drivers/rtc/rtc-ds1390.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * rtc-ds1390.c -- driver for the Dallas/Maxim DS1390/93/94 SPI RTC
   4  *
   5  * Copyright (C) 2008 Mercury IMC Ltd
   6  * Written by Mark Jackson <mpfj@mimc.co.uk>
   7  *
   8  * NOTE: Currently this driver only supports the bare minimum for read
   9  * and write the RTC. The extra features provided by the chip family
  10  * (alarms, trickle charger, different control registers) are unavailable.
  11  */
  12
  13 #include <linux/init.h>
  14 #include <linux/module.h>
  15 #include <linux/platform_device.h>
  16 #include <linux/rtc.h>
  17 #include <linux/spi/spi.h>
  18 #include <linux/bcd.h>
  19 #include <linux/slab.h>
  20 #include <linux/of.h>
  21
  22 #define DS1390_REG_100THS               0x00
  23 #define DS1390_REG_SECONDS              0x01
  24 #define DS1390_REG_MINUTES              0x02
  25 #define DS1390_REG_HOURS                0x03
  26 #define DS1390_REG_DAY                  0x04
  27 #define DS1390_REG_DATE                 0x05
  28 #define DS1390_REG_MONTH_CENT           0x06
  29 #define DS1390_REG_YEAR                 0x07
  30
  31 #define DS1390_REG_ALARM_100THS         0x08
  32 #define DS1390_REG_ALARM_SECONDS        0x09
  33 #define DS1390_REG_ALARM_MINUTES        0x0A
  34 #define DS1390_REG_ALARM_HOURS          0x0B
  35 #define DS1390_REG_ALARM_DAY_DATE       0x0C
  36
  37 #define DS1390_REG_CONTROL              0x0D
  38 #define DS1390_REG_STATUS               0x0E
  39 #define DS1390_REG_TRICKLE              0x0F
  40
  41 #define DS1390_TRICKLE_CHARGER_ENABLE   0xA0
  42 #define DS1390_TRICKLE_CHARGER_250_OHM  0x01
  43 #define DS1390_TRICKLE_CHARGER_2K_OHM   0x02
  44 #define DS1390_TRICKLE_CHARGER_4K_OHM   0x03
  45 #define DS1390_TRICKLE_CHARGER_NO_DIODE 0x04
  46 #define DS1390_TRICKLE_CHARGER_DIODE    0x08
  47
  48 struct ds1390 {
  49         struct rtc_device *rtc;
  50         u8 txrx_buf[9]; /* cmd + 8 registers */
  51 };
  52
  53 static void ds1390_set_reg(struct device *dev, unsigned char address,
  54                            unsigned char data)
  55 {
  56         struct spi_device *spi = to_spi_device(dev);
  57         unsigned char buf[2];
  58
  59         /* MSB must be '1' to write */
  60         buf[0] = address | 0x80;
  61         buf[1] = data;
  62
  63         spi_write(spi, buf, 2);
  64 }
  65
  66 static int ds1390_get_reg(struct device *dev, unsigned char address,
  67                                 unsigned char *data)
  68 {
  69         struct spi_device *spi = to_spi_device(dev);
  70         struct ds1390 *chip = dev_get_drvdata(dev);
  71         int status;
  72
  73         if (!data)
  74                 return -EINVAL;
  75
  76         /* Clear MSB to indicate read */
  77         chip->txrx_buf[0] = address & 0x7f;
  78         /* do the i/o */
  79         status = spi_write_then_read(spi, chip->txrx_buf, 1, chip->txrx_buf, 1);
  80         if (status != 0)
  81                 return status;
  82
  83         *data = chip->txrx_buf[0];
  84
  85         return 0;
  86 }
  87
  88 static void ds1390_trickle_of_init(struct spi_device *spi)
  89 {
  90         u32 ohms = 0;
  91         u8 value;
  92
  93         if (of_property_read_u32(spi->dev.of_node, "trickle-resistor-ohms",
  94                                  &ohms))
  95                 goto out;
  96
  97         /* Enable charger */
  98         value = DS1390_TRICKLE_CHARGER_ENABLE;
  99         if (of_property_read_bool(spi->dev.of_node, "trickle-diode-disable"))
 100                 value |= DS1390_TRICKLE_CHARGER_NO_DIODE;
 101         else
 102                 value |= DS1390_TRICKLE_CHARGER_DIODE;
 103
 104         /* Resistor select */
 105         switch (ohms) {
 106         case 250:
 107                 value |= DS1390_TRICKLE_CHARGER_250_OHM;
 108                 break;
 109         case 2000:
 110                 value |= DS1390_TRICKLE_CHARGER_2K_OHM;
 111                 break;
 112         case 4000:
 113                 value |= DS1390_TRICKLE_CHARGER_4K_OHM;
 114                 break;
 115         default:
 116                 dev_warn(&spi->dev,
 117                          "Unsupported ohm value %02ux in dt\n", ohms);
