linux/drivers/rtc/class.c
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   1/*
   2 * RTC subsystem, base class
   3 *
   4 * Copyright (C) 2005 Tower Technologies
   5 * Author: Alessandro Zummo <a.zummo@towertech.it>
   6 *
   7 * class skeleton from drivers/hwmon/hwmon.c
   8 *
   9 * This program is free software; you can redistribute it and/or modify
  10 * it under the terms of the GNU General Public License version 2 as
  11 * published by the Free Software Foundation.
  12*/
  13
  14#include <linux/module.h>
  15#include <linux/rtc.h>
  16#include <linux/kdev_t.h>
  17#include <linux/idr.h>
  18#include <linux/slab.h>
  19#include <linux/workqueue.h>
  20
  21#include "rtc-core.h"
  22
  23
  24static DEFINE_IDA(rtc_ida);
  25struct class *rtc_class;
  26
  27static void rtc_device_release(struct device *dev)
  28{
  29        struct rtc_device *rtc = to_rtc_device(dev);
  30        ida_simple_remove(&rtc_ida, rtc->id);
  31        kfree(rtc);
  32}
  33
  34#ifdef CONFIG_RTC_HCTOSYS_DEVICE
  35/* Result of the last RTC to system clock attempt. */
  36int rtc_hctosys_ret = -ENODEV;
  37#endif
  38
  39#if defined(CONFIG_PM) && defined(CONFIG_RTC_HCTOSYS_DEVICE)
  40/*
  41 * On suspend(), measure the delta between one RTC and the
  42 * system's wall clock; restore it on resume().
  43 */
  44
  45static struct timespec old_rtc, old_system, old_delta;
  46
  47
  48static int rtc_suspend(struct device *dev, pm_message_t mesg)
  49{
  50        struct rtc_device       *rtc = to_rtc_device(dev);
  51        struct rtc_time         tm;
  52        struct timespec         delta, delta_delta;
  53        if (strcmp(dev_name(&rtc->dev), CONFIG_RTC_HCTOSYS_DEVICE) != 0)
  54                return 0;
  55
  56        /* snapshot the current RTC and system time at suspend*/
  57        rtc_read_time(rtc, &tm);
  58        getnstimeofday(&old_system);
  59        rtc_tm_to_time(&tm, &old_rtc.tv_sec);
  60
  61
  62        /*
  63         * To avoid drift caused by repeated suspend/resumes,
  64         * which each can add ~1 second drift error,
  65         * try to compensate so the difference in system time
  66         * and rtc time stays close to constant.
  67         */
  68        delta = timespec_sub(old_system, old_rtc);
  69        delta_delta = timespec_sub(delta, old_delta);
  70        if (delta_delta.tv_sec < -2 || delta_delta.tv_sec >= 2) {
  71                /*
  72                 * if delta_delta is too large, assume time correction
  73                 * has occured and set old_delta to the current delta.
  74                 */
  75                old_delta = delta;
  76        } else {
  77                /* Otherwise try to adjust old_system to compensate */
  78                old_system = timespec_sub(old_system, delta_delta);
  79        }
  80
  81        return 0;
  82}
  83
  84static int rtc_resume(struct device *dev)
  85{
  86        struct rtc_device       *rtc = to_rtc_device(dev);
  87        struct rtc_time         tm;
  88        struct timespec         new_system, new_rtc;
  89        struct timespec         sleep_time;
  90
  91        rtc_hctosys_ret = -ENODEV;
  92        if (strcmp(dev_name(&rtc->dev), CONFIG_RTC_HCTOSYS_DEVICE) != 0)
  93                return 0;
  94
  95        /* snapshot the current rtc and system time at resume */
  96        getnstimeofday(&new_system);
  97        rtc_read_time(rtc, &tm);
  98        if (rtc_valid_tm(&tm) != 0) {
  99                pr_debug("%s:  bogus resume time\n", dev_name(&rtc->dev));
 100                return 0;
 101        }
 102        rtc_tm_to_time(&tm, &new_rtc.tv_sec);
 103        new_rtc.tv_nsec = 0;
 104
 105        if (new_rtc.tv_sec < old_rtc.tv_sec) {
 106                pr_debug("%s:  time travel!\n", dev_name(&rtc->dev));
 107                return 0;
 108        }
 109
 110        /* calculate the RTC time delta (sleep time)*/
 111        sleep_time = timespec_sub(new_rtc, old_rtc);
 112
 113        /*
 114         * Since these RTC suspend/resume handlers are not called
 115         * at the very end of suspend or the start of resume,
 116         * some run-time may pass on either sides of the sleep time
 117         * so subtract kernel run-time between rtc_suspend to rtc_resume
 118         * to keep things accurate.
 119         */
 120        sleep_time = timespec_sub(sleep_time,
 121                        timespec_sub(new_system, old_system));
 122
 123        if (sleep_time.tv_sec >= 0)
 124                timekeeping_inject_sleeptime(&sleep_time);
 125        rtc_hctosys_ret = 0;
 126        return 0;
 127}
 128
 129#else
 130#define rtc_suspend     NULL
 131#define rtc_resume      NULL
 132#endif
 133
 134
 135/**
 136 * rtc_device_register - register w/ RTC class
 137 * @dev: the device to register
 138 *
 139 * rtc_device_unregister() must be called when the class device is no
 140 * longer needed.
