Merge branch 'timers-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip

* 'timers-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
  hrtimer: Make lookup table const
  RTC: Disable CONFIG_RTC_CLASS from being built as a module
  timers: Fix alarmtimer build issues when CONFIG_RTC_CLASS=n
  timers: Remove delayed irqwork from alarmtimers implementation
  timers: Improve alarmtimer comments and minor fixes
  timers: Posix interface for alarm-timers
  timers: Introduce in-kernel alarm-timer interface
  timers: Add rb_init_node() to allow for stack allocated rb nodes
  time: Add timekeeping_inject_sleeptime

3 files changed, 748 insertions, 4 deletions

diff --git a/kernel/time/Makefile b/kernel/time/Makefile
index b0425991e9a..e2fd74b8e8c 100644
--- a/kernel/time/Makefile
+++ b/kernel/time/Makefile
@@ -1,5 +1,5 @@
 obj-y += timekeeping.o ntp.o clocksource.o jiffies.o timer_list.o timecompare.o
-obj-y += timeconv.o posix-clock.o
+obj-y += timeconv.o posix-clock.o alarmtimer.o
 
 obj-$(CONFIG_GENERIC_CLOCKEVENTS_BUILD)         += clockevents.o
 obj-$(CONFIG_GENERIC_CLOCKEVENTS)               += tick-common.o
diff --git a/kernel/time/alarmtimer.c b/kernel/time/alarmtimer.c
new file mode 100644
index 00000000000..9265014cb4d
--- /dev/null
+++ b/kernel/time/alarmtimer.c
@@ -0,0 +1,694 @@
+/*
+ * Alarmtimer interface
+ *
+ * This interface provides a timer which is similarto hrtimers,
+ * but triggers a RTC alarm if the box is suspend.
+ *
+ * This interface is influenced by the Android RTC Alarm timer
+ * interface.
+ *
+ * Copyright (C) 2010 IBM Corperation
+ *
+ * Author: John Stultz <john.stultz@linaro.org>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+#include <linux/time.h>
+#include <linux/hrtimer.h>
+#include <linux/timerqueue.h>
+#include <linux/rtc.h>
+#include <linux/alarmtimer.h>
+#include <linux/mutex.h>
+#include <linux/platform_device.h>
+#include <linux/posix-timers.h>
+#include <linux/workqueue.h>
+#include <linux/freezer.h>
+
+/**
+ * struct alarm_base - Alarm timer bases
+ * @lock:               Lock for syncrhonized access to the base
+ * @timerqueue:         Timerqueue head managing the list of events
+ * @timer:              hrtimer used to schedule events while running
+ * @gettime:            Function to read the time correlating to the base
+ * @base_clockid:       clockid for the base
+ */
+static struct alarm_base {
+        spinlock_t              lock;
+        struct timerqueue_head  timerqueue;
+        struct hrtimer          timer;
+        ktime_t                 (*gettime)(void);
+        clockid_t               base_clockid;
+} alarm_bases[ALARM_NUMTYPE];
+
+#ifdef CONFIG_RTC_CLASS
+/* rtc timer and device for setting alarm wakeups at suspend */
+static struct rtc_timer         rtctimer;
+static struct rtc_device        *rtcdev;
+#endif
+
+/* freezer delta & lock used to handle clock_nanosleep triggered wakeups */
+static ktime_t freezer_delta;
+static DEFINE_SPINLOCK(freezer_delta_lock);
+
+
+/**
+ * alarmtimer_enqueue - Adds an alarm timer to an alarm_base timerqueue
+ * @base: pointer to the base where the timer is being run
+ * @alarm: pointer to alarm being enqueued.
+ *
+ * Adds alarm to a alarm_base timerqueue and if necessary sets
+ * an hrtimer to run.
+ *
+ * Must hold base->lock when calling.
