/*
 *  linux/drivers/i2c/chips/ds1337.c
 *
 *  Copyright (C) 2005 James Chapman <jchapman@katalix.com>
 *
 *      based on linux/drivers/acorn/char/pcf8583.c
 *  Copyright (C) 2000 Russell King
 *
 * 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 Dallas Semiconductor DS1337 and DS1339 real time clock chip
 */

#include <linux/module.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/i2c.h>
#include <linux/string.h>
#include <linux/rtc.h>          /* get the user-level API */
#include <linux/bcd.h>
#include <linux/list.h>

/* Device registers */
#define DS1337_REG_HOUR         2
#define DS1337_REG_DAY          3
#define DS1337_REG_DATE         4
#define DS1337_REG_MONTH        5
#define DS1337_REG_CONTROL      14
#define DS1337_REG_STATUS       15

/* FIXME - how do we export these interface constants? */
#define DS1337_GET_DATE         0
#define DS1337_SET_DATE         1

/*
 * Functions declaration
 */
static unsigned short normal_i2c[] = { 0x68, I2C_CLIENT_END };

I2C_CLIENT_INSMOD_1(ds1337);

static int ds1337_attach_adapter(struct i2c_adapter *adapter);
static int ds1337_detect(struct i2c_adapter *adapter, int address, int kind);
static void ds1337_init_client(struct i2c_client *client);
static int ds1337_detach_client(struct i2c_client *client);
static int ds1337_command(struct i2c_client *client, unsigned int cmd,
                          void *arg);

/*
 * Driver data (common to all clients)
 */
static struct i2c_driver ds1337_driver = {
        .driver = {
                .name   = "ds1337",
        },
        .attach_adapter = ds1337_attach_adapter,
        .detach_client  = ds1337_detach_client,
        .command        = ds1337_command,
};

/*
 * Client data (each client gets its own)
 */
struct ds1337_data {
        struct i2c_client client;
        struct list_head list;
};

/*
 * Internal variables
 */
static LIST_HEAD(ds1337_clients);

static inline int ds1337_read(struct i2c_client *client, u8 reg, u8 *value)
{
        s32 tmp = i2c_smbus_read_byte_data(client, reg);

        if (tmp < 0)
                return -EIO;

        *value = tmp;

        return 0;
}

/*
 * Chip access functions
 */
static int ds1337_get_datetime(struct i2c_client *client, struct rtc_time *dt)
{
        int result;
        u8 buf[7];
        u8 val;
        struct i2c_msg msg[2];
        u8 offs = 0;

        if (!dt) {
                dev_dbg(&client->dev, "%s: EINVAL: dt=NULL\n", __FUNCTION__);
                return -EINVAL;
        }

        msg[0].addr = client->addr;
        msg[0].flags = 0;
        msg[0].len = 1;
        msg[0].buf = &offs;

        msg[1].addr = client->addr;
        msg[1].flags = I2C_M_RD;
        msg[1].len = sizeof(buf);
        msg[1].buf = &buf[0];

        result = i2c_transfer(client->adapter, msg, 2);

        dev_dbg(&client->dev, "%s: [%d] %02x %02x %02x %02x %02x %02x %02x\n",
                __FUNCTION__, result, buf[0], buf[1], buf[2], buf[3],
                buf[4], buf[5], buf[6]);

        if (result == 2) {
                dt->tm_sec = BCD2BIN(buf[0]);
                dt->tm_min = BCD2BIN(buf[1]);
                val = buf[2] & 0x3f;
                dt->tm_hour = BCD2BIN(val);
                dt->tm_wday = BCD2BIN(buf[3]) - 1;
                dt->tm_mday = BCD2BIN(buf[4]);
                val = buf[5] & 0x7f;
                dt->tm_mon = BCD2BIN(val) - 1;
                dt->tm_year = BCD2BIN(buf[6]);
                if (buf[5] & 0x80)
                        dt->tm_year += 100;

