// SPDX-License-Identifier: GPL-2.0+
/*
* This file contains the functions which manage clocksource drivers.
*
* Copyright (C) 2004, 2005 IBM, John Stultz (johnstul@us.ibm.com)
*/
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/device.h>
#include <linux/clocksource.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/sched.h> /* for spin_unlock_irq() using preempt_count() m68k */
#include <linux/tick.h>
#include <linux/kthread.h>
#include "tick-internal.h"
#include "timekeeping_internal.h"
/**
* clocks_calc_mult_shift - calculate mult/shift factors for scaled math of clocks
* @mult: pointer to mult variable
* @shift: pointer to shift variable
* @from: frequency to convert from
* @to: frequency to convert to
* @maxsec: guaranteed runtime conversion range in seconds
*
* The function evaluates the shift/mult pair for the scaled math
* operations of clocksources and clockevents.
*
* @to and @from are frequency values in HZ. For clock sources @to is
* NSEC_PER_SEC == 1GHz and @from is the counter frequency. For clock
* event @to is the counter frequency and @from is NSEC_PER_SEC.
*
* The @maxsec conversion range argument controls the time frame in
* seconds which must be covered by the runtime conversion with the
* calculated mult and shift factors. This guarantees that no 64bit
* overflow happens when the input value of the conversion is
* multiplied with the calculated mult factor. Larger ranges may
* reduce the conversion accuracy by chosing smaller mult and shift
* factors.
*/
void
clocks_calc_mult_shift(u32 *mult, u32 *shift, u32 from, u32 to, u32 maxsec)
{
u64 tmp;
u32 sft, sftacc= 32;
/*
* Calculate the shift factor which is limiting the conversion
* range:
*/
tmp = ((u64)maxsec * from) >> 32;
while (tmp) {
tmp >>=1;
sftacc--;
}
/*
* Find the conversion shift/mult pair which has the best
* accuracy and fits the maxsec conversion range:
*/
for (sft = 32; sft > 0; sft--) {
tmp = (u64) to << sft;
tmp += from / 2;
do_div(tmp, from);
if ((tmp >> sftacc) == 0)
break;
}
*mult = tmp;
*shift = sft;
}
EXPORT_SYMBOL_GPL(clocks_calc_mult_shift);
/*[Clocksource internal variables]---------
* curr_clocksource:
* currently selected clocksource.
* suspend_clocksource:
* used to calculate the suspend time.
* clocksource_list:
* linked list with the registered clocksources
* clocksource_mutex:
* protects manipulations to curr_clocksource and the clocksource_list
* override_name:
* Name of the user-specified clocksource.
*/
static struct clocksource *curr_clocksource;
static struct clocksource *suspend_clocksource;
static LIST_HEAD(clocksource_list);
static DEFINE_MUTEX(clocksource_mutex);
static char override_name[CS_NAME_LEN];
static int finished_booting;
static u64 suspend_start;
#ifdef [31mCONFIG_CLOCKSOURCE_WATCHDOG[0m
static void clocksource_watchdog_work(struct work_struct *work);
static void clocksource_select(void);
static LIST_HEAD(watchdog_list);
static struct clocksource *watchdog;
static struct timer_list watchdog_timer;
static DECLARE_WORK(watchdog_work, clocksource_watchdog_work);
static DEFINE_SPINLOCK(watchdog_lock);
static int watchdog_running;
static atomic_t watchdog_reset_pending;
static inline void clocksource_watchdog_lock(unsigned long *flags)
{
spin_lock_irqsave(&watchdog_lock, *flags);
}
static inline void clocksource_watchdog_unlock(unsigned long *flags)
{
spin_unlock_irqrestore(&watchdog_lock, *flags);
}
static int clocksource_watchdog_kthread(void *data);
static void __clocksource_change_rating(struct clocksource *cs, int rating);
/*
* Interval: 0.5sec Threshold: 0.0625s
*/
#define WATCHDOG_INTERVAL (HZ >> 1)
#define WATCHDOG_THRESHOLD (NSEC_PER_SEC >> 4)
static void clocksource_watchdog_work(struct work_struct *work)
{
/*
* We cannot directly run clocksource_watchdog_kthread() here, because
* clocksource_select() calls timekeeping_notify() which uses
* stop_machine(). One cannot use stop_machine() from a workqueue() due
* lock inversions wrt CPU hotplug.
*
* Also, we only ever run this work once or twice during the lifetime
* of the kernel, so there is no point in creating a more permanent
* kthread for this.
