// SPDX-License-Identifier: GPL-2.0
/*
 * Nuvoton NCT6694 RTC driver based on USB interface.
 *
 * Copyright (C) 2025 Nuvoton Technology Corp.
 */

#include <linux/bcd.h>
#include <linux/irqdomain.h>
#include <linux/kernel.h>
#include <linux/mfd/nct6694.h>
#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/rtc.h>
#include <linux/slab.h>

/*
 * USB command module type for NCT6694 RTC controller.
 * This defines the module type used for communication with the NCT6694
 * RTC controller over the USB interface.
 */
#define NCT6694_RTC_MOD         0x08

/* Command 00h - RTC Time */
#define NCT6694_RTC_TIME        0x0000
#define NCT6694_RTC_TIME_SEL    0x00

/* Command 01h - RTC Alarm */
#define NCT6694_RTC_ALARM       0x01
#define NCT6694_RTC_ALARM_SEL   0x00

/* Command 02h - RTC Status */
#define NCT6694_RTC_STATUS      0x02
#define NCT6694_RTC_STATUS_SEL  0x00

#define NCT6694_RTC_IRQ_INT_EN  BIT(0)  /* Transmit a USB INT-in when RTC alarm */
#define NCT6694_RTC_IRQ_GPO_EN  BIT(5)  /* Trigger a GPO Low Pulse when RTC alarm */

#define NCT6694_RTC_IRQ_EN      (NCT6694_RTC_IRQ_INT_EN | NCT6694_RTC_IRQ_GPO_EN)
#define NCT6694_RTC_IRQ_STS     BIT(0)  /* Write 1 clear IRQ status */

struct __packed nct6694_rtc_time {
        u8 sec;
        u8 min;
        u8 hour;
        u8 week;
        u8 day;
        u8 month;
        u8 year;
};

struct __packed nct6694_rtc_alarm {
        u8 sec;
        u8 min;
        u8 hour;
        u8 alarm_en;
        u8 alarm_pend;
};

struct __packed nct6694_rtc_status {
        u8 irq_en;
        u8 irq_pend;
};

union __packed nct6694_rtc_msg {
        struct nct6694_rtc_time time;
        struct nct6694_rtc_alarm alarm;
        struct nct6694_rtc_status sts;
};

struct nct6694_rtc_data {
        struct nct6694 *nct6694;
        struct rtc_device *rtc;
        union nct6694_rtc_msg *msg;
        int irq;
};

static int nct6694_rtc_read_time(struct device *dev, struct rtc_time *tm)
{
        struct nct6694_rtc_data *data = dev_get_drvdata(dev);
        struct nct6694_rtc_time *time = &data->msg->time;
        static const struct nct6694_cmd_header cmd_hd = {
                .mod = NCT6694_RTC_MOD,
                .cmd = NCT6694_RTC_TIME,
                .sel = NCT6694_RTC_TIME_SEL,
                .len = cpu_to_le16(sizeof(*time))
        };
        int ret;

        ret = nct6694_read_msg(data->nct6694, &cmd_hd, time);
        if (ret)
                return ret;

        tm->tm_sec = bcd2bin(time->sec);                /* tm_sec expect 0 ~ 59 */
        tm->tm_min = bcd2bin(time->min);                /* tm_min expect 0 ~ 59 */
        tm->tm_hour = bcd2bin(time->hour);              /* tm_hour expect 0 ~ 23 */
        tm->tm_wday = bcd2bin(time->week) - 1;          /* tm_wday expect 0 ~ 6 */
        tm->tm_mday = bcd2bin(time->day);               /* tm_mday expect 1 ~ 31 */
        tm->tm_mon = bcd2bin(time->month) - 1;          /* tm_month expect 0 ~ 11 */
        tm->tm_year = bcd2bin(time->year) + 100;        /* tm_year expect since 1900 */

        return ret;
}

static int nct6694_rtc_set_time(struct device *dev, struct rtc_time *tm)
{
        struct nct6694_rtc_data *data = dev_get_drvdata(dev);
        struct nct6694_rtc_time *time = &data->msg->time;
        static const struct nct6694_cmd_header cmd_hd = {
                .mod = NCT6694_RTC_MOD,
                .cmd = NCT6694_RTC_TIME,
                .sel = NCT6694_RTC_TIME_SEL,
                .len = cpu_to_le16(sizeof(*time))
        };

        time->sec = bin2bcd(tm->tm_sec);
        time->min = bin2bcd(tm->tm_min);
        time->hour = bin2bcd(tm->tm_hour);
        time->week = bin2bcd(tm->tm_wday + 1);
        time->day = bin2bcd(tm->tm_mday);
        time->month = bin2bcd(tm->tm_mon + 1);
        time->year = bin2bcd(tm->tm_year - 100);

        return nct6694_write_msg(data->nct6694, &cmd_hd, time);
}

static int nct6694_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alrm)
{
        struct nct6694_rtc_data *data = dev_get_drvdata(dev);
        struct nct6694_rtc_alarm *alarm = &data->msg->alarm;
        static const struct nct6694_cmd_header cmd_hd = {
                .mod = NCT6694_RTC_MOD,
                .cmd = NCT6694_RTC_ALARM,
                .sel = NCT6694_RTC_ALARM_SEL,
                .len = cpu_to_le16(sizeof(*alarm))
        };
        int ret;

        ret = nct6694_read_msg(data->nct6694, &cmd_hd, alarm);
        if (ret)
                return ret;

        alrm->time.tm_sec = bcd2bin(alarm->sec);
        alrm->time.tm_min = bcd2bin(alarm->min);
        alrm->time.tm_hour = bcd2bin(alarm->hour);
        alrm->enabled = alarm->alarm_en;
        alrm->pending = alarm->alarm_pend;

