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 #include <linux/slab.h>
  23 #include <linux/of.h>
  24
  25 #define DS1390_REG_100THS               0x00
  26 #define DS1390_REG_SECONDS              0x01
  27 #define DS1390_REG_MINUTES              0x02
  28 #define DS1390_REG_HOURS                0x03
  29 #define DS1390_REG_DAY                  0x04
  30 #define DS1390_REG_DATE                 0x05
  31 #define DS1390_REG_MONTH_CENT           0x06
  32 #define DS1390_REG_YEAR                 0x07
  33
  34 #define DS1390_REG_ALARM_100THS         0x08
  35 #define DS1390_REG_ALARM_SECONDS        0x09
  36 #define DS1390_REG_ALARM_MINUTES        0x0A
  37 #define DS1390_REG_ALARM_HOURS          0x0B
  38 #define DS1390_REG_ALARM_DAY_DATE       0x0C
  39
  40 #define DS1390_REG_CONTROL              0x0D
  41 #define DS1390_REG_STATUS               0x0E
  42 #define DS1390_REG_TRICKLE              0x0F
  43
  44 #define DS1390_TRICKLE_CHARGER_ENABLE   0xA0
  45 #define DS1390_TRICKLE_CHARGER_250_OHM  0x01
  46 #define DS1390_TRICKLE_CHARGER_2K_OHM   0x02
  47 #define DS1390_TRICKLE_CHARGER_4K_OHM   0x03
  48 #define DS1390_TRICKLE_CHARGER_NO_DIODE 0x04
  49 #define DS1390_TRICKLE_CHARGER_DIODE    0x08
  50
  51 struct ds1390 {
  52         struct rtc_device *rtc;
  53         u8 txrx_buf[9]; /* cmd + 8 registers */
  54 };
  55
  56 static void ds1390_set_reg(struct device *dev, unsigned char address,
  57                            unsigned char data)
  58 {
  59         struct spi_device *spi = to_spi_device(dev);
  60         unsigned char buf[2];
  61
  62         /* MSB must be '1' to write */
  63         buf[0] = address | 0x80;
  64         buf[1] = data;
  65
  66         spi_write(spi, buf, 2);
  67 }
  68
  69 static int ds1390_get_reg(struct device *dev, unsigned char address,
  70                                 unsigned char *data)
  71 {
  72         struct spi_device *spi = to_spi_device(dev);
  73         struct ds1390 *chip = dev_get_drvdata(dev);
  74         int status;
  75
  76         if (!data)
  77                 return -EINVAL;
  78
  79         /* Clear MSB to indicate read */
  80         chip->txrx_buf[0] = address & 0x7f;
  81         /* do the i/o */
  82         status = spi_write_then_read(spi, chip->txrx_buf, 1, chip->txrx_buf, 1);
  83         if (status != 0)
  84                 return status;
  85
  86         *data = chip->txrx_buf[0];
  87
  88         return 0;
  89 }
  90
  91 static void ds1390_trickle_of_init(struct spi_device *spi)
  92 {
  93         u32 ohms = 0;
  94         u8 value;
  95
  96         if (of_property_read_u32(spi->dev.of_node, "trickle-resistor-ohms",
  97                                  &ohms))
  98                 goto out;
  99
 100         /* Enable charger */
 101         value = DS1390_TRICKLE_CHARGER_ENABLE;
 102         if (of_property_read_bool(spi->dev.of_node, "trickle-diode-disable"))
 103                 value |= DS1390_TRICKLE_CHARGER_NO_DIODE;
 104         else
 105                 value |= DS1390_TRICKLE_CHARGER_DIODE;
 106
 107         /* Resistor select */
 108         switch (ohms) {
 109         case 250:
 110                 value |= DS1390_TRICKLE_CHARGER_250_OHM;
 111                 break;
 112         case 2000:
 113                 value |= DS1390_TRICKLE_CHARGER_2K_OHM;
 114                 break;
 115         case 4000:
 116                 value |= DS1390_TRICKLE_CHARGER_4K_OHM;
 117                 break;
 118         default:
 119                 dev_warn(&spi->dev,
 120                          "Unsupported ohm value %02ux in dt\n", ohms);
 121                 return;
 122         }
 123
 124         ds1390_set_reg(&spi->dev, DS1390_REG_TRICKLE, value);
 125
 126 out:
 127         return;
 128 }
 129
