/*
 *  drivers/rtc/rtc-pcf8583.c
 *
 *  Copyright (C) 2000 Russell King
 *  Copyright (C) 2008 Wolfram Sang & Juergen Beisert, Pengutronix
 *
 * 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.
 *
 *  Driver for PCF8583 RTC & RAM chip
 *
 *  Converted to the generic RTC susbsystem by G. Liakhovetski (2006)
 */
#include <linux/module.h>
#include <linux/i2c.h>
#include <linux/slab.h>
#include <linux/rtc.h>
#include <linux/init.h>
#include <linux/err.h>
#include <linux/errno.h>
#include <linux/bcd.h>

struct rtc_mem {
        unsigned int    loc;
        unsigned int    nr;
        unsigned char   *data;
};

struct pcf8583 {
        struct rtc_device *rtc;
        unsigned char ctrl;
};

#define CTRL_STOP       0x80
#define CTRL_HOLD       0x40
#define CTRL_32KHZ      0x00
#define CTRL_MASK       0x08
#define CTRL_ALARMEN    0x04
#define CTRL_ALARM      0x02
#define CTRL_TIMER      0x01


static struct i2c_driver pcf8583_driver;

#define get_ctrl(x)    ((struct pcf8583 *)i2c_get_clientdata(x))->ctrl
#define set_ctrl(x, v) get_ctrl(x) = v

#define CMOS_YEAR       (64 + 128)
#define CMOS_CHECKSUM   (63)

static int pcf8583_get_datetime(struct i2c_client *client, struct rtc_time *dt)
{
        unsigned char buf[8], addr[1] = { 1 };
        struct i2c_msg msgs[2] = {
                {
                        .addr = client->addr,
                        .flags = 0,
                        .len = 1,
                        .buf = addr,
                }, {
                        .addr = client->addr,
                        .flags = I2C_M_RD,
                        .len = 6,
                        .buf = buf,
                }
        };
        int ret;

        memset(buf, 0, sizeof(buf));

        ret = i2c_transfer(client->adapter, msgs, 2);
        if (ret == 2) {
                dt->tm_year = buf[4] >> 6;
                dt->tm_wday = buf[5] >> 5;

                buf[4] &= 0x3f;
                buf[5] &= 0x1f;

                dt->tm_sec = bcd2bin(buf[1]);
                dt->tm_min = bcd2bin(buf[2]);
                dt->tm_hour = bcd2bin(buf[3]);
                dt->tm_mday = bcd2bin(buf[4]);
                dt->tm_mon = bcd2bin(buf[5]) - 1;
        }

        return ret == 2 ? 0 : -EIO;
}

static int pcf8583_set_datetime(struct i2c_client *client, struct rtc_time *dt, int datetoo)
{
        unsigned char buf[8];
        int ret, len = 6;

        buf[0] = 0;
        buf[1] = get_ctrl(client) | 0x80;
        buf[2] = 0;
        buf[3] = bin2bcd(dt->tm_sec);
        buf[4] = bin2bcd(dt->tm_min);
        buf[5] = bin2bcd(dt->tm_hour);

        if (datetoo) {
                len = 8;
                buf[6] = bin2bcd(dt->tm_mday) | (dt->tm_year << 6);
                buf[7] = bin2bcd(dt->tm_mon + 1)  | (dt->tm_wday << 5);
        }

        ret = i2c_master_send(client, (char *)buf, len);
        if (ret != len)
                return -EIO;

        buf[1] = get_ctrl(client);
        ret = i2c_master_send(client, (char *)buf, 2);

        return ret == 2 ? 0 : -EIO;
}

static int pcf8583_get_ctrl(struct i2c_client *client, unsigned char *ctrl)
{
        *ctrl = get_ctrl(client);
        return 0;
}

static int pcf8583_set_ctrl(struct i2c_client *client, unsigned char *ctrl)
{
        unsigned char buf[2];

        buf[0] = 0;
        buf[1] = *ctrl;
        set_ctrl(client, *ctrl);

        return i2c_master_send(client, (char *)buf, 2);
}

static int pcf8583_read_mem(struct i2c_client *client, struct rtc_mem *mem)
{
        unsigned char addr[1];
        struct i2c_msg msgs[2] = {
                {
                        .addr = client->addr,
                        .flags = 0,
                        .len = 1,
                        .buf = addr,
                }, {
                        .addr = client->addr,
                        .flags = I2C_M_RD,
                        .len = mem->nr,
                        .buf = mem->data,
                }
        };

        if (mem->loc < 8)
                return -EINVAL;

        addr[0] = mem->loc;

