drivers/rtc/rtc-ds1390.c

0001 // SPDX-License-Identifier: GPL-2.0-only
0002 /*
0003  * rtc-ds1390.c -- driver for the Dallas/Maxim DS1390/93/94 SPI RTC
0004  *
0005  * Copyright (C) 2008 Mercury IMC Ltd
0006  * Written by Mark Jackson <mpfj@mimc.co.uk>
0007  *
0008  * NOTE: Currently this driver only supports the bare minimum for read
0009  * and write the RTC. The extra features provided by the chip family
0010  * (alarms, trickle charger, different control registers) are unavailable.
0011  */
0012
0013 #include <linux/init.h>
0014 #include <linux/module.h>
0015 #include <linux/platform_device.h>
0016 #include <linux/rtc.h>
0017 #include <linux/spi/spi.h>
0018 #include <linux/bcd.h>
0019 #include <linux/slab.h>
0020 #include <linux/of.h>
0021
0022 #define DS1390_REG_100THS       0x00
0023 #define DS1390_REG_SECONDS      0x01
0024 #define DS1390_REG_MINUTES      0x02
0025 #define DS1390_REG_HOURS        0x03
0026 #define DS1390_REG_DAY          0x04
0027 #define DS1390_REG_DATE         0x05
0028 #define DS1390_REG_MONTH_CENT       0x06
0029 #define DS1390_REG_YEAR         0x07
0030
0031 #define DS1390_REG_ALARM_100THS     0x08
0032 #define DS1390_REG_ALARM_SECONDS    0x09
0033 #define DS1390_REG_ALARM_MINUTES    0x0A
0034 #define DS1390_REG_ALARM_HOURS      0x0B
0035 #define DS1390_REG_ALARM_DAY_DATE   0x0C
0036
0037 #define DS1390_REG_CONTROL      0x0D
0038 #define DS1390_REG_STATUS       0x0E
0039 #define DS1390_REG_TRICKLE      0x0F
0040
0041 #define DS1390_TRICKLE_CHARGER_ENABLE   0xA0
0042 #define DS1390_TRICKLE_CHARGER_250_OHM  0x01
0043 #define DS1390_TRICKLE_CHARGER_2K_OHM   0x02
0044 #define DS1390_TRICKLE_CHARGER_4K_OHM   0x03
0045 #define DS1390_TRICKLE_CHARGER_NO_DIODE 0x04
0046 #define DS1390_TRICKLE_CHARGER_DIODE    0x08
0047
0048 struct ds1390 {
0049     struct rtc_device *rtc;
0050     u8 txrx_buf[9]; /* cmd + 8 registers */
0051 };
0052
0053 static void ds1390_set_reg(struct device *dev, unsigned char address,
0054                unsigned char data)
0055 {
0056     struct spi_device *spi = to_spi_device(dev);
0057     unsigned char buf[2];
0058
0059     /* MSB must be '1' to write */
0060     buf[0] = address | 0x80;
0061     buf[1] = data;
0062
0063     spi_write(spi, buf, 2);
0064 }
0065
0066 static int ds1390_get_reg(struct device *dev, unsigned char address,
0067                 unsigned char *data)
0068 {
0069     struct spi_device *spi = to_spi_device(dev);
0070     struct ds1390 *chip = dev_get_drvdata(dev);
0071     int status;
0072
0073     if (!data)
0074         return -EINVAL;
0075
0076     /* Clear MSB to indicate read */
0077     chip->txrx_buf[0] = address & 0x7f;
0078     /* do the i/o */
0079     status = spi_write_then_read(spi, chip->txrx_buf, 1, chip->txrx_buf, 1);
0080     if (status != 0)
0081         return status;
0082
0083     *data = chip->txrx_buf[0];
0084
0085     return 0;
0086 }
0087
0088 static void ds1390_trickle_of_init(struct spi_device *spi)
0089 {
0090     u32 ohms = 0;
0091     u8 value;
0092
0093     if (of_property_read_u32(spi->dev.of_node, "trickle-resistor-ohms",
0094                  &ohms))
0095         goto out;
0096
0097     /* Enable charger */
0098     value = DS1390_TRICKLE_CHARGER_ENABLE;
0099     if (of_property_read_bool(spi->dev.of_node, "trickle-diode-disable"))
0100         value |= DS1390_TRICKLE_CHARGER_NO_DIODE;
0101     else
0102         value |= DS1390_TRICKLE_CHARGER_DIODE;
0103
0104     /* Resistor select */
0105     switch (ohms) {
0106     case 250:
0107         value |= DS1390_TRICKLE_CHARGER_250_OHM;
0108         break;
0109     case 2000:
0110         value |= DS1390_TRICKLE_CHARGER_2K_OHM;
0111         break;
0112     case 4000:
0113         value |= DS1390_TRICKLE_CHARGER_4K_OHM;
0114         break;
0115     default:
0116         dev_warn(&spi->dev,
0117              "Unsupported ohm value %02ux in dt\n", ohms);
0118         return;
0119     }
0120
0121     ds1390_set_reg(&spi->dev, DS1390_REG_TRICKLE, value);