+ */
+static void alarmtimer_enqueue(struct alarm_base *base, struct alarm *alarm)
+{
+        timerqueue_add(&base->timerqueue, &alarm->node);
+        if (&alarm->node == timerqueue_getnext(&base->timerqueue)) {
+                hrtimer_try_to_cancel(&base->timer);
+                hrtimer_start(&base->timer, alarm->node.expires,
+                                HRTIMER_MODE_ABS);
+        }
+}
+
+/**
+ * alarmtimer_remove - Removes an alarm timer from an alarm_base timerqueue
+ * @base: pointer to the base where the timer is running
+ * @alarm: pointer to alarm being removed
+ *
+ * Removes alarm to a alarm_base timerqueue and if necessary sets
+ * a new timer to run.
+ *
+ * Must hold base->lock when calling.
+ */
+static void alarmtimer_remove(struct alarm_base *base, struct alarm *alarm)
+{
+        struct timerqueue_node *next = timerqueue_getnext(&base->timerqueue);
+
+        timerqueue_del(&base->timerqueue, &alarm->node);
+        if (next == &alarm->node) {
+                hrtimer_try_to_cancel(&base->timer);
+                next = timerqueue_getnext(&base->timerqueue);
+                if (!next)
+                        return;
+                hrtimer_start(&base->timer, next->expires, HRTIMER_MODE_ABS);
+        }
+}
+
+
+/**
+ * alarmtimer_fired - Handles alarm hrtimer being fired.
+ * @timer: pointer to hrtimer being run
+ *
+ * When a alarm timer fires, this runs through the timerqueue to
+ * see which alarms expired, and runs those. If there are more alarm
+ * timers queued for the future, we set the hrtimer to fire when
+ * when the next future alarm timer expires.
+ */
+static enum hrtimer_restart alarmtimer_fired(struct hrtimer *timer)
+{
+        struct alarm_base *base = container_of(timer, struct alarm_base, timer);
+        struct timerqueue_node *next;
+        unsigned long flags;
+        ktime_t now;
+        int ret = HRTIMER_NORESTART;
+
+        spin_lock_irqsave(&base->lock, flags);
+        now = base->gettime();
+        while ((next = timerqueue_getnext(&base->timerqueue))) {
+                struct alarm *alarm;
+                ktime_t expired = next->expires;
+
+                if (expired.tv64 >= now.tv64)
+                        break;
+
+                alarm = container_of(next, struct alarm, node);
+
+                timerqueue_del(&base->timerqueue, &alarm->node);
+                alarm->enabled = 0;
+                /* Re-add periodic timers */
+                if (alarm->period.tv64) {
+                        alarm->node.expires = ktime_add(expired, alarm->period);
+                        timerqueue_add(&base->timerqueue, &alarm->node);
+                        alarm->enabled = 1;
+                }
+                spin_unlock_irqrestore(&base->lock, flags);
+                if (alarm->function)
+                        alarm->function(alarm);
+                spin_lock_irqsave(&base->lock, flags);
+        }
+
+        if (next) {
+                hrtimer_set_expires(&base->timer, next->expires);
+                ret = HRTIMER_RESTART;
+        }
+        spin_unlock_irqrestore(&base->lock, flags);
+
+        return ret;
+
+}
+
+#ifdef CONFIG_RTC_CLASS
+/**
+ * alarmtimer_suspend - Suspend time callback
+ * @dev: unused
+ * @state: unused
+ *
+ * When we are going into suspend, we look through the bases
+ * to see which is the soonest timer to expire. We then
+ * set an rtc timer to fire that far into the future, which
+ * will wake us from suspend.
