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 int tmp; 52 u8 buf[9] = {0x80}; /* write cmd + 8 data bytes */ 53 u8 * const data = &buf[1]; /* ptr to first data byte */ 54 55 dev_dbg(dev, "%s secs=%d, mins=%d, " 56 "hours=%d, mday=%d, mon=%d, year=%d, wday=%d\n", 57 "write", tm->tm_sec, tm->tm_min, 58 tm->tm_hour, tm->tm_mday, 59 tm->tm_mon, tm->tm_year, tm->tm_wday); 60 61 if (tm->tm_year < 100) { 62 dev_warn(&spi->dev, "unsupported date (before 2000-01-01).\n"); 63 return -EINVAL; 64 } 65 66 tmp = spi_w8r8(spi, M41T93_REG_FLAGS); 67 if (tmp < 0) 68 return tmp; 69 70 if (tmp & M41T93_FLAG_OF) { 71 dev_warn(&spi->dev, "OF bit is set, resetting.\n"); 72 m41t93_set_reg(spi, M41T93_REG_FLAGS, tmp & ~M41T93_FLAG_OF); 73 74 tmp = spi_w8r8(spi, M41T93_REG_FLAGS); 75 if (tmp < 0) { 76 return tmp; 77 } else if (tmp & M41T93_FLAG_OF) { 78 /* OF cannot be immediately reset: oscillator has to be 79 * restarted. */ 80 u8 reset_osc = buf[M41T93_REG_ST_SEC] | M41T93_FLAG_ST; 81 82 dev_warn(&spi->dev, 83 "OF bit is still set, kickstarting clock.\n"); 84 m41t93_set_reg(spi, M41T93_REG_ST_SEC, reset_osc); 85 reset_osc &= ~M41T93_FLAG_ST; 86 m41t93_set_reg(spi, M41T93_REG_ST_SEC, reset_osc); 87 } 88 } 89 90 data[M41T93_REG_SSEC] = 0; 91 data[M41T93_REG_ST_SEC] = bin2bcd(tm->tm_sec); 92 data[M41T93_REG_MIN] = bin2bcd(tm->tm_min); 93 data[M41T93_REG_CENT_HOUR] = bin2bcd(tm->tm_hour) | 94 ((tm->tm_year/100-1) << 6); 95 data[M41T93_REG_DAY] = bin2bcd(tm->tm_mday); 96 data[M41T93_REG_WDAY] = bin2bcd(tm->tm_wday + 1); 97 data[M41T93_REG_MON] = bin2bcd(tm->tm_mon + 1); 98 data[M41T93_REG_YEAR] = bin2bcd(tm->tm_year % 100); 99 100 return spi_write(spi, buf, sizeof(buf)); 101 } 102 103 104 static int m41t93_get_time(struct device *dev, struct rtc_time *tm) 105 { 106 struct spi_device *spi = to_spi_device(dev); 107 const u8 start_addr = 0; 108 u8 buf[8]; 109 int century_after_1900; 110 int tmp; 111 int ret = 0; 112 113 /* Check status of clock. Two states must be considered: 114 1. halt bit (HT) is set: the clock is running but update of readout 115 registers has been disabled due to power failure. This is normal 116 case after poweron. Time is valid after resetting HT bit. 117 2. oscillator fail bit (OF) is set: time is invalid. 118 */ 119 tmp = spi_w8r8(spi, M41T93_REG_ALM_HOUR_HT); 120 if (tmp < 0) 121 return tmp; 122 123 if (tmp & M41T93_FLAG_HT) { 124 dev_dbg(&spi->dev, "HT bit is set, reenable clock update.\n"); 125 m41t93_set_reg(spi, M41T93_REG_ALM_HOUR_HT, 126 tmp & ~M41T93_FLAG_HT); 127 } 128 129 tmp = spi_w8r8(spi, M41T93_REG_FLAGS); 130 if (tmp < 0) 131 return tmp; 132 133 if (tmp & M41T93_FLAG_OF) { 134 ret = -EINVAL; 135 dev_warn(&spi->dev, "OF bit is set, write time to restart.\n"); 136 } 137 138 if (tmp & M41T93_FLAG_BL) 139 dev_warn(&spi->dev, "BL bit is set, replace battery.\n"); 140 141 /* read actual time/date */ 142 tmp = spi_write_then_read(spi, &start_addr, 1, buf, sizeof(buf)); 143 if (tmp < 0) 144 return tmp; 145 146 tm->tm_sec = bcd2bin(buf[M41T93_REG_ST_SEC]); 147 tm->tm_min = bcd2bin(buf[M41T93_REG_MIN]); 148 tm->tm_hour = bcd2bin(buf[M41T93_REG_CENT_HOUR] & 0x3f); 149 tm->tm_mday = bcd2bin(buf[M41T93_REG_DAY]); 150 tm->tm_mon = bcd2bin(buf[M41T93_REG_MON]) - 1; 151 tm->tm_wday = bcd2bin(buf[M41T93_REG_WDAY] & 0x0f) - 1; 152 153 century_after_1900 = (buf[M41T93_REG_CENT_HOUR] >> 6) + 1; 154 tm->tm_year = bcd2bin(buf[M41T93_REG_YEAR]) + century_after_1900 * 100; 155 156 dev_dbg(dev, "%s secs=%d, mins=%d, " 157 "hours=%d, mday=%d, mon=%d, year=%d, wday=%d\n", 158 "read", tm->tm_sec, tm->tm_min, 159 tm->tm_hour, tm->tm_mday, 160 tm->tm_mon, tm->tm_year, tm->tm_wday); 161 162 return ret < 0 ? ret : rtc_valid_tm(tm); 163 } 164 165 166 static const struct rtc_class_ops m41t93_rtc_ops = { 167 .read_time = m41t93_get_time, 168 .set_time = m41t93_set_time, 169 }; 170 171 static struct spi_driver m41t93_driver; 172 173 static int m41t93_probe(struct spi_device *spi) 174 { 175 struct rtc_device *rtc; 176 int res; 177 178 spi->bits_per_word = 8; 179 spi_setup(spi); 180 181 res = spi_w8r8(spi, M41T93_REG_WDAY); 182 if (res < 0 || (res & 0xf8) != 0) { 183 dev_err(&spi->dev, "not found 0x%x.\n", res); 184 return -ENODEV; 185 } 186 187 rtc = devm_rtc_device_register(&spi->dev, m41t93_driver.driver.name, 188 &m41t93_rtc_ops, THIS_MODULE); 189 if (IS_ERR(rtc)) 190 return PTR_ERR(rtc); 191 192 spi_set_drvdata(spi, rtc); 193 194 return 0; 195 } 196 197 static struct spi_driver m41t93_driver = { 198 .driver = { 199 .name = "rtc-m41t93", 200 }, 201 .probe = m41t93_probe, 202 }; 203 204 module_spi_driver(m41t93_driver); 205 206 MODULE_AUTHOR("Nikolaus Voss <n.voss@weinmann.de>"); 207 MODULE_DESCRIPTION("Driver for ST M41T93 SPI RTC"); 208 MODULE_LICENSE("GPL"); 209 MODULE_ALIAS("spi:rtc-m41t93"); 210