v4.19.13 snapshot.
diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c
new file mode 100644
index 0000000..0e6e97a
--- /dev/null
+++ b/kernel/time/clocksource.c
@@ -0,0 +1,1246 @@
+/*
+ * linux/kernel/time/clocksource.c
+ *
+ * This file contains the functions which manage clocksource drivers.
+ *
+ * Copyright (C) 2004, 2005 IBM, John Stultz (johnstul@us.ibm.com)
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ *
+ * TODO WishList:
+ * o Allow clocksource drivers to be unregistered
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/device.h>
+#include <linux/clocksource.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/sched.h> /* for spin_unlock_irq() using preempt_count() m68k */
+#include <linux/tick.h>
+#include <linux/kthread.h>
+
+#include "tick-internal.h"
+#include "timekeeping_internal.h"
+
+/**
+ * clocks_calc_mult_shift - calculate mult/shift factors for scaled math of clocks
+ * @mult: pointer to mult variable
+ * @shift: pointer to shift variable
+ * @from: frequency to convert from
+ * @to: frequency to convert to
+ * @maxsec: guaranteed runtime conversion range in seconds
+ *
+ * The function evaluates the shift/mult pair for the scaled math
+ * operations of clocksources and clockevents.
+ *
+ * @to and @from are frequency values in HZ. For clock sources @to is
+ * NSEC_PER_SEC == 1GHz and @from is the counter frequency. For clock
+ * event @to is the counter frequency and @from is NSEC_PER_SEC.
+ *
+ * The @maxsec conversion range argument controls the time frame in
+ * seconds which must be covered by the runtime conversion with the
+ * calculated mult and shift factors. This guarantees that no 64bit
+ * overflow happens when the input value of the conversion is
+ * multiplied with the calculated mult factor. Larger ranges may
+ * reduce the conversion accuracy by chosing smaller mult and shift
+ * factors.
+ */
+void
+clocks_calc_mult_shift(u32 *mult, u32 *shift, u32 from, u32 to, u32 maxsec)
+{
+ u64 tmp;
+ u32 sft, sftacc= 32;
+
+ /*
+ * Calculate the shift factor which is limiting the conversion
+ * range:
+ */
+ tmp = ((u64)maxsec * from) >> 32;
+ while (tmp) {
+ tmp >>=1;
+ sftacc--;
+ }
+
+ /*
+ * Find the conversion shift/mult pair which has the best
+ * accuracy and fits the maxsec conversion range:
+ */
+ for (sft = 32; sft > 0; sft--) {
+ tmp = (u64) to << sft;
+ tmp += from / 2;
+ do_div(tmp, from);
+ if ((tmp >> sftacc) == 0)
+ break;
+ }
+ *mult = tmp;
+ *shift = sft;
+}
+EXPORT_SYMBOL_GPL(clocks_calc_mult_shift);
+
+/*[Clocksource internal variables]---------
+ * curr_clocksource:
+ * currently selected clocksource.
+ * suspend_clocksource:
+ * used to calculate the suspend time.
+ * clocksource_list:
+ * linked list with the registered clocksources
+ * clocksource_mutex:
+ * protects manipulations to curr_clocksource and the clocksource_list
+ * override_name:
+ * Name of the user-specified clocksource.
+ */
+static struct clocksource *curr_clocksource;
+static struct clocksource *suspend_clocksource;
+static LIST_HEAD(clocksource_list);
+static DEFINE_MUTEX(clocksource_mutex);
+static char override_name[CS_NAME_LEN];
+static int finished_booting;
+static u64 suspend_start;
+
+#ifdef CONFIG_CLOCKSOURCE_WATCHDOG
+static void clocksource_watchdog_work(struct work_struct *work);
+static void clocksource_select(void);
+
+static LIST_HEAD(watchdog_list);
+static struct clocksource *watchdog;
+static struct timer_list watchdog_timer;
+static DECLARE_WORK(watchdog_work, clocksource_watchdog_work);
+static DEFINE_SPINLOCK(watchdog_lock);
+static int watchdog_running;
+static atomic_t watchdog_reset_pending;
+
+static void inline clocksource_watchdog_lock(unsigned long *flags)
+{
+ spin_lock_irqsave(&watchdog_lock, *flags);
+}
+
+static void inline clocksource_watchdog_unlock(unsigned long *flags)
+{
+ spin_unlock_irqrestore(&watchdog_lock, *flags);
+}
+
+static int clocksource_watchdog_kthread(void *data);
+static void __clocksource_change_rating(struct clocksource *cs, int rating);
+
+/*
+ * Interval: 0.5sec Threshold: 0.0625s
+ */
+#define WATCHDOG_INTERVAL (HZ >> 1)
+#define WATCHDOG_THRESHOLD (NSEC_PER_SEC >> 4)
+
+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 CONFIG_ARCH_USES_GETTIMEOFFSET
+
+static struct clocksource *clocksource_find_best(bool oneshot, bool skipcur)
+{
+ struct clocksource *cs;
+
+ if (!finished_booting || list_empty(&clocksource_list))
+ return NULL;
+
+ /*
+ * We pick the clocksource with the highest rating. If oneshot
+ * mode is active, we pick the highres valid clocksource with
+ * the best rating.
