drivers/rtc/rtc-m41t94.c

   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");