// SPDX-License-Identifier: GPL-2.0

  /*
   * RTC subsystem, base class
   *
   * Copyright (C) 2005 Tower Technologies
   * Author: Alessandro Zummo <a.zummo@towertech.it>
   *
   * class skeleton from drivers/hwmon/hwmon.c

   */

  #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

  #include <linux/module.h>

  #include <linux/of.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);
  }

  #ifdef CONFIG_RTC_HCTOSYS_DEVICE
  /* Result of the last RTC to system clock attempt. */
  int rtc_hctosys_ret = -ENODEV;

  
  /* IMPORTANT: the RTC only stores whole seconds. It is arbitrary
   * whether it stores the most close value or the value with partial
   * seconds truncated. However, it is important that we use it to store
   * the truncated value. This is because otherwise it is necessary,
   * in an rtc sync function, to read both xtime.tv_sec and
   * xtime.tv_nsec. On some processors (i.e. ARM), an atomic read
   * of >32bits is not possible. So storing the most close value would
   * slow down the sync API. So here we have the truncated value and
   * the best guess is to add 0.5s.
   */
  
  static void rtc_hctosys(struct rtc_device *rtc)
  {
  	int err;
  	struct rtc_time tm;
  	struct timespec64 tv64 = {
  		.tv_nsec = NSEC_PER_SEC >> 1,
  	};
  
  	err = rtc_read_time(rtc, &tm);
  	if (err) {
  		dev_err(rtc->dev.parent,
  			"hctosys: unable to read the hardware clock
  ");
  		goto err_read;
  	}
  
  	tv64.tv_sec = rtc_tm_to_time64(&tm);
  
  #if BITS_PER_LONG == 32
  	if (tv64.tv_sec > INT_MAX) {
  		err = -ERANGE;
  		goto err_read;
  	}
  #endif
  
  	err = do_settimeofday64(&tv64);
  
  	dev_info(rtc->dev.parent, "setting system clock to %ptR UTC (%lld)
  ",
  		 &tm, (long long)tv64.tv_sec);
  
  err_read:
  	rtc_hctosys_ret = err;
  }

  #endif

  #if defined(CONFIG_PM_SLEEP) && 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 timespec64 old_rtc, old_system, old_delta;

  static int rtc_suspend(struct device *dev)

  {
  	struct rtc_device	*rtc = to_rtc_device(dev);
  	struct rtc_time		tm;

  	struct timespec64	delta, delta_delta;

  	int err;

  	if (timekeeping_rtc_skipsuspend())

  		return 0;

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

  		return 0;

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

  	err = rtc_read_time(rtc, &tm);
  	if (err < 0) {
  		pr_debug("%s:  fail to read rtc time
  ", dev_name(&rtc->dev));
  		return 0;
  	}

  	ktime_get_real_ts64(&old_system);

  	old_rtc.tv_sec = rtc_tm_to_time64(&tm);

  	/*
  	 * 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 = timespec64_sub(old_system, old_rtc);
  	delta_delta = timespec64_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 occurred and set old_delta to the current delta.

  		 */
  		old_delta = delta;
  	} else {
  		/* Otherwise try to adjust old_system to compensate */

  		old_system = timespec64_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 timespec64	new_system, new_rtc;
  	struct timespec64	sleep_time;

  	int err;

  	if (timekeeping_rtc_skipresume())

  		return 0;

  	rtc_hctosys_ret = -ENODEV;

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

  		return 0;

  	/* snapshot the current rtc and system time at resume */

  	ktime_get_real_ts64(&new_system);

  	err = rtc_read_time(rtc, &tm);
  	if (err < 0) {
  		pr_debug("%s:  fail to read rtc time
  ", dev_name(&rtc->dev));
  		return 0;
  	}

  	new_rtc.tv_sec = rtc_tm_to_time64(&tm);

  	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 = timespec64_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 = timespec64_sub(sleep_time,

  				    timespec64_sub(new_system, old_system));

  	if (sleep_time.tv_sec >= 0)

  		timekeeping_inject_sleeptime64(&sleep_time);

  	rtc_hctosys_ret = 0;

  	return 0;
  }

  static SIMPLE_DEV_PM_OPS(rtc_class_dev_pm_ops, rtc_suspend, rtc_resume);
  #define RTC_CLASS_DEV_PM_OPS	(&rtc_class_dev_pm_ops)

  #else

  #define RTC_CLASS_DEV_PM_OPS	NULL

  #endif

  /* Ensure the caller will set the id before releasing the device */

  static struct rtc_device *rtc_allocate_device(void)
  {
  	struct rtc_device *rtc;
  
  	rtc = kzalloc(sizeof(*rtc), GFP_KERNEL);
  	if (!rtc)
  		return NULL;
  
  	device_initialize(&rtc->dev);