*
* If kthread_run fails the next watchdog scan over the
* watchdog_list will find the unstable clock again.
*/
kthread_run(clocksource_watchdog_kthread, NULL, "kwatchdog");
}
static void __clocksource_unstable(struct clocksource *cs)
{
cs->flags &= ~(CLOCK_SOURCE_VALID_FOR_HRES | CLOCK_SOURCE_WATCHDOG);
cs->flags |= CLOCK_SOURCE_UNSTABLE;
/*
* If the clocksource is registered clocksource_watchdog_kthread() will
* re-rate and re-select.
*/
if (list_empty(&cs->list)) {
cs->rating = 0;
return;
}
if (cs->mark_unstable)
cs->mark_unstable(cs);
/* kick clocksource_watchdog_kthread() */
if (finished_booting)
schedule_work(&watchdog_work);
}
/**
* clocksource_mark_unstable - mark clocksource unstable via watchdog
* @cs: clocksource to be marked unstable
*
* This function is called by the x86 TSC code to mark clocksources as unstable;
* it defers demotion and re-selection to a kthread.
*/
void clocksource_mark_unstable(struct clocksource *cs)
{
unsigned long flags;
spin_lock_irqsave(&watchdog_lock, flags);
if (!(cs->flags & CLOCK_SOURCE_UNSTABLE)) {
if (!list_empty(&cs->list) && list_empty(&cs->wd_list))
list_add(&cs->wd_list, &watchdog_list);
__clocksource_unstable(cs);
}
spin_unlock_irqrestore(&watchdog_lock, flags);
}
static void clocksource_watchdog(struct timer_list *unused)
{
struct clocksource *cs;
u64 csnow, wdnow, cslast, wdlast, delta;
int64_t wd_nsec, cs_nsec;
int next_cpu, reset_pending;
spin_lock(&watchdog_lock);
if (!watchdog_running)
goto out;
reset_pending = atomic_read(&watchdog_reset_pending);
list_for_each_entry(cs, &watchdog_list, wd_list) {
/* Clocksource already marked unstable? */
if (cs->flags & CLOCK_SOURCE_UNSTABLE) {
if (finished_booting)
schedule_work(&watchdog_work);
continue;
}
local_irq_disable();
csnow = cs->read(cs);
wdnow = watchdog->read(watchdog);
local_irq_enable();
/* Clocksource initialized ? */
if (!(cs->flags & CLOCK_SOURCE_WATCHDOG) ||
atomic_read(&watchdog_reset_pending)) {
cs->flags |= CLOCK_SOURCE_WATCHDOG;
cs->wd_last = wdnow;
cs->cs_last = csnow;
continue;
}
delta = clocksource_delta(wdnow, cs->wd_last, watchdog->mask);
wd_nsec = clocksource_cyc2ns(delta, watchdog->mult,
watchdog->shift);
delta = clocksource_delta(csnow, cs->cs_last, cs->mask);
cs_nsec = clocksource_cyc2ns(delta, cs->mult, cs->shift);
wdlast = cs->wd_last; /* save these in case we print them */
cslast = cs->cs_last;
cs->cs_last = csnow;
cs->wd_last = wdnow;
if (atomic_read(&watchdog_reset_pending))
continue;
/* Check the deviation from the watchdog clocksource. */
if (abs(cs_nsec - wd_nsec) > WATCHDOG_THRESHOLD) {
pr_warn("timekeeping watchdog on CPU%d: Marking clocksource '%s' as unstable because the skew is too large:\n",
smp_processor_id(), cs->name);
pr_warn(" '%s' wd_now: %llx wd_last: %llx mask: %llx\n",
watchdog->name, wdnow, wdlast, watchdog->mask);
pr_warn(" '%s' cs_now: %llx cs_last: %llx mask: %llx\n",
cs->name, csnow, cslast, cs->mask);
__clocksource_unstable(cs);
continue;
}
if (cs == curr_clocksource && cs->tick_stable)
cs->tick_stable(cs);
if (!(cs->flags & CLOCK_SOURCE_VALID_FOR_HRES) &&
(cs->flags & CLOCK_SOURCE_IS_CONTINUOUS) &&
(watchdog->flags & CLOCK_SOURCE_IS_CONTINUOUS)) {
/* Mark it valid for high-res. */
cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES;
/*
* clocksource_done_booting() will sort it if
* finished_booting is not set yet.