+ */
+ list_for_each_entry(cs, &clocksource_list, list) {
+ if (skipcur && cs == curr_clocksource)
+ continue;
+ if (oneshot && !(cs->flags & CLOCK_SOURCE_VALID_FOR_HRES))
+ continue;
+ return cs;
+ }
+ return NULL;
+}
+
+static void __clocksource_select(bool skipcur)
+{
+ bool oneshot = tick_oneshot_mode_active();
+ struct clocksource *best, *cs;
+
+ /* Find the best suitable clocksource */
+ best = clocksource_find_best(oneshot, skipcur);
+ if (!best)
+ return;
+
+ if (!strlen(override_name))
+ goto found;
+
+ /* Check for the override clocksource. */
+ list_for_each_entry(cs, &clocksource_list, list) {
+ if (skipcur && cs == curr_clocksource)
+ continue;
+ if (strcmp(cs->name, override_name) != 0)
+ continue;
+ /*
+ * Check to make sure we don't switch to a non-highres
+ * capable clocksource if the tick code is in oneshot
+ * mode (highres or nohz)
+ */
+ if (!(cs->flags & CLOCK_SOURCE_VALID_FOR_HRES) && oneshot) {
+ /* Override clocksource cannot be used. */
+ if (cs->flags & CLOCK_SOURCE_UNSTABLE) {
+ pr_warn("Override clocksource %s is unstable and not HRT compatible - cannot switch while in HRT/NOHZ mode\n",
+ cs->name);
+ override_name[0] = 0;
+ } else {
+ /*
+ * The override cannot be currently verified.
+ * Deferring to let the watchdog check.
+ */
+ pr_info("Override clocksource %s is not currently HRT compatible - deferring\n",
+ cs->name);
+ }
+ } else
+ /* Override clocksource can be used. */
+ best = cs;
+ break;
+ }
+
+found:
+ if (curr_clocksource != best && !timekeeping_notify(best)) {
+ pr_info("Switched to clocksource %s\n", best->name);
+ curr_clocksource = best;
+ }
+}
+
+/**
+ * clocksource_select - Select the best clocksource available
+ *
+ * Private function. Must hold clocksource_mutex when called.
+ *
+ * Select the clocksource with the best rating, or the clocksource,
+ * which is selected by userspace override.
+ */
+static void clocksource_select(void)
+{
+ __clocksource_select(false);
+}
+
+static void clocksource_select_fallback(void)
+{
+ __clocksource_select(true);
+}
+
+#else /* !CONFIG_ARCH_USES_GETTIMEOFFSET */
+static inline void clocksource_select(void) { }
+static inline void clocksource_select_fallback(void) { }
+
+#endif
+
+/*
+ * clocksource_done_booting - Called near the end of core bootup
+ *
+ * Hack to avoid lots of clocksource churn at boot time.
+ * We use fs_initcall because we want this to start before
+ * device_initcall but after subsys_initcall.
+ */
+static int __init clocksource_done_booting(void)
+{
+ mutex_lock(&clocksource_mutex);
+ curr_clocksource = clocksource_default_clock();
+ finished_booting = 1;
+ /*
+ * Run the watchdog first to eliminate unstable clock sources
+ */
+ __clocksource_watchdog_kthread();
+ clocksource_select();
+ mutex_unlock(&clocksource_mutex);
+ return 0;
+}
+fs_initcall(clocksource_done_booting);
+
+/*
+ * Enqueue the clocksource sorted by rating
+ */
+static void clocksource_enqueue(struct clocksource *cs)
+{
+ struct list_head *entry = &clocksource_list;
+ struct clocksource *tmp;
+
+ list_for_each_entry(tmp, &clocksource_list, list) {
+ /* Keep track of the place, where to insert */
+ if (tmp->rating < cs->rating)
+ break;
+ entry = &tmp->list;
+ }
+ list_add(&cs->list, entry);
+}
+
+/**
+ * __clocksource_update_freq_scale - Used update clocksource with new freq
+ * @cs: clocksource to be registered
+ * @scale: Scale factor multiplied against freq to get clocksource hz
+ * @freq: clocksource frequency (cycles per second) divided by scale
+ *
+ * This should only be called from the clocksource->enable() method.
