/*
 * 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.
*/

#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;
#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;
        }

        getnstimeofday64(&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 occured 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 */
        getnstimeofday64(&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


/**
 * 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 of_id = -1, id = -1, err;

        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);
                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;

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

        /* 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 = 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\n",
                        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\n",
                        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 void devm_rtc_device_release(struct device *dev, void *res)
{
        struct rtc_device *rtc = *(struct rtc_device **)res;

        rtc_device_unregister(rtc);
}

static int devm_rtc_device_match(struct device *dev, void *res, void *data)
{
        struct rtc **r = res;

        return *r == data;
}

/**
 * devm_rtc_device_register - resource managed rtc_device_register()
 * @dev: the device to register
 * @name: the name of the device
 * @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. See rtc_device_register()
 * for more information.
 */

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 **ptr, *rtc;

        ptr = devres_alloc(devm_rtc_device_release, sizeof(*ptr), GFP_KERNEL);
        if (!ptr)
                return ERR_PTR(-ENOMEM);

        rtc = rtc_device_register(name, dev, ops, owner);
        if (!IS_ERR(rtc)) {
                *ptr = rtc;
                devres_add(dev, ptr);
        } else {
                devres_free(ptr);
        }

        return rtc;
}
EXPORT_SYMBOL_GPL(devm_rtc_device_register);

/**
 * devm_rtc_device_unregister - resource managed devm_rtc_device_unregister()
 * @dev: the device to unregister
 * @rtc: the RTC class device to unregister
 *
 * Deallocated a rtc allocated with devm_rtc_device_register(). Normally this
 * function will not need to be called and the resource management code will
 * ensure that the resource is freed.
 */
void devm_rtc_device_unregister(struct device *dev, struct rtc_device *rtc)
{
        int rc;

        rc = devres_release(dev, devm_rtc_device_release,
                                devm_rtc_device_match, rtc);
        WARN_ON(rc);
}
EXPORT_SYMBOL_GPL(devm_rtc_device_unregister);

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();
        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");