/*
 * An i2c driver for the Xicor/Intersil X1205 RTC
 * Copyright 2004 Karen Spearel
 * Copyright 2005 Alessandro Zummo
 *
 * please send all reports to:
 *      Karen Spearel <kas111 at gmail dot com>
 *      Alessandro Zummo <a.zummo@towertech.it>
 *
 * based on a lot of other RTC drivers.
 *
 * Information and datasheet:
 * http://www.intersil.com/cda/deviceinfo/0,1477,X1205,00.html
 *
 * 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/delay.h>
#include <linux/module.h>
#include <linux/bitops.h>

/* offsets into CCR area */

#define CCR_SEC                 0
#define CCR_MIN                 1
#define CCR_HOUR                2
#define CCR_MDAY                3
#define CCR_MONTH               4
#define CCR_YEAR                5
#define CCR_WDAY                6
#define CCR_Y2K                 7

#define X1205_REG_SR            0x3F    /* status register */
#define X1205_REG_Y2K           0x37
#define X1205_REG_DW            0x36
#define X1205_REG_YR            0x35
#define X1205_REG_MO            0x34
#define X1205_REG_DT            0x33
#define X1205_REG_HR            0x32
#define X1205_REG_MN            0x31
#define X1205_REG_SC            0x30
#define X1205_REG_DTR           0x13
#define X1205_REG_ATR           0x12
#define X1205_REG_INT           0x11
#define X1205_REG_0             0x10
#define X1205_REG_Y2K1          0x0F
#define X1205_REG_DWA1          0x0E
#define X1205_REG_YRA1          0x0D
#define X1205_REG_MOA1          0x0C
#define X1205_REG_DTA1          0x0B
#define X1205_REG_HRA1          0x0A
#define X1205_REG_MNA1          0x09
#define X1205_REG_SCA1          0x08
#define X1205_REG_Y2K0          0x07
#define X1205_REG_DWA0          0x06
#define X1205_REG_YRA0          0x05
#define X1205_REG_MOA0          0x04
#define X1205_REG_DTA0          0x03
#define X1205_REG_HRA0          0x02
#define X1205_REG_MNA0          0x01
#define X1205_REG_SCA0          0x00

#define X1205_CCR_BASE          0x30    /* Base address of CCR */
#define X1205_ALM0_BASE         0x00    /* Base address of ALARM0 */

#define X1205_SR_RTCF           0x01    /* Clock failure */
#define X1205_SR_WEL            0x02    /* Write Enable Latch */
#define X1205_SR_RWEL           0x04    /* Register Write Enable */
#define X1205_SR_AL0            0x20    /* Alarm 0 match */

#define X1205_DTR_DTR0          0x01
#define X1205_DTR_DTR1          0x02
#define X1205_DTR_DTR2          0x04

#define X1205_HR_MIL            0x80    /* Set in ccr.hour for 24 hr mode */

#define X1205_INT_AL0E          0x20    /* Alarm 0 enable */

static struct i2c_driver x1205_driver;

/*
 * In the routines that deal directly with the x1205 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 x1205_get_datetime(struct i2c_client *client, struct rtc_time *tm,
                                unsigned char reg_base)
{
        unsigned char dt_addr[2] = { 0, reg_base };
        unsigned char buf[8];
        int i;

        struct i2c_msg msgs[] = {
                {/* setup read ptr */
                        .addr = client->addr,
                        .len = 2,
                        .buf = dt_addr
                },
                {/* read date */
                        .addr = client->addr,
                        .flags = I2C_M_RD,
                        .len = 8,
                        .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 - sec=%02x, min=%02x, hr=%02x, "
                "mday=%02x, mon=%02x, year=%02x, wday=%02x, y2k=%02x\n",
                __func__,
                buf[0], buf[1], buf[2], buf[3],
                buf[4], buf[5], buf[6], buf[7]);

