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1// SPDX-License-Identifier: GPL-2.0-only2/* rtc-max6916.c3 *4 * Driver for MAXIM max6916 Low Current, SPI Compatible5 * Real Time Clock6 *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 0x0121#define MAX6916_MINUTES_REG 0x0222#define MAX6916_HOURS_REG 0x0323#define MAX6916_DATE_REG 0x0424#define MAX6916_MONTH_REG 0x0525#define MAX6916_DAY_REG 0x0626#define MAX6916_YEAR_REG 0x0727#define MAX6916_CONTROL_REG 0x0828#define MAX6916_STATUS_REG 0x0C29#define MAX6916_CLOCK_BURST 0x3F30 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