drivers/rtc/rtc-max6902.c

   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
  32 static 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
  45 static 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
  56 static 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 0;
  89 }
  90
  91 static 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, MAX6902_REG_CONTROL, 0);
  97
  98         max6902_set_reg(dev, MAX6902_REG_SECONDS, bin2bcd(dt->tm_sec));
  99         max6902_set_reg(dev, MAX6902_REG_MINUTES, bin2bcd(dt->tm_min));
 100         max6902_set_reg(dev, MAX6902_REG_HOURS, bin2bcd(dt->tm_hour));
 101
 102         max6902_set_reg(dev, MAX6902_REG_DATE, bin2bcd(dt->tm_mday));
 103         max6902_set_reg(dev, MAX6902_REG_MONTH, bin2bcd(dt->tm_mon + 1));
 104         max6902_set_reg(dev, MAX6902_REG_DAY, bin2bcd(dt->tm_wday));
 105         max6902_set_reg(dev, MAX6902_REG_YEAR, bin2bcd(dt->tm_year % 100));
 106         max6902_set_reg(dev, MAX6902_REG_CENTURY, 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, MAX6902_REG_CONTROL, 0x80);
 114
 115         return 0;
 116 }
 117
 118 static const struct rtc_class_ops max6902_rtc_ops = {
 119         .read_time      = max6902_read_time,
 120         .set_time       = max6902_set_time,
 121 };
 122
 123 static int 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 = devm_rtc_device_register(&spi->dev, "max6902",
 138                                 &max6902_rtc_ops, THIS_MODULE);
 139         if (IS_ERR(rtc))
 140                 return PTR_ERR(rtc);
 141
 142         spi_set_drvdata(spi, rtc);
 143         return 0;
 144 }
 145
 146 static struct spi_driver max6902_driver = {
 147         .driver = {
 148                 .name   = "rtc-max6902",
 149         },
 150         .probe  = max6902_probe,
 151 };
 152
 153 module_spi_driver(max6902_driver);
 154
 155 MODULE_DESCRIPTION("max6902 spi RTC driver");
 156 MODULE_AUTHOR("Raphael Assenat");
 157 MODULE_LICENSE("GPL");
 158 MODULE_ALIAS("spi:rtc-max6902");