1 /* 2 * Driver for ST M41T94 SPI RTC 3 * 4 * Copyright (C) 2008 Kim B. Heino 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 11 #include <linux/module.h> 12 #include <linux/kernel.h> 13 #include <linux/platform_device.h> 14 #include <linux/rtc.h> 15 #include <linux/spi/spi.h> 16 #include <linux/bcd.h> 17 18 #define M41T94_REG_SECONDS 0x01 19 #define M41T94_REG_MINUTES 0x02 20 #define M41T94_REG_HOURS 0x03 21 #define M41T94_REG_WDAY 0x04 22 #define M41T94_REG_DAY 0x05 23 #define M41T94_REG_MONTH 0x06 24 #define M41T94_REG_YEAR 0x07 25 #define M41T94_REG_HT 0x0c 26 27 #define M41T94_BIT_HALT 0x40 28 #define M41T94_BIT_STOP 0x80 29 #define M41T94_BIT_CB 0x40 30 #define M41T94_BIT_CEB 0x80 31 32 static int m41t94_set_time(struct device *dev, struct rtc_time *tm) 33 { 34 struct spi_device *spi = to_spi_device(dev); 35 u8 buf[8]; /* write cmd + 7 registers */ 36 37 dev_dbg(dev, "%s secs=%d, mins=%d, " 38 "hours=%d, mday=%d, mon=%d, year=%d, wday=%d\n", 39 "write", tm->tm_sec, tm->tm_min, 40 tm->tm_hour, tm->tm_mday, 41 tm->tm_mon, tm->tm_year, tm->tm_wday); 42 43 buf[0] = 0x80 | M41T94_REG_SECONDS; /* write time + date */ 44 buf[M41T94_REG_SECONDS] = bin2bcd(tm->tm_sec); 45 buf[M41T94_REG_MINUTES] = bin2bcd(tm->tm_min); 46 buf[M41T94_REG_HOURS] = bin2bcd(tm->tm_hour); 47 buf[M41T94_REG_WDAY] = bin2bcd(tm->tm_wday + 1); 48 buf[M41T94_REG_DAY] = bin2bcd(tm->tm_mday); 49 buf[M41T94_REG_MONTH] = bin2bcd(tm->tm_mon + 1); 50 51 buf[M41T94_REG_HOURS] |= M41T94_BIT_CEB; 52 if (tm->tm_year >= 100) 53 buf[M41T94_REG_HOURS] |= M41T94_BIT_CB; 54 buf[M41T94_REG_YEAR] = bin2bcd(tm->tm_year % 100); 55 56 return spi_write(spi, buf, 8); 57 } 58 59 static int m41t94_read_time(struct device *dev, struct rtc_time *tm) 60 { 61 struct spi_device *spi = to_spi_device(dev); 62 u8 buf[2]; 63 int ret, hour; 64 65 /* clear halt update bit */ 66 ret = spi_w8r8(spi, M41T94_REG_HT); 67 if (ret < 0) 68 return ret; 69 if (ret & M41T94_BIT_HALT) { 70 buf[0] = 0x80 | M41T94_REG_HT; 71 buf[1] = ret & ~M41T94_BIT_HALT; 72 spi_write(spi, buf, 2); 73 } 74 75 /* clear stop bit */ 76 ret = spi_w8r8(spi, M41T94_REG_SECONDS); 77 if (ret < 0) 78 return ret; 79 if (ret & M41T94_BIT_STOP) { 80 buf[0] = 0x80 | M41T94_REG_SECONDS; 81 buf[1] = ret & ~M41T94_BIT_STOP; 82 spi_write(spi, buf, 2); 83 } 84 85 tm->tm_sec = bcd2bin(spi_w8r8(spi, M41T94_REG_SECONDS)); 86 tm->tm_min = bcd2bin(spi_w8r8(spi, M41T94_REG_MINUTES)); 87 hour = spi_w8r8(spi, M41T94_REG_HOURS); 88 tm->tm_hour = bcd2bin(hour & 0x3f); 89 tm->tm_wday = bcd2bin(spi_w8r8(spi, M41T94_REG_WDAY)) - 1; 90 tm->tm_mday = bcd2bin(spi_w8r8(spi, M41T94_REG_DAY)); 91 tm->tm_mon = bcd2bin(spi_w8r8(spi, M41T94_REG_MONTH)) - 1; 92 tm->tm_year = bcd2bin(spi_w8r8(spi, M41T94_REG_YEAR)); 93 if ((hour & M41T94_BIT_CB) || !(hour & M41T94_BIT_CEB)) 94 tm->tm_year += 100; 95 96 dev_dbg(dev, "%s secs=%d, mins=%d, " 97 "hours=%d, mday=%d, mon=%d, year=%d, wday=%d\n", 98 "read", tm->tm_sec, tm->tm_min, 99 tm->tm_hour, tm->tm_mday, 100 tm->tm_mon, tm->tm_year, tm->tm_wday); 101 102 /* initial clock setting can be undefined */ 103 return rtc_valid_tm(tm); 104 } 105 106 static const struct rtc_class_ops m41t94_rtc_ops = { 107 .read_time = m41t94_read_time, 108 .set_time = m41t94_set_time, 109 }; 110 111 static struct spi_driver m41t94_driver; 112 113 static int m41t94_probe(struct spi_device *spi) 114 { 115 struct rtc_device *rtc; 116 int res; 117 118 spi->bits_per_word = 8; 119 spi_setup(spi); 120 121 res = spi_w8r8(spi, M41T94_REG_SECONDS); 122 if (res < 0) { 123 dev_err(&spi->dev, "not found.\n"); 124 return res; 125 } 126 127 rtc = devm_rtc_device_register(&spi->dev, m41t94_driver.driver.name, 128 &m41t94_rtc_ops, THIS_MODULE); 129 if (IS_ERR(rtc)) 130 return PTR_ERR(rtc); 131 132 spi_set_drvdata(spi, rtc); 133 134 return 0; 135 } 136 137 static struct spi_driver m41t94_driver = { 138 .driver = { 139 .name = "rtc-m41t94", 140 .owner = THIS_MODULE, 141 }, 142 .probe = m41t94_probe, 143 }; 144 145 module_spi_driver(m41t94_driver); 146 147 MODULE_AUTHOR("Kim B. Heino <Kim.Heino@bluegiga.com>"); 148 MODULE_DESCRIPTION("Driver for ST M41T94 SPI RTC"); 149 MODULE_LICENSE("GPL"); 150 MODULE_ALIAS("spi:rtc-m41t94"); 151