  	/* Drivers can revise this default after allocating the device. */
  	rtc->set_offset_nsec =  NSEC_PER_SEC / 2;

  	rtc->irq_freq = 1;
  	rtc->max_user_freq = 64;
  	rtc->dev.class = rtc_class;
  	rtc->dev.groups = rtc_get_dev_attribute_groups();
  	rtc->dev.release = rtc_device_release;
  
  	mutex_init(&rtc->ops_lock);
  	spin_lock_init(&rtc->irq_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, rtc);

  	/* Init uie timer */

  	rtc_timer_init(&rtc->uie_rtctimer, rtc_uie_update_irq, 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;
  
  	return rtc;
  }

  static int rtc_device_get_id(struct device *dev)
  {
  	int of_id = -1, id = -1;
  
  	if (dev->of_node)
  		of_id = of_alias_get_id(dev->of_node, "rtc");
  	else if (dev->parent && dev->parent->of_node)
  		of_id = of_alias_get_id(dev->parent->of_node, "rtc");
  
  	if (of_id >= 0) {
  		id = ida_simple_get(&rtc_ida, of_id, of_id + 1, GFP_KERNEL);
  		if (id < 0)
  			dev_warn(dev, "/aliases ID %d not available
  ", of_id);
  	}
  
  	if (id < 0)
  		id = ida_simple_get(&rtc_ida, 0, 0, GFP_KERNEL);
  
  	return id;
  }

  static void rtc_device_get_offset(struct rtc_device *rtc)
  {
  	time64_t range_secs;
  	u32 start_year;
  	int ret;
  
  	/*
  	 * If RTC driver did not implement the range of RTC hardware device,
  	 * then we can not expand the RTC range by adding or subtracting one
  	 * offset.
  	 */
  	if (rtc->range_min == rtc->range_max)
  		return;
  
  	ret = device_property_read_u32(rtc->dev.parent, "start-year",
  				       &start_year);
  	if (!ret) {
  		rtc->start_secs = mktime64(start_year, 1, 1, 0, 0, 0);
  		rtc->set_start_time = true;
  	}
  
  	/*
  	 * If user did not implement the start time for RTC driver, then no
  	 * need to expand the RTC range.
  	 */
  	if (!rtc->set_start_time)
  		return;
  
  	range_secs = rtc->range_max - rtc->range_min + 1;
  
  	/*
  	 * If the start_secs is larger than the maximum seconds (rtc->range_max)
  	 * supported by RTC hardware or the maximum seconds of new expanded
  	 * range (start_secs + rtc->range_max - rtc->range_min) is less than
  	 * rtc->range_min, which means the minimum seconds (rtc->range_min) of
  	 * RTC hardware will be mapped to start_secs by adding one offset, so
  	 * the offset seconds calculation formula should be:
  	 * rtc->offset_secs = rtc->start_secs - rtc->range_min;
  	 *
  	 * If the start_secs is larger than the minimum seconds (rtc->range_min)
  	 * supported by RTC hardware, then there is one region is overlapped
  	 * between the original RTC hardware range and the new expanded range,
  	 * and this overlapped region do not need to be mapped into the new
  	 * expanded range due to it is valid for RTC device. So the minimum
  	 * seconds of RTC hardware (rtc->range_min) should be mapped to
  	 * rtc->range_max + 1, then the offset seconds formula should be:
  	 * rtc->offset_secs = rtc->range_max - rtc->range_min + 1;
  	 *
  	 * If the start_secs is less than the minimum seconds (rtc->range_min),
  	 * which is similar to case 2. So the start_secs should be mapped to
  	 * start_secs + rtc->range_max - rtc->range_min + 1, then the
  	 * offset seconds formula should be:
  	 * rtc->offset_secs = -(rtc->range_max - rtc->range_min + 1);
  	 *
  	 * Otherwise the offset seconds should be 0.
  	 */
  	if (rtc->start_secs > rtc->range_max ||
  	    rtc->start_secs + range_secs - 1 < rtc->range_min)
  		rtc->offset_secs = rtc->start_secs - rtc->range_min;
  	else if (rtc->start_secs > rtc->range_min)
  		rtc->offset_secs = range_secs;
  	else if (rtc->start_secs < rtc->range_min)
  		rtc->offset_secs = -range_secs;
  	else
  		rtc->offset_secs = 0;
  }

  /**

   * rtc_device_unregister - removes the previously registered RTC class device
   *
   * @rtc: the RTC class device to destroy
   */

  static void rtc_device_unregister(struct rtc_device *rtc)