        /* Mask out the enable bits if these are alarm registers */
        if (reg_base < X1205_CCR_BASE)
                for (i = 0; i <= 4; i++)
                        buf[i] &= 0x7F;

        tm->tm_sec = bcd2bin(buf[CCR_SEC]);
        tm->tm_min = bcd2bin(buf[CCR_MIN]);
        tm->tm_hour = bcd2bin(buf[CCR_HOUR] & 0x3F); /* hr is 0-23 */
        tm->tm_mday = bcd2bin(buf[CCR_MDAY]);
        tm->tm_mon = bcd2bin(buf[CCR_MONTH]) - 1; /* mon is 0-11 */
        tm->tm_year = bcd2bin(buf[CCR_YEAR])
                        + (bcd2bin(buf[CCR_Y2K]) * 100) - 1900;
        tm->tm_wday = buf[CCR_WDAY];

        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 x1205_get_status(struct i2c_client *client, unsigned char *sr)
{
        static unsigned char sr_addr[2] = { 0, X1205_REG_SR };

        struct i2c_msg msgs[] = {
                {     /* setup read ptr */
                        .addr = client->addr,
                        .len = 2,
                        .buf = sr_addr
                },
                {    /* read status */
                        .addr = client->addr,
                        .flags = I2C_M_RD,
                        .len = 1,
                        .buf = sr
                },
        };

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

        return 0;
}

static int x1205_set_datetime(struct i2c_client *client, struct rtc_time *tm,
                        u8 reg_base, unsigned char alm_enable)
{
        int i, xfer;
        unsigned char rdata[10] = { 0, reg_base };
        unsigned char *buf = rdata + 2;

        static const unsigned char wel[3] = { 0, X1205_REG_SR,
                                                X1205_SR_WEL };

        static const unsigned char rwel[3] = { 0, X1205_REG_SR,
                                                X1205_SR_WEL | X1205_SR_RWEL };

        static const unsigned char diswe[3] = { 0, X1205_REG_SR, 0 };

        dev_dbg(&client->dev,
                "%s: sec=%d min=%d hour=%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);

        buf[CCR_SEC] = bin2bcd(tm->tm_sec);
        buf[CCR_MIN] = bin2bcd(tm->tm_min);

        /* set hour and 24hr bit */
        buf[CCR_HOUR] = bin2bcd(tm->tm_hour) | X1205_HR_MIL;

        buf[CCR_MDAY] = bin2bcd(tm->tm_mday);

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

        /* year, since the rtc epoch*/
        buf[CCR_YEAR] = bin2bcd(tm->tm_year % 100);
        buf[CCR_WDAY] = tm->tm_wday & 0x07;
        buf[CCR_Y2K] = bin2bcd((tm->tm_year + 1900) / 100);

        /* If writing alarm registers, set compare bits on registers 0-4 */
        if (reg_base < X1205_CCR_BASE)
                for (i = 0; i <= 4; i++)
                        buf[i] |= 0x80;

        /* this sequence is required to unlock the chip */
        xfer = i2c_master_send(client, wel, 3);
        if (xfer != 3) {
                dev_err(&client->dev, "%s: wel - %d\n", __func__, xfer);
                return -EIO;
        }

        xfer = i2c_master_send(client, rwel, 3);
        if (xfer != 3) {
                dev_err(&client->dev, "%s: rwel - %d\n", __func__, xfer);
                return -EIO;
        }

        xfer = i2c_master_send(client, rdata, sizeof(rdata));
        if (xfer != sizeof(rdata)) {
                dev_err(&client->dev,
                        "%s: result=%d addr=%02x, data=%02x\n",
                        __func__,
                         xfer, rdata[1], rdata[2]);
                return -EIO;
        }

        /* If we wrote to the nonvolatile region, wait 10msec for write cycle*/
        if (reg_base < X1205_CCR_BASE) {
                unsigned char al0e[3] = { 0, X1205_REG_INT, 0 };

                msleep(10);

                /* ...and set or clear the AL0E bit in the INT register */

                /* Need to set RWEL again as the write has cleared it */
                xfer = i2c_master_send(client, rwel, 3);
                if (xfer != 3) {
                        dev_err(&client->dev,
                                "%s: aloe rwel - %d\n",
                                __func__,
                                xfer);
                        return -EIO;
                }

                if (alm_enable)
                        al0e[2] = X1205_INT_AL0E;

                xfer = i2c_master_send(client, al0e, 3);
                if (xfer != 3) {
                        dev_err(&client->dev,
                                "%s: al0e - %d\n",
                                __func__,
                                xfer);
                        return -EIO;
                }

