// SPDX-License-Identifier: GPL-2.0-only/* rtc-max6916.c * * Driver for MAXIM  max6916 Low Current, SPI Compatible * Real Time Clock * * Author : Venkat Prashanth B U <venkat.prashanth2498@gmail.com> */ #include <linux/init.h>#include <linux/module.h>#include <linux/device.h>#include <linux/platform_device.h>#include <linux/rtc.h>#include <linux/spi/spi.h>#include <linux/bcd.h> /* Registers in max6916 rtc */ #define MAX6916_SECONDS_REG	0x01#define MAX6916_MINUTES_REG	0x02#define MAX6916_HOURS_REG	0x03#define MAX6916_DATE_REG	0x04#define MAX6916_MONTH_REG	0x05#define MAX6916_DAY_REG	0x06#define MAX6916_YEAR_REG	0x07#define MAX6916_CONTROL_REG	0x08#define MAX6916_STATUS_REG	0x0C#define MAX6916_CLOCK_BURST	0x3F static int max6916_read_reg(struct device *dev, unsigned char address,			    unsigned char *data){	struct spi_device *spi = to_spi_device(dev); 	*data = address | 0x80; 	return spi_write_then_read(spi, data, 1, data, 1);} static int max6916_write_reg(struct device *dev, unsigned char address,			     unsigned char data){	struct spi_device *spi = to_spi_device(dev);	unsigned char buf[2]; 	buf[0] = address & 0x7F;	buf[1] = data; 	return spi_write_then_read(spi, buf, 2, NULL, 0);} static int max6916_read_time(struct device *dev, struct rtc_time *dt){	struct spi_device *spi = to_spi_device(dev);	int err;	unsigned char buf[8]; 	buf[0] = MAX6916_CLOCK_BURST | 0x80; 	err = spi_write_then_read(spi, buf, 1, buf, 8); 	if (err)		return err; 	dt->tm_sec = bcd2bin(buf[0]);	dt->tm_min = bcd2bin(buf[1]);	dt->tm_hour = bcd2bin(buf[2] & 0x3F);	dt->tm_mday = bcd2bin(buf[3]);	dt->tm_mon = bcd2bin(buf[4]) - 1;	dt->tm_wday = bcd2bin(buf[5]) - 1;	dt->tm_year = bcd2bin(buf[6]) + 100; 	return 0;} static int max6916_set_time(struct device *dev, struct rtc_time *dt){	struct spi_device *spi = to_spi_device(dev);	unsigned char buf[9]; 	if (dt->tm_year < 100 || dt->tm_year > 199) {		dev_err(&spi->dev, "Year must be between 2000 and 2099. It's %d.\n",			dt->tm_year + 1900);		return -EINVAL;	} 	buf[0] = MAX6916_CLOCK_BURST & 0x7F;	buf[1] = bin2bcd(dt->tm_sec);	buf[2] = bin2bcd(dt->tm_min);	buf[3] = (bin2bcd(dt->tm_hour) & 0X3F);	buf[4] = bin2bcd(dt->tm_mday);	buf[5] = bin2bcd(dt->tm_mon + 1);	buf[6] = bin2bcd(dt->tm_wday + 1);	buf[7] = bin2bcd(dt->tm_year % 100);	buf[8] = bin2bcd(0x00); 	/* write the rtc settings */	return spi_write_then_read(spi, buf, 9, NULL, 0);} static const struct rtc_class_ops max6916_rtc_ops = {	.read_time = max6916_read_time,	.set_time = max6916_set_time,}; static int max6916_probe(struct spi_device *spi){	struct rtc_device *rtc;	unsigned char data;	int res; 	/* spi setup with max6916 in mode 3 and bits per word as 8 */	spi->mode = SPI_MODE_3;	spi->bits_per_word = 8;	spi_setup(spi); 	/* RTC Settings */	res = max6916_read_reg(&spi->dev, MAX6916_SECONDS_REG, &data);	if (res)		return res; 	/* Disable the write protect of rtc */	max6916_read_reg(&spi->dev, MAX6916_CONTROL_REG, &data);	data = data & ~(1 << 7);	max6916_write_reg(&spi->dev, MAX6916_CONTROL_REG, data); 	/*Enable oscillator,disable oscillator stop flag, glitch filter*/	max6916_read_reg(&spi->dev, MAX6916_STATUS_REG, &data);	data = data & 0x1B;	max6916_write_reg(&spi->dev, MAX6916_STATUS_REG, data); 	/* display the settings */	max6916_read_reg(&spi->dev, MAX6916_CONTROL_REG, &data);	dev_info(&spi->dev, "MAX6916 RTC CTRL Reg = 0x%02x\n", data); 	max6916_read_reg(&spi->dev, MAX6916_STATUS_REG, &data);	dev_info(&spi->dev, "MAX6916 RTC Status Reg = 0x%02x\n", data); 	rtc = devm_rtc_device_register(&spi->dev, "max6916",				       &max6916_rtc_ops, THIS_MODULE);	if (IS_ERR(rtc))		return PTR_ERR(rtc); 	spi_set_drvdata(spi, rtc); 	return 0;} static struct spi_driver max6916_driver = {	.driver = {		.name = "max6916",	},	.probe = max6916_probe,};module_spi_driver(max6916_driver); MODULE_DESCRIPTION("MAX6916 SPI RTC DRIVER");MODULE_AUTHOR("Venkat Prashanth B U <venkat.prashanth2498@gmail.com>");MODULE_LICENSE("GPL v2");