*/
if (!finished_booting)
continue;
/*
* If this is not the current clocksource let
* the watchdog thread reselect it. Due to the
* change to high res this clocksource might
* be preferred now. If it is the current
* clocksource let the tick code know about
* that change.
*/
if (cs != curr_clocksource) {
cs->flags |= CLOCK_SOURCE_RESELECT;
schedule_work(&watchdog_work);
} else {
tick_clock_notify();
}
}
}
/*
* We only clear the watchdog_reset_pending, when we did a
* full cycle through all clocksources.
*/
if (reset_pending)
atomic_dec(&watchdog_reset_pending);
/*
* Cycle through CPUs to check if the CPUs stay synchronized
* to each other.
*/
next_cpu = cpumask_next(raw_smp_processor_id(), cpu_online_mask);
if (next_cpu >= nr_cpu_ids)
next_cpu = cpumask_first(cpu_online_mask);
watchdog_timer.expires += WATCHDOG_INTERVAL;
add_timer_on(&watchdog_timer, next_cpu);
out:
spin_unlock(&watchdog_lock);
}
static inline void clocksource_start_watchdog(void)
{
if (watchdog_running || !watchdog || list_empty(&watchdog_list))
return;
timer_setup(&watchdog_timer, clocksource_watchdog, 0);
watchdog_timer.expires = jiffies + WATCHDOG_INTERVAL;
add_timer_on(&watchdog_timer, cpumask_first(cpu_online_mask));
watchdog_running = 1;
}
static inline void clocksource_stop_watchdog(void)
{
if (!watchdog_running || (watchdog && !list_empty(&watchdog_list)))
return;
del_timer(&watchdog_timer);
watchdog_running = 0;
}
static inline void clocksource_reset_watchdog(void)
{
struct clocksource *cs;
list_for_each_entry(cs, &watchdog_list, wd_list)
cs->flags &= ~CLOCK_SOURCE_WATCHDOG;
}
static void clocksource_resume_watchdog(void)
{
atomic_inc(&watchdog_reset_pending);
}
static void clocksource_enqueue_watchdog(struct clocksource *cs)
{
INIT_LIST_HEAD(&cs->wd_list);
if (cs->flags & CLOCK_SOURCE_MUST_VERIFY) {
/* cs is a clocksource to be watched. */
list_add(&cs->wd_list, &watchdog_list);
cs->flags &= ~CLOCK_SOURCE_WATCHDOG;
} else {
/* cs is a watchdog. */
if (cs->flags & CLOCK_SOURCE_IS_CONTINUOUS)
cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES;
}
}
static void clocksource_select_watchdog(bool fallback)
{
struct clocksource *cs, *old_wd;
unsigned long flags;
spin_lock_irqsave(&watchdog_lock, flags);
/* save current watchdog */
old_wd = watchdog;
if (fallback)
watchdog = NULL;
list_for_each_entry(cs, &clocksource_list, list) {
/* cs is a clocksource to be watched. */
if (cs->flags & CLOCK_SOURCE_MUST_VERIFY)
continue;
/* Skip current if we were requested for a fallback. */
if (fallback && cs == old_wd)
continue;
/* Pick the best watchdog. */
if (!watchdog || cs->rating > watchdog->rating)
watchdog = cs;
}
/* If we failed to find a fallback restore the old one. */
if (!watchdog)
watchdog = old_wd;
/* If we changed the watchdog we need to reset cycles. */
if (watchdog != old_wd)
clocksource_reset_watchdog();
/* Check if the watchdog timer needs to be started. */
clocksource_start_watchdog();
spin_unlock_irqrestore(&watchdog_lock, flags);
}
static void clocksource_dequeue_watchdog(struct clocksource *cs)
{
if (cs != watchdog) {
if (cs->flags & CLOCK_SOURCE_MUST_VERIFY) {
/* cs is a watched clocksource. */
list_del_init(&cs->wd_list);
/* Check if the watchdog timer needs to be stopped. */
clocksource_stop_watchdog();
}
}
}
static int __clocksource_watchdog_kthread(void)
{
struct clocksource *cs, *tmp;
unsigned long flags;
int select = 0;
spin_lock_irqsave(&watchdog_lock, flags);
list_for_each_entry_safe(cs, tmp, &watchdog_list, wd_list) {
if (cs->flags & CLOCK_SOURCE_UNSTABLE) {
list_del_init(&cs->wd_list);
__clocksource_change_rating(cs, 0);
select = 1;
}
if (cs->flags & CLOCK_SOURCE_RESELECT) {
cs->flags &= ~CLOCK_SOURCE_RESELECT;
select = 1;
}
}
/* Check if the watchdog timer needs to be stopped. */
clocksource_stop_watchdog();
spin_unlock_irqrestore(&watchdog_lock, flags);
return select;
}
static int clocksource_watchdog_kthread(void *data)
{
mutex_lock(&clocksource_mutex);
