1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * Driver for ST M41T94 SPI RTC 4 * 5 * Copyright (C) 2008 Kim B. Heino 6 */ 7 8 #include <linux/module.h> 9 #include <linux/kernel.h> 10 #include <linux/platform_device.h> 11 #include <linux/rtc.h> 12 #include <linux/spi/spi.h> 13 #include <linux/bcd.h> 14 15 #define M41T94_REG_SECONDS 0x01 16 #define M41T94_REG_MINUTES 0x02 17 #define M41T94_REG_HOURS 0x03 18 #define M41T94_REG_WDAY 0x04 19 #define M41T94_REG_DAY 0x05 20 #define M41T94_REG_MONTH 0x06 21 #define M41T94_REG_YEAR 0x07 22 #define M41T94_REG_HT 0x0c 23 24 #define M41T94_BIT_HALT 0x40 25 #define M41T94_BIT_STOP 0x80 26 #define M41T94_BIT_CB 0x40 27 #define M41T94_BIT_CEB 0x80 28 29 static int m41t94_set_time(struct device *dev, struct rtc_time *tm) 30 { 31 struct spi_device *spi = to_spi_device(dev); 32 u8 buf[8]; /* write cmd + 7 registers */ 33 34 dev_dbg(dev, "%s secs=%d, mins=%d, " 35 "hours=%d, mday=%d, mon=%d, year=%d, wday=%d\n", 36 "write", tm->tm_sec, tm->tm_min, 37 tm->tm_hour, tm->tm_mday, 38 tm->tm_mon, tm->tm_year, tm->tm_wday); 39 40 buf[0] = 0x80 | M41T94_REG_SECONDS; /* write time + date */ 41 buf[M41T94_REG_SECONDS] = bin2bcd(tm->tm_sec); 42 buf[M41T94_REG_MINUTES] = bin2bcd(tm->tm_min); 43 buf[M41T94_REG_HOURS] = bin2bcd(tm->tm_hour); 44 buf[M41T94_REG_WDAY] = bin2bcd(tm->tm_wday + 1); 45 buf[M41T94_REG_DAY] = bin2bcd(tm->tm_mday); 46 buf[M41T94_REG_MONTH] = bin2bcd(tm->tm_mon + 1); 47 48 buf[M41T94_REG_HOURS] |= M41T94_BIT_CEB; 49 if (tm->tm_year >= 100) 50 buf[M41T94_REG_HOURS] |= M41T94_BIT_CB; 51 buf[M41T94_REG_YEAR] = bin2bcd(tm->tm_year % 100); 52 53 return spi_write(spi, buf, 8); 54 } 55 56 static int m41t94_read_time(struct device *dev, struct rtc_time *tm) 57 { 58 struct spi_device *spi = to_spi_device(dev); 59 u8 buf[2]; 60 int ret, hour; 61 62 /* clear halt update bit */ 63 ret = spi_w8r8(spi, M41T94_REG_HT); 64 if (ret < 0) 65 return ret; 66 if (ret & M41T94_BIT_HALT) { 67 buf[0] = 0x80 | M41T94_REG_HT; 68 buf[1] = ret & ~M41T94_BIT_HALT; 69 spi_write(spi, buf, 2); 70 } 71 72 /* clear stop bit */ 73 ret = spi_w8r8(spi, M41T94_REG_SECONDS); 74 if (ret < 0) 75 return ret; 76 if (ret & M41T94_BIT_STOP) { 77 buf[0] = 0x80 | M41T94_REG_SECONDS; 78 buf[1] = ret & ~M41T94_BIT_STOP; 79 spi_write(spi, buf, 2); 80 } 81 82 tm->tm_sec = bcd2bin(spi_w8r8(spi, M41T94_REG_SECONDS)); 83 tm->tm_min = bcd2bin(spi_w8r8(spi, M41T94_REG_MINUTES)); 84 hour = spi_w8r8(spi, M41T94_REG_HOURS); 85 tm->tm_hour = bcd2bin(hour & 0x3f); 86 tm->tm_wday = bcd2bin(spi_w8r8(spi, M41T94_REG_WDAY)) - 1; 87 tm->tm_mday = bcd2bin(spi_w8r8(spi, M41T94_REG_DAY)); 88 tm->tm_mon = bcd2bin(spi_w8r8(spi, M41T94_REG_MONTH)) - 1; 89 tm->tm_year = bcd2bin(spi_w8r8(spi, M41T94_REG_YEAR)); 90 if ((hour & M41T94_BIT_CB) || !(hour & M41T94_BIT_CEB)) 91 tm->tm_year += 100; 92 93 dev_dbg(dev, "%s secs=%d, mins=%d, " 94 "hours=%d, mday=%d, mon=%d, year=%d, wday=%d\n", 95 "read", tm->tm_sec, tm->tm_min, 96 tm->tm_hour, tm->tm_mday, 97 tm->tm_mon, tm->tm_year, tm->tm_wday); 98 99 return 0; 100 } 101 102 static const struct rtc_class_ops m41t94_rtc_ops = { 103 .read_time = m41t94_read_time, 104 .set_time = m41t94_set_time, 105 }; 106 107 static struct spi_driver m41t94_driver; 108 109 static int m41t94_probe(struct spi_device *spi) 110 { 111 struct rtc_device *rtc; 112 int res; 113 114 spi->bits_per_word = 8; 115 spi_setup(spi); 116 117 res = spi_w8r8(spi, M41T94_REG_SECONDS); 118 if (res < 0) { 119 dev_err(&spi->dev, "not found.\n"); 120 return res; 121 } 122 123 rtc = devm_rtc_device_register(&spi->dev, m41t94_driver.driver.name, 124 &m41t94_rtc_ops, THIS_MODULE); 125 if (IS_ERR(rtc)) 126 return PTR_ERR(rtc); 127 128 spi_set_drvdata(spi, rtc); 129 130 return 0; 131 } 132 133 static struct spi_driver m41t94_driver = { 134 .driver = { 135 .name = "rtc-m41t94", 136 }, 137 .probe = m41t94_probe, 138 }; 139 140 module_spi_driver(m41t94_driver); 141 142 MODULE_AUTHOR("Kim B. Heino <Kim.Heino@bluegiga.com>"); 143 MODULE_DESCRIPTION("Driver for ST M41T94 SPI RTC"); 144 MODULE_LICENSE("GPL"); 145 MODULE_ALIAS("spi:rtc-m41t94"); 146