1 // SPDX-License-Identifier: GPL-2.0-only 2 /* drivers/rtc/rtc-max6902.c 3 * 4 * Copyright (C) 2006 8D Technologies inc. 5 * Copyright (C) 2004 Compulab Ltd. 6 * 7 * Driver for MAX6902 spi RTC 8 */ 9 10 #include <linux/module.h> 11 #include <linux/kernel.h> 12 #include <linux/platform_device.h> 13 #include <linux/init.h> 14 #include <linux/rtc.h> 15 #include <linux/spi/spi.h> 16 #include <linux/bcd.h> 17 18 #define MAX6902_REG_SECONDS 0x01 19 #define MAX6902_REG_MINUTES 0x03 20 #define MAX6902_REG_HOURS 0x05 21 #define MAX6902_REG_DATE 0x07 22 #define MAX6902_REG_MONTH 0x09 23 #define MAX6902_REG_DAY 0x0B 24 #define MAX6902_REG_YEAR 0x0D 25 #define MAX6902_REG_CONTROL 0x0F 26 #define MAX6902_REG_CENTURY 0x13 27 28 static int max6902_set_reg(struct device *dev, unsigned char address, 29 unsigned char data) 30 { 31 struct spi_device *spi = to_spi_device(dev); 32 unsigned char buf[2]; 33 34 /* MSB must be '0' to write */ 35 buf[0] = address & 0x7f; 36 buf[1] = data; 37 38 return spi_write_then_read(spi, buf, 2, NULL, 0); 39 } 40 41 static int max6902_get_reg(struct device *dev, unsigned char address, 42 unsigned char *data) 43 { 44 struct spi_device *spi = to_spi_device(dev); 45 46 /* Set MSB to indicate read */ 47 *data = address | 0x80; 48 49 return spi_write_then_read(spi, data, 1, data, 1); 50 } 51 52 static int max6902_read_time(struct device *dev, struct rtc_time *dt) 53 { 54 int err, century; 55 struct spi_device *spi = to_spi_device(dev); 56 unsigned char buf[8]; 57 58 buf[0] = 0xbf; /* Burst read */ 59 60 err = spi_write_then_read(spi, buf, 1, buf, 8); 61 if (err != 0) 62 return err; 63 64 /* The chip sends data in this order: 65 * Seconds, Minutes, Hours, Date, Month, Day, Year */ 66 dt->tm_sec = bcd2bin(buf[0]); 67 dt->tm_min = bcd2bin(buf[1]); 68 dt->tm_hour = bcd2bin(buf[2]); 69 dt->tm_mday = bcd2bin(buf[3]); 70 dt->tm_mon = bcd2bin(buf[4]) - 1; 71 dt->tm_wday = bcd2bin(buf[5]); 72 dt->tm_year = bcd2bin(buf[6]); 73 74 /* Read century */ 75 err = max6902_get_reg(dev, MAX6902_REG_CENTURY, &buf[0]); 76 if (err != 0) 77 return err; 78 79 century = bcd2bin(buf[0]) * 100; 80 81 dt->tm_year += century; 82 dt->tm_year -= 1900; 83 84 return 0; 85 } 86 87 static int max6902_set_time(struct device *dev, struct rtc_time *dt) 88 { 89 dt->tm_year = dt->tm_year + 1900; 90 91 /* Remove write protection */ 92 max6902_set_reg(dev, MAX6902_REG_CONTROL, 0); 93 94 max6902_set_reg(dev, MAX6902_REG_SECONDS, bin2bcd(dt->tm_sec)); 95 max6902_set_reg(dev, MAX6902_REG_MINUTES, bin2bcd(dt->tm_min)); 96 max6902_set_reg(dev, MAX6902_REG_HOURS, bin2bcd(dt->tm_hour)); 97 98 max6902_set_reg(dev, MAX6902_REG_DATE, bin2bcd(dt->tm_mday)); 99 max6902_set_reg(dev, MAX6902_REG_MONTH, bin2bcd(dt->tm_mon + 1)); 100 max6902_set_reg(dev, MAX6902_REG_DAY, bin2bcd(dt->tm_wday)); 101 max6902_set_reg(dev, MAX6902_REG_YEAR, bin2bcd(dt->tm_year % 100)); 102 max6902_set_reg(dev, MAX6902_REG_CENTURY, bin2bcd(dt->tm_year / 100)); 103 104 /* Compulab used a delay here. However, the datasheet 105 * does not mention a delay being required anywhere... */ 106 /* delay(2000); */ 107 108 /* Write protect */ 109 max6902_set_reg(dev, MAX6902_REG_CONTROL, 0x80); 110 111 return 0; 112 } 113 114 static const struct rtc_class_ops max6902_rtc_ops = { 115 .read_time = max6902_read_time, 116 .set_time = max6902_set_time, 117 }; 118 119 static int max6902_probe(struct spi_device *spi) 120 { 121 struct rtc_device *rtc; 122 unsigned char tmp; 123 int res; 124 125 spi->mode = SPI_MODE_3; 126 spi->bits_per_word = 8; 127 spi_setup(spi); 128 129 res = max6902_get_reg(&spi->dev, MAX6902_REG_SECONDS, &tmp); 130 if (res != 0) 131 return res; 132 133 rtc = devm_rtc_device_register(&spi->dev, "max6902", 134 &max6902_rtc_ops, THIS_MODULE); 135 if (IS_ERR(rtc)) 136 return PTR_ERR(rtc); 137 138 spi_set_drvdata(spi, rtc); 139 return 0; 140 } 141 142 static struct spi_driver max6902_driver = { 143 .driver = { 144 .name = "rtc-max6902", 145 }, 146 .probe = max6902_probe, 147 }; 148 149 module_spi_driver(max6902_driver); 150 151 MODULE_DESCRIPTION("max6902 spi RTC driver"); 152 MODULE_AUTHOR("Raphael Assenat"); 153 MODULE_LICENSE("GPL"); 154 MODULE_ALIAS("spi:rtc-max6902"); 155