 118                 return;
 119         }
 120
 121         ds1390_set_reg(&spi->dev, DS1390_REG_TRICKLE, value);
 122
 123 out:
 124         return;
 125 }
 126
 127 static int ds1390_read_time(struct device *dev, struct rtc_time *dt)
 128 {
 129         struct spi_device *spi = to_spi_device(dev);
 130         struct ds1390 *chip = dev_get_drvdata(dev);
 131         int status;
 132
 133         /* build the message */
 134         chip->txrx_buf[0] = DS1390_REG_SECONDS;
 135
 136         /* do the i/o */
 137         status = spi_write_then_read(spi, chip->txrx_buf, 1, chip->txrx_buf, 8);
 138         if (status != 0)
 139                 return status;
 140
 141         /* The chip sends data in this order:
 142          * Seconds, Minutes, Hours, Day, Date, Month / Century, Year */
 143         dt->tm_sec      = bcd2bin(chip->txrx_buf[0]);
 144         dt->tm_min      = bcd2bin(chip->txrx_buf[1]);
 145         dt->tm_hour     = bcd2bin(chip->txrx_buf[2]);
 146         dt->tm_wday     = bcd2bin(chip->txrx_buf[3]);
 147         dt->tm_mday     = bcd2bin(chip->txrx_buf[4]);
 148         /* mask off century bit */
 149         dt->tm_mon      = bcd2bin(chip->txrx_buf[5] & 0x7f) - 1;
 150         /* adjust for century bit */
 151         dt->tm_year = bcd2bin(chip->txrx_buf[6]) + ((chip->txrx_buf[5] & 0x80) ? 100 : 0);
 152
 153         return 0;
 154 }
 155
 156 static int ds1390_set_time(struct device *dev, struct rtc_time *dt)
 157 {
 158         struct spi_device *spi = to_spi_device(dev);
 159         struct ds1390 *chip = dev_get_drvdata(dev);
 160
 161         /* build the message */
 162         chip->txrx_buf[0] = DS1390_REG_SECONDS | 0x80;
 163         chip->txrx_buf[1] = bin2bcd(dt->tm_sec);
 164         chip->txrx_buf[2] = bin2bcd(dt->tm_min);
 165         chip->txrx_buf[3] = bin2bcd(dt->tm_hour);
 166         chip->txrx_buf[4] = bin2bcd(dt->tm_wday);
 167         chip->txrx_buf[5] = bin2bcd(dt->tm_mday);
 168         chip->txrx_buf[6] = bin2bcd(dt->tm_mon + 1) |
 169                                 ((dt->tm_year > 99) ? 0x80 : 0x00);
 170         chip->txrx_buf[7] = bin2bcd(dt->tm_year % 100);
 171
 172         /* do the i/o */
 173         return spi_write_then_read(spi, chip->txrx_buf, 8, NULL, 0);
 174 }
 175
 176 static const struct rtc_class_ops ds1390_rtc_ops = {
 177         .read_time      = ds1390_read_time,
 178         .set_time       = ds1390_set_time,
 179 };
 180
 181 static int ds1390_probe(struct spi_device *spi)
 182 {
 183         unsigned char tmp;
 184         struct ds1390 *chip;
 185         int res;
 186
 187         spi->mode = SPI_MODE_3;
 188         spi->bits_per_word = 8;
 189         spi_setup(spi);
 190
 191         chip = devm_kzalloc(&spi->dev, sizeof(*chip), GFP_KERNEL);
 192         if (!chip)
 193                 return -ENOMEM;
 194
 195         spi_set_drvdata(spi, chip);
 196
 197         res = ds1390_get_reg(&spi->dev, DS1390_REG_SECONDS, &tmp);
 198         if (res != 0) {
 199                 dev_err(&spi->dev, "unable to read device\n");
 200                 return res;
 201         }
 202
 203         if (spi->dev.of_node)
 204                 ds1390_trickle_of_init(spi);
 205
 206         chip->rtc = devm_rtc_device_register(&spi->dev, "ds1390",
 207                                         &ds1390_rtc_ops, THIS_MODULE);
 208         if (IS_ERR(chip->rtc)) {
 209                 dev_err(&spi->dev, "unable to register device\n");
 210                 res = PTR_ERR(chip->rtc);
 211         }
 212
 213         return res;
 214 }
 215
 216 static const struct of_device_id ds1390_of_match[] = {
 217         { .compatible = "dallas,ds1390" },
 218         {}
 219 };
 220 MODULE_DEVICE_TABLE(of, ds1390_of_match);
 221
 222 static struct spi_driver ds1390_driver = {
 223         .driver = {
 224                 .name   = "rtc-ds1390",
 225                 .of_match_table = of_match_ptr(ds1390_of_match),
 226         },
 227         .probe  = ds1390_probe,
 228 };
 229
 230 module_spi_driver(ds1390_driver);
 231
 232 MODULE_DESCRIPTION("Dallas/Maxim DS1390/93/94 SPI RTC driver");
 233 MODULE_AUTHOR("Mark Jackson <mpfj@mimc.co.uk>");
 234 MODULE_LICENSE("GPL");
 235 MODULE_ALIAS("spi:rtc-ds1390");