drivers/rtc/rtc-ds1390.c

   1 /*
   2  * rtc-ds1390.c -- driver for the Dallas/Maxim DS1390/93/94 SPI RTC
   3  *
   4  * Copyright (C) 2008 Mercury IMC Ltd
   5  * Written by Mark Jackson <mpfj@mimc.co.uk>
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License version 2 as
   9  * published by the Free Software Foundation.
  10  *
  11  * NOTE: Currently this driver only supports the bare minimum for read
  12  * and write the RTC. The extra features provided by the chip family
  13  * (alarms, trickle charger, different control registers) are unavailable.
  14  */
  15
  16 #include <linux/init.h>
  17 #include <linux/module.h>
  18 #include <linux/platform_device.h>
  19 #include <linux/rtc.h>
  20 #include <linux/spi/spi.h>
  21 #include <linux/bcd.h>
  22
  23 #define DS1390_REG_100THS               0x00
  24 #define DS1390_REG_SECONDS              0x01
  25 #define DS1390_REG_MINUTES              0x02
  26 #define DS1390_REG_HOURS                0x03
  27 #define DS1390_REG_DAY                  0x04
  28 #define DS1390_REG_DATE                 0x05
  29 #define DS1390_REG_MONTH_CENT           0x06
  30 #define DS1390_REG_YEAR                 0x07
  31
  32 #define DS1390_REG_ALARM_100THS         0x08
  33 #define DS1390_REG_ALARM_SECONDS        0x09
  34 #define DS1390_REG_ALARM_MINUTES        0x0A
  35 #define DS1390_REG_ALARM_HOURS          0x0B
  36 #define DS1390_REG_ALARM_DAY_DATE       0x0C
  37
  38 #define DS1390_REG_CONTROL              0x0D
  39 #define DS1390_REG_STATUS               0x0E
  40 #define DS1390_REG_TRICKLE              0x0F
  41
  42 struct ds1390 {
  43         struct rtc_device *rtc;
  44         u8 txrx_buf[9]; /* cmd + 8 registers */
  45 };
  46
  47 static int ds1390_get_reg(struct device *dev, unsigned char address,
  48                                 unsigned char *data)
  49 {
  50         struct spi_device *spi = to_spi_device(dev);
  51         struct ds1390 *chip = dev_get_drvdata(dev);
  52         int status;
  53
  54         if (!data)
  55                 return -EINVAL;
  56
  57         /* Clear MSB to indicate read */
  58         chip->txrx_buf[0] = address & 0x7f;
  59         /* do the i/o */
  60         status = spi_write_then_read(spi, chip->txrx_buf, 1, chip->txrx_buf, 1);
  61         if (status != 0)
  62                 return status;
  63
  64         *data = chip->txrx_buf[1];
  65
  66         return 0;
  67 }
  68
  69 static int ds1390_read_time(struct device *dev, struct rtc_time *dt)
  70 {
  71         struct spi_device *spi = to_spi_device(dev);
  72         struct ds1390 *chip = dev_get_drvdata(dev);
  73         int status;
  74
  75         /* build the message */
  76         chip->txrx_buf[0] = DS1390_REG_SECONDS;
  77
  78         /* do the i/o */
  79         status = spi_write_then_read(spi, chip->txrx_buf, 1, chip->txrx_buf, 8);
  80         if (status != 0)
  81                 return status;
  82
  83         /* The chip sends data in this order:
  84          * Seconds, Minutes, Hours, Day, Date, Month / Century, Year */
  85         dt->tm_sec      = bcd2bin(chip->txrx_buf[0]);
  86         dt->tm_min      = bcd2bin(chip->txrx_buf[1]);
  87         dt->tm_hour     = bcd2bin(chip->txrx_buf[2]);
  88         dt->tm_wday     = bcd2bin(chip->txrx_buf[3]);
  89         dt->tm_mday     = bcd2bin(chip->txrx_buf[4]);
  90         /* mask off century bit */
