/*
   * RTC subsystem, base class
   *
   * Copyright (C) 2005 Tower Technologies
   * Author: Alessandro Zummo <a.zummo@towertech.it>
   *
   * class skeleton from drivers/hwmon/hwmon.c
   *
   * 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/module.h>
  #include <linux/rtc.h>
  #include <linux/kdev_t.h>
  #include <linux/idr.h>

  #include <linux/slab.h>

  #include <linux/workqueue.h>

  #include "rtc-core.h"

  static DEFINE_IDA(rtc_ida);

  struct class *rtc_class;

  static void rtc_device_release(struct device *dev)

  {

  	struct rtc_device *rtc = to_rtc_device(dev);

  	ida_simple_remove(&rtc_ida, rtc->id);

  	kfree(rtc);
  }

  #if defined(CONFIG_PM) && defined(CONFIG_RTC_HCTOSYS_DEVICE)
  
  /*
   * On suspend(), measure the delta between one RTC and the
   * system's wall clock; restore it on resume().
   */

  static struct timespec old_rtc, old_system, old_delta;

  
  static int rtc_suspend(struct device *dev, pm_message_t mesg)
  {
  	struct rtc_device	*rtc = to_rtc_device(dev);
  	struct rtc_time		tm;

  	struct timespec		delta, delta_delta;

  	if (strcmp(dev_name(&rtc->dev), CONFIG_RTC_HCTOSYS_DEVICE) != 0)

  		return 0;

  	/* snapshot the current RTC and system time at suspend*/

  	rtc_read_time(rtc, &tm);

  	getnstimeofday(&old_system);
  	rtc_tm_to_time(&tm, &old_rtc.tv_sec);
  
  
  	/*
  	 * To avoid drift caused by repeated suspend/resumes,
  	 * which each can add ~1 second drift error,
  	 * try to compensate so the difference in system time
  	 * and rtc time stays close to constant.
  	 */
  	delta = timespec_sub(old_system, old_rtc);
  	delta_delta = timespec_sub(delta, old_delta);

  	if (delta_delta.tv_sec < -2 || delta_delta.tv_sec >= 2) {

  		/*
  		 * if delta_delta is too large, assume time correction
  		 * has occured and set old_delta to the current delta.
  		 */
  		old_delta = delta;
  	} else {
  		/* Otherwise try to adjust old_system to compensate */
  		old_system = timespec_sub(old_system, delta_delta);
  	}

  	return 0;
  }
  
  static int rtc_resume(struct device *dev)
  {
  	struct rtc_device	*rtc = to_rtc_device(dev);
  	struct rtc_time		tm;

  	struct timespec		new_system, new_rtc;
  	struct timespec		sleep_time;

  	if (strcmp(dev_name(&rtc->dev), CONFIG_RTC_HCTOSYS_DEVICE) != 0)

  		return 0;

  	/* snapshot the current rtc and system time at resume */
  	getnstimeofday(&new_system);

  	rtc_read_time(rtc, &tm);
  	if (rtc_valid_tm(&tm) != 0) {

  		pr_debug("%s:  bogus resume time
  ", dev_name(&rtc->dev));

  		return 0;
  	}

  	rtc_tm_to_time(&tm, &new_rtc.tv_sec);
  	new_rtc.tv_nsec = 0;

  	if (new_rtc.tv_sec < old_rtc.tv_sec) {
  		pr_debug("%s:  time travel!
  ", dev_name(&rtc->dev));

  		return 0;
  	}

  	/* calculate the RTC time delta (sleep time)*/
  	sleep_time = timespec_sub(new_rtc, old_rtc);
  
  	/*
  	 * Since these RTC suspend/resume handlers are not called
  	 * at the very end of suspend or the start of resume,
  	 * some run-time may pass on either sides of the sleep time
  	 * so subtract kernel run-time between rtc_suspend to rtc_resume
  	 * to keep things accurate.
  	 */
  	sleep_time = timespec_sub(sleep_time,
  			timespec_sub(new_system, old_system));

  	if (sleep_time.tv_sec >= 0)
  		timekeeping_inject_sleeptime(&sleep_time);

  	return 0;
  }
  
  #else
  #define rtc_suspend	NULL
  #define rtc_resume	NULL
  #endif

  /**
   * rtc_device_register - register w/ RTC class
   * @dev: the device to register
   *
   * rtc_device_unregister() must be called when the class device is no
   * longer needed.
   *
   * Returns the pointer to the new struct class device.
   */
  struct rtc_device *rtc_device_register(const char *name, struct device *dev,

  					const struct rtc_class_ops *ops,

  					struct module *owner)
  {
  	struct rtc_device *rtc;

  	struct rtc_wkalrm alrm;

  	int id, err;

  	id = ida_simple_get(&rtc_ida, 0, 0, GFP_KERNEL);
  	if (id < 0) {
  		err = id;

  		goto exit;
  	}

  	rtc = kzalloc(sizeof(struct rtc_device), GFP_KERNEL);
  	if (rtc == NULL) {
  		err = -ENOMEM;

  		goto exit_ida;

