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// 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");
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