// 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
  ", __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
  ", __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,
  			const struct i2c_device_id *id)
  {
  	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", 0 },
  	{ }
  };

  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");