  {

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

  	rtc_proc_del_device(rtc);

  	cdev_device_del(&rtc->char_dev, &rtc->dev);

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

  }

  static void devm_rtc_release_device(struct device *dev, void *res)
  {
  	struct rtc_device *rtc = *(struct rtc_device **)res;

  	rtc_nvmem_unregister(rtc);

  	if (rtc->registered)
  		rtc_device_unregister(rtc);
  	else
  		put_device(&rtc->dev);
  }
  
  struct rtc_device *devm_rtc_allocate_device(struct device *dev)
  {
  	struct rtc_device **ptr, *rtc;
  	int id, err;
  
  	id = rtc_device_get_id(dev);
  	if (id < 0)
  		return ERR_PTR(id);
  
  	ptr = devres_alloc(devm_rtc_release_device, sizeof(*ptr), GFP_KERNEL);
  	if (!ptr) {
  		err = -ENOMEM;
  		goto exit_ida;
  	}
  
  	rtc = rtc_allocate_device();
  	if (!rtc) {
  		err = -ENOMEM;
  		goto exit_devres;
  	}
  
  	*ptr = rtc;
  	devres_add(dev, ptr);
  
  	rtc->id = id;
  	rtc->dev.parent = dev;
  	dev_set_name(&rtc->dev, "rtc%d", id);
  
  	return rtc;
  
  exit_devres:
  	devres_free(ptr);
  exit_ida:
  	ida_simple_remove(&rtc_ida, id);
  	return ERR_PTR(err);
  }
  EXPORT_SYMBOL_GPL(devm_rtc_allocate_device);
  
  int __rtc_register_device(struct module *owner, struct rtc_device *rtc)
  {
  	struct rtc_wkalrm alrm;
  	int err;

  	if (!rtc->ops) {
  		dev_dbg(&rtc->dev, "no ops set
  ");

  		return -EINVAL;

  	}

  
  	rtc->owner = owner;

  	rtc_device_get_offset(rtc);

  
  	/* 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);
  
  	rtc_dev_prepare(rtc);
  
  	err = cdev_device_add(&rtc->char_dev, &rtc->dev);
  	if (err)
  		dev_warn(rtc->dev.parent, "failed to add char device %d:%d
  ",
  			 MAJOR(rtc->dev.devt), rtc->id);
  	else
  		dev_dbg(rtc->dev.parent, "char device (%d:%d)
  ",
  			MAJOR(rtc->dev.devt), rtc->id);
  
  	rtc_proc_add_device(rtc);
  
  	rtc->registered = true;
  	dev_info(rtc->dev.parent, "registered as %s
  ",
  		 dev_name(&rtc->dev));

  #ifdef CONFIG_RTC_HCTOSYS_DEVICE
  	if (!strcmp(dev_name(&rtc->dev), CONFIG_RTC_HCTOSYS_DEVICE))

  		rtc_hctosys(rtc);

  #endif

  	return 0;
  }
  EXPORT_SYMBOL_GPL(__rtc_register_device);

  /**
   * devm_rtc_device_register - resource managed rtc_device_register()
   * @dev: the device to register
   * @name: the name of the device (unused)
   * @ops: the rtc operations structure
   * @owner: the module owner
   *
   * @return a struct rtc on success, or an ERR_PTR on error
   *
   * Managed rtc_device_register(). The rtc_device returned from this function
   * are automatically freed on driver detach.
   * This function is deprecated, use devm_rtc_allocate_device and
   * rtc_register_device instead
   */
  struct rtc_device *devm_rtc_device_register(struct device *dev,

  					    const char *name,
  					    const struct rtc_class_ops *ops,
  					    struct module *owner)

  {
  	struct rtc_device *rtc;
  	int err;
  
  	rtc = devm_rtc_allocate_device(dev);
  	if (IS_ERR(rtc))
  		return rtc;
  
  	rtc->ops = ops;
  
  	err = __rtc_register_device(owner, rtc);
  	if (err)
  		return ERR_PTR(err);
  
  	return rtc;
  }
  EXPORT_SYMBOL_GPL(devm_rtc_device_register);

  static int __init rtc_init(void)
  {
  	rtc_class = class_create(THIS_MODULE, "rtc");
  	if (IS_ERR(rtc_class)) {

  		pr_err("couldn't create class
  ");

  		return PTR_ERR(rtc_class);
  	}

  	rtc_class->pm = RTC_CLASS_DEV_PM_OPS;

  	rtc_dev_init();

  	return 0;
  }

  subsys_initcall(rtc_init);