                /* and wait 10msec again for this write to complete */
                msleep(10);
        }

        /* disable further writes */
        xfer = i2c_master_send(client, diswe, 3);
        if (xfer != 3) {
                dev_err(&client->dev, "%s: diswe - %d\n", __func__, xfer);
                return -EIO;
        }

        return 0;
}

static int x1205_fix_osc(struct i2c_client *client)
{
        int err;
        struct rtc_time tm;

        memset(&tm, 0, sizeof(tm));

        err = x1205_set_datetime(client, &tm, X1205_CCR_BASE, 0);
        if (err < 0)
                dev_err(&client->dev, "unable to restart the oscillator\n");

        return err;
}

static int x1205_get_dtrim(struct i2c_client *client, int *trim)
{
        unsigned char dtr;
        static unsigned char dtr_addr[2] = { 0, X1205_REG_DTR };

        struct i2c_msg msgs[] = {
                {       /* setup read ptr */
                        .addr = client->addr,
                        .len = 2,
                        .buf = dtr_addr
                },
                {      /* read dtr */
                        .addr = client->addr,
                        .flags = I2C_M_RD,
                        .len = 1,
                        .buf = &dtr
                },
        };

        /* read dtr register */
        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 dtr=%x\n", __func__, dtr);

        *trim = 0;

        if (dtr & X1205_DTR_DTR0)
                *trim += 20;

        if (dtr & X1205_DTR_DTR1)
                *trim += 10;

        if (dtr & X1205_DTR_DTR2)
                *trim = -*trim;

        return 0;
}

static int x1205_get_atrim(struct i2c_client *client, int *trim)
{
        s8 atr;
        static unsigned char atr_addr[2] = { 0, X1205_REG_ATR };

        struct i2c_msg msgs[] = {
                {/* setup read ptr */
                        .addr = client->addr,
                        .len = 2,
                        .buf = atr_addr
                },
                {/* read atr */
                        .addr = client->addr,
                        .flags = I2C_M_RD,
                        .len = 1,
                        .buf = &atr
                },
        };

        /* read atr register */
        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 atr=%x\n", __func__, atr);

        /* atr is a two's complement value on 6 bits,
         * perform sign extension. The formula is
         * Catr = (atr * 0.25pF) + 11.00pF.
         */
        atr = sign_extend32(atr, 5);

        dev_dbg(&client->dev, "%s: raw atr=%x (%d)\n", __func__, atr, atr);

        *trim = (atr * 250) + 11000;

        dev_dbg(&client->dev, "%s: real=%d\n", __func__, *trim);

        return 0;
}

struct x1205_limit {
        unsigned char reg, mask, min, max;
};

static int x1205_validate_client(struct i2c_client *client)
{
        int i, xfer;

        /* Probe array. We will read the register at the specified
         * address and check if the given bits are zero.
         */
        static const unsigned char probe_zero_pattern[] = {
                /* register, mask */
                X1205_REG_SR,   0x18,
                X1205_REG_DTR,  0xF8,
                X1205_REG_ATR,  0xC0,
                X1205_REG_INT,  0x18,
                X1205_REG_0,    0xFF,
        };

        static const struct x1205_limit probe_limits_pattern[] = {
                /* register, mask, min, max */
                { X1205_REG_Y2K,        0xFF,   19,     20      },
                { X1205_REG_DW,         0xFF,   0,      6       },
                { X1205_REG_YR,         0xFF,   0,      99      },
                { X1205_REG_MO,         0xFF,   0,      12      },
                { X1205_REG_DT,         0xFF,   0,      31      },
                { X1205_REG_HR,         0x7F,   0,      23      },
                { X1205_REG_MN,         0xFF,   0,      59      },
                { X1205_REG_SC,         0xFF,   0,      59      },
                { X1205_REG_Y2K1,       0xFF,   19,     20      },
                { X1205_REG_Y2K0,       0xFF,   19,     20      },
        };