        return i2c_transfer(client->adapter, msgs, 2) == 2 ? 0 : -EIO;
}

static int pcf8583_write_mem(struct i2c_client *client, struct rtc_mem *mem)
{
        unsigned char buf[9];
        int ret;

        if (mem->loc < 8 || mem->nr > 8)
                return -EINVAL;

        buf[0] = mem->loc;
        memcpy(buf + 1, mem->data, mem->nr);

        ret = i2c_master_send(client, buf, mem->nr + 1);
        return ret == mem->nr + 1 ? 0 : -EIO;
}

static int pcf8583_rtc_read_time(struct device *dev, struct rtc_time *tm)
{
        struct i2c_client *client = to_i2c_client(dev);
        unsigned char ctrl, year[2];
        struct rtc_mem mem = {
                .loc = CMOS_YEAR,
                .nr = sizeof(year),
                .data = year
        };
        int real_year, year_offset, err;

        /*
         * Ensure that the RTC is running.
         */
        pcf8583_get_ctrl(client, &ctrl);
        if (ctrl & (CTRL_STOP | CTRL_HOLD)) {
                unsigned char new_ctrl = ctrl & ~(CTRL_STOP | CTRL_HOLD);

                dev_warn(dev, "resetting control %02x -> %02x\n",
                        ctrl, new_ctrl);

                err = pcf8583_set_ctrl(client, &new_ctrl);
                if (err < 0)
                        return err;
        }

        if (pcf8583_get_datetime(client, tm) ||
            pcf8583_read_mem(client, &mem))
                return -EIO;

        real_year = year[0];

        /*
         * The RTC year holds the LSB two bits of the current
         * year, which should reflect the LSB two bits of the
         * CMOS copy of the year.  Any difference indicates
         * that we have to correct the CMOS version.
         */
        year_offset = tm->tm_year - (real_year & 3);
        if (year_offset < 0)
                /*
                 * RTC year wrapped.  Adjust it appropriately.
                 */
                year_offset += 4;

        tm->tm_year = (real_year + year_offset + year[1] * 100) - 1900;

        return 0;
}

static int pcf8583_rtc_set_time(struct device *dev, struct rtc_time *tm)
{
        struct i2c_client *client = to_i2c_client(dev);
        unsigned char year[2], chk;
        struct rtc_mem cmos_year  = {
                .loc = CMOS_YEAR,
                .nr = sizeof(year),
                .data = year
        };
        struct rtc_mem cmos_check = {
                .loc = CMOS_CHECKSUM,
                .nr = 1,
                .data = &chk
        };
        unsigned int proper_year = tm->tm_year + 1900;
        int ret;

        /*
         * The RTC's own 2-bit year must reflect the least
         * significant two bits of the CMOS year.
         */

        ret = pcf8583_set_datetime(client, tm, 1);
        if (ret)
                return ret;

        ret = pcf8583_read_mem(client, &cmos_check);
        if (ret)
                return ret;

        ret = pcf8583_read_mem(client, &cmos_year);
        if (ret)
                return ret;

        chk -= year[1] + year[0];

        year[1] = proper_year / 100;
        year[0] = proper_year % 100;

        chk += year[1] + year[0];

        ret = pcf8583_write_mem(client, &cmos_year);

        if (ret)
                return ret;

        ret = pcf8583_write_mem(client, &cmos_check);

        return ret;
}

static const struct rtc_class_ops pcf8583_rtc_ops = {
        .read_time      = pcf8583_rtc_read_time,
        .set_time       = pcf8583_rtc_set_time,
};

static int pcf8583_probe(struct i2c_client *client,
                                const struct i2c_device_id *id)
{
        struct pcf8583 *pcf8583;

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

        pcf8583 = devm_kzalloc(&client->dev, sizeof(struct pcf8583),
                                GFP_KERNEL);
        if (!pcf8583)
                return -ENOMEM;

        i2c_set_clientdata(client, pcf8583);

        pcf8583->rtc = devm_rtc_device_register(&client->dev,
                                pcf8583_driver.driver.name,
                                &pcf8583_rtc_ops, THIS_MODULE);

        return PTR_ERR_OR_ZERO(pcf8583->rtc);
}

static const struct i2c_device_id pcf8583_id[] = {
        { "pcf8583", 0 },
        { }
};
MODULE_DEVICE_TABLE(i2c, pcf8583_id);

static struct i2c_driver pcf8583_driver = {
        .driver = {
                .name   = "pcf8583",
        },
        .probe          = pcf8583_probe,
        .id_table       = pcf8583_id,
};

module_i2c_driver(pcf8583_driver);

MODULE_AUTHOR("Russell King");
MODULE_DESCRIPTION("PCF8583 I2C RTC driver");
MODULE_LICENSE("GPL");