 130 static int ds1390_read_time(struct device *dev, struct rtc_time *dt)
 131 {
 132         struct spi_device *spi = to_spi_device(dev);
 133         struct ds1390 *chip = dev_get_drvdata(dev);
 134         int status;
 135
 136         /* build the message */
 137         chip->txrx_buf[0] = DS1390_REG_SECONDS;
 138
 139         /* do the i/o */
 140         status = spi_write_then_read(spi, chip->txrx_buf, 1, chip->txrx_buf, 8);
 141         if (status != 0)
 142                 return status;
 143
 144         /* The chip sends data in this order:
 145          * Seconds, Minutes, Hours, Day, Date, Month / Century, Year */
 146         dt->tm_sec      = bcd2bin(chip->txrx_buf[0]);
 147         dt->tm_min      = bcd2bin(chip->txrx_buf[1]);
 148         dt->tm_hour     = bcd2bin(chip->txrx_buf[2]);
 149         dt->tm_wday     = bcd2bin(chip->txrx_buf[3]);
 150         dt->tm_mday     = bcd2bin(chip->txrx_buf[4]);
 151         /* mask off century bit */
 152         dt->tm_mon      = bcd2bin(chip->txrx_buf[5] & 0x7f) - 1;
 153         /* adjust for century bit */
 154         dt->tm_year = bcd2bin(chip->txrx_buf[6]) + ((chip->txrx_buf[5] & 0x80) ? 100 : 0);
 155
 156         return rtc_valid_tm(dt);
 157 }
 158
 159 static int ds1390_set_time(struct device *dev, struct rtc_time *dt)
 160 {
 161         struct spi_device *spi = to_spi_device(dev);
 162         struct ds1390 *chip = dev_get_drvdata(dev);
 163
 164         /* build the message */
 165         chip->txrx_buf[0] = DS1390_REG_SECONDS | 0x80;
 166         chip->txrx_buf[1] = bin2bcd(dt->tm_sec);
 167         chip->txrx_buf[2] = bin2bcd(dt->tm_min);
 168         chip->txrx_buf[3] = bin2bcd(dt->tm_hour);
 169         chip->txrx_buf[4] = bin2bcd(dt->tm_wday);
 170         chip->txrx_buf[5] = bin2bcd(dt->tm_mday);
 171         chip->txrx_buf[6] = bin2bcd(dt->tm_mon + 1) |
 172                                 ((dt->tm_year > 99) ? 0x80 : 0x00);
 173         chip->txrx_buf[7] = bin2bcd(dt->tm_year % 100);
 174
 175         /* do the i/o */
 176         return spi_write_then_read(spi, chip->txrx_buf, 8, NULL, 0);
 177 }
 178
 179 static const struct rtc_class_ops ds1390_rtc_ops = {
 180         .read_time      = ds1390_read_time,
 181         .set_time       = ds1390_set_time,
 182 };
 183
 184 static int ds1390_probe(struct spi_device *spi)
 185 {
 186         unsigned char tmp;
 187         struct ds1390 *chip;
 188         int res;
 189
 190         spi->mode = SPI_MODE_3;
 191         spi->bits_per_word = 8;
 192         spi_setup(spi);
 193
 194         chip = devm_kzalloc(&spi->dev, sizeof(*chip), GFP_KERNEL);
 195         if (!chip)
 196                 return -ENOMEM;
 197
 198         spi_set_drvdata(spi, chip);
 199
 200         res = ds1390_get_reg(&spi->dev, DS1390_REG_SECONDS, &tmp);
 201         if (res != 0) {
 202                 dev_err(&spi->dev, "unable to read device\n");
 203                 return res;
 204         }
 205
 206         if (spi->dev.of_node)
 207                 ds1390_trickle_of_init(spi);
 208
 209         chip->rtc = devm_rtc_device_register(&spi->dev, "ds1390",
 210                                         &ds1390_rtc_ops, THIS_MODULE);
 211         if (IS_ERR(chip->rtc)) {
 212                 dev_err(&spi->dev, "unable to register device\n");
 213                 res = PTR_ERR(chip->rtc);
 214         }
 215
 216         return res;
 217 }
 218
 219 static struct spi_driver ds1390_driver = {
 220         .driver = {
 221                 .name   = "rtc-ds1390",
 222         },
 223         .probe  = ds1390_probe,
 224 };
 225
 226 module_spi_driver(ds1390_driver);
 227
 228 MODULE_DESCRIPTION("Dallas/Maxim DS1390/93/94 SPI RTC driver");
 229 MODULE_AUTHOR("Mark Jackson <mpfj@mimc.co.uk>");
 230 MODULE_LICENSE("GPL");
 231 MODULE_ALIAS("spi:rtc-ds1390");