+ */
+static int alarmtimer_suspend(struct device *dev)
+{
+        struct rtc_time tm;
+        ktime_t min, now;
+        unsigned long flags;
+        int i;
+
+        spin_lock_irqsave(&freezer_delta_lock, flags);
+        min = freezer_delta;
+        freezer_delta = ktime_set(0, 0);
+        spin_unlock_irqrestore(&freezer_delta_lock, flags);
+
+        /* If we have no rtcdev, just return */
+        if (!rtcdev)
+                return 0;
+
+        /* Find the soonest timer to expire*/
+        for (i = 0; i < ALARM_NUMTYPE; i++) {
+                struct alarm_base *base = &alarm_bases[i];
+                struct timerqueue_node *next;
+                ktime_t delta;
+
+                spin_lock_irqsave(&base->lock, flags);
+                next = timerqueue_getnext(&base->timerqueue);
+                spin_unlock_irqrestore(&base->lock, flags);
+                if (!next)
+                        continue;
+                delta = ktime_sub(next->expires, base->gettime());
+                if (!min.tv64 || (delta.tv64 < min.tv64))
+                        min = delta;
+        }
+        if (min.tv64 == 0)
+                return 0;
+
+        /* XXX - Should we enforce a minimum sleep time? */
+        WARN_ON(min.tv64 < NSEC_PER_SEC);
+
+        /* Setup an rtc timer to fire that far in the future */
+        rtc_timer_cancel(rtcdev, &rtctimer);
+        rtc_read_time(rtcdev, &tm);
+        now = rtc_tm_to_ktime(tm);
+        now = ktime_add(now, min);
+
+        rtc_timer_start(rtcdev, &rtctimer, now, ktime_set(0, 0));
+
+        return 0;
+}
+#else
+static int alarmtimer_suspend(struct device *dev)
+{
+        return 0;
+}
+#endif
+
+static void alarmtimer_freezerset(ktime_t absexp, enum alarmtimer_type type)
+{
+        ktime_t delta;
+        unsigned long flags;
+        struct alarm_base *base = &alarm_bases[type];
+
+        delta = ktime_sub(absexp, base->gettime());
+
+        spin_lock_irqsave(&freezer_delta_lock, flags);
+        if (!freezer_delta.tv64 || (delta.tv64 < freezer_delta.tv64))
+                freezer_delta = delta;
+        spin_unlock_irqrestore(&freezer_delta_lock, flags);
+}
+
+
+/**
+ * alarm_init - Initialize an alarm structure
+ * @alarm: ptr to alarm to be initialized
+ * @type: the type of the alarm
+ * @function: callback that is run when the alarm fires
+ */
+void alarm_init(struct alarm *alarm, enum alarmtimer_type type,
+                void (*function)(struct alarm *))
+{
+        timerqueue_init(&alarm->node);
+        alarm->period = ktime_set(0, 0);
+        alarm->function = function;
+        alarm->type = type;
+        alarm->enabled = 0;
+}
+
+/**
+ * alarm_start - Sets an alarm to fire
+ * @alarm: ptr to alarm to set
+ * @start: time to run the alarm
+ * @period: period at which the alarm will recur
+ */
+void alarm_start(struct alarm *alarm, ktime_t start, ktime_t period)
+{
+        struct alarm_base *base = &alarm_bases[alarm->type];
+        unsigned long flags;
+
+        spin_lock_irqsave(&base->lock, flags);
+        if (alarm->enabled)
+                alarmtimer_remove(base, alarm);
+        alarm->node.expires = start;
+        alarm->period = period;
+        alarmtimer_enqueue(base, alarm);
+        alarm->enabled = 1;
+        spin_unlock_irqrestore(&base->lock, flags);
+}
+
+/**
+ * alarm_cancel - Tries to cancel an alarm timer
+ * @alarm: ptr to alarm to be canceled
+ */
+void alarm_cancel(struct alarm *alarm)
+{
+        struct alarm_base *base = &alarm_bases[alarm->type];
+        unsigned long flags;
+
+        spin_lock_irqsave(&base->lock, flags);
+        if (alarm->enabled)
+                alarmtimer_remove(base, alarm);
+        alarm->enabled = 0;
+        spin_unlock_irqrestore(&base->lock, flags);
+}
+
+
+/**
+ * clock2alarm - helper that converts from clockid to alarmtypes
+ * @clockid: clockid.
+ */
+static enum alarmtimer_type clock2alarm(clockid_t clockid)
+{
+        if (clockid == CLOCK_REALTIME_ALARM)
+                return ALARM_REALTIME;
+        if (clockid == CLOCK_BOOTTIME_ALARM)
+                return ALARM_BOOTTIME;
+        return -1;
+}
+
+/**
+ * alarm_handle_timer - Callback for posix timers
+ * @alarm: alarm that fired
+ *
+ * Posix timer callback for expired alarm timers.
