drivers/rtc/rtc-m41t94.c

   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
  32 static 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
  59 static 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
 106 static const struct rtc_class_ops m41t94_rtc_ops = {
 107         .read_time      = m41t94_read_time,
 108         .set_time       = m41t94_set_time,
 109 };
 110
 111 static struct spi_driver m41t94_driver;
 112
 113 static 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 = devm_rtc_device_register(&spi->dev, m41t94_driver.driver.name,
 128                                         &m41t94_rtc_ops, THIS_MODULE);
 129         if (IS_ERR(rtc))
 130                 return PTR_ERR(rtc);
 131
 132         spi_set_drvdata(spi, rtc);
 133
 134         return 0;
 135 }
 136
 137 static struct spi_driver m41t94_driver = {
 138         .driver = {
 139                 .name   = "rtc-m41t94",
 140                 .owner  = THIS_MODULE,
 141         },
 142         .probe  = m41t94_probe,
 143 };
 144
 145 module_spi_driver(m41t94_driver);
 146
 147 MODULE_AUTHOR("Kim B. Heino <Kim.Heino@bluegiga.com>");
 148 MODULE_DESCRIPTION("Driver for ST M41T94 SPI RTC");
 149 MODULE_LICENSE("GPL");
 150 MODULE_ALIAS("spi:rtc-m41t94");