// SPDX-License-Identifier: GPL-2.0-only
/*
 * An rtc driver for the Dallas DS1553
 *
 * Copyright (C) 2006 Atsushi Nemoto <anemo@mba.ocn.ne.jp>
 */

#include <linux/bcd.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/gfp.h>
#include <linux/delay.h>
#include <linux/jiffies.h>
#include <linux/interrupt.h>
#include <linux/rtc.h>
#include <linux/platform_device.h>
#include <linux/io.h>
#include <linux/module.h>

#define RTC_REG_SIZE            0x2000
#define RTC_OFFSET              0x1ff0

#define RTC_FLAGS               (RTC_OFFSET + 0)
#define RTC_SECONDS_ALARM       (RTC_OFFSET + 2)
#define RTC_MINUTES_ALARM       (RTC_OFFSET + 3)
#define RTC_HOURS_ALARM         (RTC_OFFSET + 4)
#define RTC_DATE_ALARM          (RTC_OFFSET + 5)
#define RTC_INTERRUPTS          (RTC_OFFSET + 6)
#define RTC_WATCHDOG            (RTC_OFFSET + 7)
#define RTC_CONTROL             (RTC_OFFSET + 8)
#define RTC_CENTURY             (RTC_OFFSET + 8)
#define RTC_SECONDS             (RTC_OFFSET + 9)
#define RTC_MINUTES             (RTC_OFFSET + 10)
#define RTC_HOURS               (RTC_OFFSET + 11)
#define RTC_DAY                 (RTC_OFFSET + 12)
#define RTC_DATE                (RTC_OFFSET + 13)
#define RTC_MONTH               (RTC_OFFSET + 14)
#define RTC_YEAR                (RTC_OFFSET + 15)

#define RTC_CENTURY_MASK        0x3f
#define RTC_SECONDS_MASK        0x7f
#define RTC_DAY_MASK            0x07

/* Bits in the Control/Century register */
#define RTC_WRITE               0x80
#define RTC_READ                0x40

/* Bits in the Seconds register */
#define RTC_STOP                0x80

/* Bits in the Flags register */
#define RTC_FLAGS_AF            0x40
#define RTC_FLAGS_BLF           0x10

/* Bits in the Interrupts register */
#define RTC_INTS_AE             0x80

struct rtc_plat_data {
        struct rtc_device *rtc;
        void __iomem *ioaddr;
        unsigned long last_jiffies;
        int irq;
        unsigned int irqen;
        int alrm_sec;
        int alrm_min;
        int alrm_hour;
        int alrm_mday;
        spinlock_t lock;
};

static int ds1553_rtc_set_time(struct device *dev, struct rtc_time *tm)
{
        struct rtc_plat_data *pdata = dev_get_drvdata(dev);
        void __iomem *ioaddr = pdata->ioaddr;
        u8 century;

        century = bin2bcd((tm->tm_year + 1900) / 100);

        writeb(RTC_WRITE, pdata->ioaddr + RTC_CONTROL);

        writeb(bin2bcd(tm->tm_year % 100), ioaddr + RTC_YEAR);
        writeb(bin2bcd(tm->tm_mon + 1), ioaddr + RTC_MONTH);
        writeb(bin2bcd(tm->tm_wday) & RTC_DAY_MASK, ioaddr + RTC_DAY);
        writeb(bin2bcd(tm->tm_mday), ioaddr + RTC_DATE);
        writeb(bin2bcd(tm->tm_hour), ioaddr + RTC_HOURS);
        writeb(bin2bcd(tm->tm_min), ioaddr + RTC_MINUTES);
        writeb(bin2bcd(tm->tm_sec) & RTC_SECONDS_MASK, ioaddr + RTC_SECONDS);

        /* RTC_CENTURY and RTC_CONTROL share same register */
        writeb(RTC_WRITE | (century & RTC_CENTURY_MASK), ioaddr + RTC_CENTURY);
        writeb(century & RTC_CENTURY_MASK, ioaddr + RTC_CONTROL);
        return 0;
}

static int ds1553_rtc_read_time(struct device *dev, struct rtc_time *tm)
{
        struct rtc_plat_data *pdata = dev_get_drvdata(dev);
        void __iomem *ioaddr = pdata->ioaddr;
        unsigned int year, month, day, hour, minute, second, week;
        unsigned int century;

