/*
 * An I2C driver for the PCF85063 RTC
 * Copyright 2014 Rose Technology
 *
 * Author: Søren Andersen <san@rosetechnology.dk>
 * Maintainers: http://www.nslu2-linux.org/
 *
 * based on the other drivers in this same directory.
 *
 * 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/bcd.h>
#include <linux/rtc.h>
#include <linux/module.h>

/*
 * Information for this driver was pulled from the following datasheets.
 *
 *  http://www.nxp.com/documents/data_sheet/PCF85063A.pdf
 *  http://www.nxp.com/documents/data_sheet/PCF85063TP.pdf
 *
 *  PCF85063A -- Rev. 6 — 18 November 2015
 *  PCF85063TP -- Rev. 4 — 6 May 2015
*/

#define PCF85063_REG_CTRL1              0x00 /* status */
#define PCF85063_REG_CTRL1_STOP         BIT(5)
#define PCF85063_REG_CTRL2              0x01

#define PCF85063_REG_SC                 0x04 /* datetime */
#define PCF85063_REG_SC_OS              0x80
#define PCF85063_REG_MN                 0x05
#define PCF85063_REG_HR                 0x06
#define PCF85063_REG_DM                 0x07
#define PCF85063_REG_DW                 0x08
#define PCF85063_REG_MO                 0x09
#define PCF85063_REG_YR                 0x0A

static struct i2c_driver pcf85063_driver;

static int pcf85063_stop_clock(struct i2c_client *client, u8 *ctrl1)
{
        int rc;
        u8 reg;

        rc = i2c_smbus_read_byte_data(client, PCF85063_REG_CTRL1);
        if (rc < 0) {
                dev_err(&client->dev, "Failing to stop the clock\n");
                return -EIO;
        }

        /* stop the clock */
        reg = rc | PCF85063_REG_CTRL1_STOP;

        rc = i2c_smbus_write_byte_data(client, PCF85063_REG_CTRL1, reg);
        if (rc < 0) {
                dev_err(&client->dev, "Failing to stop the clock\n");
                return -EIO;
        }

        *ctrl1 = reg;

        return 0;
}

static int pcf85063_start_clock(struct i2c_client *client, u8 ctrl1)
{
        int rc;

        /* start the clock */
        ctrl1 &= ~PCF85063_REG_CTRL1_STOP;

        rc = i2c_smbus_write_byte_data(client, PCF85063_REG_CTRL1, ctrl1);
        if (rc < 0) {
                dev_err(&client->dev, "Failing to start the clock\n");
                return -EIO;
        }

        return 0;
}

static int pcf85063_rtc_read_time(struct device *dev, struct rtc_time *tm)
{
        struct i2c_client *client = to_i2c_client(dev);
        int rc;
        u8 regs[7];

        /*
         * while reading, the time/date registers are blocked and not updated
         * anymore until the access is finished. To not lose a second
         * event, the access must be finished within one second. So, read all
         * time/date registers in one turn.
         */
        rc = i2c_smbus_read_i2c_block_data(client, PCF85063_REG_SC,
                                           sizeof(regs), regs);
        if (rc != sizeof(regs)) {
                dev_err(&client->dev, "date/time register read error\n");
                return -EIO;
        }

        /* if the clock has lost its power it makes no sense to use its time */
        if (regs[0] & PCF85063_REG_SC_OS) {
                dev_warn(&client->dev, "Power loss detected, invalid time\n");
                return -EINVAL;
        }

        tm->tm_sec = bcd2bin(regs[0] & 0x7F);
        tm->tm_min = bcd2bin(regs[1] & 0x7F);
        tm->tm_hour = bcd2bin(regs[2] & 0x3F); /* rtc hr 0-23 */
        tm->tm_mday = bcd2bin(regs[3] & 0x3F);
        tm->tm_wday = regs[4] & 0x07;
        tm->tm_mon = bcd2bin(regs[5] & 0x1F) - 1; /* rtc mn 1-12 */
        tm->tm_year = bcd2bin(regs[6]);
        tm->tm_year += 100;

        return 0;
}

static int pcf85063_rtc_set_time(struct device *dev, struct rtc_time *tm)
{
        struct i2c_client *client = to_i2c_client(dev);
        int rc;
        u8 regs[7];
        u8 ctrl1;

        if ((tm->tm_year < 100) || (tm->tm_year > 199))
                return -EINVAL;

        /*
         * to accurately set the time, reset the divider chain and keep it in
         * reset state until all time/date registers are written
         */
        rc = pcf85063_stop_clock(client, &ctrl1);
        if (rc != 0)
                return rc;

        /* hours, minutes and seconds */
        regs[0] = bin2bcd(tm->tm_sec) & 0x7F; /* clear OS flag */

        regs[1] = bin2bcd(tm->tm_min);
        regs[2] = bin2bcd(tm->tm_hour);

        /* Day of month, 1 - 31 */
        regs[3] = bin2bcd(tm->tm_mday);

        /* Day, 0 - 6 */
        regs[4] = tm->tm_wday & 0x07;

        /* month, 1 - 12 */
        regs[5] = bin2bcd(tm->tm_mon + 1);

        /* year and century */
        regs[6] = bin2bcd(tm->tm_year - 100);

        /* write all registers at once */
        rc = i2c_smbus_write_i2c_block_data(client, PCF85063_REG_SC,
                                            sizeof(regs), regs);
        if (rc < 0) {
                dev_err(&client->dev, "date/time register write error\n");
                return rc;
        }

        /*
         * Write the control register as a separate action since the size of
         * the register space is different between the PCF85063TP and
         * PCF85063A devices.  The rollover point can not be used.
         */
        rc = pcf85063_start_clock(client, ctrl1);
        if (rc != 0)
                return rc;

        return 0;
}

static const struct rtc_class_ops pcf85063_rtc_ops = {
        .read_time      = pcf85063_rtc_read_time,
        .set_time       = pcf85063_rtc_set_time
};

static int pcf85063_probe(struct i2c_client *client,
                                const struct i2c_device_id *id)
{
        struct rtc_device *rtc;
        int err;

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

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

        err = i2c_smbus_read_byte_data(client, PCF85063_REG_CTRL1);
        if (err < 0) {
                dev_err(&client->dev, "RTC chip is not present\n");
                return err;
        }

        rtc = devm_rtc_device_register(&client->dev,
                                       pcf85063_driver.driver.name,
                                       &pcf85063_rtc_ops, THIS_MODULE);

        return PTR_ERR_OR_ZERO(rtc);
}

static const struct i2c_device_id pcf85063_id[] = {
        { "pcf85063", 0 },
        { }
};
MODULE_DEVICE_TABLE(i2c, pcf85063_id);

#ifdef CONFIG_OF
static const struct of_device_id pcf85063_of_match[] = {
        { .compatible = "nxp,pcf85063" },
        {}
};
MODULE_DEVICE_TABLE(of, pcf85063_of_match);
#endif

static struct i2c_driver pcf85063_driver = {
        .driver         = {
                .name   = "rtc-pcf85063",
                .of_match_table = of_match_ptr(pcf85063_of_match),
        },
        .probe          = pcf85063_probe,
        .id_table       = pcf85063_id,
};

module_i2c_driver(pcf85063_driver);

MODULE_AUTHOR("Søren Andersen <san@rosetechnology.dk>");
MODULE_DESCRIPTION("PCF85063 RTC driver");
MODULE_LICENSE("GPL");