LXR linux/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
  29static 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
  56static 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
 102static const struct rtc_class_ops m41t94_rtc_ops = {
 103        .read_time      = m41t94_read_time,
 104        .set_time       = m41t94_set_time,
 105};
 106
 107static struct spi_driver m41t94_driver;
 108
 109static 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
 133static struct spi_driver m41t94_driver = {
 134        .driver = {
 135                .name   = "rtc-m41t94",
 136        },
 137        .probe  = m41t94_probe,
 138};
 139
 140module_spi_driver(m41t94_driver);
 141
 142MODULE_AUTHOR("Kim B. Heino <Kim.Heino@bluegiga.com>");
 143MODULE_DESCRIPTION("Driver for ST M41T94 SPI RTC");
 144MODULE_LICENSE("GPL");
 145MODULE_ALIAS("spi:rtc-m41t94");
 146