        /* check that registers have bits a 0 where expected */
        for (i = 0; i < ARRAY_SIZE(probe_zero_pattern); i += 2) {
                unsigned char buf;

                unsigned char addr[2] = { 0, probe_zero_pattern[i] };

                struct i2c_msg msgs[2] = {
                        {
                                .addr = client->addr,
                                .len = 2,
                                .buf = addr
                        },
                        {
                                .addr = client->addr,
                                .flags = I2C_M_RD,
                                .len = 1,
                                .buf = &buf
                        },
                };

                xfer = i2c_transfer(client->adapter, msgs, 2);
                if (xfer != 2) {
                        dev_err(&client->dev,
                                "%s: could not read register %x\n",
                                __func__, probe_zero_pattern[i]);

                        return -EIO;
                }

                if ((buf & probe_zero_pattern[i+1]) != 0) {
                        dev_err(&client->dev,
                                "%s: register=%02x, zero pattern=%d, value=%x\n",
                                __func__, probe_zero_pattern[i], i, buf);

                        return -ENODEV;
                }
        }

        /* check limits (only registers with bcd values) */
        for (i = 0; i < ARRAY_SIZE(probe_limits_pattern); i++) {
                unsigned char reg, value;

                unsigned char addr[2] = { 0, probe_limits_pattern[i].reg };

                struct i2c_msg msgs[2] = {
                        {
                                .addr = client->addr,
                                .len = 2,
                                .buf = addr
                        },
                        {
                                .addr = client->addr,
                                .flags = I2C_M_RD,
                                .len = 1,
                                .buf = &reg
                        },
                };

                xfer = i2c_transfer(client->adapter, msgs, 2);
                if (xfer != 2) {
                        dev_err(&client->dev,
                                "%s: could not read register %x\n",
                                __func__, probe_limits_pattern[i].reg);

                        return -EIO;
                }

                value = bcd2bin(reg & probe_limits_pattern[i].mask);

                if (value > probe_limits_pattern[i].max ||
                        value < probe_limits_pattern[i].min) {
                        dev_dbg(&client->dev,
                                "%s: register=%x, lim pattern=%d, value=%d\n",
                                __func__, probe_limits_pattern[i].reg,
                                i, value);

                        return -ENODEV;
                }
        }

        return 0;
}

static int x1205_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alrm)
{
        int err;
        unsigned char intreg, status;
        static unsigned char int_addr[2] = { 0, X1205_REG_INT };
        struct i2c_client *client = to_i2c_client(dev);
        struct i2c_msg msgs[] = {
                { /* setup read ptr */
                        .addr = client->addr,
                        .len = 2,
                        .buf = int_addr
                },
                {/* read INT register */

                        .addr = client->addr,
                        .flags = I2C_M_RD,
                        .len = 1,
                        .buf = &intreg
                },
        };

        /* read interrupt register and status register */
        if (i2c_transfer(client->adapter, &msgs[0], 2) != 2) {
                dev_err(&client->dev, "%s: read error\n", __func__);
                return -EIO;
        }
        err = x1205_get_status(client, &status);
        if (err == 0) {
                alrm->pending = (status & X1205_SR_AL0) ? 1 : 0;
                alrm->enabled = (intreg & X1205_INT_AL0E) ? 1 : 0;
                err = x1205_get_datetime(client, &alrm->time, X1205_ALM0_BASE);
        }
        return err;
}

static int x1205_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alrm)
{
        return x1205_set_datetime(to_i2c_client(dev),
                &alrm->time, X1205_ALM0_BASE, alrm->enabled);
}

static int x1205_rtc_read_time(struct device *dev, struct rtc_time *tm)
{
        return x1205_get_datetime(to_i2c_client(dev),
                tm, X1205_CCR_BASE);
}

static int x1205_rtc_set_time(struct device *dev, struct rtc_time *tm)
{
        return x1205_set_datetime(to_i2c_client(dev),
                tm, X1205_CCR_BASE, 0);
}

