drivers/rtc/rtc-ds1347.c

   1 /* rtc-ds1347.c
   2  *
   3  * Driver for Dallas Semiconductor DS1347 Low Current, SPI Compatible
   4  * Real Time Clock
   5  *
   6  * Author : Raghavendra Chandra Ganiga <ravi23ganiga@gmail.com>
   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 /* Registers in ds1347 rtc */
  23
  24 #define DS1347_SECONDS_REG      0x01
  25 #define DS1347_MINUTES_REG      0x03
  26 #define DS1347_HOURS_REG        0x05
  27 #define DS1347_DATE_REG         0x07
  28 #define DS1347_MONTH_REG        0x09
  29 #define DS1347_DAY_REG          0x0B
  30 #define DS1347_YEAR_REG         0x0D
  31 #define DS1347_CONTROL_REG      0x0F
  32 #define DS1347_STATUS_REG       0x17
  33 #define DS1347_CLOCK_BURST      0x3F
  34
  35 static int ds1347_read_reg(struct device *dev, unsigned char address,
  36                                 unsigned char *data)
  37 {
  38         struct spi_device *spi = to_spi_device(dev);
  39
  40         *data = address | 0x80;
  41
  42         return spi_write_then_read(spi, data, 1, data, 1);
  43 }
  44
  45 static int ds1347_write_reg(struct device *dev, unsigned char address,
  46                                 unsigned char data)
  47 {
  48         struct spi_device *spi = to_spi_device(dev);
  49         unsigned char buf[2];
  50
  51         buf[0] = address & 0x7F;
  52         buf[1] = data;
  53
  54         return spi_write_then_read(spi, buf, 2, NULL, 0);
  55 }
  56
  57 static int ds1347_read_time(struct device *dev, struct rtc_time *dt)
  58 {
  59         struct spi_device *spi = to_spi_device(dev);
  60         int err;
  61         unsigned char buf[8];
  62
  63         buf[0] = DS1347_CLOCK_BURST | 0x80;
  64
  65         err = spi_write_then_read(spi, buf, 1, buf, 8);
  66         if (err)
  67                 return err;
  68
  69         dt->tm_sec = bcd2bin(buf[0]);
  70         dt->tm_min = bcd2bin(buf[1]);
  71         dt->tm_hour = bcd2bin(buf[2] & 0x3F);
  72         dt->tm_mday = bcd2bin(buf[3]);
  73         dt->tm_mon = bcd2bin(buf[4]) - 1;
  74         dt->tm_wday = bcd2bin(buf[5]) - 1;
  75         dt->tm_year = bcd2bin(buf[6]) + 100;
  76
  77         return rtc_valid_tm(dt);
  78 }
  79
  80 static int ds1347_set_time(struct device *dev, struct rtc_time *dt)
  81 {
  82         struct spi_device *spi = to_spi_device(dev);
  83         unsigned char buf[9];
  84
  85         buf[0] = DS1347_CLOCK_BURST & 0x7F;
  86         buf[1] = bin2bcd(dt->tm_sec);
  87         buf[2] = bin2bcd(dt->tm_min);
  88         buf[3] = (bin2bcd(dt->tm_hour) & 0x3F);
  89         buf[4] = bin2bcd(dt->tm_mday);
  90         buf[5] = bin2bcd(dt->tm_mon + 1);
  91         buf[6] = bin2bcd(dt->tm_wday + 1);
  92
  93         /* year in linux is from 1900 i.e in range of 100
  94         in rtc it is from 00 to 99 */
  95         dt->tm_year = dt->tm_year % 100;
  96
  97         buf[7] = bin2bcd(dt->tm_year);
  98         buf[8] = bin2bcd(0x00);
  99
 100         /* write the rtc settings */
 101         return spi_write_then_read(spi, buf, 9, NULL, 0);
 102 }
 103
 104 static const struct rtc_class_ops ds1347_rtc_ops = {
 105         .read_time = ds1347_read_time,
 106         .set_time = ds1347_set_time,
 107 };
 108
 109 static int ds1347_probe(struct spi_device *spi)
 110 {
 111         struct rtc_device *rtc;
 112         unsigned char data;
 113         int res;
 114
 115         /* spi setup with ds1347 in mode 3 and bits per word as 8 */
 116         spi->mode = SPI_MODE_3;
 117         spi->bits_per_word = 8;
 118         spi_setup(spi);
 119
 120         /* RTC Settings */
 121         res = ds1347_read_reg(&spi->dev, DS1347_SECONDS_REG, &data);
 122         if (res)
 123                 return res;
 124
 125         /* Disable the write protect of rtc */
 126         ds1347_read_reg(&spi->dev, DS1347_CONTROL_REG, &data);
 127         data = data & ~(1<<7);
 128         ds1347_write_reg(&spi->dev, DS1347_CONTROL_REG, data);
 129
 130         /* Enable the oscillator , disable the oscillator stop flag,
 131          and glitch filter to reduce current consumption */
 132         ds1347_read_reg(&spi->dev, DS1347_STATUS_REG, &data);
 133         data = data & 0x1B;
 134         ds1347_write_reg(&spi->dev, DS1347_STATUS_REG, data);
 135
 136         /* display the settings */
 137         ds1347_read_reg(&spi->dev, DS1347_CONTROL_REG, &data);
 138         dev_info(&spi->dev, "DS1347 RTC CTRL Reg = 0x%02x\n", data);
 139
 140         ds1347_read_reg(&spi->dev, DS1347_STATUS_REG, &data);
 141         dev_info(&spi->dev, "DS1347 RTC Status Reg = 0x%02x\n", data);
 142
 143         rtc = devm_rtc_device_register(&spi->dev, "ds1347",
 144                                 &ds1347_rtc_ops, THIS_MODULE);
 145
 146         if (IS_ERR(rtc))
 147                 return PTR_ERR(rtc);
 148
 149         spi_set_drvdata(spi, rtc);
 150
 151         return 0;
 152 }
 153
 154 static struct spi_driver ds1347_driver = {
 155         .driver = {
 156                 .name = "ds1347",
 157                 .owner = THIS_MODULE,
 158         },
 159         .probe = ds1347_probe,
 160 };
 161
 162 module_spi_driver(ds1347_driver);
 163
 164 MODULE_DESCRIPTION("DS1347 SPI RTC DRIVER");
 165 MODULE_AUTHOR("Raghavendra C Ganiga <ravi23ganiga@gmail.com>");
 166 MODULE_LICENSE("GPL v2");