drivers/rtc/rtc-max6902.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /* drivers/rtc/rtc-max6902.c
   3  *
   4  * Copyright (C) 2006 8D Technologies inc.
   5  * Copyright (C) 2004 Compulab Ltd.
   6  *
   7  * Driver for MAX6902 spi RTC
   8  */
   9
  10 #include <linux/module.h>
  11 #include <linux/kernel.h>
  12 #include <linux/platform_device.h>
  13 #include <linux/init.h>
  14 #include <linux/rtc.h>
  15 #include <linux/spi/spi.h>
  16 #include <linux/bcd.h>
  17
  18 #define MAX6902_REG_SECONDS             0x01
  19 #define MAX6902_REG_MINUTES             0x03
  20 #define MAX6902_REG_HOURS               0x05
  21 #define MAX6902_REG_DATE                0x07
  22 #define MAX6902_REG_MONTH               0x09
  23 #define MAX6902_REG_DAY                 0x0B
  24 #define MAX6902_REG_YEAR                0x0D
  25 #define MAX6902_REG_CONTROL             0x0F
  26 #define MAX6902_REG_CENTURY             0x13
  27
  28 static int max6902_set_reg(struct device *dev, unsigned char address,
  29                                 unsigned char data)
  30 {
  31         struct spi_device *spi = to_spi_device(dev);
  32         unsigned char buf[2];
  33
  34         /* MSB must be '0' to write */
  35         buf[0] = address & 0x7f;
  36         buf[1] = data;
  37
  38         return spi_write_then_read(spi, buf, 2, NULL, 0);
  39 }
  40
  41 static int max6902_get_reg(struct device *dev, unsigned char address,
  42                                 unsigned char *data)
  43 {
  44         struct spi_device *spi = to_spi_device(dev);
  45
  46         /* Set MSB to indicate read */
  47         *data = address | 0x80;
  48
  49         return spi_write_then_read(spi, data, 1, data, 1);
  50 }
  51
  52 static int max6902_read_time(struct device *dev, struct rtc_time *dt)
  53 {
  54         int err, century;
  55         struct spi_device *spi = to_spi_device(dev);
  56         unsigned char buf[8];
  57
  58         buf[0] = 0xbf;  /* Burst read */
  59
  60         err = spi_write_then_read(spi, buf, 1, buf, 8);
  61         if (err != 0)
  62                 return err;
  63
  64         /* The chip sends data in this order:
  65          * Seconds, Minutes, Hours, Date, Month, Day, Year */
  66         dt->tm_sec      = bcd2bin(buf[0]);
  67         dt->tm_min      = bcd2bin(buf[1]);
  68         dt->tm_hour     = bcd2bin(buf[2]);
  69         dt->tm_mday     = bcd2bin(buf[3]);
  70         dt->tm_mon      = bcd2bin(buf[4]) - 1;
  71         dt->tm_wday     = bcd2bin(buf[5]);
  72         dt->tm_year     = bcd2bin(buf[6]);
  73
  74         /* Read century */
  75         err = max6902_get_reg(dev, MAX6902_REG_CENTURY, &buf[0]);
  76         if (err != 0)
  77                 return err;
  78
  79         century = bcd2bin(buf[0]) * 100;
  80
  81         dt->tm_year += century;
  82         dt->tm_year -= 1900;
  83
  84         return 0;
  85 }
  86
  87 static int max6902_set_time(struct device *dev, struct rtc_time *dt)
  88 {
  89         dt->tm_year = dt->tm_year + 1900;
  90
  91         /* Remove write protection */
  92         max6902_set_reg(dev, MAX6902_REG_CONTROL, 0);
  93
  94         max6902_set_reg(dev, MAX6902_REG_SECONDS, bin2bcd(dt->tm_sec));
  95         max6902_set_reg(dev, MAX6902_REG_MINUTES, bin2bcd(dt->tm_min));
  96         max6902_set_reg(dev, MAX6902_REG_HOURS, bin2bcd(dt->tm_hour));
  97
  98         max6902_set_reg(dev, MAX6902_REG_DATE, bin2bcd(dt->tm_mday));
  99         max6902_set_reg(dev, MAX6902_REG_MONTH, bin2bcd(dt->tm_mon + 1));
 100         max6902_set_reg(dev, MAX6902_REG_DAY, bin2bcd(dt->tm_wday));
 101         max6902_set_reg(dev, MAX6902_REG_YEAR, bin2bcd(dt->tm_year % 100));
 102         max6902_set_reg(dev, MAX6902_REG_CENTURY, bin2bcd(dt->tm_year / 100));
 103
 104         /* Compulab used a delay here. However, the datasheet
 105          * does not mention a delay being required anywhere... */
 106         /* delay(2000); */
 107
 108         /* Write protect */
 109         max6902_set_reg(dev, MAX6902_REG_CONTROL, 0x80);
 110
 111         return 0;
 112 }
 113
 114 static const struct rtc_class_ops max6902_rtc_ops = {
 115         .read_time      = max6902_read_time,
 116         .set_time       = max6902_set_time,
 117 };
 118
 119 static int max6902_probe(struct spi_device *spi)
 120 {
 121         struct rtc_device *rtc;
 122         unsigned char tmp;
 123         int res;
 124
 125         spi->mode = SPI_MODE_3;
 126         spi->bits_per_word = 8;
 127         spi_setup(spi);
 128
 129         res = max6902_get_reg(&spi->dev, MAX6902_REG_SECONDS, &tmp);
 130         if (res != 0)
 131                 return res;
 132
 133         rtc = devm_rtc_device_register(&spi->dev, "max6902",
 134                                 &max6902_rtc_ops, THIS_MODULE);
 135         if (IS_ERR(rtc))
 136                 return PTR_ERR(rtc);
 137
 138         spi_set_drvdata(spi, rtc);
 139         return 0;
 140 }
 141
 142 static struct spi_driver max6902_driver = {
 143         .driver = {
 144                 .name   = "rtc-max6902",
 145         },
 146         .probe  = max6902_probe,
 147 };
 148
 149 module_spi_driver(max6902_driver);
 150
 151 MODULE_DESCRIPTION("max6902 spi RTC driver");
 152 MODULE_AUTHOR("Raphael Assenat");
 153 MODULE_LICENSE("GPL");
 154 MODULE_ALIAS("spi:rtc-max6902");