_select(true); |
|
} |
|
|
|
clocksource_watchdog_lock(&flags); |
|
clocksource_dequeue_watchdog(cs); |
|
list_del_init(&cs->list); |
|
clocksource_watchdog_unlock(&flags); |
|
|
|
return 0; |
|
} |
|
|
|
/** |
|
* clocksource_unregister - remove a registered clocksource |
|
* @cs: clocksource to be unregistered |
|
*/ |
|
int clocksource_unregister(struct clocksource *cs) |
|
{ |
|
int ret = 0; |
|
|
|
mutex_lock(&clocksource_mutex); |
|
if (!list_empty(&cs->list)) |
|
ret = clocksource_unbind(cs); |
|
mutex_unlock(&clocksource_mutex); |
|
return ret; |
|
} |
|
EXPORT_SYMBOL(clocksource_unregister); |
|
|
|
#ifdef CONFIG_SYSFS |
|
/** |
|
* current_clocksource_show - sysfs interface for current clocksource |
|
* @dev: unused |
|
* @attr: unused |
|
* @buf: char buffer to be filled with clocksource list |
|
* |
|
* Provides sysfs interface for listing current clocksource. |
|
*/ |
|
static ssize_t current_clocksource_show(struct device *dev, |
|
struct device_attribute *attr, |
|
char *buf) |
|
{ |
|
ssize_t count = 0; |
|
|
|
mutex_lock(&clocksource_mutex); |
|
count = snprintf(buf, PAGE_SIZE, "%s\n", curr_clocksource->name); |
|
mutex_unlock(&clocksource_mutex); |
|
|
|
return count; |
|
} |
|
|
|
ssize_t sysfs_get_uname(const char *buf, char *dst, size_t cnt) |
|
{ |
|
size_t ret = cnt; |
|
|
|
/* strings from sysfs write are not 0 terminated! */ |
|
if (!cnt || cnt >= CS_NAME_LEN) |
|
return -EINVAL; |
|
|
|
/* strip of \n: */ |
|
if (buf[cnt-1] == '\n') |
|
cnt--; |
|
if (cnt > 0) |
|
memcpy(dst, buf, cnt); |
|
dst[cnt] = 0; |
|
return ret; |
|
} |
|
|
|
/** |
|
* current_clocksource_store - interface for manually overriding clocksource |
|
* @dev: unused |
|
* @attr: unused |
|
* @buf: name of override clocksource |
|
* @count: length of buffer |
|
* |
|
* Takes input from sysfs interface for manually overriding the default |
|
* clocksource selection. |
|
*/ |
|
static ssize_t current_clocksource_store(struct device *dev, |
|
struct device_attribute *attr, |
|
const char *buf, size_t count) |
|
{ |
|
ssize_t ret; |
|
|
|
mutex_lock(&clocksource_mutex); |
|
|
|
ret = sysfs_get_uname(buf, override_name, count); |
|
if (ret >= 0) |
|
clocksource_select(); |
|
|
|
mutex_unlock(&clocksource_mutex); |
|
|
|
return ret; |
|
} |
|
static DEVICE_ATTR_RW(current_clocksource); |
|
|
|
/** |
|
* unbind_clocksource_store - interface for manually unbinding clocksource |
|
* @dev: unused |
|
* @attr: unused |
|
* @buf: unused |
|
* @count: length of buffer |
|
* |
|
* Takes input from sysfs interface for manually unbinding a clocksource. |
|
*/ |
|
static ssize_t unbind_clocksource_store(struct device *dev, |
|
struct device_attribute *attr, |
|
const char *buf, size_t count) |
|
{ |
|
struct clocksource *cs; |
|
char name[CS_NAME_LEN]; |
|
ssize_t ret; |
|
|
|
ret = sysfs_get_uname(buf, name, count); |
|
if (ret < 0) |
|
return ret; |
|
|
|
ret = -ENODEV; |
|
mutex_lock(&clocksource_mutex); |
|
list_for_each_entry(cs, &clocksource_list, list) { |
|
if (strcmp(cs->name, name)) |
|
continue; |
|
ret = clocksource_unbind(cs); |
|
break; |