 141 *
 142 * Returns the pointer to the new struct class device.
 143 */
 144struct rtc_device *rtc_device_register(const char *name, struct device *dev,
 145                                        const struct rtc_class_ops *ops,
 146                                        struct module *owner)
 147{
 148        struct rtc_device *rtc;
 149        struct rtc_wkalrm alrm;
 150        int id, err;
 151
 152        id = ida_simple_get(&rtc_ida, 0, 0, GFP_KERNEL);
 153        if (id < 0) {
 154                err = id;
 155                goto exit;
 156        }
 157
 158        rtc = kzalloc(sizeof(struct rtc_device), GFP_KERNEL);
 159        if (rtc == NULL) {
 160                err = -ENOMEM;
 161                goto exit_ida;
 162        }
 163
 164        rtc->id = id;
 165        rtc->ops = ops;
 166        rtc->owner = owner;
 167        rtc->irq_freq = 1;
 168        rtc->max_user_freq = 64;
 169        rtc->dev.parent = dev;
 170        rtc->dev.class = rtc_class;
 171        rtc->dev.release = rtc_device_release;
 172
 173        mutex_init(&rtc->ops_lock);
 174        spin_lock_init(&rtc->irq_lock);
 175        spin_lock_init(&rtc->irq_task_lock);
 176        init_waitqueue_head(&rtc->irq_queue);
 177
 178        /* Init timerqueue */
 179        timerqueue_init_head(&rtc->timerqueue);
 180        INIT_WORK(&rtc->irqwork, rtc_timer_do_work);
 181        /* Init aie timer */
 182        rtc_timer_init(&rtc->aie_timer, rtc_aie_update_irq, (void *)rtc);
 183        /* Init uie timer */
 184        rtc_timer_init(&rtc->uie_rtctimer, rtc_uie_update_irq, (void *)rtc);
 185        /* Init pie timer */
 186        hrtimer_init(&rtc->pie_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
 187        rtc->pie_timer.function = rtc_pie_update_irq;
 188        rtc->pie_enabled = 0;
 189
 190        /* Check to see if there is an ALARM already set in hw */
 191        err = __rtc_read_alarm(rtc, &alrm);
 192
 193        if (!err && !rtc_valid_tm(&alrm.time))
 194                rtc_initialize_alarm(rtc, &alrm);
 195
 196        strlcpy(rtc->name, name, RTC_DEVICE_NAME_SIZE);
 197        dev_set_name(&rtc->dev, "rtc%d", id);
 198
 199        rtc_dev_prepare(rtc);
 200
 201        err = device_register(&rtc->dev);
 202        if (err) {
 203                put_device(&rtc->dev);
 204                goto exit_kfree;
 205        }
 206
 207        rtc_dev_add_device(rtc);
 208        rtc_sysfs_add_device(rtc);
 209        rtc_proc_add_device(rtc);
 210
 211        dev_info(dev, "rtc core: registered %s as %s\n",
 212                        rtc->name, dev_name(&rtc->dev));
 213
 214        return rtc;
 215
 216exit_kfree:
 217        kfree(rtc);
 218
 219exit_ida:
 220        ida_simple_remove(&rtc_ida, id);
 221
 222exit:
 223        dev_err(dev, "rtc core: unable to register %s, err = %d\n",
 224                        name, err);
 225        return ERR_PTR(err);
 226}
 227EXPORT_SYMBOL_GPL(rtc_device_register);
 228
 229
 230/**
 231 * rtc_device_unregister - removes the previously registered RTC class device
 232 *
 233 * @rtc: the RTC class device to destroy
 234 */
 235void rtc_device_unregister(struct rtc_device *rtc)
 236{
 237        if (get_device(&rtc->dev) != NULL) {
 238                mutex_lock(&rtc->ops_lock);
 239                /* remove innards of this RTC, then disable it, before
 240                 * letting any rtc_class_open() users access it again
 241                 */
 242                rtc_sysfs_del_device(rtc);
 243                rtc_dev_del_device(rtc);
 244                rtc_proc_del_device(rtc);
 245                device_unregister(&rtc->dev);
 246                rtc->ops = NULL;
 247                mutex_unlock(&rtc->ops_lock);
 248                put_device(&rtc->dev);
 249        }
 250}
 251EXPORT_SYMBOL_GPL(rtc_device_unregister);
 252
 253static int __init rtc_init(void)
 254{
 255        rtc_class = class_create(THIS_MODULE, "rtc");
 256        if (IS_ERR(rtc_class)) {
 257                printk(KERN_ERR "%s: couldn't create class\n", __FILE__);
 258                return PTR_ERR(rtc_class);
 259        }
 260        rtc_class->suspend = rtc_suspend;
 261        rtc_class->resume = rtc_resume;
 262        rtc_dev_init();
 263        rtc_sysfs_init(rtc_class);
 264        return 0;
 265}
 266
 267static void __exit rtc_exit(void)
 268{
 269        rtc_dev_exit();
 270        class_destroy(rtc_class);
 271        ida_destroy(&rtc_ida);
 272}
 273
 274subsys_initcall(rtc_init);
 275module_exit(rtc_exit);
 276
 277MODULE_AUTHOR("Alessandro Zummo <a.zummo@towertech.it>");
 278MODULE_DESCRIPTION("RTC class support");
 279MODULE_LICENSE("GPL");
 280
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