+ */
+static void alarm_handle_timer(struct alarm *alarm)
+{
+        struct k_itimer *ptr = container_of(alarm, struct k_itimer,
+                                                it.alarmtimer);
+        if (posix_timer_event(ptr, 0) != 0)
+                ptr->it_overrun++;
+}
+
+/**
+ * alarm_clock_getres - posix getres interface
+ * @which_clock: clockid
+ * @tp: timespec to fill
+ *
+ * Returns the granularity of underlying alarm base clock
+ */
+static int alarm_clock_getres(const clockid_t which_clock, struct timespec *tp)
+{
+        clockid_t baseid = alarm_bases[clock2alarm(which_clock)].base_clockid;
+
+        return hrtimer_get_res(baseid, tp);
+}
+
+/**
+ * alarm_clock_get - posix clock_get interface
+ * @which_clock: clockid
+ * @tp: timespec to fill.
+ *
+ * Provides the underlying alarm base time.
+ */
+static int alarm_clock_get(clockid_t which_clock, struct timespec *tp)
+{
+        struct alarm_base *base = &alarm_bases[clock2alarm(which_clock)];
+
+        *tp = ktime_to_timespec(base->gettime());
+        return 0;
+}
+
+/**
+ * alarm_timer_create - posix timer_create interface
+ * @new_timer: k_itimer pointer to manage
+ *
+ * Initializes the k_itimer structure.
+ */
+static int alarm_timer_create(struct k_itimer *new_timer)
+{
+        enum  alarmtimer_type type;
+        struct alarm_base *base;
+
+        if (!capable(CAP_WAKE_ALARM))
+                return -EPERM;
+
+        type = clock2alarm(new_timer->it_clock);
+        base = &alarm_bases[type];
+        alarm_init(&new_timer->it.alarmtimer, type, alarm_handle_timer);
+        return 0;
+}
+
+/**
+ * alarm_timer_get - posix timer_get interface
+ * @new_timer: k_itimer pointer
+ * @cur_setting: itimerspec data to fill
+ *
+ * Copies the itimerspec data out from the k_itimer
+ */
+static void alarm_timer_get(struct k_itimer *timr,
+                                struct itimerspec *cur_setting)
+{
+        cur_setting->it_interval =
+                        ktime_to_timespec(timr->it.alarmtimer.period);
+        cur_setting->it_value =
+                        ktime_to_timespec(timr->it.alarmtimer.node.expires);
+        return;
+}
+
+/**
+ * alarm_timer_del - posix timer_del interface
+ * @timr: k_itimer pointer to be deleted
+ *
+ * Cancels any programmed alarms for the given timer.
+ */
+static int alarm_timer_del(struct k_itimer *timr)
+{
+        alarm_cancel(&timr->it.alarmtimer);
+        return 0;
+}
+
+/**
+ * alarm_timer_set - posix timer_set interface
+ * @timr: k_itimer pointer to be deleted
+ * @flags: timer flags
+ * @new_setting: itimerspec to be used
+ * @old_setting: itimerspec being replaced
+ *
+ * Sets the timer to new_setting, and starts the timer.
