drivers/rtc/rtc-max6916.c

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