  	}
  
  	rtc->id = id;
  	rtc->ops = ops;
  	rtc->owner = owner;

  	rtc->irq_freq = 1;

  	rtc->max_user_freq = 64;

  	rtc->dev.parent = dev;
  	rtc->dev.class = rtc_class;
  	rtc->dev.release = rtc_device_release;

  
  	mutex_init(&rtc->ops_lock);
  	spin_lock_init(&rtc->irq_lock);
  	spin_lock_init(&rtc->irq_task_lock);

  	init_waitqueue_head(&rtc->irq_queue);

  	/* Init timerqueue */
  	timerqueue_init_head(&rtc->timerqueue);

  	INIT_WORK(&rtc->irqwork, rtc_timer_do_work);

  	/* Init aie timer */

  	rtc_timer_init(&rtc->aie_timer, rtc_aie_update_irq, (void *)rtc);

  	/* Init uie timer */

  	rtc_timer_init(&rtc->uie_rtctimer, rtc_uie_update_irq, (void *)rtc);

  	/* Init pie timer */
  	hrtimer_init(&rtc->pie_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
  	rtc->pie_timer.function = rtc_pie_update_irq;
  	rtc->pie_enabled = 0;

  	/* Check to see if there is an ALARM already set in hw */
  	err = __rtc_read_alarm(rtc, &alrm);
  
  	if (!err && !rtc_valid_tm(&alrm.time))

  		rtc_initialize_alarm(rtc, &alrm);

  	strlcpy(rtc->name, name, RTC_DEVICE_NAME_SIZE);

  	dev_set_name(&rtc->dev, "rtc%d", id);

  	rtc_dev_prepare(rtc);

  	err = device_register(&rtc->dev);

  	if (err) {
  		put_device(&rtc->dev);

  		goto exit_kfree;

  	}

  	rtc_dev_add_device(rtc);

  	rtc_sysfs_add_device(rtc);

  	rtc_proc_add_device(rtc);

  	dev_info(dev, "rtc core: registered %s as %s
  ",

  			rtc->name, dev_name(&rtc->dev));

  
  	return rtc;
  
  exit_kfree:
  	kfree(rtc);

  exit_ida:
  	ida_simple_remove(&rtc_ida, id);

  
  exit:

  	dev_err(dev, "rtc core: unable to register %s, err = %d
  ",
  			name, err);

  	return ERR_PTR(err);
  }
  EXPORT_SYMBOL_GPL(rtc_device_register);
  
  
  /**
   * rtc_device_unregister - removes the previously registered RTC class device
   *
   * @rtc: the RTC class device to destroy
   */
  void rtc_device_unregister(struct rtc_device *rtc)
  {

  	if (get_device(&rtc->dev) != NULL) {

  		mutex_lock(&rtc->ops_lock);
  		/* remove innards of this RTC, then disable it, before
  		 * letting any rtc_class_open() users access it again
  		 */

  		rtc_sysfs_del_device(rtc);

  		rtc_dev_del_device(rtc);

  		rtc_proc_del_device(rtc);

  		device_unregister(&rtc->dev);

  		rtc->ops = NULL;
  		mutex_unlock(&rtc->ops_lock);

  		put_device(&rtc->dev);

  	}

  }
  EXPORT_SYMBOL_GPL(rtc_device_unregister);

  static int __init rtc_init(void)
  {
  	rtc_class = class_create(THIS_MODULE, "rtc");
  	if (IS_ERR(rtc_class)) {
  		printk(KERN_ERR "%s: couldn't create class
  ", __FILE__);
  		return PTR_ERR(rtc_class);
  	}

  	rtc_class->suspend = rtc_suspend;
  	rtc_class->resume = rtc_resume;

  	rtc_dev_init();

  	rtc_sysfs_init(rtc_class);

  	return 0;
  }
  
  static void __exit rtc_exit(void)
  {

  	rtc_dev_exit();

  	class_destroy(rtc_class);

  	ida_destroy(&rtc_ida);

  }

  subsys_initcall(rtc_init);

  module_exit(rtc_exit);

  MODULE_AUTHOR("Alessandro Zummo <a.zummo@towertech.it>");

  MODULE_DESCRIPTION("RTC class support");
  MODULE_LICENSE("GPL");