drivers/rtc/rtc-m41t93.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  *
   4  * Driver for ST M41T93 SPI RTC
   5  *
   6  * (c) 2010 Nikolaus Voss, Weinmann Medical GmbH
   7  */
   8
   9 #include <linux/bcd.h>
  10 #include <linux/kernel.h>
  11 #include <linux/module.h>
  12 #include <linux/platform_device.h>
  13 #include <linux/rtc.h>
  14 #include <linux/spi/spi.h>
  15
  16 #define M41T93_REG_SSEC                 0
  17 #define M41T93_REG_ST_SEC               1
  18 #define M41T93_REG_MIN                  2
  19 #define M41T93_REG_CENT_HOUR            3
  20 #define M41T93_REG_WDAY                 4
  21 #define M41T93_REG_DAY                  5
  22 #define M41T93_REG_MON                  6
  23 #define M41T93_REG_YEAR                 7
  24
  25
  26 #define M41T93_REG_ALM_HOUR_HT          0xc
  27 #define M41T93_REG_FLAGS                0xf
  28
  29 #define M41T93_FLAG_ST                  (1 << 7)
  30 #define M41T93_FLAG_OF                  (1 << 2)
  31 #define M41T93_FLAG_BL                  (1 << 4)
  32 #define M41T93_FLAG_HT                  (1 << 6)
  33
  34 static inline int m41t93_set_reg(struct spi_device *spi, u8 addr, u8 data)
  35 {
  36         u8 buf[2];
  37
  38         /* MSB must be '1' to write */
  39         buf[0] = addr | 0x80;
  40         buf[1] = data;
  41
  42         return spi_write(spi, buf, sizeof(buf));
  43 }
  44
  45 static int m41t93_set_time(struct device *dev, struct rtc_time *tm)
  46 {
  47         struct spi_device *spi = to_spi_device(dev);
  48         int tmp;
  49         u8 buf[9] = {0x80};        /* write cmd + 8 data bytes */
  50         u8 * const data = &buf[1]; /* ptr to first data byte */
  51
  52         dev_dbg(dev, "%s secs=%d, mins=%d, "
  53                 "hours=%d, mday=%d, mon=%d, year=%d, wday=%d\n",
  54                 "write", tm->tm_sec, tm->tm_min,
  55                 tm->tm_hour, tm->tm_mday,
  56                 tm->tm_mon, tm->tm_year, tm->tm_wday);
  57
  58         if (tm->tm_year < 100) {
  59                 dev_warn(&spi->dev, "unsupported date (before 2000-01-01).\n");
  60                 return -EINVAL;
  61         }
  62
  63         tmp = spi_w8r8(spi, M41T93_REG_FLAGS);
  64         if (tmp < 0)
  65                 return tmp;
  66
  67         if (tmp & M41T93_FLAG_OF) {
  68                 dev_warn(&spi->dev, "OF bit is set, resetting.\n");
  69                 m41t93_set_reg(spi, M41T93_REG_FLAGS, tmp & ~M41T93_FLAG_OF);
  70
  71                 tmp = spi_w8r8(spi, M41T93_REG_FLAGS);
  72                 if (tmp < 0) {
  73                         return tmp;
  74                 } else if (tmp & M41T93_FLAG_OF) {
  75                         /* OF cannot be immediately reset: oscillator has to be
  76                          * restarted. */
  77                         u8 reset_osc = buf[M41T93_REG_ST_SEC] | M41T93_FLAG_ST;
  78
  79                         dev_warn(&spi->dev,
  80                                  "OF bit is still set, kickstarting clock.\n");
  81                         m41t93_set_reg(spi, M41T93_REG_ST_SEC, reset_osc);
  82                         reset_osc &= ~M41T93_FLAG_ST;
  83                         m41t93_set_reg(spi, M41T93_REG_ST_SEC, reset_osc);
  84                 }
  85         }
  86
  87         data[M41T93_REG_SSEC]           = 0;
  88         data[M41T93_REG_ST_SEC]         = bin2bcd(tm->tm_sec);
  89         data[M41T93_REG_MIN]            = bin2bcd(tm->tm_min);
  90         data[M41T93_REG_CENT_HOUR]      = bin2bcd(tm->tm_hour) |
  91                                                 ((tm->tm_year/100-1) << 6);
  92         data[M41T93_REG_DAY]            = bin2bcd(tm->tm_mday);
  93         data[M41T93_REG_WDAY]           = bin2bcd(tm->tm_wday + 1);
  94         data[M41T93_REG_MON]            = bin2bcd(tm->tm_mon + 1);
  95         data[M41T93_REG_YEAR]           = bin2bcd(tm->tm_year % 100);
  96
  97         return spi_write(spi, buf, sizeof(buf));
  98 }
  99
 100
 101 static int m41t93_get_time(struct device *dev, struct rtc_time *tm)
 102 {
 103         struct spi_device *spi = to_spi_device(dev);
 104         const u8 start_addr = 0;
 105         u8 buf[8];
 106         int century_after_1900;
 107         int tmp;
 108         int ret = 0;
 109
 110         /* Check status of clock. Two states must be considered:
 111            1. halt bit (HT) is set: the clock is running but update of readout
 112               registers has been disabled due to power failure. This is normal
 113               case after poweron. Time is valid after resetting HT bit.
