// SPDX-License-Identifier: GPL-2.0-only
/*
 * An rtc driver for the Dallas DS1742
 *
 * Copyright (C) 2006 Atsushi Nemoto <anemo@mba.ocn.ne.jp>
 *
 * Copyright (C) 2006 Torsten Ertbjerg Rasmussen <tr@newtec.dk>
 *  - nvram size determined from resource
 *  - this ds1742 driver now supports ds1743.
 */

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

#define RTC_SIZE                8

#define RTC_CONTROL             0
#define RTC_CENTURY             0
#define RTC_SECONDS             1
#define RTC_MINUTES             2
#define RTC_HOURS               3
#define RTC_DAY                 4
#define RTC_DATE                5
#define RTC_MONTH               6
#define RTC_YEAR                7

#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 Day register */
#define RTC_BATT_FLAG           0x80

struct rtc_plat_data {
        void __iomem *ioaddr_nvram;
        void __iomem *ioaddr_rtc;
        unsigned long last_jiffies;
};

static int ds1742_rtc_set_time(struct device *dev, struct rtc_time *tm)
{
        struct rtc_plat_data *pdata = dev_get_drvdata(dev);
        void __iomem *ioaddr = pdata->ioaddr_rtc;
        u8 century;

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

        writeb(RTC_WRITE, 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 ds1742_rtc_read_time(struct device *dev, struct rtc_time *tm)
{
        struct rtc_plat_data *pdata = dev_get_drvdata(dev);
        void __iomem *ioaddr = pdata->ioaddr_rtc;
        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 const struct rtc_class_ops ds1742_rtc_ops = {
        .read_time      = ds1742_rtc_read_time,
        .set_time       = ds1742_rtc_set_time,
};

static int ds1742_nvram_read(void *priv, unsigned int pos, void *val,
                             size_t bytes)
{
        struct rtc_plat_data *pdata = priv;
        void __iomem *ioaddr = pdata->ioaddr_nvram;
        u8 *buf = val;

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

static int ds1742_nvram_write(void *priv, unsigned int pos, void *val,
                              size_t bytes)
{
        struct rtc_plat_data *pdata = priv;
        void __iomem *ioaddr = pdata->ioaddr_nvram;
        u8 *buf = val;

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

static int ds1742_rtc_probe(struct platform_device *pdev)
{
        struct rtc_device *rtc;
        struct resource *res;
        unsigned int cen, sec;
        struct rtc_plat_data *pdata;
        void __iomem *ioaddr;
        int ret = 0;
        struct nvmem_config nvmem_cfg = {
                .name = "ds1742_nvram",
                .reg_read = ds1742_nvram_read,
                .reg_write = ds1742_nvram_write,
        };


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

        ioaddr = devm_platform_get_and_ioremap_resource(pdev, 0, &res);
        if (IS_ERR(ioaddr))
                return PTR_ERR(ioaddr);

        pdata->ioaddr_nvram = ioaddr;
        pdata->ioaddr_rtc = ioaddr + resource_size(res) - RTC_SIZE;

        nvmem_cfg.size = resource_size(res) - RTC_SIZE;
        nvmem_cfg.priv = pdata;

        /* turn RTC on if it was not on */
        ioaddr = pdata->ioaddr_rtc;
        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_DAY) & RTC_BATT_FLAG))
                dev_warn(&pdev->dev, "voltage-low detected.\n");

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

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

        rtc->ops = &ds1742_rtc_ops;

        ret = devm_rtc_register_device(rtc);
        if (ret)
                return ret;

        devm_rtc_nvmem_register(rtc, &nvmem_cfg);

        return 0;
}

static const struct of_device_id __maybe_unused ds1742_rtc_of_match[] = {
        { .compatible = "maxim,ds1742", },
        { }
};
MODULE_DEVICE_TABLE(of, ds1742_rtc_of_match);

static struct platform_driver ds1742_rtc_driver = {
        .probe          = ds1742_rtc_probe,
        .driver         = {
                .name   = "rtc-ds1742",
                .of_match_table = of_match_ptr(ds1742_rtc_of_match),
        },
};

module_platform_driver(ds1742_rtc_driver);

MODULE_AUTHOR("Atsushi Nemoto <anemo@mba.ocn.ne.jp>");
MODULE_DESCRIPTION("Dallas DS1742 RTC driver");
MODULE_LICENSE("GPL");
MODULE_ALIAS("platform:rtc-ds1742");