+ *
+ * This *SHOULD NOT* be called directly! Please use the
+ * __clocksource_update_freq_hz() or __clocksource_update_freq_khz() helper
+ * functions.
+ */
+void __clocksource_update_freq_scale(struct clocksource *cs, u32 scale, u32 freq)
+{
+ u64 sec;
+
+ /*
+ * Default clocksources are *special* and self-define their mult/shift.
+ * But, you're not special, so you should specify a freq value.
+ */
+ if (freq) {
+ /*
+ * Calc the maximum number of seconds which we can run before
+ * wrapping around. For clocksources which have a mask > 32-bit
+ * we need to limit the max sleep time to have a good
+ * conversion precision. 10 minutes is still a reasonable
+ * amount. That results in a shift value of 24 for a
+ * clocksource with mask >= 40-bit and f >= 4GHz. That maps to
+ * ~ 0.06ppm granularity for NTP.
+ */
+ sec = cs->mask;
+ do_div(sec, freq);
+ do_div(sec, scale);
+ if (!sec)
+ sec = 1;
+ else if (sec > 600 && cs->mask > UINT_MAX)
+ sec = 600;
+
+ clocks_calc_mult_shift(&cs->mult, &cs->shift, freq,
+ NSEC_PER_SEC / scale, sec * scale);
+ }
+ /*
+ * Ensure clocksources that have large 'mult' values don't overflow
+ * when adjusted.
+ */
+ cs->maxadj = clocksource_max_adjustment(cs);
+ while (freq && ((cs->mult + cs->maxadj < cs->mult)
+ || (cs->mult - cs->maxadj > cs->mult))) {
+ cs->mult >>= 1;
+ cs->shift--;
+ cs->maxadj = clocksource_max_adjustment(cs);
+ }
+
+ /*
+ * Only warn for *special* clocksources that self-define
+ * their mult/shift values and don't specify a freq.
+ */
+ WARN_ONCE(cs->mult + cs->maxadj < cs->mult,
+ "timekeeping: Clocksource %s might overflow on 11%% adjustment\n",
+ cs->name);
+
+ clocksource_update_max_deferment(cs);
+
+ pr_info("%s: mask: 0x%llx max_cycles: 0x%llx, max_idle_ns: %lld ns\n",
+ cs->name, cs->mask, cs->max_cycles, cs->max_idle_ns);
+}
+EXPORT_SYMBOL_GPL(__clocksource_update_freq_scale);
+
+/**
+ * __clocksource_register_scale - Used to install new clocksources
+ * @cs: clocksource to be registered
+ * @scale: Scale factor multiplied against freq to get clocksource hz
+ * @freq: clocksource frequency (cycles per second) divided by scale
+ *
+ * Returns -EBUSY if registration fails, zero otherwise.
+ *
+ * This *SHOULD NOT* be called directly! Please use the
+ * clocksource_register_hz() or clocksource_register_khz helper functions.