        return ret;
}

static int nct6694_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alrm)
{
        struct nct6694_rtc_data *data = dev_get_drvdata(dev);
        struct nct6694_rtc_alarm *alarm = &data->msg->alarm;
        static const struct nct6694_cmd_header cmd_hd = {
                .mod = NCT6694_RTC_MOD,
                .cmd = NCT6694_RTC_ALARM,
                .sel = NCT6694_RTC_ALARM_SEL,
                .len = cpu_to_le16(sizeof(*alarm))
        };

        alarm->sec = bin2bcd(alrm->time.tm_sec);
        alarm->min = bin2bcd(alrm->time.tm_min);
        alarm->hour = bin2bcd(alrm->time.tm_hour);
        alarm->alarm_en = alrm->enabled ? NCT6694_RTC_IRQ_EN : 0;
        alarm->alarm_pend = 0;

        return nct6694_write_msg(data->nct6694, &cmd_hd, alarm);
}

static int nct6694_rtc_alarm_irq_enable(struct device *dev, unsigned int enabled)
{
        struct nct6694_rtc_data *data = dev_get_drvdata(dev);
        struct nct6694_rtc_status *sts = &data->msg->sts;
        static const struct nct6694_cmd_header cmd_hd = {
                .mod = NCT6694_RTC_MOD,
                .cmd = NCT6694_RTC_STATUS,
                .sel = NCT6694_RTC_STATUS_SEL,
                .len = cpu_to_le16(sizeof(*sts))
        };

        if (enabled)
                sts->irq_en |= NCT6694_RTC_IRQ_EN;
        else
                sts->irq_en &= ~NCT6694_RTC_IRQ_EN;

        sts->irq_pend = 0;

        return nct6694_write_msg(data->nct6694, &cmd_hd, sts);
}

static const struct rtc_class_ops nct6694_rtc_ops = {
        .read_time = nct6694_rtc_read_time,
        .set_time = nct6694_rtc_set_time,
        .read_alarm = nct6694_rtc_read_alarm,
        .set_alarm = nct6694_rtc_set_alarm,
        .alarm_irq_enable = nct6694_rtc_alarm_irq_enable,
};

static irqreturn_t nct6694_irq(int irq, void *dev_id)
{
        struct nct6694_rtc_data *data = dev_id;
        struct nct6694_rtc_status *sts = &data->msg->sts;
        static const struct nct6694_cmd_header cmd_hd = {
                .mod = NCT6694_RTC_MOD,
                .cmd = NCT6694_RTC_STATUS,
                .sel = NCT6694_RTC_STATUS_SEL,
                .len = cpu_to_le16(sizeof(*sts))
        };
        int ret;

        rtc_lock(data->rtc);

        sts->irq_en = NCT6694_RTC_IRQ_EN;
        sts->irq_pend = NCT6694_RTC_IRQ_STS;
        ret = nct6694_write_msg(data->nct6694, &cmd_hd, sts);
        if (ret) {
                rtc_unlock(data->rtc);
                return IRQ_NONE;
        }

        rtc_update_irq(data->rtc, 1, RTC_IRQF | RTC_AF);

        rtc_unlock(data->rtc);

        return IRQ_HANDLED;
}

static void nct6694_irq_dispose_mapping(void *d)
{
        struct nct6694_rtc_data *data = d;

        irq_dispose_mapping(data->irq);
}

static int nct6694_rtc_probe(struct platform_device *pdev)
{
        struct nct6694_rtc_data *data;
        struct nct6694 *nct6694 = dev_get_drvdata(pdev->dev.parent);
        int ret;

        data = devm_kzalloc(&pdev->dev, sizeof(*data), GFP_KERNEL);
        if (!data)
                return -ENOMEM;

        data->msg = devm_kzalloc(&pdev->dev, sizeof(union nct6694_rtc_msg),
                                 GFP_KERNEL);
        if (!data->msg)
                return -ENOMEM;

        data->irq = irq_create_mapping(nct6694->domain, NCT6694_IRQ_RTC);
        if (!data->irq)
                return -EINVAL;

        ret = devm_add_action_or_reset(&pdev->dev, nct6694_irq_dispose_mapping,
                                       data);
        if (ret)
                return ret;

        ret = devm_device_init_wakeup(&pdev->dev);
        if (ret)
                return dev_err_probe(&pdev->dev, ret, "Failed to init wakeup\n");

        data->rtc = devm_rtc_allocate_device(&pdev->dev);
        if (IS_ERR(data->rtc))
                return PTR_ERR(data->rtc);

        data->nct6694 = nct6694;
        data->rtc->ops = &nct6694_rtc_ops;
        data->rtc->range_min = RTC_TIMESTAMP_BEGIN_2000;
        data->rtc->range_max = RTC_TIMESTAMP_END_2099;

        platform_set_drvdata(pdev, data);

        ret = devm_request_threaded_irq(&pdev->dev, data->irq, NULL,
                                        nct6694_irq, IRQF_ONESHOT,
                                        "rtc-nct6694", data);
        if (ret < 0)
                return dev_err_probe(&pdev->dev, ret, "Failed to request irq\n");

        return devm_rtc_register_device(data->rtc);
}

static struct platform_driver nct6694_rtc_driver = {
        .driver = {
                .name   = "nct6694-rtc",
        },
        .probe          = nct6694_rtc_probe,
};

module_platform_driver(nct6694_rtc_driver);

MODULE_DESCRIPTION("USB-RTC driver for NCT6694");
MODULE_AUTHOR("Ming Yu <tmyu0@nuvoton.com>");
MODULE_LICENSE("GPL");
MODULE_ALIAS("platform:nct6694-rtc");