 114            2. oscillator fail bit (OF) is set: time is invalid.
 115         */
 116         tmp = spi_w8r8(spi, M41T93_REG_ALM_HOUR_HT);
 117         if (tmp < 0)
 118                 return tmp;
 119
 120         if (tmp & M41T93_FLAG_HT) {
 121                 dev_dbg(&spi->dev, "HT bit is set, reenable clock update.\n");
 122                 m41t93_set_reg(spi, M41T93_REG_ALM_HOUR_HT,
 123                                tmp & ~M41T93_FLAG_HT);
 124         }
 125
 126         tmp = spi_w8r8(spi, M41T93_REG_FLAGS);
 127         if (tmp < 0)
 128                 return tmp;
 129
 130         if (tmp & M41T93_FLAG_OF) {
 131                 ret = -EINVAL;
 132                 dev_warn(&spi->dev, "OF bit is set, write time to restart.\n");
 133         }
 134
 135         if (tmp & M41T93_FLAG_BL)
 136                 dev_warn(&spi->dev, "BL bit is set, replace battery.\n");
 137
 138         /* read actual time/date */
 139         tmp = spi_write_then_read(spi, &start_addr, 1, buf, sizeof(buf));
 140         if (tmp < 0)
 141                 return tmp;
 142
 143         tm->tm_sec      = bcd2bin(buf[M41T93_REG_ST_SEC]);
 144         tm->tm_min      = bcd2bin(buf[M41T93_REG_MIN]);
 145         tm->tm_hour     = bcd2bin(buf[M41T93_REG_CENT_HOUR] & 0x3f);
 146         tm->tm_mday     = bcd2bin(buf[M41T93_REG_DAY]);
 147         tm->tm_mon      = bcd2bin(buf[M41T93_REG_MON]) - 1;
 148         tm->tm_wday     = bcd2bin(buf[M41T93_REG_WDAY] & 0x0f) - 1;
 149
 150         century_after_1900 = (buf[M41T93_REG_CENT_HOUR] >> 6) + 1;
 151         tm->tm_year = bcd2bin(buf[M41T93_REG_YEAR]) + century_after_1900 * 100;
 152
 153         dev_dbg(dev, "%s secs=%d, mins=%d, "
 154                 "hours=%d, mday=%d, mon=%d, year=%d, wday=%d\n",
 155                 "read", tm->tm_sec, tm->tm_min,
 156                 tm->tm_hour, tm->tm_mday,
 157                 tm->tm_mon, tm->tm_year, tm->tm_wday);
 158
 159         return ret;
 160 }
 161
 162
 163 static const struct rtc_class_ops m41t93_rtc_ops = {
 164         .read_time      = m41t93_get_time,
 165         .set_time       = m41t93_set_time,
 166 };
 167
 168 static struct spi_driver m41t93_driver;
 169
 170 static int m41t93_probe(struct spi_device *spi)
 171 {
 172         struct rtc_device *rtc;
 173         int res;
 174
 175         spi->bits_per_word = 8;
 176         spi_setup(spi);
 177
 178         res = spi_w8r8(spi, M41T93_REG_WDAY);
 179         if (res < 0 || (res & 0xf8) != 0) {
 180                 dev_err(&spi->dev, "not found 0x%x.\n", res);
 181                 return -ENODEV;
 182         }
 183
 184         rtc = devm_rtc_device_register(&spi->dev, m41t93_driver.driver.name,
 185                                         &m41t93_rtc_ops, THIS_MODULE);
 186         if (IS_ERR(rtc))
 187                 return PTR_ERR(rtc);
 188
 189         spi_set_drvdata(spi, rtc);
 190
 191         return 0;
 192 }
 193
 194 static struct spi_driver m41t93_driver = {
 195         .driver = {
 196                 .name   = "rtc-m41t93",
 197         },
 198         .probe  = m41t93_probe,
 199 };
 200
 201 module_spi_driver(m41t93_driver);
 202
 203 MODULE_AUTHOR("Nikolaus Voss <n.voss@weinmann.de>");
 204 MODULE_DESCRIPTION("Driver for ST M41T93 SPI RTC");
 205 MODULE_LICENSE("GPL");
 206 MODULE_ALIAS("spi:rtc-m41t93");