timers: Introduce in-kernel alarm-timer interface

This provides the in kernel interface and infrastructure for
alarm-timers.

Alarm-timers are a hybrid style timer, similar to hrtimers,
but when the system is suspended, the RTC device is set to
fire and wake the system for when the soonest alarm-timer
expires.

The concept for Alarm-timers was inspired by the Android Alarm
driver (by Arve Hjønnevåg) found in the Android kernel tree.

See: http://android.git.kernel.org/?p=kernel/common.git;a=blob;f=drivers/rtc/alarm.c;h=1250edfbdf3302f5e4ea6194847c6ef4bb7beb1c;hb=android-2.6.36

This in-kernel interface should be fairly compatible with the
Android alarm driver in-kernel interface, but has the advantage
of utilizing the new RTC timerqueue code instead of doing direct
RTC manipulation.

CC: Arve Hjønnevåg <arve@android.com>
CC: Thomas Gleixner <tglx@linutronix.de>
CC: Alessandro Zummo <a.zummo@towertech.it>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: John Stultz <john.stultz@linaro.org>

2 files changed, 376 insertions, 1 deletions

diff --git a/kernel/time/Makefile b/kernel/time/Makefile
index b0425991e9ac..e2fd74b8e8c2 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 000000000000..48c2ee949e61
--- /dev/null
+++ b/kernel/time/alarmtimer.c
@@ -0,0 +1,375 @@
+/*
+ * 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>
+
+
+static struct alarm_base {
+        spinlock_t              lock;
+        struct timerqueue_head  timerqueue;
+        struct hrtimer          timer;
+        ktime_t                 (*gettime)(void);
+        clockid_t               base_clockid;
+        struct work_struct      irqwork;
+} alarm_bases[ALARM_NUMTYPE];
+
+static struct rtc_timer         rtctimer;
+static struct rtc_device        *rtcdev;
+
+static ktime_t freezer_delta;
+static DEFINE_SPINLOCK(freezer_delta_lock);
+
+
+/**************************************************************************
+ * alarmtimer management code
+ */
+
+/*
+ * 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_do_work - Handles alarm being fired.
+ * @work: pointer to workqueue being run
+ *
+ * When a timer fires, this runs through the timerqueue to see
+ * which alarm timers, and run those that expired. If there are
+ * more alarm timers queued, we set the hrtimer to fire in the
+ * future.
+ */
+void alarmtimer_do_work(struct work_struct *work)
+{
+        struct alarm_base *base = container_of(work, struct alarm_base,
+                                                irqwork);
+        struct timerqueue_node *next;
+        unsigned long flags;
+        ktime_t now;
+
+        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_start(&base->timer, next->expires,
+                                HRTIMER_MODE_ABS);
+        }
+        spin_unlock_irqrestore(&base->lock, flags);
+}
+
+
+/*
+ * alarmtimer_fired - Handles alarm hrtimer being fired.
+ * @timer: pointer to hrtimer being run
+ *
+ * When a timer fires, this schedules the do_work function to
+ * be run.
+ */
+static enum hrtimer_restart alarmtimer_fired(struct hrtimer *timer)
+{
+        struct alarm_base *base = container_of(timer, struct alarm_base, timer);
+        schedule_work(&base->irqwork);
+        return HRTIMER_NORESTART;
+}
+
+
+/*
+ * 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;
+}
+
+
+/**************************************************************************
+ * alarm kernel interface code
+ */
+
+/*
+ * 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
+ *
+ * In-kernel interface to initializes the alarm structure.
+ */
+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
+ *
+ * In-kernel interface set an alarm timer.
+ */
+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
+ *
+ * In-kernel interface to cancel an alarm timer.
+ */
+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);
+}
+
+
+
+/**************************************************************************
+ * alarmtimer initialization code
+ */
+
+/* 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;
+
+        /* 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;
+                INIT_WORK(&alarm_bases[i].irqwork, alarmtimer_do_work);
+        }
+        error = platform_driver_register(&alarmtimer_driver);
+        platform_device_register_simple("alarmtimer", -1, NULL, 0);
+
+        return error;
+}
+device_initcall(alarmtimer_init);
+
+/**
+ * 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;
+}
+late_initcall(alarmtimer_init_late);