+ */
+int __clocksource_register_scale(struct clocksource *cs, u32 scale, u32 freq)
+{
+ unsigned long flags;
+
+ /* Initialize mult/shift and max_idle_ns */
+ __clocksource_update_freq_scale(cs, scale, freq);
+
+ /* Add clocksource to the clocksource list */
+ mutex_lock(&clocksource_mutex);
+
+ clocksource_watchdog_lock(&flags);
+ clocksource_enqueue(cs);
+ clocksource_enqueue_watchdog(cs);
+ clocksource_watchdog_unlock(&flags);
+
+ clocksource_select();
+ clocksource_select_watchdog(false);
+ __clocksource_suspend_select(cs);
+ mutex_unlock(&clocksource_mutex);
+ return 0;
+}
+EXPORT_SYMBOL_GPL(__clocksource_register_scale);
+
+static void __clocksource_change_rating(struct clocksource *cs, int rating)
+{
+ list_del(&cs->list);
+ cs->rating = rating;
+ clocksource_enqueue(cs);
+}
+
+/**
+ * clocksource_change_rating - Change the rating of a registered clocksource
+ * @cs: clocksource to be changed
+ * @rating: new rating
+ */
+void clocksource_change_rating(struct clocksource *cs, int rating)
+{
+ unsigned long flags;
+
+ mutex_lock(&clocksource_mutex);
+ clocksource_watchdog_lock(&flags);
+ __clocksource_change_rating(cs, rating);
+ clocksource_watchdog_unlock(&flags);
+
+ clocksource_select();
+ clocksource_select_watchdog(false);
+ clocksource_suspend_select(false);
+ mutex_unlock(&clocksource_mutex);
+}
+EXPORT_SYMBOL(clocksource_change_rating);
+
+/*
+ * Unbind clocksource @cs. Called with clocksource_mutex held
+ */
+static int clocksource_unbind(struct clocksource *cs)
+{
+ unsigned long flags;
+
+ if (clocksource_is_watchdog(cs)) {
+ /* Select and try to install a replacement watchdog. */
+ clocksource_select_watchdog(true);
+ if (clocksource_is_watchdog(cs))
+ return -EBUSY;
+ }
+
+ if (cs == curr_clocksource) {
+ /* Select and try to install a replacement clock source */
+ clocksource_select_fallback();
+ if (curr_clocksource == cs)
+ return -EBUSY;
+ }
+
+ if (clocksource_is_suspend(cs)) {
+ /*
+ * Select and try to install a replacement suspend clocksource.
+ * If no replacement suspend clocksource, we will just let the
+ * clocksource go and have no suspend clocksource.
+ */
+ clocksource_suspend_select(true);
+ }
+
+ clocksource_watchdog_lock(&flags);
+ clocksource_dequeue_watchdog(cs);
+ list_del_init(&cs->list);
+ clocksource_watchdog_unlock(&flags);
+
+ return 0;
+}
+
+/**
+ * clocksource_unregister - remove a registered clocksource
+ * @cs: clocksource to be unregistered
+ */
+int clocksource_unregister(struct clocksource *cs)
+{
+ int ret = 0;
+
+ mutex_lock(&clocksource_mutex);
+ if (!list_empty(&cs->list))
+ ret = clocksource_unbind(cs);
+ mutex_unlock(&clocksource_mutex);
+ return ret;
+}
+EXPORT_SYMBOL(clocksource_unregister);
+
+#ifdef CONFIG_SYSFS
+/**
+ * current_clocksource_show - sysfs interface for current clocksource
+ * @dev: unused
+ * @attr: unused
+ * @buf: char buffer to be filled with clocksource list
+ *
+ * Provides sysfs interface for listing current clocksource.
+ */
+static ssize_t current_clocksource_show(struct device *dev,
+ struct device_attribute *attr,
+ char *buf)
+{
+ ssize_t count = 0;
+
+ mutex_lock(&clocksource_mutex);
+ count = snprintf(buf, PAGE_SIZE, "%s\n", curr_clocksource->name);
+ mutex_unlock(&clocksource_mutex);
+
+ return count;
+}
+
+ssize_t sysfs_get_uname(const char *buf, char *dst, size_t cnt)
+{
+ size_t ret = cnt;
+
+ /* strings from sysfs write are not 0 terminated! */
+ if (!cnt || cnt >= CS_NAME_LEN)
+ return -EINVAL;
+
+ /* strip of \n: */
+ if (buf[cnt-1] == '\n')
+ cnt--;
+ if (cnt > 0)
+ memcpy(dst, buf, cnt);
+ dst[cnt] = 0;
+ return ret;
+}
+
+/**
+ * current_clocksource_store - interface for manually overriding clocksource
+ * @dev: unused
+ * @attr: unused
+ * @buf: name of override clocksource
+ * @count: length of buffer
+ *
+ * Takes input from sysfs interface for manually overriding the default
+ * clocksource selection.
+ */
+static ssize_t current_clocksource_store(struct device *dev,
+ struct device_attribute *attr,
+ const char *buf, size_t count)
+{
+ ssize_t ret;
+
+ mutex_lock(&clocksource_mutex);
+
+ ret = sysfs_get_uname(buf, override_name, count);
+ if (ret >= 0)
+ clocksource_select();
+
+ mutex_unlock(&clocksource_mutex);
+
+ return ret;
+}
+static DEVICE_ATTR_RW(current_clocksource);
+
+/**
+ * unbind_clocksource_store - interface for manually unbinding clocksource
+ * @dev: unused
+ * @attr: unused
+ * @buf: unused
+ * @count: length of buffer
+ *
+ * Takes input from sysfs interface for manually unbinding a clocksource.
