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#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  15
  16#include <linux/module.h>
  17#include <linux/rtc.h>
  18#include <linux/kdev_t.h>
  19#include <linux/idr.h>
  20#include <linux/slab.h>
  21#include <linux/workqueue.h>
  22
  23#include "rtc-core.h"
  24
  25
  26static DEFINE_IDA(rtc_ida);
  27struct class *rtc_class;
  28
  29static void rtc_device_release(struct device *dev)
  30{
  31        struct rtc_device *rtc = to_rtc_device(dev);
  32        ida_simple_remove(&rtc_ida, rtc->id);
  33        kfree(rtc);
  34}
  35
  36#ifdef CONFIG_RTC_HCTOSYS_DEVICE
  37/* Result of the last RTC to system clock attempt. */
  38int rtc_hctosys_ret = -ENODEV;
  39#endif
  40
  41#if defined(CONFIG_PM) && defined(CONFIG_RTC_HCTOSYS_DEVICE)
  42/*
  43 * On suspend(), measure the delta between one RTC and the
  44 * system's wall clock; restore it on resume().
  45 */
  46
  47static struct timespec old_rtc, old_system, old_delta;
  48
  49
  50static int rtc_suspend(struct device *dev, pm_message_t mesg)
  51{
  52        struct rtc_device       *rtc = to_rtc_device(dev);
  53        struct rtc_time         tm;
  54        struct timespec         delta, delta_delta;
  55
  56        if (has_persistent_clock())
  57                return 0;
  58
  59        if (strcmp(dev_name(&rtc->dev), CONFIG_RTC_HCTOSYS_DEVICE) != 0)
  60                return 0;
  61
  62        /* snapshot the current RTC and system time at suspend*/
  63        rtc_read_time(rtc, &tm);
  64        getnstimeofday(&old_system);
  65        rtc_tm_to_time(&tm, &old_rtc.tv_sec);
  66
  67
  68        /*
  69         * To avoid drift caused by repeated suspend/resumes,
  70         * which each can add ~1 second drift error,
  71         * try to compensate so the difference in system time
  72         * and rtc time stays close to constant.
  73         */
  74        delta = timespec_sub(old_system, old_rtc);
  75        delta_delta = timespec_sub(delta, old_delta);
  76        if (delta_delta.tv_sec < -2 || delta_delta.tv_sec >= 2) {
  77                /*
  78                 * if delta_delta is too large, assume time correction
  79                 * has occured and set old_delta to the current delta.
  80                 */
  81                old_delta = delta;
  82        } else {
  83                /* Otherwise try to adjust old_system to compensate */
  84                old_system = timespec_sub(old_system, delta_delta);
  85        }
  86
  87        return 0;
  88}
  89
  90static int rtc_resume(struct device *dev)
  91{
  92        struct rtc_device       *rtc = to_rtc_device(dev);
  93        struct rtc_time         tm;
  94        struct timespec         new_system, new_rtc;
  95        struct timespec         sleep_time;
  96
  97        if (has_persistent_clock())
  98                return 0;
  99
 100        rtc_hctosys_ret = -ENODEV;
 101        if (strcmp(dev_name(&rtc->dev), CONFIG_RTC_HCTOSYS_DEVICE) != 0)
 102                return 0;
 103
 104        /* snapshot the current rtc and system time at resume */
 105        getnstimeofday(&new_system);
 106        rtc_read_time(rtc, &tm);
 107        if (rtc_valid_tm(&tm) != 0) {
 108                pr_debug("%s:  bogus resume time\n", dev_name(&rtc->dev));
 109                return 0;
 110        }
 111        rtc_tm_to_time(&tm, &new_rtc.tv_sec);
 112        new_rtc.tv_nsec = 0;
 113
 114        if (new_rtc.tv_sec < old_rtc.tv_sec) {
 115                pr_debug("%s:  time travel!\n", dev_name(&rtc->dev));
 116                return 0;
 117        }
 118
 119        /* calculate the RTC time delta (sleep time)*/
 120        sleep_time = timespec_sub(new_rtc, old_rtc);
 121
 122        /*
 123         * Since these RTC suspend/resume handlers are not called
 124         * at the very end of suspend or the start of resume,
 125         * some run-time may pass on either sides of the sleep time
 126         * so subtract kernel run-time between rtc_suspend to rtc_resume
 127         * to keep things accurate.
 128         */
 129        sleep_time = timespec_sub(sleep_time,
 130                        timespec_sub(new_system, old_system));
 131
 132        if (sleep_time.tv_sec >= 0)
 133                timekeeping_inject_sleeptime(&sleep_time);
 134        rtc_hctosys_ret = 0;
 135        return 0;
 136}
 137
 138#else
 139#define rtc_suspend     NULL
 140#define rtc_resume      NULL
 141#endif
 142
 143
 144/**
 145 * rtc_device_register - register w/ RTC class
 146 * @dev: the device to register
 147 *
 148 * rtc_device_unregister() must be called when the class device is no
 149 * longer needed.
 150 *
 151 * Returns the pointer to the new struct class device.