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

                return 0;
        }

        dev_err(&client->dev, "error reading data! %d\n", result);
        return -EIO;
}

static int ds1337_set_datetime(struct i2c_client *client, struct rtc_time *dt)
{
        int result;
        u8 buf[8];
        u8 val;
        struct i2c_msg msg[1];

        if (!dt) {
                dev_dbg(&client->dev, "%s: EINVAL: dt=NULL\n", __FUNCTION__);
                return -EINVAL;
        }

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

        buf[0] = 0;             /* reg offset */
        buf[1] = BIN2BCD(dt->tm_sec);
        buf[2] = BIN2BCD(dt->tm_min);
        buf[3] = BIN2BCD(dt->tm_hour);
        buf[4] = BIN2BCD(dt->tm_wday + 1);
        buf[5] = BIN2BCD(dt->tm_mday);
        buf[6] = BIN2BCD(dt->tm_mon + 1);
        val = dt->tm_year;
        if (val >= 100) {
                val -= 100;
                buf[6] |= (1 << 7);
        }
        buf[7] = BIN2BCD(val);

        msg[0].addr = client->addr;
        msg[0].flags = 0;
        msg[0].len = sizeof(buf);
        msg[0].buf = &buf[0];

        result = i2c_transfer(client->adapter, msg, 1);
        if (result == 1)
                return 0;

        dev_err(&client->dev, "error writing data! %d\n", result);
        return -EIO;
}

static int ds1337_command(struct i2c_client *client, unsigned int cmd,
                          void *arg)
{
        dev_dbg(&client->dev, "%s: cmd=%d\n", __FUNCTION__, cmd);

        switch (cmd) {
        case DS1337_GET_DATE:
                return ds1337_get_datetime(client, arg);

        case DS1337_SET_DATE:
                return ds1337_set_datetime(client, arg);

        default:
                return -EINVAL;
        }
}

/*
 * Public API for access to specific device. Useful for low-level
 * RTC access from kernel code.
 */
int ds1337_do_command(int bus, int cmd, void *arg)
{
        struct list_head *walk;
        struct list_head *tmp;
        struct ds1337_data *data;

        list_for_each_safe(walk, tmp, &ds1337_clients) {
                data = list_entry(walk, struct ds1337_data, list);
                if (data->client.adapter->nr == bus)
                        return ds1337_command(&data->client, cmd, arg);
        }

        return -ENODEV;
}

static int ds1337_attach_adapter(struct i2c_adapter *adapter)
{
        return i2c_probe(adapter, &addr_data, ds1337_detect);
}

/*
 * The following function does more than just detection. If detection
 * succeeds, it also registers the new chip.
 */
static int ds1337_detect(struct i2c_adapter *adapter, int address, int kind)
{
        struct i2c_client *new_client;
        struct ds1337_data *data;
        int err = 0;
        const char *name = "";

        if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE_DATA |
                                     I2C_FUNC_I2C))
                goto exit;

        if (!(data = kzalloc(sizeof(struct ds1337_data), GFP_KERNEL))) {
                err = -ENOMEM;
                goto exit;
        }
        INIT_LIST_HEAD(&data->list);

        /* The common I2C client data is placed right before the
         * DS1337-specific data. 
         */
        new_client = &data->client;
        i2c_set_clientdata(new_client, data);
        new_client->addr = address;
        new_client->adapter = adapter;
        new_client->driver = &ds1337_driver;
        new_client->flags = 0;

        /*
         * Now we do the remaining detection. A negative kind means that
         * the driver was loaded with no force parameter (default), so we
         * must both detect and identify the chip. A zero kind means that
         * the driver was loaded with the force parameter, the detection
         * step shall be skipped. A positive kind means that the driver
         * was loaded with the force parameter and a given kind of chip is
         * requested, so both the detection and the identification steps
         * are skipped.
         *
         * For detection, we read registers that are most likely to cause
         * detection failure, i.e. those that have more bits with fixed
         * or reserved values.
         */

        /* Default to an DS1337 if forced */
        if (kind == 0)
                kind = ds1337;

        if (kind < 0) {         /* detection and identification */
                u8 data;

