/*
 * Driver for TI BQ32000 RTC.
 *
 * Copyright (C) 2009 Semihalf.
 * Copyright (C) 2014 Pavel Machek <pavel@denx.de>
 *
 * 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.
 *
 * You can get hardware description at
 * http://www.ti.com/lit/ds/symlink/bq32000.pdf
 */

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

#define BQ32K_SECONDS           0x00    /* Seconds register address */
#define BQ32K_SECONDS_MASK      0x7F    /* Mask over seconds value */
#define BQ32K_STOP              0x80    /* Oscillator Stop flat */

#define BQ32K_MINUTES           0x01    /* Minutes register address */
#define BQ32K_MINUTES_MASK      0x7F    /* Mask over minutes value */
#define BQ32K_OF                0x80    /* Oscillator Failure flag */

#define BQ32K_HOURS_MASK        0x3F    /* Mask over hours value */
#define BQ32K_CENT              0x40    /* Century flag */
#define BQ32K_CENT_EN           0x80    /* Century flag enable bit */

#define BQ32K_CALIBRATION       0x07    /* CAL_CFG1, calibration and control */
#define BQ32K_TCH2              0x08    /* Trickle charge enable */
#define BQ32K_CFG2              0x09    /* Trickle charger control */

struct bq32k_regs {
        uint8_t         seconds;
        uint8_t         minutes;
        uint8_t         cent_hours;
        uint8_t         day;
        uint8_t         date;
        uint8_t         month;
        uint8_t         years;
};

static struct i2c_driver bq32k_driver;

static int bq32k_read(struct device *dev, void *data, uint8_t off, uint8_t len)
{
        struct i2c_client *client = to_i2c_client(dev);
        struct i2c_msg msgs[] = {
                {
                        .addr = client->addr,
                        .flags = 0,
                        .len = 1,
                        .buf = &off,
                }, {
                        .addr = client->addr,
                        .flags = I2C_M_RD,
                        .len = len,
                        .buf = data,
                }
        };

        if (i2c_transfer(client->adapter, msgs, 2) == 2)
                return 0;

        return -EIO;
}

static int bq32k_write(struct device *dev, void *data, uint8_t off, uint8_t len)
{
        struct i2c_client *client = to_i2c_client(dev);
        uint8_t buffer[len + 1];

        buffer[0] = off;
        memcpy(&buffer[1], data, len);

        if (i2c_master_send(client, buffer, len + 1) == len + 1)
                return 0;

        return -EIO;
}

static int bq32k_rtc_read_time(struct device *dev, struct rtc_time *tm)
{
        struct bq32k_regs regs;
        int error;

        error = bq32k_read(dev, &regs, 0, sizeof(regs));
        if (error)
                return error;

        tm->tm_sec = bcd2bin(regs.seconds & BQ32K_SECONDS_MASK);
        tm->tm_min = bcd2bin(regs.minutes & BQ32K_SECONDS_MASK);
        tm->tm_hour = bcd2bin(regs.cent_hours & BQ32K_HOURS_MASK);
        tm->tm_mday = bcd2bin(regs.date);
        tm->tm_wday = bcd2bin(regs.day) - 1;
        tm->tm_mon = bcd2bin(regs.month) - 1;
        tm->tm_year = bcd2bin(regs.years) +
                                ((regs.cent_hours & BQ32K_CENT) ? 100 : 0);

        return rtc_valid_tm(tm);
}

static int bq32k_rtc_set_time(struct device *dev, struct rtc_time *tm)
{
        struct bq32k_regs regs;

        regs.seconds = bin2bcd(tm->tm_sec);
        regs.minutes = bin2bcd(tm->tm_min);
        regs.cent_hours = bin2bcd(tm->tm_hour) | BQ32K_CENT_EN;
        regs.day = bin2bcd(tm->tm_wday + 1);
        regs.date = bin2bcd(tm->tm_mday);
        regs.month = bin2bcd(tm->tm_mon + 1);

        if (tm->tm_year >= 100) {
                regs.cent_hours |= BQ32K_CENT;
                regs.years = bin2bcd(tm->tm_year - 100);
        } else
                regs.years = bin2bcd(tm->tm_year);

        return bq32k_write(dev, &regs, 0, sizeof(regs));
}

static const struct rtc_class_ops bq32k_rtc_ops = {
        .read_time      = bq32k_rtc_read_time,
        .set_time       = bq32k_rtc_set_time,
};

static int trickle_charger_of_init(struct device *dev, struct device_node *node)
{
        unsigned char reg;
        int error;
        u32 ohms = 0;

        if (of_property_read_u32(node, "trickle-resistor-ohms" , &ohms))
                return 0;

        switch (ohms) {
        case 180+940:
                /*
                 * TCHE[3:0] == 0x05, TCH2 == 1, TCFE == 0 (charging
                 * over diode and 940ohm resistor)
                 */

                if (of_property_read_bool(node, "trickle-diode-disable")) {
                        dev_err(dev, "diode and resistor mismatch\n");
                        return -EINVAL;
                }
                reg = 0x05;
                break;

        case 180+20000:
                /* diode disabled */

                if (!of_property_read_bool(node, "trickle-diode-disable")) {
                        dev_err(dev, "bq32k: diode and resistor mismatch\n");
                        return -EINVAL;
                }
                reg = 0x45;
                break;

        default:
                dev_err(dev, "invalid resistor value (%d)\n", ohms);
                return -EINVAL;
        }

        error = bq32k_write(dev, &reg, BQ32K_CFG2, 1);
        if (error)
                return error;

        reg = 0x20;
        error = bq32k_write(dev, &reg, BQ32K_TCH2, 1);
        if (error)
                return error;

        dev_info(dev, "Enabled trickle RTC battery charge.\n");
        return 0;
}

static int bq32k_probe(struct i2c_client *client,
                                const struct i2c_device_id *id)
{
        struct device *dev = &client->dev;
        struct rtc_device *rtc;
        uint8_t reg;
        int error;

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

        /* Check Oscillator Stop flag */
        error = bq32k_read(dev, &reg, BQ32K_SECONDS, 1);
        if (!error && (reg & BQ32K_STOP)) {
                dev_warn(dev, "Oscillator was halted. Restarting...\n");
                reg &= ~BQ32K_STOP;
                error = bq32k_write(dev, &reg, BQ32K_SECONDS, 1);
        }
        if (error)
                return error;

        /* Check Oscillator Failure flag */
        error = bq32k_read(dev, &reg, BQ32K_MINUTES, 1);
        if (!error && (reg & BQ32K_OF)) {
                dev_warn(dev, "Oscillator Failure. Check RTC battery.\n");
                reg &= ~BQ32K_OF;
                error = bq32k_write(dev, &reg, BQ32K_MINUTES, 1);
        }
        if (error)
                return error;

        if (client->dev.of_node)
                trickle_charger_of_init(dev, client->dev.of_node);

        rtc = devm_rtc_device_register(&client->dev, bq32k_driver.driver.name,
                                                &bq32k_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 bq32k_id[] = {
        { "bq32000", 0 },
        { }
};
MODULE_DEVICE_TABLE(i2c, bq32k_id);

static struct i2c_driver bq32k_driver = {
        .driver = {
                .name   = "bq32k",
        },
        .probe          = bq32k_probe,
        .id_table       = bq32k_id,
};

module_i2c_driver(bq32k_driver);

MODULE_AUTHOR("Semihalf, Piotr Ziecik <kosmo@semihalf.com>");
MODULE_DESCRIPTION("TI BQ32000 I2C RTC driver");
MODULE_LICENSE("GPL");