 152 */
 153struct rtc_device *rtc_device_register(const char *name, struct device *dev,
 154                                        const struct rtc_class_ops *ops,
 155                                        struct module *owner)
 156{
 157        struct rtc_device *rtc;
 158        struct rtc_wkalrm alrm;
 159        int id, err;
 160
 161        id = ida_simple_get(&rtc_ida, 0, 0, GFP_KERNEL);
 162        if (id < 0) {
 163                err = id;
 164                goto exit;
 165        }
 166
 167        rtc = kzalloc(sizeof(struct rtc_device), GFP_KERNEL);
 168        if (rtc == NULL) {
 169                err = -ENOMEM;
 170                goto exit_ida;
 171        }
 172
 173        rtc->id = id;
 174        rtc->ops = ops;
 175        rtc->owner = owner;
 176        rtc->irq_freq = 1;
 177        rtc->max_user_freq = 64;
 178        rtc->dev.parent = dev;
 179        rtc->dev.class = rtc_class;
 180        rtc->dev.release = rtc_device_release;
 181
 182        mutex_init(&rtc->ops_lock);
 183        spin_lock_init(&rtc->irq_lock);
 184        spin_lock_init(&rtc->irq_task_lock);
 185        init_waitqueue_head(&rtc->irq_queue);
 186
 187        /* Init timerqueue */
 188        timerqueue_init_head(&rtc->timerqueue);
 189        INIT_WORK(&rtc->irqwork, rtc_timer_do_work);
 190        /* Init aie timer */
 191        rtc_timer_init(&rtc->aie_timer, rtc_aie_update_irq, (void *)rtc);
 192        /* Init uie timer */
 193        rtc_timer_init(&rtc->uie_rtctimer, rtc_uie_update_irq, (void *)rtc);
 194        /* Init pie timer */
 195        hrtimer_init(&rtc->pie_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
 196        rtc->pie_timer.function = rtc_pie_update_irq;
 197        rtc->pie_enabled = 0;
 198
 199        /* Check to see if there is an ALARM already set in hw */
 200        err = __rtc_read_alarm(rtc, &alrm);
 201
 202        if (!err && !rtc_valid_tm(&alrm.time))
 203                rtc_initialize_alarm(rtc, &alrm);
 204
 205        strlcpy(rtc->name, name, RTC_DEVICE_NAME_SIZE);
 206        dev_set_name(&rtc->dev, "rtc%d", id);
 207
 208        rtc_dev_prepare(rtc);
 209
 210        err = device_register(&rtc->dev);
 211        if (err) {
 212                put_device(&rtc->dev);
 213                goto exit_kfree;
 214        }
 215
 216        rtc_dev_add_device(rtc);
 217        rtc_sysfs_add_device(rtc);
 218        rtc_proc_add_device(rtc);
 219
 220        dev_info(dev, "rtc core: registered %s as %s\n",
 221                        rtc->name, dev_name(&rtc->dev));
 222
 223        return rtc;
 224
 225exit_kfree:
 226        kfree(rtc);
 227
 228exit_ida:
 229        ida_simple_remove(&rtc_ida, id);
 230
 231exit:
 232        dev_err(dev, "rtc core: unable to register %s, err = %d\n",
 233                        name, err);
 234        return ERR_PTR(err);
 235}
 236EXPORT_SYMBOL_GPL(rtc_device_register);
 237
 238
 239/**
 240 * rtc_device_unregister - removes the previously registered RTC class device
 241 *
 242 * @rtc: the RTC class device to destroy
 243 */
 244void rtc_device_unregister(struct rtc_device *rtc)
 245{
 246        if (get_device(&rtc->dev) != NULL) {
 247                mutex_lock(&rtc->ops_lock);
 248                /* remove innards of this RTC, then disable it, before
 249                 * letting any rtc_class_open() users access it again
 250                 */
 251                rtc_sysfs_del_device(rtc);
 252                rtc_dev_del_device(rtc);
 253                rtc_proc_del_device(rtc);
 254                device_unregister(&rtc->dev);
 255                rtc->ops = NULL;
 256                mutex_unlock(&rtc->ops_lock);
 257                put_device(&rtc->dev);
 258        }
 259}
 260EXPORT_SYMBOL_GPL(rtc_device_unregister);
 261
 262static int __init rtc_init(void)
 263{
 264        rtc_class = class_create(THIS_MODULE, "rtc");
 265        if (IS_ERR(rtc_class)) {
 266                pr_err("couldn't create class\n");
 267                return PTR_ERR(rtc_class);
 268        }
 269        rtc_class->suspend = rtc_suspend;
 270        rtc_class->resume = rtc_resume;
 271        rtc_dev_init();
 272        rtc_sysfs_init(rtc_class);
 273        return 0;
 274}
 275
 276static void __exit rtc_exit(void)
 277{
 278        rtc_dev_exit();
 279        class_destroy(rtc_class);
 280        ida_destroy(&rtc_ida);
 281}
 282
 283subsys_initcall(rtc_init);
 284module_exit(rtc_exit);
 285
 286MODULE_AUTHOR("Alessandro Zummo <a.zummo@towertech.it>");
 287MODULE_DESCRIPTION("RTC class support");
 288MODULE_LICENSE("GPL");
 289
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