                /* Check that status register bits 6-2 are zero */
                if ((ds1337_read(new_client, DS1337_REG_STATUS, &data) < 0) ||
                    (data & 0x7c))
                        goto exit_free;

                /* Check for a valid day register value */
                if ((ds1337_read(new_client, DS1337_REG_DAY, &data) < 0) ||
                    (data == 0) || (data & 0xf8))
                        goto exit_free;

                /* Check for a valid date register value */
                if ((ds1337_read(new_client, DS1337_REG_DATE, &data) < 0) ||
                    (data == 0) || (data & 0xc0) || ((data & 0x0f) > 9) ||
                    (data >= 0x32))
                        goto exit_free;

                /* Check for a valid month register value */
                if ((ds1337_read(new_client, DS1337_REG_MONTH, &data) < 0) ||
                    (data == 0) || (data & 0x60) || ((data & 0x0f) > 9) ||
                    ((data >= 0x13) && (data <= 0x19)))
                        goto exit_free;

                /* Check that control register bits 6-5 are zero */
                if ((ds1337_read(new_client, DS1337_REG_CONTROL, &data) < 0) ||
                    (data & 0x60))
                        goto exit_free;

                kind = ds1337;
        }

        if (kind == ds1337)
                name = "ds1337";

        /* We can fill in the remaining client fields */
        strlcpy(new_client->name, name, I2C_NAME_SIZE);

        /* Tell the I2C layer a new client has arrived */
        if ((err = i2c_attach_client(new_client)))
                goto exit_free;

        /* Initialize the DS1337 chip */
        ds1337_init_client(new_client);

        /* Add client to local list */
        list_add(&data->list, &ds1337_clients);

        return 0;

exit_free:
        kfree(data);
exit:
        return err;
}

static void ds1337_init_client(struct i2c_client *client)
{
        u8 status, control;

        /* On some boards, the RTC isn't configured by boot firmware.
         * Handle that case by starting/configuring the RTC now.
         */
        status = i2c_smbus_read_byte_data(client, DS1337_REG_STATUS);
        control = i2c_smbus_read_byte_data(client, DS1337_REG_CONTROL);

        if ((status & 0x80) || (control & 0x80)) {
                /* RTC not running */
                u8 buf[1+16];   /* First byte is interpreted as address */
                struct i2c_msg msg[1];

                dev_dbg(&client->dev, "%s: RTC not running!\n", __FUNCTION__);

                /* Initialize all, including STATUS and CONTROL to zero */
                memset(buf, 0, sizeof(buf));

                /* Write valid values in the date/time registers */
                buf[1+DS1337_REG_DAY] = 1;
                buf[1+DS1337_REG_DATE] = 1;
                buf[1+DS1337_REG_MONTH] = 1;

                msg[0].addr = client->addr;
                msg[0].flags = 0;
                msg[0].len = sizeof(buf);
                msg[0].buf = &buf[0];

                i2c_transfer(client->adapter, msg, 1);
        } else {
                /* Running: ensure that device is set in 24-hour mode */
                s32 val;

                val = i2c_smbus_read_byte_data(client, DS1337_REG_HOUR);
                if ((val >= 0) && (val & (1 << 6)))
                        i2c_smbus_write_byte_data(client, DS1337_REG_HOUR,
                                                  val & 0x3f);
        }
}

static int ds1337_detach_client(struct i2c_client *client)
{
        int err;
        struct ds1337_data *data = i2c_get_clientdata(client);

        if ((err = i2c_detach_client(client)))
                return err;

        list_del(&data->list);
        kfree(data);
        return 0;
}

static int __init ds1337_init(void)
{
        return i2c_add_driver(&ds1337_driver);
}

static void __exit ds1337_exit(void)
{
        i2c_del_driver(&ds1337_driver);
}

MODULE_AUTHOR("James Chapman <jchapman@katalix.com>");
MODULE_DESCRIPTION("DS1337 RTC driver");
MODULE_LICENSE("GPL");

EXPORT_SYMBOL_GPL(ds1337_do_command);

module_init(ds1337_init);
module_exit(ds1337_exit);