LXR linux/drivers/rtc/rtc-max6916.c

   1// SPDX-License-Identifier: GPL-2.0-only
   2/* rtc-max6916.c
   3 *
   4 * Driver for MAXIM  max6916 Low Current, SPI Compatible
   5 * Real Time Clock
   6 *
   7 * Author : Venkat Prashanth B U <venkat.prashanth2498@gmail.com>
   8 */
   9
  10#include <linux/init.h>
  11#include <linux/module.h>
  12#include <linux/device.h>
  13#include <linux/platform_device.h>
  14#include <linux/rtc.h>
  15#include <linux/spi/spi.h>
  16#include <linux/bcd.h>
  17
  18/* Registers in max6916 rtc */
  19
  20#define MAX6916_SECONDS_REG     0x01
  21#define MAX6916_MINUTES_REG     0x02
  22#define MAX6916_HOURS_REG       0x03
  23#define MAX6916_DATE_REG        0x04
  24#define MAX6916_MONTH_REG       0x05
  25#define MAX6916_DAY_REG 0x06
  26#define MAX6916_YEAR_REG        0x07
  27#define MAX6916_CONTROL_REG     0x08
  28#define MAX6916_STATUS_REG      0x0C
  29#define MAX6916_CLOCK_BURST     0x3F
  30
  31static int max6916_read_reg(struct device *dev, unsigned char address,
  32                            unsigned char *data)
  33{
  34        struct spi_device *spi = to_spi_device(dev);
  35
  36        *data = address | 0x80;
  37
  38        return spi_write_then_read(spi, data, 1, data, 1);
  39}
  40
  41static int max6916_write_reg(struct device *dev, unsigned char address,
  42                             unsigned char data)
  43{
  44        struct spi_device *spi = to_spi_device(dev);
  45        unsigned char buf[2];
  46
  47        buf[0] = address & 0x7F;
  48        buf[1] = data;
  49
  50        return spi_write_then_read(spi, buf, 2, NULL, 0);
  51}
  52
  53static int max6916_read_time(struct device *dev, struct rtc_time *dt)
  54{
  55        struct spi_device *spi = to_spi_device(dev);
  56        int err;
  57        unsigned char buf[8];
  58
  59        buf[0] = MAX6916_CLOCK_BURST | 0x80;
  60
  61        err = spi_write_then_read(spi, buf, 1, buf, 8);
  62
  63        if (err)
  64                return err;
  65
  66        dt->tm_sec = bcd2bin(buf[0]);
  67        dt->tm_min = bcd2bin(buf[1]);
  68        dt->tm_hour = bcd2bin(buf[2] & 0x3F);
  69        dt->tm_mday = bcd2bin(buf[3]);
  70        dt->tm_mon = bcd2bin(buf[4]) - 1;
  71        dt->tm_wday = bcd2bin(buf[5]) - 1;
  72        dt->tm_year = bcd2bin(buf[6]) + 100;
  73
  74        return 0;
  75}
  76
  77static int max6916_set_time(struct device *dev, struct rtc_time *dt)
  78{
  79        struct spi_device *spi = to_spi_device(dev);
  80        unsigned char buf[9];
  81
  82        if (dt->tm_year < 100 || dt->tm_year > 199) {
  83                dev_err(&spi->dev, "Year must be between 2000 and 2099. It's %d.\n",
  84                        dt->tm_year + 1900);
  85                return -EINVAL;
  86        }
  87
  88        buf[0] = MAX6916_CLOCK_BURST & 0x7F;
  89        buf[1] = bin2bcd(dt->tm_sec);
  90        buf[2] = bin2bcd(dt->tm_min);
  91        buf[3] = (bin2bcd(dt->tm_hour) & 0X3F);
  92        buf[4] = bin2bcd(dt->tm_mday);
  93        buf[5] = bin2bcd(dt->tm_mon + 1);
  94        buf[6] = bin2bcd(dt->tm_wday + 1);
  95        buf[7] = bin2bcd(dt->tm_year % 100);
  96        buf[8] = bin2bcd(0x00);
  97
  98        /* write the rtc settings */
  99        return spi_write_then_read(spi, buf, 9, NULL, 0);
 100}
 101
 102static const struct rtc_class_ops max6916_rtc_ops = {
 103        .read_time = max6916_read_time,
 104        .set_time = max6916_set_time,
 105};
 106
 107static int max6916_probe(struct spi_device *spi)
 108{
 109        struct rtc_device *rtc;
 110        unsigned char data;
 111        int res;
 112
 113        /* spi setup with max6916 in mode 3 and bits per word as 8 */
 114        spi->mode = SPI_MODE_3;
 115        spi->bits_per_word = 8;
 116        spi_setup(spi);
 117
 118        /* RTC Settings */
 119        res = max6916_read_reg(&spi->dev, MAX6916_SECONDS_REG, &data);
 120        if (res)
 121                return res;
 122
 123        /* Disable the write protect of rtc */
 124        max6916_read_reg(&spi->dev, MAX6916_CONTROL_REG, &data);
 125        data = data & ~(1 << 7);
 126        max6916_write_reg(&spi->dev, MAX6916_CONTROL_REG, data);
 127
 128        /*Enable oscillator,disable oscillator stop flag, glitch filter*/
 129        max6916_read_reg(&spi->dev, MAX6916_STATUS_REG, &data);
 130        data = data & 0x1B;
 131        max6916_write_reg(&spi->dev, MAX6916_STATUS_REG, data);
 132
 133        /* display the settings */
 134        max6916_read_reg(&spi->dev, MAX6916_CONTROL_REG, &data);
 135        dev_info(&spi->dev, "MAX6916 RTC CTRL Reg = 0x%02x\n", data);
 136
 137        max6916_read_reg(&spi->dev, MAX6916_STATUS_REG, &data);
 138        dev_info(&spi->dev, "MAX6916 RTC Status Reg = 0x%02x\n", data);
 139
 140        rtc = devm_rtc_device_register(&spi->dev, "max6916",
 141                                       &max6916_rtc_ops, THIS_MODULE);
 142        if (IS_ERR(rtc))
 143                return PTR_ERR(rtc);
 144
 145        spi_set_drvdata(spi, rtc);
 146
 147        return 0;
 148}
 149
 150static struct spi_driver max6916_driver = {
 151        .driver = {
 152                .name = "max6916",
 153        },
 154        .probe = max6916_probe,
 155};
 156module_spi_driver(max6916_driver);
 157
 158MODULE_DESCRIPTION("MAX6916 SPI RTC DRIVER");
 159MODULE_AUTHOR("Venkat Prashanth B U <venkat.prashanth2498@gmail.com>");
 160MODULE_LICENSE("GPL v2");
 161