rtc-pcf8583.c

Go to the documentation of this file.

/*
 *  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/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 = { CMOS_YEAR, sizeof(year), 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);

        printk(KERN_WARNING "RTC: resetting control %02x -> %02x\n",
               ctrl, new_ctrl);

        if ((err = pcf8583_set_ctrl(client, &new_ctrl)) < 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  = { CMOS_YEAR, sizeof(year), year };
    struct rtc_mem cmos_check = { CMOS_CHECKSUM, 1, &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;
    int err;

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

    pcf8583 = kzalloc(sizeof(struct pcf8583), GFP_KERNEL);
    if (!pcf8583)
        return -ENOMEM;

    i2c_set_clientdata(client, pcf8583);

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

    if (IS_ERR(pcf8583->rtc)) {
        err = PTR_ERR(pcf8583->rtc);
        goto exit_kfree;
    }

    return 0;

exit_kfree:
    kfree(pcf8583);
    return err;
}

static int __devexit pcf8583_remove(struct i2c_client *client)
{
    struct pcf8583 *pcf8583 = i2c_get_clientdata(client);

    if (pcf8583->rtc)
        rtc_device_unregister(pcf8583->rtc);
    kfree(pcf8583);
    return 0;
}

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",
        .owner  = THIS_MODULE,
    },
    .probe      = pcf8583_probe,
    .remove     = __devexit_p(pcf8583_remove),
    .id_table   = pcf8583_id,
};

module_i2c_driver(pcf8583_driver);

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