drivers/rtc/rtc-m41t93.c

   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 = spi_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                 .owner  = THIS_MODULE,
 204         },
 205         .probe  = m41t93_probe,
 206         .remove = __devexit_p(m41t93_remove),
 207 };
 208
 209 module_spi_driver(m41t93_driver);
 210
 211 MODULE_AUTHOR("Nikolaus Voss <n.voss@weinmann.de>");
 212 MODULE_DESCRIPTION("Driver for ST M41T93 SPI RTC");
 213 MODULE_LICENSE("GPL");
 214 MODULE_ALIAS("spi:rtc-m41t93");