// SPDX-License-Identifier: GPL-2.0-only
/*
 * An rtc/i2c driver for the EM Microelectronic EM3027
 * Copyright 2011 CompuLab, Ltd.
 *
 * Author: Mike Rapoport <mike@compulab.co.il>
 *
 * Based on rtc-ds1672.c by Alessandro Zummo <a.zummo@towertech.it>
 */

#include <linux/i2c.h>
#include <linux/rtc.h>
#include <linux/bcd.h>
#include <linux/module.h>
#include <linux/of.h>

/* Registers */
#define EM3027_REG_ON_OFF_CTRL  0x00
#define EM3027_REG_IRQ_CTRL     0x01
#define EM3027_REG_IRQ_FLAGS    0x02
#define EM3027_REG_STATUS       0x03
#define EM3027_REG_RST_CTRL     0x04

#define EM3027_REG_WATCH_SEC    0x08
#define EM3027_REG_WATCH_MIN    0x09
#define EM3027_REG_WATCH_HOUR   0x0a
#define EM3027_REG_WATCH_DATE   0x0b
#define EM3027_REG_WATCH_DAY    0x0c
#define EM3027_REG_WATCH_MON    0x0d
#define EM3027_REG_WATCH_YEAR   0x0e

#define EM3027_REG_ALARM_SEC    0x10
#define EM3027_REG_ALARM_MIN    0x11
#define EM3027_REG_ALARM_HOUR   0x12
#define EM3027_REG_ALARM_DATE   0x13
#define EM3027_REG_ALARM_DAY    0x14
#define EM3027_REG_ALARM_MON    0x15
#define EM3027_REG_ALARM_YEAR   0x16

static struct i2c_driver em3027_driver;

static int em3027_get_time(struct device *dev, struct rtc_time *tm)
{
        struct i2c_client *client = to_i2c_client(dev);

        unsigned char addr = EM3027_REG_WATCH_SEC;
        unsigned char buf[7];

        struct i2c_msg msgs[] = {
                {/* setup read addr */
                        .addr = client->addr,
                        .len = 1,
                        .buf = &addr
                },
                {/* read time/date */
                        .addr = client->addr,
                        .flags = I2C_M_RD,
                        .len = 7,
                        .buf = buf
                },
        };

        /* read time/date registers */
        if ((i2c_transfer(client->adapter, &msgs[0], 2)) != 2) {
                dev_err(&client->dev, "%s: read error\n", __func__);
                return -EIO;
        }

        tm->tm_sec      = bcd2bin(buf[0]);
        tm->tm_min      = bcd2bin(buf[1]);
        tm->tm_hour     = bcd2bin(buf[2]);
        tm->tm_mday     = bcd2bin(buf[3]);
        tm->tm_wday     = bcd2bin(buf[4]);
        tm->tm_mon      = bcd2bin(buf[5]) - 1;
        tm->tm_year     = bcd2bin(buf[6]) + 100;

        return 0;
}

static int em3027_set_time(struct device *dev, struct rtc_time *tm)
{
        struct i2c_client *client = to_i2c_client(dev);
        unsigned char buf[8];

        struct i2c_msg msg = {
                .addr = client->addr,
                .len = 8,
                .buf = buf,     /* write time/date */
        };

        buf[0] = EM3027_REG_WATCH_SEC;
        buf[1] = bin2bcd(tm->tm_sec);
        buf[2] = bin2bcd(tm->tm_min);
        buf[3] = bin2bcd(tm->tm_hour);
        buf[4] = bin2bcd(tm->tm_mday);
        buf[5] = bin2bcd(tm->tm_wday);
        buf[6] = bin2bcd(tm->tm_mon + 1);
        buf[7] = bin2bcd(tm->tm_year % 100);

        /* write time/date registers */
        if ((i2c_transfer(client->adapter, &msg, 1)) != 1) {
                dev_err(&client->dev, "%s: write error\n", __func__);
                return -EIO;
        }

        return 0;
}

static const struct rtc_class_ops em3027_rtc_ops = {
        .read_time = em3027_get_time,
        .set_time = em3027_set_time,
};

static int em3027_probe(struct i2c_client *client)
{
        struct rtc_device *rtc;

        if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
                return -ENODEV;

        rtc = devm_rtc_device_register(&client->dev, em3027_driver.driver.name,
                                  &em3027_rtc_ops, THIS_MODULE);
        if (IS_ERR(rtc))
                return PTR_ERR(rtc);

        i2c_set_clientdata(client, rtc);

        return 0;
}

static const struct i2c_device_id em3027_id[] = {
        { "em3027" },
        { }
};
MODULE_DEVICE_TABLE(i2c, em3027_id);

#ifdef CONFIG_OF
static const struct of_device_id em3027_of_match[] = {
        { .compatible = "emmicro,em3027", },
        {}
};
MODULE_DEVICE_TABLE(of, em3027_of_match);
#endif

static struct i2c_driver em3027_driver = {
        .driver = {
                   .name = "rtc-em3027",
                   .of_match_table = of_match_ptr(em3027_of_match),
        },
        .probe = em3027_probe,
        .id_table = em3027_id,
};

module_i2c_driver(em3027_driver);

MODULE_AUTHOR("Mike Rapoport <mike@compulab.co.il>");
MODULE_DESCRIPTION("EM Microelectronic EM3027 RTC driver");
MODULE_LICENSE("GPL");