1 /* 2 * 3 * Driver for ST M41T93 SPI RTC 4 * 5 * (c) 2010 Nikolaus Voss, Weinmann Medical GmbH 6 * 7 * This program is free software; you can redistribute it and/or modify 8 * it under the terms of the GNU General Public License version 2 as 9 * published by the Free Software Foundation. 10 */ 11 12 #include <linux/bcd.h> 13 #include <linux/kernel.h> 14 #include <linux/module.h> 15 #include <linux/platform_device.h> 16 #include <linux/rtc.h> 17 #include <linux/spi/spi.h> 18 19 #define M41T93_REG_SSEC 0 20 #define M41T93_REG_ST_SEC 1 21 #define M41T93_REG_MIN 2 22 #define M41T93_REG_CENT_HOUR 3 23 #define M41T93_REG_WDAY 4 24 #define M41T93_REG_DAY 5 25 #define M41T93_REG_MON 6 26 #define M41T93_REG_YEAR 7 27 28 29 #define M41T93_REG_ALM_HOUR_HT 0xc 30 #define M41T93_REG_FLAGS 0xf 31 32 #define M41T93_FLAG_ST (1 << 7) 33 #define M41T93_FLAG_OF (1 << 2) 34 #define M41T93_FLAG_BL (1 << 4) 35 #define M41T93_FLAG_HT (1 << 6) 36 37 static inline int m41t93_set_reg(struct spi_device *spi, u8 addr, u8 data) 38 { 39 u8 buf[2]; 40 41 /* MSB must be '1' to write */ 42 buf[0] = addr | 0x80; 43 buf[1] = data; 44 45 return spi_write(spi, buf, sizeof(buf)); 46 } 47 48 static int m41t93_set_time(struct device *dev, struct rtc_time *tm) 49 { 50 struct spi_device *spi = to_spi_device(dev); 51 u8 buf[9] = {0x80}; /* write cmd + 8 data bytes */ 52 u8 * const data = &buf[1]; /* ptr to first data byte */ 53 54 dev_dbg(dev, "%s secs=%d, mins=%d, " 55 "hours=%d, mday=%d, mon=%d, year=%d, wday=%d\n", 56 "write", tm->tm_sec, tm->tm_min, 57 tm->tm_hour, tm->tm_mday, 58 tm->tm_mon, tm->tm_year, tm->tm_wday); 59 60 if (tm->tm_year < 100) { 61 dev_warn(&spi->dev, "unsupported date (before 2000-01-01).\n"); 62 return -EINVAL; 63 } 64 65 data[M41T93_REG_SSEC] = 0; 66 data[M41T93_REG_ST_SEC] = bin2bcd(tm->tm_sec); 67 data[M41T93_REG_MIN] = bin2bcd(tm->tm_min); 68 data[M41T93_REG_CENT_HOUR] = bin2bcd(tm->tm_hour) | 69 ((tm->tm_year/100-1) << 6); 70 data[M41T93_REG_DAY] = bin2bcd(tm->tm_mday); 71 data[M41T93_REG_WDAY] = bin2bcd(tm->tm_wday + 1); 72 data[M41T93_REG_MON] = bin2bcd(tm->tm_mon + 1); 73 data[M41T93_REG_YEAR] = bin2bcd(tm->tm_year % 100); 74 75 return spi_write(spi, buf, sizeof(buf)); 76 } 77 78 79 static int m41t93_get_time(struct device *dev, struct rtc_time *tm) 80 { 81 struct spi_device *spi = to_spi_device(dev); 82 const u8 start_addr = 0; 83 u8 buf[8]; 84 int century_after_1900; 85 int tmp; 86 int ret = 0; 87 88 /* Check status of clock. Two states must be considered: 89 1. halt bit (HT) is set: the clock is running but update of readout 90 registers has been disabled due to power failure. This is normal 91 case after poweron. Time is valid after resetting HT bit. 92 2. oscillator fail bit (OF) is set. Oscillator has be stopped and 93 time is invalid: 94 a) OF can be immeditely reset. 95 b) OF cannot be immediately reset: oscillator has to be restarted. 96 */ 97 tmp = spi_w8r8(spi, M41T93_REG_ALM_HOUR_HT); 98 if (tmp < 0) 99 return tmp; 100 101 if (tmp & M41T93_FLAG_HT) { 102 dev_dbg(&spi->dev, "HT bit is set, reenable clock update.