if (__clocksource_watchdog_kthread())
clocksource_select();
mutex_unlock(&clocksource_mutex);
return 0;
}
static bool clocksource_is_watchdog(struct clocksource *cs)
{
return cs == watchdog;
}
#else /* CONFIG_CLOCKSOURCE_WATCHDOG */
static void clocksource_enqueue_watchdog(struct clocksource *cs)
{
if (cs->flags & CLOCK_SOURCE_IS_CONTINUOUS)
cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES;
}
static void clocksource_select_watchdog(bool fallback) { }
static inline void clocksource_dequeue_watchdog(struct clocksource *cs) { }
static inline void clocksource_resume_watchdog(void) { }
static inline int __clocksource_watchdog_kthread(void) { return 0; }
static bool clocksource_is_watchdog(struct clocksource *cs) { return false; }
void clocksource_mark_unstable(struct clocksource *cs) { }
static inline void clocksource_watchdog_lock(unsigned long *flags) { }
static inline void clocksource_watchdog_unlock(unsigned long *flags) { }
#endif /* CONFIG_CLOCKSOURCE_WATCHDOG */
static bool clocksource_is_suspend(struct clocksource *cs)
{
return cs == suspend_clocksource;
}
static void __clocksource_suspend_select(struct clocksource *cs)
{
/*
* Skip the clocksource which will be stopped in suspend state.
*/
if (!(cs->flags & CLOCK_SOURCE_SUSPEND_NONSTOP))
return;
/*
* The nonstop clocksource can be selected as the suspend clocksource to
* calculate the suspend time, so it should not supply suspend/resume
* interfaces to suspend the nonstop clocksource when system suspends.
*/
if (cs->suspend || cs->resume) {
pr_warn("Nonstop clocksource %s should not supply suspend/resume interfaces\n",
cs->name);
}
/* Pick the best rating. */
if (!suspend_clocksource || cs->rating > suspend_clocksource->rating)
suspend_clocksource = cs;
}
/**
* clocksource_suspend_select - Select the best clocksource for suspend timing
* @fallback: if select a fallback clocksource
*/
static void clocksource_suspend_select(bool fallback)
{
struct clocksource *cs, *old_suspend;
old_suspend = suspend_clocksource;
if (fallback)
suspend_clocksource = NULL;
list_for_each_entry(cs, &clocksource_list, list) {
/* Skip current if we were requested for a fallback. */
if (fallback && cs == old_suspend)
continue;
__clocksource_suspend_select(cs);
}
}
/**
* clocksource_start_suspend_timing - Start measuring the suspend timing
* @cs: current clocksource from timekeeping
* @start_cycles: current cycles from timekeeping
*
* This function will save the start cycle values of suspend timer to calculate
* the suspend time when resuming system.
*
* This function is called late in the suspend process from timekeeping_suspend(),
* that means processes are freezed, non-boot cpus and interrupts are disabled
* now. It is therefore possible to start the suspend timer without taking the
* clocksource mutex.
*/
void clocksource_start_suspend_timing(struct clocksource *cs, u64 start_cycles)
{
if (!suspend_clocksource)
return;
/*
* If current clocksource is the suspend timer, we should use the
* tkr_mono.cycle_last value as suspend_start to avoid same reading
* from suspend timer.
*/
if (clocksource_is_suspend(cs)) {
suspend_start = start_cycles;
return;
}
if (suspend_clocksource->enable &&
suspend_clocksource->enable(suspend_clocksource)) {
pr_warn_once("Failed to enable the non-suspend-able clocksource.\n");
return;
}
suspend_start = suspend_clocksource->read(suspend_clocksource);
}
/**
* clocksource_stop_suspend_timing - Stop measuring the suspend timing
* @cs: current clocksource from timekeeping
* @cycle_now: current cycles from timekeeping
*
* This function will calculate the suspend time from suspend timer.
*
* Returns nanoseconds since suspend started, 0 if no usable suspend clocksource.
*
* This function is called early in the resume process from timekeeping_resume(),
* that means there is only one cpu, no processes are running and the interrupts
* are disabled. It is therefore possible to stop the suspend timer without
* taking the clocksource mutex.
