drivers/rtc/class.c - linux - Git at Google

 // 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);
 	mutex_destroy(&rtc->ops_lock);
 	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\n");
 		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)\n",
 		 &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\n", 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\n", 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!\n", 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.
 	 * The default is what most RTCs do: Increment seconds exactly one
 	 * second after the write happened. This adds a default transport
 	 * time of 5ms which is at least halfways close to reality.
 	 */
 	rtc->set_offset_nsec = NSEC_PER_SEC + 5 * NSEC_PER_MSEC;

 	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;

 	set_bit(RTC_FEATURE_ALARM, rtc->features);

 	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\n", 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;
 }

 static void devm_rtc_unregister_device(void *data)
 {
 	struct rtc_device *rtc = data;

 	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);
 }

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

 	put_device(&rtc->dev);
 }

 struct rtc_device *devm_rtc_allocate_device(struct device *dev)
 {
 	struct rtc_device *rtc;
 	int id, err;

 	id = rtc_device_get_id(dev);
 	if (id < 0)
 		return ERR_PTR(id);

 	rtc = rtc_allocate_device();
 	if (!rtc) {
 		ida_simple_remove(&rtc_ida, id);
 		return ERR_PTR(-ENOMEM);
 	}

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

 	err = devm_add_action_or_reset(dev, devm_rtc_release_device, rtc);
 	if (err)
 		return ERR_PTR(err);

 	return rtc;
 }
 EXPORT_SYMBOL_GPL(devm_rtc_allocate_device);

 int __devm_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\n");
 		return -EINVAL;
 	}

 	if (!rtc->ops->set_alarm)
 		clear_bit(RTC_FEATURE_ALARM, rtc->features);

 	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\n",
 			 MAJOR(rtc->dev.devt), rtc->id);
 	else
 		dev_dbg(rtc->dev.parent, "char device (%d:%d)\n",
 			MAJOR(rtc->dev.devt), rtc->id);

 	rtc_proc_add_device(rtc);

 	dev_info(rtc->dev.parent, "registered as %s\n",
 		 dev_name(&rtc->dev));

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

 	return devm_add_action_or_reset(rtc->dev.parent,
 					devm_rtc_unregister_device, rtc);
 }
 EXPORT_SYMBOL_GPL(__devm_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 = __devm_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\n");
 		return PTR_ERR(rtc_class);
 	}
 	rtc_class->pm = RTC_CLASS_DEV_PM_OPS;
 	rtc_dev_init();
 	return 0;
 }
 subsys_initcall(rtc_init);
	// 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);
	mutex_destroy(&rtc->ops_lock);
	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\n");
	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)\n",
	&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\n", 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\n", 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!\n", 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.
	* The default is what most RTCs do: Increment seconds exactly one
	* second after the write happened. This adds a default transport
	* time of 5ms which is at least halfways close to reality.
	*/
	rtc->set_offset_nsec = NSEC_PER_SEC + 5 * NSEC_PER_MSEC;

	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;

	set_bit(RTC_FEATURE_ALARM, rtc->features);

	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\n", 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;
	}

	static void devm_rtc_unregister_device(void *data)
	{
	struct rtc_device *rtc = data;

	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);
	}

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

	put_device(&rtc->dev);
	}

	struct rtc_device devm_rtc_allocate_device(struct device dev)
	{
	struct rtc_device *rtc;
	int id, err;

	id = rtc_device_get_id(dev);
	if (id < 0)
	return ERR_PTR(id);

	rtc = rtc_allocate_device();
	if (!rtc) {
	ida_simple_remove(&rtc_ida, id);
	return ERR_PTR(-ENOMEM);
	}

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

	err = devm_add_action_or_reset(dev, devm_rtc_release_device, rtc);
	if (err)
	return ERR_PTR(err);

	return rtc;
	}
	EXPORT_SYMBOL_GPL(devm_rtc_allocate_device);

	int __devm_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\n");
	return -EINVAL;
	}

	if (!rtc->ops->set_alarm)
	clear_bit(RTC_FEATURE_ALARM, rtc->features);

	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\n",
	MAJOR(rtc->dev.devt), rtc->id);
	else
	dev_dbg(rtc->dev.parent, "char device (%d:%d)\n",
	MAJOR(rtc->dev.devt), rtc->id);

	rtc_proc_add_device(rtc);

	dev_info(rtc->dev.parent, "registered as %s\n",
	dev_name(&rtc->dev));

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

	return devm_add_action_or_reset(rtc->dev.parent,
	devm_rtc_unregister_device, rtc);
	}
	EXPORT_SYMBOL_GPL(__devm_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 = __devm_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\n");
	return PTR_ERR(rtc_class);
	}
	rtc_class->pm = RTC_CLASS_DEV_PM_OPS;
	rtc_dev_init();
	return 0;
	}
	subsys_initcall(rtc_init);