drivers/rtc/rtc-ds3234.c

   1 /* rtc-ds3234.c
   2  *
   3  * Driver for Dallas Semiconductor (DS3234) SPI RTC with Integrated Crystal
   4  * and SRAM.
   5  *
   6  * Copyright (C) 2008 MIMOMax Wireless Ltd.
   7  *
   8  * This program is free software; you can redistribute it and/or modify
   9  * it under the terms of the GNU General Public License version 2 as
  10  * published by the Free Software Foundation.
  11  *
  12  */
  13
  14 #include <linux/init.h>
  15 #include <linux/module.h>
  16 #include <linux/device.h>
  17 #include <linux/platform_device.h>
  18 #include <linux/rtc.h>
  19 #include <linux/spi/spi.h>
  20 #include <linux/bcd.h>
  21
  22 #define DS3234_REG_SECONDS      0x00
  23 #define DS3234_REG_MINUTES      0x01
  24 #define DS3234_REG_HOURS        0x02
  25 #define DS3234_REG_DAY          0x03
  26 #define DS3234_REG_DATE         0x04
  27 #define DS3234_REG_MONTH        0x05
  28 #define DS3234_REG_YEAR         0x06
  29 #define DS3234_REG_CENTURY      (1 << 7) /* Bit 7 of the Month register */
  30
  31 #define DS3234_REG_CONTROL      0x0E
  32 #define DS3234_REG_CONT_STAT    0x0F
  33
  34 static int ds3234_set_reg(struct device *dev, unsigned char address,
  35                                 unsigned char data)
  36 {
  37         struct spi_device *spi = to_spi_device(dev);
  38         unsigned char buf[2];
  39
  40         /* MSB must be '1' to indicate write */
  41         buf[0] = address | 0x80;
  42         buf[1] = data;
  43
  44         return spi_write_then_read(spi, buf, 2, NULL, 0);
  45 }
  46
  47 static int ds3234_get_reg(struct device *dev, unsigned char address,
  48                                 unsigned char *data)
  49 {
  50         struct spi_device *spi = to_spi_device(dev);
  51
  52         *data = address & 0x7f;
  53
  54         return spi_write_then_read(spi, data, 1, data, 1);
  55 }
  56
  57 static int ds3234_read_time(struct device *dev, struct rtc_time *dt)
  58 {
  59         int err;
  60         unsigned char buf[8];
  61         struct spi_device *spi = to_spi_device(dev);
  62
  63         buf[0] = 0x00; /* Start address */
  64
  65         err = spi_write_then_read(spi, buf, 1, buf, 8);
  66         if (err != 0)
  67                 return err;
  68
  69         /* Seconds, Minutes, Hours, Day, Date, Month, Year */
  70         dt->tm_sec      = bcd2bin(buf[0]);
  71         dt->tm_min      = bcd2bin(buf[1]);
  72         dt->tm_hour     = bcd2bin(buf[2] & 0x3f);
  73         dt->tm_wday     = bcd2bin(buf[3]) - 1; /* 0 = Sun */
  74         dt->tm_mday     = bcd2bin(buf[4]);
  75         dt->tm_mon      = bcd2bin(buf[5] & 0x1f) - 1; /* 0 = Jan */
  76         dt->tm_year     = bcd2bin(buf[6] & 0xff) + 100; /* Assume 20YY */
  77
  78         return rtc_valid_tm(dt);
  79 }
  80
  81 static int ds3234_set_time(struct device *dev, struct rtc_time *dt)
  82 {
  83         ds3234_set_reg(dev, DS3234_REG_SECONDS, bin2bcd(dt->tm_sec));
  84         ds3234_set_reg(dev, DS3234_REG_MINUTES, bin2bcd(dt->tm_min));
  85         ds3234_set_reg(dev, DS3234_REG_HOURS, bin2bcd(dt->tm_hour) & 0x3f);
  86
  87         /* 0 = Sun */
  88         ds3234_set_reg(dev, DS3234_REG_DAY, bin2bcd(dt->tm_wday + 1));
  89         ds3234_set_reg(dev, DS3234_REG_DATE, bin2bcd(dt->tm_mday));
  90
  91         /* 0 = Jan */
  92         ds3234_set_reg(dev, DS3234_REG_MONTH, bin2bcd(dt->tm_mon + 1));
  93
  94         /* Assume 20YY although we just want to make sure not to go negative. */
  95         if (dt->tm_year > 100)
  96                 dt->tm_year -= 100;
  97
  98         ds3234_set_reg(dev, DS3234_REG_YEAR, bin2bcd(dt->tm_year));
  99
 100         return 0;
 101 }
 102
 103 static const struct rtc_class_ops ds3234_rtc_ops = {
 104         .read_time      = ds3234_read_time,
 105         .set_time       = ds3234_set_time,
 106 };
 107
 108 static int ds3234_probe(struct spi_device *spi)
 109 {
 110         struct rtc_device *rtc;
 111         unsigned char tmp;
 112         int res;
 113
 114         spi->mode = SPI_MODE_3;
 115         spi->bits_per_word = 8;
 116         spi_setup(spi);
 117
 118         res = ds3234_get_reg(&spi->dev, DS3234_REG_SECONDS, &tmp);
 119         if (res != 0)
 120                 return res;
 121
 122         /* Control settings
 123          *
 124          * CONTROL_REG
 125          * BIT 7        6       5       4       3       2       1       0
 126          *     EOSC     BBSQW   CONV    RS2     RS1     INTCN   A2IE    A1IE
 127          *
 128          *     0        0       0       1       1       1       0       0
 129          *
 130          * CONTROL_STAT_REG
 131          * BIT 7        6       5       4       3       2       1       0
 132          *     OSF      BB32kHz CRATE1  CRATE0  EN32kHz BSY     A2F     A1F
 133          *
 134          *     1        0       0       0       1       0       0       0
 135          */
 136         ds3234_get_reg(&spi->dev, DS3234_REG_CONTROL, &tmp);
 137         ds3234_set_reg(&spi->dev, DS3234_REG_CONTROL, tmp & 0x1c);
 138
 139         ds3234_get_reg(&spi->dev, DS3234_REG_CONT_STAT, &tmp);
 140         ds3234_set_reg(&spi->dev, DS3234_REG_CONT_STAT, tmp & 0x88);
 141
 142         /* Print our settings */
 143         ds3234_get_reg(&spi->dev, DS3234_REG_CONTROL, &tmp);
 144         dev_info(&spi->dev, "Control Reg: 0x%02x\n", tmp);
 145
 146         ds3234_get_reg(&spi->dev, DS3234_REG_CONT_STAT, &tmp);
 147         dev_info(&spi->dev, "Ctrl/Stat Reg: 0x%02x\n", tmp);
 148
 149         rtc = devm_rtc_device_register(&spi->dev, "ds3234",
 150                                 &ds3234_rtc_ops, THIS_MODULE);
 151         if (IS_ERR(rtc))
 152                 return PTR_ERR(rtc);
 153
 154         spi_set_drvdata(spi, rtc);
 155
 156         return 0;
 157 }
 158
 159 static struct spi_driver ds3234_driver = {
 160         .driver = {
 161                 .name    = "ds3234",
 162                 .owner  = THIS_MODULE,
 163         },
 164         .probe   = ds3234_probe,
 165 };
 166
 167 module_spi_driver(ds3234_driver);
 168
 169 MODULE_DESCRIPTION("DS3234 SPI RTC driver");
 170 MODULE_AUTHOR("Dennis Aberilla <denzzzhome@yahoo.com>");
 171 MODULE_LICENSE("GPL");
 172 MODULE_ALIAS("spi:ds3234");