\n"); 103 m41t93_set_reg(spi, M41T93_REG_ALM_HOUR_HT, 104 tmp & ~M41T93_FLAG_HT); 105 } 106 107 tmp = spi_w8r8(spi, M41T93_REG_FLAGS); 108 if (tmp < 0) 109 return tmp; 110 111 if (tmp & M41T93_FLAG_OF) { 112 ret = -EINVAL; 113 dev_warn(&spi->dev, "OF bit is set, resetting.\n"); 114 m41t93_set_reg(spi, M41T93_REG_FLAGS, tmp & ~M41T93_FLAG_OF); 115 116 tmp = spi_w8r8(spi, M41T93_REG_FLAGS); 117 if (tmp < 0) 118 return tmp; 119 else if (tmp & M41T93_FLAG_OF) { 120 u8 reset_osc = buf[M41T93_REG_ST_SEC] | M41T93_FLAG_ST; 121 122 dev_warn(&spi->dev, 123 "OF bit is still set, kickstarting clock.\n"); 124 m41t93_set_reg(spi, M41T93_REG_ST_SEC, reset_osc); 125 reset_osc &= ~M41T93_FLAG_ST; 126 m41t93_set_reg(spi, M41T93_REG_ST_SEC, reset_osc); 127 } 128 } 129 130 if (tmp & M41T93_FLAG_BL) 131 dev_warn(&spi->dev, "BL bit is set, replace battery.\n"); 132 133 /* read actual time/date */ 134 tmp = spi_write_then_read(spi, &start_addr, 1, buf, sizeof(buf)); 135 if (tmp < 0) 136 return tmp; 137 138 tm->tm_sec = bcd2bin(buf[M41T93_REG_ST_SEC]); 139 tm->tm_min = bcd2bin(buf[M41T93_REG_MIN]); 140 tm->tm_hour = bcd2bin(buf[M41T93_REG_CENT_HOUR] & 0x3f); 141 tm->tm_mday = bcd2bin(buf[M41T93_REG_DAY]); 142 tm->tm_mon = bcd2bin(buf[M41T93_REG_MON]) - 1; 143 tm->tm_wday = bcd2bin(buf[M41T93_REG_WDAY] & 0x0f) - 1; 144 145 century_after_1900 = (buf[M41T93_REG_CENT_HOUR] >> 6) + 1; 146 tm->tm_year = bcd2bin(buf[M41T93_REG_YEAR]) + century_after_1900 * 100; 147 148 dev_dbg(dev, "%s secs=%d, mins=%d, " 149 "hours=%d, mday=%d, mon=%d, year=%d, wday=%d\n", 150 "read", tm->tm_sec, tm->tm_min, 151 tm->tm_hour, tm->tm_mday, 152 tm->tm_mon, tm->tm_year, tm->tm_wday); 153 154 return ret < 0 ? ret : rtc_valid_tm(tm); 155 } 156 157 158 static const struct rtc_class_ops m41t93_rtc_ops = { 159 .read_time = m41t93_get_time, 160 .set_time = m41t93_set_time, 161 }; 162 163 static struct spi_driver m41t93_driver; 164 165 static int __devinit m41t93_probe(struct spi_device *spi) 166 { 167 struct rtc_device *rtc; 168 int res; 169 170 spi->bits_per_word = 8; 171 spi_setup(spi); 172 173 res = spi_w8r8(spi, M41T93_REG_WDAY); 174 if (res < 0 || (res & 0xf8) != 0) { 175 dev_err(&spi->dev, "not found 0x%x.\n", res); 176 return -ENODEV; 177 } 178 179 rtc = rtc_device_register(m41t93_driver.driver.name, 180 &spi->dev, &m41t93_rtc_ops, THIS_MODULE); 181 if (IS_ERR(rtc)) 182 return PTR_ERR(rtc); 183 184 dev_set_drvdata(&spi->dev, rtc); 185 186 return 0; 187 } 188 189 190 static int __devexit m41t93_remove(struct spi_device *spi) 191 { 192 struct rtc_device *rtc = platform_get_drvdata(spi); 193 194 if (rtc) 195 rtc_device_unregister(rtc); 196 197 return 0; 198 } 199 200 static struct spi_driver m41t93_driver = { 201 .driver = { 202 .name = "rtc-m41t93", 203 .bus = &spi_bus_type, 204 .owner = THIS_MODULE, 205 }, 206 .probe = m41t93_probe, 207 .remove = __devexit_p(m41t93_remove), 208 }; 209 210 static __init int m41t93_init(void) 211 { 212 return spi_register_driver(&m41t93_driver); 213 } 214 module_init(m41t93_init); 215 216 static __exit void m41t93_exit(void) 217 { 218 spi_unregister_driver(&m41t93_driver); 219 } 220 module_exit(m41t93_exit); 221 222 MODULE_AUTHOR("Nikolaus Voss <n.voss@weinmann.de>"); 223 MODULE_DESCRIPTION("Driver for ST M41T93 SPI RTC"); 224 MODULE_LICENSE("GPL"); 225 MODULE_ALIAS("spi:rtc-m41t93"); 226