  91         dt->tm_mon      = bcd2bin(chip->txrx_buf[5] & 0x7f) - 1;
  92         /* adjust for century bit */
  93         dt->tm_year = bcd2bin(chip->txrx_buf[6]) + ((chip->txrx_buf[5] & 0x80) ? 100 : 0);
  94
  95         return rtc_valid_tm(dt);
  96 }
  97
  98 static int ds1390_set_time(struct device *dev, struct rtc_time *dt)
  99 {
 100         struct spi_device *spi = to_spi_device(dev);
 101         struct ds1390 *chip = dev_get_drvdata(dev);
 102
 103         /* build the message */
 104         chip->txrx_buf[0] = DS1390_REG_SECONDS | 0x80;
 105         chip->txrx_buf[1] = bin2bcd(dt->tm_sec);
 106         chip->txrx_buf[2] = bin2bcd(dt->tm_min);
 107         chip->txrx_buf[3] = bin2bcd(dt->tm_hour);
 108         chip->txrx_buf[4] = bin2bcd(dt->tm_wday);
 109         chip->txrx_buf[5] = bin2bcd(dt->tm_mday);
 110         chip->txrx_buf[6] = bin2bcd(dt->tm_mon + 1) |
 111                                 ((dt->tm_year > 99) ? 0x80 : 0x00);
 112         chip->txrx_buf[7] = bin2bcd(dt->tm_year % 100);
 113
 114         /* do the i/o */
 115         return spi_write_then_read(spi, chip->txrx_buf, 8, NULL, 0);
 116 }
 117
 118 static const struct rtc_class_ops ds1390_rtc_ops = {
 119         .read_time      = ds1390_read_time,
 120         .set_time       = ds1390_set_time,
 121 };
 122
 123 static int __devinit ds1390_probe(struct spi_device *spi)
 124 {
 125         unsigned char tmp;
 126         struct ds1390 *chip;
 127         int res;
 128
 129         spi->mode = SPI_MODE_3;
 130         spi->bits_per_word = 8;
 131         spi_setup(spi);
 132
 133         chip = kzalloc(sizeof *chip, GFP_KERNEL);
 134         if (!chip) {
 135                 dev_err(&spi->dev, "unable to allocate device memory\n");
 136                 return -ENOMEM;
 137         }
 138         dev_set_drvdata(&spi->dev, chip);
 139
 140         res = ds1390_get_reg(&spi->dev, DS1390_REG_SECONDS, &tmp);
 141         if (res != 0) {
 142                 dev_err(&spi->dev, "unable to read device\n");
 143                 kfree(chip);
 144                 return res;
 145         }
 146
 147         chip->rtc = rtc_device_register("ds1390",
 148                                 &spi->dev, &ds1390_rtc_ops, THIS_MODULE);
 149         if (IS_ERR(chip->rtc)) {
 150                 dev_err(&spi->dev, "unable to register device\n");
 151                 res = PTR_ERR(chip->rtc);
 152                 kfree(chip);
 153         }
 154
 155         return res;
 156 }
 157
 158 static int __devexit ds1390_remove(struct spi_device *spi)
 159 {
 160         struct ds1390 *chip = platform_get_drvdata(spi);
 161
 162         rtc_device_unregister(chip->rtc);
 163         kfree(chip);
 164
 165         return 0;
 166 }
 167
 168 static struct spi_driver ds1390_driver = {
 169         .driver = {
 170                 .name   = "rtc-ds1390",
 171                 .owner  = THIS_MODULE,
 172         },
 173         .probe  = ds1390_probe,
 174         .remove = __devexit_p(ds1390_remove),
 175 };
 176
 177 static __init int ds1390_init(void)
 178 {
 179         return spi_register_driver(&ds1390_driver);
 180 }
 181 module_init(ds1390_init);
 182
 183 static __exit void ds1390_exit(void)
 184 {
 185         spi_unregister_driver(&ds1390_driver);
 186 }
 187 module_exit(ds1390_exit);
 188
 189 MODULE_DESCRIPTION("Dallas/Maxim DS1390/93/94 SPI RTC driver");
 190 MODULE_AUTHOR("Mark Jackson <mpfj@mimc.co.uk>");
 191 MODULE_LICENSE("GPL");