|
} |
|
mutex_unlock(&clocksource_mutex); |
|
|
|
return ret ? ret : count; |
|
} |
|
static DEVICE_ATTR_WO(unbind_clocksource); |
|
|
|
/** |
|
* available_clocksource_show - sysfs interface for listing clocksource |
|
* @dev: unused |
|
* @attr: unused |
|
* @buf: char buffer to be filled with clocksource list |
|
* |
|
* Provides sysfs interface for listing registered clocksources |
|
*/ |
|
static ssize_t available_clocksource_show(struct device *dev, |
|
struct device_attribute *attr, |
|
char *buf) |
|
{ |
|
struct clocksource *src; |
|
ssize_t count = 0; |
|
|
|
mutex_lock(&clocksource_mutex); |
|
list_for_each_entry(src, &clocksource_list, list) { |
|
/* |
|
* Don't show non-HRES clocksource if the tick code is |
|
* in one shot mode (highres=on or nohz=on) |
|
*/ |
|
if (!tick_oneshot_mode_active() || |
|
(src->flags & CLOCK_SOURCE_VALID_FOR_HRES)) |
|
count += snprintf(buf + count, |
|
max((ssize_t)PAGE_SIZE - count, (ssize_t)0), |
|
"%s ", src->name); |
|
} |
|
mutex_unlock(&clocksource_mutex); |
|
|
|
count += snprintf(buf + count, |
|
max((ssize_t)PAGE_SIZE - count, (ssize_t)0), "\n"); |
|
|
|
return count; |
|
} |
|
static DEVICE_ATTR_RO(available_clocksource); |
|
|
|
static struct attribute *clocksource_attrs[] = { |
|
&dev_attr_current_clocksource.attr, |
|
&dev_attr_unbind_clocksource.attr, |
|
&dev_attr_available_clocksource.attr, |
|
NULL |
|
}; |
|
ATTRIBUTE_GROUPS(clocksource); |
|
|
|
static struct bus_type clocksource_subsys = { |
|
.name = "clocksource", |
|
.dev_name = "clocksource", |
|
}; |
|
|
|
static struct device device_clocksource = { |
|
.id = 0, |
|
.bus = &clocksource_subsys, |
|
.groups = clocksource_groups, |
|
}; |
|
|
|
static int __init init_clocksource_sysfs(void) |
|
{ |
|
int error = subsys_system_register(&clocksource_subsys, NULL); |
|
|
|
if (!error) |
|
error = device_register(&device_clocksource); |
|
|
|
return error; |
|
} |
|
|
|
device_initcall(init_clocksource_sysfs); |
|
#endif /* CONFIG_SYSFS */ |
|
|
|
/** |
|
* boot_override_clocksource - boot clock override |
|
* @str: override name |
|
* |
|
* Takes a clocksource= boot argument and uses it |
|
* as the clocksource override name. |
|
*/ |
|
static int __init boot_override_clocksource(char* str) |
|
{ |
|
mutex_lock(&clocksource_mutex); |
|
if (str) |
|
strlcpy(override_name, str, sizeof(override_name)); |
|
mutex_unlock(&clocksource_mutex); |
|
return 1; |
|
} |
|
|
|
__setup("clocksource=", boot_override_clocksource); |
|
|
|
/** |
|
* boot_override_clock - Compatibility layer for deprecated boot option |
|
* @str: override name |
|
* |
|
* DEPRECATED! Takes a clock= boot argument and uses it |
|
* as the clocksource override name |
|
*/ |
|
static int __init boot_override_clock(char* str) |
|
{ |
|
if (!strcmp(str, "pmtmr")) { |
|
pr_warn("clock=pmtmr is deprecated - use clocksource=acpi_pm\n"); |
|
return boot_override_clocksource("acpi_pm"); |
|
} |
|
pr_warn("clock= boot option is deprecated - use clocksource=xyz\n"); |
|
return boot_override_clocksource(str); |
|
} |
|
|
|
__setup("clock=", boot_override_clock);
|
|
|