+ */
+static ssize_t unbind_clocksource_store(struct device *dev,
+ struct device_attribute *attr,
+ const char *buf, size_t count)
+{
+ struct clocksource *cs;
+ char name[CS_NAME_LEN];
+ ssize_t ret;
+
+ ret = sysfs_get_uname(buf, name, count);
+ if (ret < 0)
+ return ret;
+
+ ret = -ENODEV;
+ mutex_lock(&clocksource_mutex);
+ list_for_each_entry(cs, &clocksource_list, list) {
+ if (strcmp(cs->name, name))
+ continue;
+ ret = clocksource_unbind(cs);
+ break;
+ }
+ mutex_unlock(&clocksource_mutex);
+
+ return ret ? ret : count;
+}
+static DEVICE_ATTR_WO(unbind_clocksource);
+
+/**
+ * available_clocksource_show - sysfs interface for listing clocksource
+ * @dev: unused
+ * @attr: unused
+ * @buf: char buffer to be filled with clocksource list
+ *
+ * Provides sysfs interface for listing registered clocksources
+ */
+static ssize_t available_clocksource_show(struct device *dev,
+ struct device_attribute *attr,
+ char *buf)
+{
+ struct clocksource *src;
+ ssize_t count = 0;
+
+ mutex_lock(&clocksource_mutex);
+ list_for_each_entry(src, &clocksource_list, list) {
+ /*
+ * Don't show non-HRES clocksource if the tick code is
+ * in one shot mode (highres=on or nohz=on)
+ */
+ if (!tick_oneshot_mode_active() ||
+ (src->flags & CLOCK_SOURCE_VALID_FOR_HRES))
+ count += snprintf(buf + count,
+ max((ssize_t)PAGE_SIZE - count, (ssize_t)0),
+ "%s ", src->name);
+ }
+ mutex_unlock(&clocksource_mutex);
+
+ count += snprintf(buf + count,
+ max((ssize_t)PAGE_SIZE - count, (ssize_t)0), "\n");
+
+ return count;
+}
+static DEVICE_ATTR_RO(available_clocksource);
+
+static struct attribute *clocksource_attrs[] = {
+ &dev_attr_current_clocksource.attr,
+ &dev_attr_unbind_clocksource.attr,
+ &dev_attr_available_clocksource.attr,
+ NULL
+};
+ATTRIBUTE_GROUPS(clocksource);
+
+static struct bus_type clocksource_subsys = {
+ .name = "clocksource",
+ .dev_name = "clocksource",
+};
+
+static struct device device_clocksource = {
+ .id = 0,
+ .bus = &clocksource_subsys,
+ .groups = clocksource_groups,
+};
+
+static int __init init_clocksource_sysfs(void)
+{
+ int error = subsys_system_register(&clocksource_subsys, NULL);
+
+ if (!error)
+ error = device_register(&device_clocksource);
+
+ return error;
+}
+
+device_initcall(init_clocksource_sysfs);
+#endif /* CONFIG_SYSFS */
+
+/**
+ * boot_override_clocksource - boot clock override
+ * @str: override name
+ *
+ * Takes a clocksource= boot argument and uses it
+ * as the clocksource override name.
+ */
+static int __init boot_override_clocksource(char* str)
+{
+ mutex_lock(&clocksource_mutex);
+ if (str)
+ strlcpy(override_name, str, sizeof(override_name));
+ mutex_unlock(&clocksource_mutex);
+ return 1;
+}
+
+__setup("clocksource=", boot_override_clocksource);
+
+/**
+ * boot_override_clock - Compatibility layer for deprecated boot option
+ * @str: override name
+ *
+ * DEPRECATED! Takes a clock= boot argument and uses it
+ * as the clocksource override name
+ */
+static int __init boot_override_clock(char* str)
+{
+ if (!strcmp(str, "pmtmr")) {
+ pr_warn("clock=pmtmr is deprecated - use clocksource=acpi_pm\n");
+ return boot_override_clocksource("acpi_pm");
+ }
+ pr_warn("clock= boot option is deprecated - use clocksource=xyz\n");
+ return boot_override_clocksource(str);
+}
+
+__setup("clock=", boot_override_clock);