LXR linux/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
  28static 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
  41static 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
  52static 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
  87static 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
 114static const struct rtc_class_ops max6902_rtc_ops = {
 115        .read_time      = max6902_read_time,
 116        .set_time       = max6902_set_time,
 117};
 118
 119static 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
 142static struct spi_driver max6902_driver = {
 143        .driver = {
 144                .name   = "rtc-max6902",
 145        },
 146        .probe  = max6902_probe,
 147};
 148
 149module_spi_driver(max6902_driver);
 150
 151MODULE_DESCRIPTION("max6902 spi RTC driver");
 152MODULE_AUTHOR("Raphael Assenat");
 153MODULE_LICENSE("GPL");
 154MODULE_ALIAS("spi:rtc-max6902");
 155