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
  31 static 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
  41 static 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
  53 static 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
  77 static 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
 102 static const struct rtc_class_ops max6916_rtc_ops = {
 103         .read_time = max6916_read_time,
 104         .set_time = max6916_set_time,
 105 };
 106
 107 static 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
 150 static struct spi_driver max6916_driver = {
 151         .driver = {
 152                 .name = "max6916",
 153         },
 154         .probe = max6916_probe,
 155 };
 156 module_spi_driver(max6916_driver);
 157
 158 MODULE_DESCRIPTION("MAX6916 SPI RTC DRIVER");
 159 MODULE_AUTHOR("Venkat Prashanth B U <venkat.prashanth2498@gmail.com>");
 160 MODULE_LICENSE("GPL v2");