0122
0123 out:
0124     return;
0125 }
0126
0127 static int ds1390_read_time(struct device *dev, struct rtc_time *dt)
0128 {
0129     struct spi_device *spi = to_spi_device(dev);
0130     struct ds1390 *chip = dev_get_drvdata(dev);
0131     int status;
0132
0133     /* build the message */
0134     chip->txrx_buf[0] = DS1390_REG_SECONDS;
0135
0136     /* do the i/o */
0137     status = spi_write_then_read(spi, chip->txrx_buf, 1, chip->txrx_buf, 8);
0138     if (status != 0)
0139         return status;
0140
0141     /* The chip sends data in this order:
0142      * Seconds, Minutes, Hours, Day, Date, Month / Century, Year */
0143     dt->tm_sec  = bcd2bin(chip->txrx_buf[0]);
0144     dt->tm_min  = bcd2bin(chip->txrx_buf[1]);
0145     dt->tm_hour = bcd2bin(chip->txrx_buf[2]);
0146     dt->tm_wday = bcd2bin(chip->txrx_buf[3]);
0147     dt->tm_mday = bcd2bin(chip->txrx_buf[4]);
0148     /* mask off century bit */
0149     dt->tm_mon  = bcd2bin(chip->txrx_buf[5] & 0x7f) - 1;
0150     /* adjust for century bit */
0151     dt->tm_year = bcd2bin(chip->txrx_buf[6]) + ((chip->txrx_buf[5] & 0x80) ? 100 : 0);
0152
0153     return 0;
0154 }
0155
0156 static int ds1390_set_time(struct device *dev, struct rtc_time *dt)
0157 {
0158     struct spi_device *spi = to_spi_device(dev);
0159     struct ds1390 *chip = dev_get_drvdata(dev);
0160
0161     /* build the message */
0162     chip->txrx_buf[0] = DS1390_REG_SECONDS | 0x80;
0163     chip->txrx_buf[1] = bin2bcd(dt->tm_sec);
0164     chip->txrx_buf[2] = bin2bcd(dt->tm_min);
0165     chip->txrx_buf[3] = bin2bcd(dt->tm_hour);
0166     chip->txrx_buf[4] = bin2bcd(dt->tm_wday);
0167     chip->txrx_buf[5] = bin2bcd(dt->tm_mday);
0168     chip->txrx_buf[6] = bin2bcd(dt->tm_mon + 1) |
0169                 ((dt->tm_year > 99) ? 0x80 : 0x00);
0170     chip->txrx_buf[7] = bin2bcd(dt->tm_year % 100);
0171
0172     /* do the i/o */
0173     return spi_write_then_read(spi, chip->txrx_buf, 8, NULL, 0);
0174 }
0175
0176 static const struct rtc_class_ops ds1390_rtc_ops = {
0177     .read_time  = ds1390_read_time,
0178     .set_time   = ds1390_set_time,
0179 };
0180
0181 static int ds1390_probe(struct spi_device *spi)
0182 {
0183     unsigned char tmp;
0184     struct ds1390 *chip;
0185     int res;
0186
0187     spi->mode = SPI_MODE_3;
0188     spi->bits_per_word = 8;
0189     spi_setup(spi);
0190
0191     chip = devm_kzalloc(&spi->dev, sizeof(*chip), GFP_KERNEL);
0192     if (!chip)
0193         return -ENOMEM;
0194
0195     spi_set_drvdata(spi, chip);
0196
0197     res = ds1390_get_reg(&spi->dev, DS1390_REG_SECONDS, &tmp);
0198     if (res != 0) {
0199         dev_err(&spi->dev, "unable to read device\n");
0200         return res;
0201     }
0202
0203     if (spi->dev.of_node)
0204         ds1390_trickle_of_init(spi);
0205
0206     chip->rtc = devm_rtc_device_register(&spi->dev, "ds1390",
0207                     &ds1390_rtc_ops, THIS_MODULE);
0208     if (IS_ERR(chip->rtc)) {
0209         dev_err(&spi->dev, "unable to register device\n");
0210         res = PTR_ERR(chip->rtc);
0211     }
0212
0213     return res;
0214 }
0215
0216 static const struct of_device_id ds1390_of_match[] = {
0217     { .compatible = "dallas,ds1390" },
0218     {}
0219 };
0220 MODULE_DEVICE_TABLE(of, ds1390_of_match);
0221
0222 static const struct spi_device_id ds1390_spi_ids[] = {
0223     { .name = "ds1390" },
0224     {}
0225 };
0226 MODULE_DEVICE_TABLE(spi, ds1390_spi_ids);
0227
0228 static struct spi_driver ds1390_driver = {
0229     .driver = {
0230         .name   = "rtc-ds1390",
0231         .of_match_table = of_match_ptr(ds1390_of_match),
0232     },
0233     .probe  = ds1390_probe,
0234     .id_table = ds1390_spi_ids,
0235 };
0236
0237 module_spi_driver(ds1390_driver);
0238
0239 MODULE_DESCRIPTION("Dallas/Maxim DS1390/93/94 SPI RTC driver");
0240 MODULE_AUTHOR("Mark Jackson <mpfj@mimc.co.uk>");
0241 MODULE_LICENSE("GPL");
0242 MODULE_ALIAS("spi:rtc-ds1390");