+ */
+static int alarm_timer_set(struct k_itimer *timr, int flags,
+                                struct itimerspec *new_setting,
+                                struct itimerspec *old_setting)
+{
+        /* Save old values */
+        old_setting->it_interval =
+                        ktime_to_timespec(timr->it.alarmtimer.period);
+        old_setting->it_value =
+                        ktime_to_timespec(timr->it.alarmtimer.node.expires);
+
+        /* If the timer was already set, cancel it */
+        alarm_cancel(&timr->it.alarmtimer);
+
+        /* start the timer */
+        alarm_start(&timr->it.alarmtimer,
+                        timespec_to_ktime(new_setting->it_value),
+                        timespec_to_ktime(new_setting->it_interval));
+        return 0;
+}
+
+/**
+ * alarmtimer_nsleep_wakeup - Wakeup function for alarm_timer_nsleep
+ * @alarm: ptr to alarm that fired
+ *
+ * Wakes up the task that set the alarmtimer
+ */
+static void alarmtimer_nsleep_wakeup(struct alarm *alarm)
+{
+        struct task_struct *task = (struct task_struct *)alarm->data;
+
+        alarm->data = NULL;
+        if (task)
+                wake_up_process(task);
+}
+
+/**
+ * alarmtimer_do_nsleep - Internal alarmtimer nsleep implementation
+ * @alarm: ptr to alarmtimer
+ * @absexp: absolute expiration time
+ *
+ * Sets the alarm timer and sleeps until it is fired or interrupted.
+ */
+static int alarmtimer_do_nsleep(struct alarm *alarm, ktime_t absexp)
+{
+        alarm->data = (void *)current;
+        do {
+                set_current_state(TASK_INTERRUPTIBLE);
+                alarm_start(alarm, absexp, ktime_set(0, 0));
+                if (likely(alarm->data))
+                        schedule();
+
+                alarm_cancel(alarm);
+        } while (alarm->data && !signal_pending(current));
+
+        __set_current_state(TASK_RUNNING);
+
+        return (alarm->data == NULL);
+}
+
+
+/**
+ * update_rmtp - Update remaining timespec value
+ * @exp: expiration time
+ * @type: timer type
+ * @rmtp: user pointer to remaining timepsec value
+ *
+ * Helper function that fills in rmtp value with time between
+ * now and the exp value
+ */
+static int update_rmtp(ktime_t exp, enum  alarmtimer_type type,
+                        struct timespec __user *rmtp)
+{
+        struct timespec rmt;
+        ktime_t rem;
+
+        rem = ktime_sub(exp, alarm_bases[type].gettime());
+
+        if (rem.tv64 <= 0)
+                return 0;
+        rmt = ktime_to_timespec(rem);
+
+        if (copy_to_user(rmtp, &rmt, sizeof(*rmtp)))
+                return -EFAULT;
+
+        return 1;
+
+}
+
+/**
+ * alarm_timer_nsleep_restart - restartblock alarmtimer nsleep
+ * @restart: ptr to restart block
+ *
+ * Handles restarted clock_nanosleep calls
+ */
+static long __sched alarm_timer_nsleep_restart(struct restart_block *restart)
+{
+        enum  alarmtimer_type type = restart->nanosleep.index;
+        ktime_t exp;
+        struct timespec __user  *rmtp;
+        struct alarm alarm;
+        int ret = 0;
+
+        exp.tv64 = restart->nanosleep.expires;
+        alarm_init(&alarm, type, alarmtimer_nsleep_wakeup);
+
+        if (alarmtimer_do_nsleep(&alarm, exp))
+                goto out;
+
+        if (freezing(current))
+                alarmtimer_freezerset(exp, type);
+
+        rmtp = restart->nanosleep.rmtp;
+        if (rmtp) {
+                ret = update_rmtp(exp, type, rmtp);
+                if (ret <= 0)
+                        goto out;
+        }
+
+
+        /* The other values in restart are already filled in */
+        ret = -ERESTART_RESTARTBLOCK;
+out:
+        return ret;
+}
+
+/**
+ * alarm_timer_nsleep - alarmtimer nanosleep
+ * @which_clock: clockid
+ * @flags: determins abstime or relative
+ * @tsreq: requested sleep time (abs or rel)
+ * @rmtp: remaining sleep time saved
+ *
