linux/drivers/rtc/rtc-ds1390.c
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   1/*
   2 * rtc-ds1390.c -- driver for the Dallas/Maxim DS1390/93/94 SPI RTC
   3 *
   4 * Copyright (C) 2008 Mercury IMC Ltd
   5 * Written by Mark Jackson <mpfj@mimc.co.uk>
   6 *
   7 * This program is free software; you can redistribute it and/or modify
   8 * it under the terms of the GNU General Public License version 2 as
   9 * published by the Free Software Foundation.
  10 *
  11 * NOTE: Currently this driver only supports the bare minimum for read
  12 * and write the RTC. The extra features provided by the chip family
  13 * (alarms, trickle charger, different control registers) are unavailable.
  14 */
  15
  16#include <linux/init.h>
  17#include <linux/module.h>
  18#include <linux/platform_device.h>
  19#include <linux/rtc.h>
  20#include <linux/spi/spi.h>
  21#include <linux/bcd.h>
  22#include <linux/slab.h>
  23
  24#define DS1390_REG_100THS               0x00
  25#define DS1390_REG_SECONDS              0x01
  26#define DS1390_REG_MINUTES              0x02
  27#define DS1390_REG_HOURS                0x03
  28#define DS1390_REG_DAY                  0x04
  29#define DS1390_REG_DATE                 0x05
  30#define DS1390_REG_MONTH_CENT           0x06
  31#define DS1390_REG_YEAR                 0x07
  32
  33#define DS1390_REG_ALARM_100THS         0x08
  34#define DS1390_REG_ALARM_SECONDS        0x09
  35#define DS1390_REG_ALARM_MINUTES        0x0A
  36#define DS1390_REG_ALARM_HOURS          0x0B
  37#define DS1390_REG_ALARM_DAY_DATE       0x0C
  38
  39#define DS1390_REG_CONTROL              0x0D
  40#define DS1390_REG_STATUS               0x0E
  41#define DS1390_REG_TRICKLE              0x0F
  42
  43struct ds1390 {
  44        struct rtc_device *rtc;
  45        u8 txrx_buf[9]; /* cmd + 8 registers */
  46};
  47
  48static int ds1390_get_reg(struct device *dev, unsigned char address,
  49                                unsigned char *data)
  50{
  51        struct spi_device *spi = to_spi_device(dev);
  52        struct ds1390 *chip = dev_get_drvdata(dev);
  53        int status;
  54
  55        if (!data)
  56                return -EINVAL;
  57
  58        /* Clear MSB to indicate read */
  59        chip->txrx_buf[0] = address & 0x7f;
  60        /* do the i/o */
  61        status = spi_write_then_read(spi, chip->txrx_buf, 1, chip->txrx_buf, 1);
  62        if (status != 0)
  63                return status;
  64
  65        *data = chip->txrx_buf[1];
  66
  67        return 0;
  68}
  69
  70static int ds1390_read_time(struct device *dev, struct rtc_time *dt)
  71{
  72        struct spi_device *spi = to_spi_device(dev);
  73        struct ds1390 *chip = dev_get_drvdata(dev);
  74        int status;
  75
  76        /* build the message */
  77        chip->txrx_buf[0] = DS1390_REG_SECONDS;
  78
  79        /* do the i/o */
  80        status = spi_write_then_read(spi, chip->txrx_buf, 1, chip->txrx_buf, 8);
  81        if (status != 0)
  82                return status;
  83
  84        /* The chip sends data in this order:
  85         * Seconds, Minutes, Hours, Day, Date, Month / Century, Year */
  86        dt->tm_sec      = bcd2bin(chip->txrx_buf[0]);
  87        dt->tm_min      = bcd2bin(chip->txrx_buf[1]);
  88        dt->tm_hour     = bcd2bin(chip->txrx_buf[2]);
  89        dt->tm_wday     = bcd2bin(chip->txrx_buf[3]);
  90        dt->tm_mday     = bcd2bin(chip->txrx_buf[4]);
  91        /* mask off century bit */
  92        dt->tm_mon      = bcd2bin(chip->txrx_buf[5] & 0x7f) - 1;
  93        /* adjust for century bit */
  94        dt->tm_year = bcd2bin(chip->txrx_buf[6]) + ((chip->txrx_buf[5] & 0x80) ? 100 : 0);
  95
  96        return rtc_valid_tm(dt);
  97}
  98
  99static int ds1390_set_time(struct device *dev, struct rtc_time *dt)
 100{
 101        struct spi_device *spi = to_spi_device(dev);
 102        struct ds1390 *chip = dev_get_drvdata(dev);
 103
 104        /* build the message */
 105        chip->txrx_buf[0] = DS1390_REG_SECONDS | 0x80;
 106        chip->txrx_buf[1] = bin2bcd(dt->tm_sec);
 107        chip->txrx_buf[2] = bin2bcd(dt->tm_min);
 108        chip->txrx_buf[3] = bin2bcd(dt->tm_hour);
 109        chip->txrx_buf[4] = bin2bcd(dt->tm_wday);
 110        chip->txrx_buf[5] = bin2bcd(dt->tm_mday);
 111        chip->txrx_buf[6] = bin2bcd(dt->tm_mon + 1) |
 112                                ((dt->tm_year > 99) ? 0x80 : 0x00);
 113        chip->txrx_buf[7] = bin2bcd(dt->tm_year % 100);
 114
 115        /* do the i/o */
 116        return spi_write_then_read(spi, chip->txrx_buf, 8, NULL, 0);
 117}
 118
 119static const struct rtc_class_ops ds1390_rtc_ops = {
 120        .read_time      = ds1390_read_time,
 121        .set_time       = ds1390_set_time,
 122};
 123
 124static int ds1390_probe(struct spi_device *spi)
 125{
 126        unsigned char tmp;
 127        struct ds1390 *chip;
 128        int res;
 129
 130        spi->mode = SPI_MODE_3;
 131        spi->bits_per_word = 8;
 132        spi_setup(spi);
 133
 134        chip = devm_kzalloc(&spi->dev, sizeof(*chip), GFP_KERNEL);
 135        if (!chip) {
 136                dev_err(&spi->dev, "unable to allocate device memory\n");
 137                return -ENOMEM;
 138        }
 139        spi_set_drvdata(spi, chip);
 140
 141        res = ds1390_get_reg(&spi->dev, DS1390_REG_SECONDS, &tmp);
 142        if (res != 0) {
 143                dev_err(&spi->dev, "unable to read device\n");
 144                return res;
 145        }
 146
 147        chip->rtc = devm_rtc_device_register(&spi->dev, "ds1390",
 148                                        &ds1390_rtc_ops, THIS_MODULE);
 149        if (IS_ERR(chip->rtc)) {
 150                dev_err(&spi->dev, "unable to register device\n");
 151                res = PTR_ERR(chip->rtc);
 152        }
 153
 154        return res;
 155}
 156
 157static struct spi_driver ds1390_driver = {
 158        .driver = {
 159                .name   = "rtc-ds1390",
 160                .owner  = THIS_MODULE,
 161        },
 162        .probe  = ds1390_probe,
 163};
 164
 165module_spi_driver(ds1390_driver);
 166
 167MODULE_DESCRIPTION("Dallas/Maxim DS1390/93/94 SPI RTC driver");
 168MODULE_AUTHOR("Mark Jackson <mpfj@mimc.co.uk>");
 169MODULE_LICENSE("GPL");
 170MODULE_ALIAS("spi:rtc-ds1390");
 171
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