/*
 * An rtc/i2c driver for the Dallas DS1672
 * Copyright 2005-06 Tower Technologies
 *
 * Author: Alessandro Zummo <a.zummo@towertech.it>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

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

#define DRV_VERSION "0.4"

/* Registers */

#define DS1672_REG_CNT_BASE     0
#define DS1672_REG_CONTROL      4
#define DS1672_REG_TRICKLE      5

#define DS1672_REG_CONTROL_EOSC 0x80

static struct i2c_driver ds1672_driver;

/*
 * In the routines that deal directly with the ds1672 hardware, we use
 * rtc_time -- month 0-11, hour 0-23, yr = calendar year-epoch
 * Epoch is initialized as 2000. Time is set to UTC.
 */
static int ds1672_get_datetime(struct i2c_client *client, struct rtc_time *tm)
{
        unsigned long time;
        unsigned char addr = DS1672_REG_CNT_BASE;
        unsigned char buf[4];

        struct i2c_msg msgs[] = {
                {/* setup read ptr */
                        .addr = client->addr,
                        .len = 1,
                        .buf = &addr
                },
                {/* read date */
                        .addr = client->addr,
                        .flags = I2C_M_RD,
                        .len = 4,
                        .buf = buf
                },
        };

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

        dev_dbg(&client->dev,
                "%s: raw read data - counters=%02x,%02x,%02x,%02x\n",
                __func__, buf[0], buf[1], buf[2], buf[3]);

        time = (buf[3] << 24) | (buf[2] << 16) | (buf[1] << 8) | buf[0];

        rtc_time_to_tm(time, tm);

        dev_dbg(&client->dev, "%s: tm is secs=%d, mins=%d, hours=%d, "
                "mday=%d, mon=%d, year=%d, wday=%d\n",
                __func__, tm->tm_sec, tm->tm_min, tm->tm_hour,
                tm->tm_mday, tm->tm_mon, tm->tm_year, tm->tm_wday);

        return 0;
}

static int ds1672_set_mmss(struct i2c_client *client, unsigned long secs)
{
        int xfer;
        unsigned char buf[6];

        buf[0] = DS1672_REG_CNT_BASE;
        buf[1] = secs & 0x000000FF;
        buf[2] = (secs & 0x0000FF00) >> 8;
        buf[3] = (secs & 0x00FF0000) >> 16;
        buf[4] = (secs & 0xFF000000) >> 24;
        buf[5] = 0;             /* set control reg to enable counting */

        xfer = i2c_master_send(client, buf, 6);
        if (xfer != 6) {
                dev_err(&client->dev, "%s: send: %d\n", __func__, xfer);
                return -EIO;
        }

        return 0;
}

static int ds1672_rtc_read_time(struct device *dev, struct rtc_time *tm)
{
        return ds1672_get_datetime(to_i2c_client(dev), tm);
}

static int ds1672_rtc_set_mmss(struct device *dev, unsigned long secs)
{
        return ds1672_set_mmss(to_i2c_client(dev), secs);
}

static int ds1672_get_control(struct i2c_client *client, u8 *status)
{
        unsigned char addr = DS1672_REG_CONTROL;

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

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

        return 0;
}

/* following are the sysfs callback functions */
static ssize_t show_control(struct device *dev, struct device_attribute *attr,
                            char *buf)
{
        struct i2c_client *client = to_i2c_client(dev);
        u8 control;
        int err;

        err = ds1672_get_control(client, &control);
        if (err)
                return err;

        return sprintf(buf, "%s\n", (control & DS1672_REG_CONTROL_EOSC)
                       ? "disabled" : "enabled");
}

static DEVICE_ATTR(control, S_IRUGO, show_control, NULL);

static const struct rtc_class_ops ds1672_rtc_ops = {
        .read_time = ds1672_rtc_read_time,
        .set_mmss = ds1672_rtc_set_mmss,
};

static int ds1672_probe(struct i2c_client *client,
                        const struct i2c_device_id *id)
{
        int err = 0;
        u8 control;
        struct rtc_device *rtc;

        dev_dbg(&client->dev, "%s\n", __func__);

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

        dev_info(&client->dev, "chip found, driver version " DRV_VERSION "\n");

        rtc = devm_rtc_device_register(&client->dev, ds1672_driver.driver.name,
                                  &ds1672_rtc_ops, THIS_MODULE);

        if (IS_ERR(rtc))
                return PTR_ERR(rtc);

        i2c_set_clientdata(client, rtc);

        /* read control register */
        err = ds1672_get_control(client, &control);
        if (err) {
                dev_warn(&client->dev, "Unable to read the control register\n");
        }

        if (control & DS1672_REG_CONTROL_EOSC)
                dev_warn(&client->dev, "Oscillator not enabled. "
                         "Set time to enable.\n");

        /* Register sysfs hooks */
        err = device_create_file(&client->dev, &dev_attr_control);
        if (err)
                dev_err(&client->dev, "Unable to create sysfs entry: %s\n",
                        dev_attr_control.attr.name);

        return 0;
}

static struct i2c_device_id ds1672_id[] = {
        { "ds1672", 0 },
        { }
};

static struct i2c_driver ds1672_driver = {
        .driver = {
                   .name = "rtc-ds1672",
                   },
        .probe = &ds1672_probe,
        .id_table = ds1672_id,
};

module_i2c_driver(ds1672_driver);

MODULE_AUTHOR("Alessandro Zummo <a.zummo@towertech.it>");
MODULE_DESCRIPTION("Dallas/Maxim DS1672 timekeeper driver");
MODULE_LICENSE("GPL");
MODULE_VERSION(DRV_VERSION);