*/
u64 clocksource_stop_suspend_timing(struct clocksource *cs, u64 cycle_now)
{
u64 now, delta, nsec = 0;
if (!suspend_clocksource)
return 0;
/*
* If current clocksource is the suspend timer, we should use the
* tkr_mono.cycle_last value from timekeeping as current cycle to
* avoid same reading from suspend timer.
*/
if (clocksource_is_suspend(cs))
now = cycle_now;
else
now = suspend_clocksource->read(suspend_clocksource);
if (now > suspend_start) {
delta = clocksource_delta(now, suspend_start,
suspend_clocksource->mask);
nsec = mul_u64_u32_shr(delta, suspend_clocksource->mult,
suspend_clocksource->shift);
}
/*
* Disable the suspend timer to save power if current clocksource is
* not the suspend timer.
*/
if (!clocksource_is_suspend(cs) && suspend_clocksource->disable)
suspend_clocksource->disable(suspend_clocksource);
return nsec;
}
/**
* clocksource_suspend - suspend the clocksource(s)
*/
void clocksource_suspend(void)
{
struct clocksource *cs;
list_for_each_entry_reverse(cs, &clocksource_list, list)
if (cs->suspend)
cs->suspend(cs);
}
/**
* clocksource_resume - resume the clocksource(s)
*/
void clocksource_resume(void)
{
struct clocksource *cs;
list_for_each_entry(cs, &clocksource_list, list)
if (cs->resume)
cs->resume(cs);
clocksource_resume_watchdog();
}
/**
* clocksource_touch_watchdog - Update watchdog
*
* Update the watchdog after exception contexts such as kgdb so as not
* to incorrectly trip the watchdog. This might fail when the kernel
* was stopped in code which holds watchdog_lock.
*/
void clocksource_touch_watchdog(void)
{
clocksource_resume_watchdog();
}
/**
* clocksource_max_adjustment- Returns max adjustment amount
* @cs: Pointer to clocksource
*
*/
static u32 clocksource_max_adjustment(struct clocksource *cs)
{
u64 ret;
/*
* We won't try to correct for more than 11% adjustments (110,000 ppm),
*/
ret = (u64)cs->mult * 11;
do_div(ret,100);
return (u32)ret;
}
/**
* clocks_calc_max_nsecs - Returns maximum nanoseconds that can be converted
* @mult: cycle to nanosecond multiplier
* @shift: cycle to nanosecond divisor (power of two)
* @maxadj: maximum adjustment value to mult (~11%)
* @mask: bitmask for two's complement subtraction of non 64 bit counters
* @max_cyc: maximum cycle value before potential overflow (does not include
* any safety margin)
*
* NOTE: This function includes a safety margin of 50%, in other words, we
* return half the number of nanoseconds the hardware counter can technically
* cover. This is done so that we can potentially detect problems caused by
* delayed timers or bad hardware, which might result in time intervals that
* are larger than what the math used can handle without overflows.
*/
u64 clocks_calc_max_nsecs(u32 mult, u32 shift, u32 maxadj, u64 mask, u64 *max_cyc)
{
u64 max_nsecs, max_cycles;
/*
* Calculate the maximum number of cycles that we can pass to the
* cyc2ns() function without overflowing a 64-bit result.
*/
max_cycles = ULLONG_MAX;
do_div(max_cycles, mult+maxadj);
/*
* The actual maximum number of cycles we can defer the clocksource is
* determined by the minimum of max_cycles and mask.
* Note: Here we subtract the maxadj to make sure we don't sleep for
* too long if there's a large negative adjustment.
*/
max_cycles = min(max_cycles, mask);
max_nsecs = clocksource_cyc2ns(max_cycles, mult - maxadj, shift);
/* return the max_cycles value as well if requested */
if (max_cyc)
*max_cyc = max_cycles;
/* Return 50% of the actual maximum, so we can detect bad values */
max_nsecs >>= 1;
return max_nsecs;
}
/**
* clocksource_update_max_deferment - Updates the clocksource max_idle_ns & max_cycles
* @cs: Pointer to clocksource to be updated
*
*/
static inline void clocksource_update_max_deferment(struct clocksource *cs)
{
cs->max_idle_ns = clocks_calc_max_nsecs(cs->mult, cs->shift,
cs->maxadj, cs->mask,
&cs->max_cycles);
}
#ifndef [31mCONFIG_ARCH_USES_GETTIMEOFFSET[0m
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);
/* 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 [31mCONFIG_SYSFS[0m
/**
* 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);