1 /* drivers/rtc/rtc-max6902.c 2 * 3 * Copyright (C) 2006 8D Technologies inc. 4 * Copyright (C) 2004 Compulab Ltd. 5 * 6 * This program is free software; you can redistribute it and/or modify 7 * it under the terms of the GNU General Public License version 2 as 8 * published by the Free Software Foundation. 9 * 10 * Driver for MAX6902 spi RTC 11 * 12 */ 13 14 #include <linux/module.h> 15 #include <linux/kernel.h> 16 #include <linux/platform_device.h> 17 #include <linux/init.h> 18 #include <linux/rtc.h> 19 #include <linux/spi/spi.h> 20 #include <linux/bcd.h> 21 22 #define MAX6902_REG_SECONDS 0x01 23 #define MAX6902_REG_MINUTES 0x03 24 #define MAX6902_REG_HOURS 0x05 25 #define MAX6902_REG_DATE 0x07 26 #define MAX6902_REG_MONTH 0x09 27 #define MAX6902_REG_DAY 0x0B 28 #define MAX6902_REG_YEAR 0x0D 29 #define MAX6902_REG_CONTROL 0x0F 30 #define MAX6902_REG_CENTURY 0x13 31 32 static int max6902_set_reg(struct device *dev, unsigned char address, 33 unsigned char data) 34 { 35 struct spi_device *spi = to_spi_device(dev); 36 unsigned char buf[2]; 37 38 /* MSB must be '0' to write */ 39 buf[0] = address & 0x7f; 40 buf[1] = data; 41 42 return spi_write_then_read(spi, buf, 2, NULL, 0); 43 } 44 45 static int max6902_get_reg(struct device *dev, unsigned char address, 46 unsigned char *data) 47 { 48 struct spi_device *spi = to_spi_device(dev); 49 50 /* Set MSB to indicate read */ 51 *data = address | 0x80; 52 53 return spi_write_then_read(spi, data, 1, data, 1); 54 } 55 56 static int max6902_read_time(struct device *dev, struct rtc_time *dt) 57 { 58 int err, century; 59 struct spi_device *spi = to_spi_device(dev); 60 unsigned char buf[8]; 61 62 buf[0] = 0xbf; /* Burst read */ 63 64 err = spi_write_then_read(spi, buf, 1, buf, 8); 65 if (err != 0) 66 return err; 67 68 /* The chip sends data in this order: 69 * Seconds, Minutes, Hours, Date, Month, Day, Year */ 70 dt->tm_sec = bcd2bin(buf[0]); 71 dt->tm_min = bcd2bin(buf[1]); 72 dt->tm_hour = bcd2bin(buf[2]); 73 dt->tm_mday = bcd2bin(buf[3]); 74 dt->tm_mon = bcd2bin(buf[4]) - 1; 75 dt->tm_wday = bcd2bin(buf[5]); 76 dt->tm_year = bcd2bin(buf[6]); 77 78 /* Read century */ 79 err = max6902_get_reg(dev, MAX6902_REG_CENTURY, &buf[0]); 80 if (err != 0) 81 return err; 82 83 century = bcd2bin(buf[0]) * 100; 84 85 dt->tm_year += century; 86 dt->tm_year -= 1900; 87 88 return rtc_valid_tm(dt); 89 } 90 91 static int max6902_set_time(struct device *dev, struct rtc_time *dt) 92 { 93 dt->tm_year = dt->tm_year + 1900; 94 95 /* Remove write protection */ 96 max6902_set_reg(dev, MAX6902_REG_CONTROL, 0); 97 98 max6902_set_reg(dev, MAX6902_REG_SECONDS, bin2bcd(dt->tm_sec)); 99 max6902_set_reg(dev, MAX6902_REG_MINUTES, bin2bcd(dt->tm_min)); 100 max6902_set_reg(dev, MAX6902_REG_HOURS, bin2bcd(dt->tm_hour)); 101 102 max6902_set_reg(dev, MAX6902_REG_DATE, bin2bcd(dt->tm_mday)); 103 max6902_set_reg(dev, MAX6902_REG_MONTH, bin2bcd(dt->tm_mon + 1)); 104 max6902_set_reg(dev, MAX6902_REG_DAY, bin2bcd(dt->tm_wday)); 105 max6902_set_reg(dev, MAX6902_REG_YEAR, bin2bcd(dt->tm_year % 100)); 106 max6902_set_reg(dev, MAX6902_REG_CENTURY, bin2bcd(dt->tm_year / 100)); 107 108 /* Compulab used a delay here. However, the datasheet 109 * does not mention a delay being required anywhere... */ 110 /* delay(2000); */ 111 112 /* Write protect */ 113 max6902_set_reg(dev, MAX6902_REG_CONTROL, 0x80); 114 115 return 0; 116 } 117 118 static const struct rtc_class_ops max6902_rtc_ops = { 119 .read_time = max6902_read_time, 120 .set_time = max6902_set_time, 121 }; 122 123 static int max6902_probe(struct spi_device *spi) 124 { 125 struct rtc_device *rtc; 126 unsigned char tmp; 127 int res; 128 129 spi->mode = SPI_MODE_3; 130 spi->bits_per_word = 8; 131 spi_setup(spi); 132 133 res = max6902_get_reg(&spi->dev, MAX6902_REG_SECONDS, &tmp); 134 if (res != 0) 135 return res; 136 137 rtc = devm_rtc_device_register(&spi->dev, "max6902", 138 &max6902_rtc_ops, THIS_MODULE); 139 if (IS_ERR(rtc)) 140 return PTR_ERR(rtc); 141 142 spi_set_drvdata(spi, rtc); 143 return 0; 144 } 145 146 static struct spi_driver max6902_driver = { 147 .driver = { 148 .name = "rtc-max6902", 149 }, 150 .probe = max6902_probe, 151 }; 152 153 module_spi_driver(max6902_driver); 154 155 MODULE_DESCRIPTION("max6902 spi RTC driver"); 156 MODULE_AUTHOR("Raphael Assenat"); 157 MODULE_LICENSE("GPL"); 158 MODULE_ALIAS("spi:rtc-max6902"); 159