+ * Handles clock_nanosleep calls against _ALARM clockids
+ */
+static int alarm_timer_nsleep(const clockid_t which_clock, int flags,
+                     struct timespec *tsreq, struct timespec __user *rmtp)
+{
+        enum  alarmtimer_type type = clock2alarm(which_clock);
+        struct alarm alarm;
+        ktime_t exp;
+        int ret = 0;
+        struct restart_block *restart;
+
+        if (!capable(CAP_WAKE_ALARM))
+                return -EPERM;
+
+        alarm_init(&alarm, type, alarmtimer_nsleep_wakeup);
+
+        exp = timespec_to_ktime(*tsreq);
+        /* Convert (if necessary) to absolute time */
+        if (flags != TIMER_ABSTIME) {
+                ktime_t now = alarm_bases[type].gettime();
+                exp = ktime_add(now, exp);
+        }
+
+        if (alarmtimer_do_nsleep(&alarm, exp))
+                goto out;
+
+        if (freezing(current))
+                alarmtimer_freezerset(exp, type);
+
+        /* abs timers don't set remaining time or restart */
+        if (flags == TIMER_ABSTIME) {
+                ret = -ERESTARTNOHAND;
+                goto out;
+        }
+
+        if (rmtp) {
+                ret = update_rmtp(exp, type, rmtp);
+                if (ret <= 0)
+                        goto out;
+        }
+
+        restart = &current_thread_info()->restart_block;
+        restart->fn = alarm_timer_nsleep_restart;
+        restart->nanosleep.index = type;
+        restart->nanosleep.expires = exp.tv64;
+        restart->nanosleep.rmtp = rmtp;
+        ret = -ERESTART_RESTARTBLOCK;
+
+out:
+        return ret;
+}
+
+
+/* Suspend hook structures */
+static const struct dev_pm_ops alarmtimer_pm_ops = {
+        .suspend = alarmtimer_suspend,
+};
+
+static struct platform_driver alarmtimer_driver = {
+        .driver = {
+                .name = "alarmtimer",
+                .pm = &alarmtimer_pm_ops,
+        }
+};
+
+/**
+ * alarmtimer_init - Initialize alarm timer code
+ *
+ * This function initializes the alarm bases and registers
+ * the posix clock ids.
+ */
+static int __init alarmtimer_init(void)
+{
+        int error = 0;
+        int i;
+        struct k_clock alarm_clock = {
+                .clock_getres   = alarm_clock_getres,
+                .clock_get      = alarm_clock_get,
+                .timer_create   = alarm_timer_create,
+                .timer_set      = alarm_timer_set,
+                .timer_del      = alarm_timer_del,
+                .timer_get      = alarm_timer_get,
+                .nsleep         = alarm_timer_nsleep,
+        };
+
+        posix_timers_register_clock(CLOCK_REALTIME_ALARM, &alarm_clock);
+        posix_timers_register_clock(CLOCK_BOOTTIME_ALARM, &alarm_clock);
+
+        /* Initialize alarm bases */
+        alarm_bases[ALARM_REALTIME].base_clockid = CLOCK_REALTIME;
+        alarm_bases[ALARM_REALTIME].gettime = &ktime_get_real;
+        alarm_bases[ALARM_BOOTTIME].base_clockid = CLOCK_BOOTTIME;
+        alarm_bases[ALARM_BOOTTIME].gettime = &ktime_get_boottime;
+        for (i = 0; i < ALARM_NUMTYPE; i++) {
+                timerqueue_init_head(&alarm_bases[i].timerqueue);
+                spin_lock_init(&alarm_bases[i].lock);
+                hrtimer_init(&alarm_bases[i].timer,
+                                alarm_bases[i].base_clockid,
+                                HRTIMER_MODE_ABS);
+                alarm_bases[i].timer.function = alarmtimer_fired;
+        }
+        error = platform_driver_register(&alarmtimer_driver);
+        platform_device_register_simple("alarmtimer", -1, NULL, 0);
+
+        return error;
+}
+device_initcall(alarmtimer_init);
+
+#ifdef CONFIG_RTC_CLASS
+/**
+ * has_wakealarm - check rtc device has wakealarm ability
+ * @dev: current device
+ * @name_ptr: name to be returned
+ *
+ * This helper function checks to see if the rtc device can wake
+ * from suspend.