static int x1205_rtc_proc(struct device *dev, struct seq_file *seq)
{
        int err, dtrim, atrim;

        err = x1205_get_dtrim(to_i2c_client(dev), &dtrim);
        if (!err)
                seq_printf(seq, "digital_trim\t: %d ppm\n", dtrim);

        err = x1205_get_atrim(to_i2c_client(dev), &atrim);
        if (!err)
                seq_printf(seq, "analog_trim\t: %d.%02d pF\n",
                        atrim / 1000, atrim % 1000);
        return 0;
}

static const struct rtc_class_ops x1205_rtc_ops = {
        .proc           = x1205_rtc_proc,
        .read_time      = x1205_rtc_read_time,
        .set_time       = x1205_rtc_set_time,
        .read_alarm     = x1205_rtc_read_alarm,
        .set_alarm      = x1205_rtc_set_alarm,
};

static ssize_t x1205_sysfs_show_atrim(struct device *dev,
                                struct device_attribute *attr, char *buf)
{
        int err, atrim;

        err = x1205_get_atrim(to_i2c_client(dev), &atrim);
        if (err)
                return err;

        return sprintf(buf, "%d.%02d pF\n", atrim / 1000, atrim % 1000);
}
static DEVICE_ATTR(atrim, S_IRUGO, x1205_sysfs_show_atrim, NULL);

static ssize_t x1205_sysfs_show_dtrim(struct device *dev,
                                struct device_attribute *attr, char *buf)
{
        int err, dtrim;

        err = x1205_get_dtrim(to_i2c_client(dev), &dtrim);
        if (err)
                return err;

        return sprintf(buf, "%d ppm\n", dtrim);
}
static DEVICE_ATTR(dtrim, S_IRUGO, x1205_sysfs_show_dtrim, NULL);

static int x1205_sysfs_register(struct device *dev)
{
        int err;

        err = device_create_file(dev, &dev_attr_atrim);
        if (err)
                return err;

        err = device_create_file(dev, &dev_attr_dtrim);
        if (err)
                device_remove_file(dev, &dev_attr_atrim);

        return err;
}

static void x1205_sysfs_unregister(struct device *dev)
{
        device_remove_file(dev, &dev_attr_atrim);
        device_remove_file(dev, &dev_attr_dtrim);
}


static int x1205_probe(struct i2c_client *client,
                        const struct i2c_device_id *id)
{
        int err = 0;
        unsigned char sr;
        struct rtc_device *rtc;

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

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

        if (x1205_validate_client(client) < 0)
                return -ENODEV;

        rtc = devm_rtc_device_register(&client->dev, x1205_driver.driver.name,
                                        &x1205_rtc_ops, THIS_MODULE);

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

        i2c_set_clientdata(client, rtc);

        /* Check for power failures and eventually enable the osc */
        err = x1205_get_status(client, &sr);
        if (!err) {
                if (sr & X1205_SR_RTCF) {
                        dev_err(&client->dev,
                                "power failure detected, "
                                "please set the clock\n");
                        udelay(50);
                        x1205_fix_osc(client);
                }
        } else {
                dev_err(&client->dev, "couldn't read status\n");
        }

        err = x1205_sysfs_register(&client->dev);
        if (err)
                dev_err(&client->dev, "Unable to create sysfs entries\n");

        return 0;
}

static int x1205_remove(struct i2c_client *client)
{
        x1205_sysfs_unregister(&client->dev);
        return 0;
}

static const struct i2c_device_id x1205_id[] = {
        { "x1205", 0 },
        { }
};
MODULE_DEVICE_TABLE(i2c, x1205_id);

static struct i2c_driver x1205_driver = {
        .driver         = {
                .name   = "rtc-x1205",
        },
        .probe          = x1205_probe,
        .remove         = x1205_remove,
        .id_table       = x1205_id,
};

module_i2c_driver(x1205_driver);

MODULE_AUTHOR(
        "Karen Spearel <kas111 at gmail dot com>, "
        "Alessandro Zummo <a.zummo@towertech.it>");
MODULE_DESCRIPTION("Xicor/Intersil X1205 RTC driver");
MODULE_LICENSE("GPL");