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rtc: add support for Maxim max6916 

Add support for Maxim max6916 RTC.

Signed-off-by: Venkat Prashanth B U <venkat.prashanth2498@gmail.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
This commit is contained in:
Venkat Prashanth B U 2016-06-01 11:59:54 +05:30 committed by Alexandre Belloni
parent 82df3e045d
commit 06776c8921
3 changed files with 177 additions and 0 deletions
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12
drivers/rtc/Kconfig
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@ -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

1
drivers/rtc/Makefile
View File

@ -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

164
drivers/rtc/rtc-max6916.c Normal file
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@ -0,0 +1,164 @@
/* 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");