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