linux/drivers/rtc/rtc-max6902.c
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   1/* drivers/rtc/rtc-max6902.c
   2 *
   3 * Copyright (C) 2006 8D Technologies inc.
   4 * Copyright (C) 2004 Compulab Ltd.
   5 *
   6 * This program is free software; you can redistribute it and/or modify
   7 * it under the terms of the GNU General Public License version 2 as
   8 * published by the Free Software Foundation.
   9 *
  10 * Driver for MAX6902 spi RTC
  11 *
  12 */
  13
  14#include <linux/module.h>
  15#include <linux/kernel.h>
  16#include <linux/platform_device.h>
  17#include <linux/init.h>
  18#include <linux/rtc.h>
  19#include <linux/spi/spi.h>
  20#include <linux/bcd.h>
  21
  22#define MAX6902_REG_SECONDS             0x01
  23#define MAX6902_REG_MINUTES             0x03
  24#define MAX6902_REG_HOURS               0x05
  25#define MAX6902_REG_DATE                0x07
  26#define MAX6902_REG_MONTH               0x09
  27#define MAX6902_REG_DAY                 0x0B
  28#define MAX6902_REG_YEAR                0x0D
  29#define MAX6902_REG_CONTROL             0x0F
  30#define MAX6902_REG_CENTURY             0x13
  31
  32static int max6902_set_reg(struct device *dev, unsigned char address,
  33                                unsigned char data)
  34{
  35        struct spi_device *spi = to_spi_device(dev);
  36        unsigned char buf[2];
  37
  38        /* MSB must be '0' to write */
  39        buf[0] = address & 0x7f;
  40        buf[1] = data;
  41
  42        return spi_write_then_read(spi, buf, 2, NULL, 0);
  43}
  44
  45static int max6902_get_reg(struct device *dev, unsigned char address,
  46                                unsigned char *data)
  47{
  48        struct spi_device *spi = to_spi_device(dev);
  49
  50        /* Set MSB to indicate read */
  51        *data = address | 0x80;
  52
  53        return spi_write_then_read(spi, data, 1, data, 1);
  54}
  55
  56static int max6902_read_time(struct device *dev, struct rtc_time *dt)
  57{
  58        int err, century;
  59        struct spi_device *spi = to_spi_device(dev);
  60        unsigned char buf[8];
  61
  62        buf[0] = 0xbf;  /* Burst read */
  63
  64        err = spi_write_then_read(spi, buf, 1, buf, 8);
  65        if (err != 0)
  66                return err;
  67
  68        /* The chip sends data in this order:
  69         * Seconds, Minutes, Hours, Date, Month, Day, Year */
  70        dt->tm_sec      = bcd2bin(buf[0]);
  71        dt->tm_min      = bcd2bin(buf[1]);
  72        dt->tm_hour     = bcd2bin(buf[2]);
  73        dt->tm_mday     = bcd2bin(buf[3]);
  74        dt->tm_mon      = bcd2bin(buf[4]) - 1;
  75        dt->tm_wday     = bcd2bin(buf[5]);
  76        dt->tm_year     = bcd2bin(buf[6]);
  77
  78        /* Read century */
  79        err = max6902_get_reg(dev, MAX6902_REG_CENTURY, &buf[0]);
  80        if (err != 0)
  81                return err;
  82
  83        century = bcd2bin(buf[0]) * 100;
  84
  85        dt->tm_year += century;
  86        dt->tm_year -= 1900;
  87
  88        return rtc_valid_tm(dt);
  89}
  90
  91static int max6902_set_time(struct device *dev, struct rtc_time *dt)
  92{
  93        dt->tm_year = dt->tm_year + 1900;
  94
  95        /* Remove write protection */
  96        max6902_set_reg(dev, 0xF, 0);
  97
  98        max6902_set_reg(dev, 0x01, bin2bcd(dt->tm_sec));
  99        max6902_set_reg(dev, 0x03, bin2bcd(dt->tm_min));
 100        max6902_set_reg(dev, 0x05, bin2bcd(dt->tm_hour));
 101
 102        max6902_set_reg(dev, 0x07, bin2bcd(dt->tm_mday));
 103        max6902_set_reg(dev, 0x09, bin2bcd(dt->tm_mon + 1));
 104        max6902_set_reg(dev, 0x0B, bin2bcd(dt->tm_wday));
 105        max6902_set_reg(dev, 0x0D, bin2bcd(dt->tm_year % 100));
 106        max6902_set_reg(dev, 0x13, bin2bcd(dt->tm_year / 100));
 107
 108        /* Compulab used a delay here. However, the datasheet
 109         * does not mention a delay being required anywhere... */
 110        /* delay(2000); */
 111
 112        /* Write protect */
 113        max6902_set_reg(dev, 0xF, 0x80);
 114
 115        return 0;
 116}
 117
 118static const struct rtc_class_ops max6902_rtc_ops = {
 119        .read_time      = max6902_read_time,
 120        .set_time       = max6902_set_time,
 121};
 122
 123static int __devinit max6902_probe(struct spi_device *spi)
 124{
 125        struct rtc_device *rtc;
 126        unsigned char tmp;
 127        int res;
 128
 129        spi->mode = SPI_MODE_3;
 130        spi->bits_per_word = 8;
 131        spi_setup(spi);
 132
 133        res = max6902_get_reg(&spi->dev, MAX6902_REG_SECONDS, &tmp);
 134        if (res != 0)
 135                return res;
 136
 137        rtc = rtc_device_register("max6902",
 138                                &spi->dev, &max6902_rtc_ops, THIS_MODULE);
 139        if (IS_ERR(rtc))
 140                return PTR_ERR(rtc);
 141
 142        dev_set_drvdata(&spi->dev, rtc);
 143        return 0;
 144}
 145
 146static int __devexit max6902_remove(struct spi_device *spi)
 147{
 148        struct rtc_device *rtc = dev_get_drvdata(&spi->dev);
 149
 150        rtc_device_unregister(rtc);
 151        return 0;
 152}
 153
 154static struct spi_driver max6902_driver = {
 155        .driver = {
 156                .name   = "rtc-max6902",
 157                .owner  = THIS_MODULE,
 158        },
 159        .probe  = max6902_probe,
 160        .remove = __devexit_p(max6902_remove),
 161};
 162
 163module_spi_driver(max6902_driver);
 164
 165MODULE_DESCRIPTION ("max6902 spi RTC driver");
 166MODULE_AUTHOR ("Raphael Assenat");
 167MODULE_LICENSE ("GPL");
 168MODULE_ALIAS("spi:rtc-max6902");
 169
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