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 const struct spi_device_id ds1390_spi_ids[] = { 223 { .name = "ds1390" }, 224 {} 225 }; 226 MODULE_DEVICE_TABLE(spi, ds1390_spi_ids); 227 228 static struct spi_driver ds1390_driver = { 229 .driver = { 230 .name = "rtc-ds1390", 231 .of_match_table = of_match_ptr(ds1390_of_match), 232 }, 233 .probe = ds1390_probe, 234 .id_table = ds1390_spi_ids, 235 }; 236 237 module_spi_driver(ds1390_driver); 238 239 MODULE_DESCRIPTION("Dallas/Maxim DS1390/93/94 SPI RTC driver"); 240 MODULE_AUTHOR("Mark Jackson <mpfj@mimc.co.uk>"); 241 MODULE_LICENSE("GPL"); 242 MODULE_ALIAS("spi:rtc-ds1390"); 243