// 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\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. */
        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\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;
}

/**
 * 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\n");
                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\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);

        rtc->registered = true;
        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 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\n");
                return PTR_ERR(rtc_class);
        }
        rtc_class->pm = RTC_CLASS_DEV_PM_OPS;
        rtc_dev_init();
        return 0;
}
subsys_initcall(rtc_init);