        /* give enough time to update RTC in case of continuous read */
        if (pdata->last_jiffies == jiffies)
                msleep(1);
        pdata->last_jiffies = jiffies;
        writeb(RTC_READ, ioaddr + RTC_CONTROL);
        second = readb(ioaddr + RTC_SECONDS) & RTC_SECONDS_MASK;
        minute = readb(ioaddr + RTC_MINUTES);
        hour = readb(ioaddr + RTC_HOURS);
        day = readb(ioaddr + RTC_DATE);
        week = readb(ioaddr + RTC_DAY) & RTC_DAY_MASK;
        month = readb(ioaddr + RTC_MONTH);
        year = readb(ioaddr + RTC_YEAR);
        century = readb(ioaddr + RTC_CENTURY) & RTC_CENTURY_MASK;
        writeb(0, ioaddr + RTC_CONTROL);
        tm->tm_sec = bcd2bin(second);
        tm->tm_min = bcd2bin(minute);
        tm->tm_hour = bcd2bin(hour);
        tm->tm_mday = bcd2bin(day);
        tm->tm_wday = bcd2bin(week);
        tm->tm_mon = bcd2bin(month) - 1;
        /* year is 1900 + tm->tm_year */
        tm->tm_year = bcd2bin(year) + bcd2bin(century) * 100 - 1900;

        return 0;
}

static void ds1553_rtc_update_alarm(struct rtc_plat_data *pdata)
{
        void __iomem *ioaddr = pdata->ioaddr;
        unsigned long flags;

        spin_lock_irqsave(&pdata->lock, flags);
        writeb(pdata->alrm_mday < 0 || (pdata->irqen & RTC_UF) ?
               0x80 : bin2bcd(pdata->alrm_mday),
               ioaddr + RTC_DATE_ALARM);
        writeb(pdata->alrm_hour < 0 || (pdata->irqen & RTC_UF) ?
               0x80 : bin2bcd(pdata->alrm_hour),
               ioaddr + RTC_HOURS_ALARM);
        writeb(pdata->alrm_min < 0 || (pdata->irqen & RTC_UF) ?
               0x80 : bin2bcd(pdata->alrm_min),
               ioaddr + RTC_MINUTES_ALARM);
        writeb(pdata->alrm_sec < 0 || (pdata->irqen & RTC_UF) ?
               0x80 : bin2bcd(pdata->alrm_sec),
               ioaddr + RTC_SECONDS_ALARM);
        writeb(pdata->irqen ? RTC_INTS_AE : 0, ioaddr + RTC_INTERRUPTS);
        readb(ioaddr + RTC_FLAGS);      /* clear interrupts */
        spin_unlock_irqrestore(&pdata->lock, flags);
}

static int ds1553_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alrm)
{
        struct rtc_plat_data *pdata = dev_get_drvdata(dev);

        if (pdata->irq <= 0)
                return -EINVAL;
        pdata->alrm_mday = alrm->time.tm_mday;
        pdata->alrm_hour = alrm->time.tm_hour;
        pdata->alrm_min = alrm->time.tm_min;
        pdata->alrm_sec = alrm->time.tm_sec;
        if (alrm->enabled)
                pdata->irqen |= RTC_AF;
        ds1553_rtc_update_alarm(pdata);
        return 0;
}

static int ds1553_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alrm)
{
        struct rtc_plat_data *pdata = dev_get_drvdata(dev);

        if (pdata->irq <= 0)
                return -EINVAL;
        alrm->time.tm_mday = pdata->alrm_mday < 0 ? 0 : pdata->alrm_mday;
        alrm->time.tm_hour = pdata->alrm_hour < 0 ? 0 : pdata->alrm_hour;
        alrm->time.tm_min = pdata->alrm_min < 0 ? 0 : pdata->alrm_min;
        alrm->time.tm_sec = pdata->alrm_sec < 0 ? 0 : pdata->alrm_sec;
        alrm->enabled = (pdata->irqen & RTC_AF) ? 1 : 0;
        return 0;
}

static irqreturn_t ds1553_rtc_interrupt(int irq, void *dev_id)
{
        struct platform_device *pdev = dev_id;
        struct rtc_plat_data *pdata = platform_get_drvdata(pdev);
        void __iomem *ioaddr = pdata->ioaddr;
        unsigned long events = 0;

        spin_lock(&pdata->lock);
        /* read and clear interrupt */
        if (readb(ioaddr + RTC_FLAGS) & RTC_FLAGS_AF) {
                events = RTC_IRQF;
                if (readb(ioaddr + RTC_SECONDS_ALARM) & 0x80)
                        events |= RTC_UF;
                else
                        events |= RTC_AF;
                rtc_update_irq(pdata->rtc, 1, events);
        }
        spin_unlock(&pdata->lock);
        return events ? IRQ_HANDLED : IRQ_NONE;
}

