linux/drivers/rtc/rtc-m41t94.c
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   1/*
   2 * Driver for ST M41T94 SPI RTC
   3 *
   4 * Copyright (C) 2008 Kim B. Heino
   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
  11#include <linux/module.h>
  12#include <linux/kernel.h>
  13#include <linux/platform_device.h>
  14#include <linux/rtc.h>
  15#include <linux/spi/spi.h>
  16#include <linux/bcd.h>
  17
  18#define M41T94_REG_SECONDS      0x01
  19#define M41T94_REG_MINUTES      0x02
  20#define M41T94_REG_HOURS        0x03
  21#define M41T94_REG_WDAY         0x04
  22#define M41T94_REG_DAY          0x05
  23#define M41T94_REG_MONTH        0x06
  24#define M41T94_REG_YEAR         0x07
  25#define M41T94_REG_HT           0x0c
  26
  27#define M41T94_BIT_HALT         0x40
  28#define M41T94_BIT_STOP         0x80
  29#define M41T94_BIT_CB           0x40
  30#define M41T94_BIT_CEB          0x80
  31
  32static int m41t94_set_time(struct device *dev, struct rtc_time *tm)
  33{
  34        struct spi_device *spi = to_spi_device(dev);
  35        u8 buf[8]; /* write cmd + 7 registers */
  36
  37        dev_dbg(dev, "%s secs=%d, mins=%d, "
  38                "hours=%d, mday=%d, mon=%d, year=%d, wday=%d\n",
  39                "write", tm->tm_sec, tm->tm_min,
  40                tm->tm_hour, tm->tm_mday,
  41                tm->tm_mon, tm->tm_year, tm->tm_wday);
  42
  43        buf[0] = 0x80 | M41T94_REG_SECONDS; /* write time + date */
  44        buf[M41T94_REG_SECONDS] = bin2bcd(tm->tm_sec);
  45        buf[M41T94_REG_MINUTES] = bin2bcd(tm->tm_min);
  46        buf[M41T94_REG_HOURS]   = bin2bcd(tm->tm_hour);
  47        buf[M41T94_REG_WDAY]    = bin2bcd(tm->tm_wday + 1);
  48        buf[M41T94_REG_DAY]     = bin2bcd(tm->tm_mday);
  49        buf[M41T94_REG_MONTH]   = bin2bcd(tm->tm_mon + 1);
  50
  51        buf[M41T94_REG_HOURS] |= M41T94_BIT_CEB;
  52        if (tm->tm_year >= 100)
  53                buf[M41T94_REG_HOURS] |= M41T94_BIT_CB;
  54        buf[M41T94_REG_YEAR] = bin2bcd(tm->tm_year % 100);
  55
  56        return spi_write(spi, buf, 8);
  57}
  58
  59static int m41t94_read_time(struct device *dev, struct rtc_time *tm)
  60{
  61        struct spi_device *spi = to_spi_device(dev);
  62        u8 buf[2];
  63        int ret, hour;
  64
  65        /* clear halt update bit */
  66        ret = spi_w8r8(spi, M41T94_REG_HT);
  67        if (ret < 0)
  68                return ret;
  69        if (ret & M41T94_BIT_HALT) {
  70                buf[0] = 0x80 | M41T94_REG_HT;
  71                buf[1] = ret & ~M41T94_BIT_HALT;
  72                spi_write(spi, buf, 2);
  73        }
  74
  75        /* clear stop bit */
  76        ret = spi_w8r8(spi, M41T94_REG_SECONDS);
  77        if (ret < 0)
  78                return ret;
  79        if (ret & M41T94_BIT_STOP) {
  80                buf[0] = 0x80 | M41T94_REG_SECONDS;
  81                buf[1] = ret & ~M41T94_BIT_STOP;
  82                spi_write(spi, buf, 2);
  83        }
  84
  85        tm->tm_sec  = bcd2bin(spi_w8r8(spi, M41T94_REG_SECONDS));
  86        tm->tm_min  = bcd2bin(spi_w8r8(spi, M41T94_REG_MINUTES));
  87        hour = spi_w8r8(spi, M41T94_REG_HOURS);
  88        tm->tm_hour = bcd2bin(hour & 0x3f);
  89        tm->tm_wday = bcd2bin(spi_w8r8(spi, M41T94_REG_WDAY)) - 1;
  90        tm->tm_mday = bcd2bin(spi_w8r8(spi, M41T94_REG_DAY));
  91        tm->tm_mon  = bcd2bin(spi_w8r8(spi, M41T94_REG_MONTH)) - 1;
  92        tm->tm_year = bcd2bin(spi_w8r8(spi, M41T94_REG_YEAR));
  93        if ((hour & M41T94_BIT_CB) || !(hour & M41T94_BIT_CEB))
  94                tm->tm_year += 100;
  95
  96        dev_dbg(dev, "%s secs=%d, mins=%d, "
  97                "hours=%d, mday=%d, mon=%d, year=%d, wday=%d\n",
  98                "read", tm->tm_sec, tm->tm_min,
  99                tm->tm_hour, tm->tm_mday,
 100                tm->tm_mon, tm->tm_year, tm->tm_wday);
 101
 102        /* initial clock setting can be undefined */
 103        return rtc_valid_tm(tm);
 104}
 105
 106static const struct rtc_class_ops m41t94_rtc_ops = {
 107        .read_time      = m41t94_read_time,
 108        .set_time       = m41t94_set_time,
 109};
 110
 111static struct spi_driver m41t94_driver;
 112
 113static int m41t94_probe(struct spi_device *spi)
 114{
 115        struct rtc_device *rtc;
 116        int res;
 117
 118        spi->bits_per_word = 8;
 119        spi_setup(spi);
 120
 121        res = spi_w8r8(spi, M41T94_REG_SECONDS);
 122        if (res < 0) {
 123                dev_err(&spi->dev, "not found.\n");
 124                return res;
 125        }
 126
 127        rtc = rtc_device_register(m41t94_driver.driver.name,
 128                &spi->dev, &m41t94_rtc_ops, THIS_MODULE);
 129        if (IS_ERR(rtc))
 130                return PTR_ERR(rtc);
 131
 132        dev_set_drvdata(&spi->dev, rtc);
 133
 134        return 0;
 135}
 136
 137static int m41t94_remove(struct spi_device *spi)
 138{
 139        struct rtc_device *rtc = spi_get_drvdata(spi);
 140
 141        if (rtc)
 142                rtc_device_unregister(rtc);
 143
 144        return 0;
 145}
 146
 147static struct spi_driver m41t94_driver = {
 148        .driver = {
 149                .name   = "rtc-m41t94",
 150                .owner  = THIS_MODULE,
 151        },
 152        .probe  = m41t94_probe,
 153        .remove = m41t94_remove,
 154};
 155
 156module_spi_driver(m41t94_driver);
 157
 158MODULE_AUTHOR("Kim B. Heino <Kim.Heino@bluegiga.com>");
 159MODULE_DESCRIPTION("Driver for ST M41T94 SPI RTC");
 160MODULE_LICENSE("GPL");
 161MODULE_ALIAS("spi:rtc-m41t94");
 162
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