+ */
+static int __init has_wakealarm(struct device *dev, void *name_ptr)
+{
+        struct rtc_device *candidate = to_rtc_device(dev);
+
+        if (!candidate->ops->set_alarm)
+                return 0;
+        if (!device_may_wakeup(candidate->dev.parent))
+                return 0;
+
+        *(const char **)name_ptr = dev_name(dev);
+        return 1;
+}
+
+/**
+ * alarmtimer_init_late - Late initializing of alarmtimer code
+ *
+ * This function locates a rtc device to use for wakealarms.
+ * Run as late_initcall to make sure rtc devices have been
+ * registered.
+ */
+static int __init alarmtimer_init_late(void)
+{
+        char *str;
+
+        /* Find an rtc device and init the rtc_timer */
+        class_find_device(rtc_class, NULL, &str, has_wakealarm);
+        if (str)
+                rtcdev = rtc_class_open(str);
+        if (!rtcdev) {
+                printk(KERN_WARNING "No RTC device found, ALARM timers will"
+                        " not wake from suspend");
+        }
+        rtc_timer_init(&rtctimer, NULL, NULL);
+
+        return 0;
+}
+#else
+static int __init alarmtimer_init_late(void)
+{
+        printk(KERN_WARNING "Kernel not built with RTC support, ALARM timers"
+                " will not wake from suspend");
+        return 0;
+}
+#endif
+late_initcall(alarmtimer_init_late);
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index 8ad5d576755..8e6a05a5915 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -596,6 +596,58 @@ void __init timekeeping_init(void)
 static struct timespec timekeeping_suspend_time;
 
 /**
+ * __timekeeping_inject_sleeptime - Internal function to add sleep interval
+ * @delta: pointer to a timespec delta value
+ *
+ * Takes a timespec offset measuring a suspend interval and properly
+ * adds the sleep offset to the timekeeping variables.
+ */
+static void __timekeeping_inject_sleeptime(struct timespec *delta)
+{
+        xtime = timespec_add(xtime, *delta);
+        wall_to_monotonic = timespec_sub(wall_to_monotonic, *delta);
+        total_sleep_time = timespec_add(total_sleep_time, *delta);
+}
+
+
+/**
+ * timekeeping_inject_sleeptime - Adds suspend interval to timeekeeping values
+ * @delta: pointer to a timespec delta value
+ *
+ * This hook is for architectures that cannot support read_persistent_clock
+ * because their RTC/persistent clock is only accessible when irqs are enabled.
+ *
+ * This function should only be called by rtc_resume(), and allows
+ * a suspend offset to be injected into the timekeeping values.
+ */
+void timekeeping_inject_sleeptime(struct timespec *delta)
+{
+        unsigned long flags;
+        struct timespec ts;
+
+        /* Make sure we don't set the clock twice */
+        read_persistent_clock(&ts);
+        if (!(ts.tv_sec == 0 && ts.tv_nsec == 0))
+                return;
+
+        write_seqlock_irqsave(&xtime_lock, flags);
+        timekeeping_forward_now();
+
+        __timekeeping_inject_sleeptime(delta);
+
+        timekeeper.ntp_error = 0;
+        ntp_clear();
+        update_vsyscall(&xtime, &wall_to_monotonic, timekeeper.clock,
+                                timekeeper.mult);
+
+        write_sequnlock_irqrestore(&xtime_lock, flags);
+
+        /* signal hrtimers about time change */
+        clock_was_set();
+}
+
+
+/**
  * timekeeping_resume - Resumes the generic timekeeping subsystem.
  *
  * This is for the generic clocksource timekeeping.
@@ -615,9 +667,7 @@ static void timekeeping_resume(void)
 
         if (timespec_compare(&ts, &timekeeping_suspend_time) > 0) {
                 ts = timespec_sub(ts, timekeeping_suspend_time);
-                xtime = timespec_add(xtime, ts);
-                wall_to_monotonic = timespec_sub(wall_to_monotonic, ts);
-                total_sleep_time = timespec_add(total_sleep_time, ts);
+                __timekeeping_inject_sleeptime(&ts);
         }
         /* re-base the last cycle value */
         timekeeper.clock->cycle_last = timekeeper.clock->read(timekeeper.clock);