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Commit 06776c89 authored by Venkat Prashanth B U's avatar Venkat Prashanth B U Committed by Alexandre Belloni
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rtc: add support for Maxim max6916 



Add support for Maxim max6916 RTC.

Signed-off-by: default avatarVenkat Prashanth B U <venkat.prashanth2498@gmail.com>
Signed-off-by: default avatarAlexandre Belloni <alexandre.belloni@free-electrons.com>
parent 82df3e04

drivers/rtc/Kconfig

+12 −0
Original line number Diff line number Diff line
@@ -670,6 +670,18 @@ config RTC_DRV_DS1390 
	  This driver can also be built as a module. If so, the module

	  will be called rtc-ds1390.



config RTC_DRV_MAX6916

	tristate "Maxim MAX6916"

	help

	  If you say yes here you will get support for the

	  Maxim MAX6916 SPI RTC chip.



	  This driver only supports the RTC feature, and not other chip

	  features such as alarms.



	  This driver can also be built as a module. If so, the module

	  will be called rtc-max6916.



config RTC_DRV_R9701

	tristate "Epson RTC-9701JE"

	help

drivers/rtc/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -85,6 +85,7 @@ obj-$(CONFIG_RTC_DRV_M48T59) += rtc-m48t59.o 
obj-$(CONFIG_RTC_DRV_M48T86)	+= rtc-m48t86.o

obj-$(CONFIG_RTC_DRV_MAX6900)	+= rtc-max6900.o

obj-$(CONFIG_RTC_DRV_MAX6902)	+= rtc-max6902.o

obj-$(CONFIG_RTC_DRV_MAX6916)	+= rtc-max6916.o

obj-$(CONFIG_RTC_DRV_MAX77686)	+= rtc-max77686.o

obj-$(CONFIG_RTC_DRV_MAX8907)	+= rtc-max8907.o

obj-$(CONFIG_RTC_DRV_MAX8925)	+= rtc-max8925.o

drivers/rtc/rtc-max6916.c

0 → 100644
+164 −0
Original line number Diff line number Diff line 
/* rtc-max6916.c

 *

 * Driver for MAXIM  max6916 Low Current, SPI Compatible

 * Real Time Clock

 *

 * Author : Venkat Prashanth B U <venkat.prashanth2498@gmail.com>

 *

 * This program is free software; you can redistribute it and/or modify

 * it under the terms of the GNU General Public License version 2 as

 * published by the Free Software Foundation.

 *

 */



#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 rtc_valid_tm(dt);

}



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");