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// SPDX-License-Identifier: GPL-2.0-only
/* drivers/rtc/rtc-max6902.c
*
* Copyright (C) 2006 8D Technologies inc.
* Copyright (C) 2004 Compulab Ltd.
*
* Driver for MAX6902 spi RTC
*/
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/platform_device.h>
#include <linux/init.h>
#include <linux/rtc.h>
#include <linux/spi/spi.h>
#include <linux/bcd.h>
#define MAX6902_REG_SECONDS 0x01
#define MAX6902_REG_MINUTES 0x03
#define MAX6902_REG_HOURS 0x05
#define MAX6902_REG_DATE 0x07
#define MAX6902_REG_MONTH 0x09
#define MAX6902_REG_DAY 0x0B
#define MAX6902_REG_YEAR 0x0D
#define MAX6902_REG_CONTROL 0x0F
#define MAX6902_REG_CENTURY 0x13
static int max6902_set_reg(struct device *dev, unsigned char address,
unsigned char data)
{
struct spi_device *spi = to_spi_device(dev);
unsigned char buf[2];
/* MSB must be '0' to write */
buf[0] = address & 0x7f;
buf[1] = data;
return spi_write_then_read(spi, buf, 2, NULL, 0);
}
static int max6902_get_reg(struct device *dev, unsigned char address,
unsigned char *data)
{
struct spi_device *spi = to_spi_device(dev);
/* Set MSB to indicate read */
*data = address | 0x80;
return spi_write_then_read(spi, data, 1, data, 1);
}
static int max6902_read_time(struct device *dev, struct rtc_time *dt)
{
int err, century;
struct spi_device *spi = to_spi_device(dev);
unsigned char buf[8];
buf[0] = 0xbf; /* Burst read */
err = spi_write_then_read(spi, buf, 1, buf, 8);
if (err != 0)
return err;
/* The chip sends data in this order:
* Seconds, Minutes, Hours, Date, Month, Day, Year */
dt->tm_sec = bcd2bin(buf[0]);
dt->tm_min = bcd2bin(buf[1]);
dt->tm_hour = bcd2bin(buf[2]);
dt->tm_mday = bcd2bin(buf[3]);
dt->tm_mon = bcd2bin(buf[4]) - 1;
dt->tm_wday = bcd2bin(buf[5]);
dt->tm_year = bcd2bin(buf[6]);
/* Read century */
err = max6902_get_reg(dev, MAX6902_REG_CENTURY, &buf[0]);
if (err != 0)
return err;
century = bcd2bin(buf[0]) * 100;
dt->tm_year += century;
dt->tm_year -= 1900;
return 0;
}
static int max6902_set_time(struct device *dev, struct rtc_time *dt)
{
dt->tm_year = dt->tm_year + 1900;
/* Remove write protection */
max6902_set_reg(dev, MAX6902_REG_CONTROL, 0);
max6902_set_reg(dev, MAX6902_REG_SECONDS, bin2bcd(dt->tm_sec));
max6902_set_reg(dev, MAX6902_REG_MINUTES, bin2bcd(dt->tm_min));
max6902_set_reg(dev, MAX6902_REG_HOURS, bin2bcd(dt->tm_hour));
max6902_set_reg(dev, MAX6902_REG_DATE, bin2bcd(dt->tm_mday));
max6902_set_reg(dev, MAX6902_REG_MONTH, bin2bcd(dt->tm_mon + 1));
max6902_set_reg(dev, MAX6902_REG_DAY, bin2bcd(dt->tm_wday));
max6902_set_reg(dev, MAX6902_REG_YEAR, bin2bcd(dt->tm_year % 100));
max6902_set_reg(dev, MAX6902_REG_CENTURY, bin2bcd(dt->tm_year / 100));
/* Compulab used a delay here. However, the datasheet
* does not mention a delay being required anywhere... */
/* delay(2000); */
/* Write protect */
max6902_set_reg(dev, MAX6902_REG_CONTROL, 0x80);
return 0;
}
static const struct rtc_class_ops max6902_rtc_ops = {
.read_time = max6902_read_time,
.set_time = max6902_set_time,
};
static int max6902_probe(struct spi_device *spi)
{
struct rtc_device *rtc;
unsigned char tmp;
int res;
spi->mode = SPI_MODE_3;
spi->bits_per_word = 8;
spi_setup(spi);
res = max6902_get_reg(&spi->dev, MAX6902_REG_SECONDS, &tmp);
if (res != 0)
return res;
rtc = devm_rtc_device_register(&spi->dev, "max6902",
&max6902_rtc_ops, THIS_MODULE);
if (IS_ERR(rtc))
return PTR_ERR(rtc);
spi_set_drvdata(spi, rtc);
return 0;
}
static struct spi_driver max6902_driver = {
.driver = {
.name = "rtc-max6902",
},
.probe = max6902_probe,
};
module_spi_driver(max6902_driver);
MODULE_DESCRIPTION("max6902 spi RTC driver");
MODULE_AUTHOR("Raphael Assenat");
MODULE_LICENSE("GPL");
MODULE_ALIAS("spi:rtc-max6902");
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