static int ds1553_rtc_alarm_irq_enable(struct device *dev, unsigned int enabled)
{
        struct rtc_plat_data *pdata = dev_get_drvdata(dev);

        if (pdata->irq <= 0)
                return -EINVAL;
        if (enabled)
                pdata->irqen |= RTC_AF;
        else
                pdata->irqen &= ~RTC_AF;
        ds1553_rtc_update_alarm(pdata);
        return 0;
}

static const struct rtc_class_ops ds1553_rtc_ops = {
        .read_time              = ds1553_rtc_read_time,
        .set_time               = ds1553_rtc_set_time,
        .read_alarm             = ds1553_rtc_read_alarm,
        .set_alarm              = ds1553_rtc_set_alarm,
        .alarm_irq_enable       = ds1553_rtc_alarm_irq_enable,
};

static int ds1553_nvram_read(void *priv, unsigned int pos, void *val,
                             size_t bytes)
{
        struct platform_device *pdev = priv;
        struct rtc_plat_data *pdata = platform_get_drvdata(pdev);
        void __iomem *ioaddr = pdata->ioaddr;
        u8 *buf = val;

        for (; bytes; bytes--)
                *buf++ = readb(ioaddr + pos++);
        return 0;
}

static int ds1553_nvram_write(void *priv, unsigned int pos, void *val,
                              size_t bytes)
{
        struct platform_device *pdev = priv;
        struct rtc_plat_data *pdata = platform_get_drvdata(pdev);
        void __iomem *ioaddr = pdata->ioaddr;
        u8 *buf = val;

        for (; bytes; bytes--)
                writeb(*buf++, ioaddr + pos++);
        return 0;
}

static int ds1553_rtc_probe(struct platform_device *pdev)
{
        unsigned int cen, sec;
        struct rtc_plat_data *pdata;
        void __iomem *ioaddr;
        int ret = 0;
        struct nvmem_config nvmem_cfg = {
                .name = "ds1553_nvram",
                .word_size = 1,
                .stride = 1,
                .size = RTC_OFFSET,
                .reg_read = ds1553_nvram_read,
                .reg_write = ds1553_nvram_write,
                .priv = pdev,
        };

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

        ioaddr = devm_platform_ioremap_resource(pdev, 0);
        if (IS_ERR(ioaddr))
                return PTR_ERR(ioaddr);
        pdata->ioaddr = ioaddr;
        pdata->irq = platform_get_irq(pdev, 0);

        /* turn RTC on if it was not on */
        sec = readb(ioaddr + RTC_SECONDS);
        if (sec & RTC_STOP) {
                sec &= RTC_SECONDS_MASK;
                cen = readb(ioaddr + RTC_CENTURY) & RTC_CENTURY_MASK;
                writeb(RTC_WRITE, ioaddr + RTC_CONTROL);
                writeb(sec, ioaddr + RTC_SECONDS);
                writeb(cen & RTC_CENTURY_MASK, ioaddr + RTC_CONTROL);
        }
        if (readb(ioaddr + RTC_FLAGS) & RTC_FLAGS_BLF)
                dev_warn(&pdev->dev, "voltage-low detected.\n");

        spin_lock_init(&pdata->lock);
        pdata->last_jiffies = jiffies;
        platform_set_drvdata(pdev, pdata);

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

        pdata->rtc->ops = &ds1553_rtc_ops;

        ret = devm_rtc_register_device(pdata->rtc);
        if (ret)
                return ret;

        if (pdata->irq > 0) {
                writeb(0, ioaddr + RTC_INTERRUPTS);
                if (devm_request_irq(&pdev->dev, pdata->irq,
                                ds1553_rtc_interrupt,
                                0, pdev->name, pdev) < 0) {
                        dev_warn(&pdev->dev, "interrupt not available.\n");
                        pdata->irq = 0;
                }
        }

        devm_rtc_nvmem_register(pdata->rtc, &nvmem_cfg);

        return 0;
}

/* work with hotplug and coldplug */
MODULE_ALIAS("platform:rtc-ds1553");

static struct platform_driver ds1553_rtc_driver = {
        .probe          = ds1553_rtc_probe,
        .driver         = {
                .name   = "rtc-ds1553",
        },
};

module_platform_driver(ds1553_rtc_driver);

MODULE_AUTHOR("Atsushi Nemoto <anemo@mba.ocn.ne.jp>");
MODULE_DESCRIPTION("Dallas DS1553 RTC driver");
MODULE_LICENSE("GPL");