[PATCH] rtc: add support for Maxim rtc max6916 v3.0

From: venkat . prashanth2498
Date: Fri May 13 2016 - 02:03:15 EST

From: venkat-prashanth <venkat.prashanth2498@xxxxxxxxx>

[PATCH] rtc: add support to maxim rtc max6916

#Change Log: from v2.0 to v3.0

- fixed the out-of-tree Makefile and suitably added
the modifications in the Makefile

- fixed the bad indented Kconfig file

-used a define instead of 0x1B as follows
#define MAX6916_REG_MAP_ADDRESS 0x1B

-moved and placed the test at the begining of the function
after the range is properly enforced
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;
}

- A magic number is a direct usage of a number
in the code,instead has been refactored in the
current version v3.0 which use defines as follows:-
-max6916_read_reg(&spi->dev,
int MAX6916_CONTROL_REG = 0x08, &data);
-max6916_write_reg(&spi->dev,
int MAX6916_CONTROL_REG= 0x08, data);
-max6916_write_reg(&spi->dev,
int MAX6916_STATUS_REG = 0x0C, data);
-max6916_read_reg(&spi->dev,
int MAX6916_CONTROL_REG = 0x08, &data);
-max6916_read_reg(&spi->dev,
int MAX6916_STATUS_REG = 0X0C, &data);
-Unnecessary test function if(dt->tm_year >= 100)
dt->tm_year -= 100;
is deleted after the range is properly enforced.
-seperated logical code sections with an empty line
and used indentation after if-statements.
---
---
Kconfig | 9 ++++
Makefile | 1 +
rtc-max6916.c | 162 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 172 insertions(+)

diff --git a/driver/rtc/Kconfig b/driver/rtc/Kconfig
index fcf87da..5321e8f 100644
--- a/driver/rtc/Kconfig
+++ b/driver/rtc/Kconfig
@@ -699,6 +699,15 @@

This driver can also be built as a module. If so, the module
will be called rtc-max6902.
+ 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 can also be built as a module. If so, the module
+ will be called rtc-max6916.
+

config RTC_DRV_R9701
tristate "Epson RTC-9701JE"
diff --git a/driver/rtc/Makefile b/driver/rtc/Makefile
index 9421959..0b3fded 100644
--- a/driver/rtc/Makefile
+++ b/driver/rtc/Makefile
@@ -85,6 +85,7 @@
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_MAX77802) += rtc-max77802.o
obj-$(CONFIG_RTC_DRV_MAX8907) += rtc-max8907.o
diff --git a/driver/rtc/rtc-max6916.c b/driver/rtc/rtc-max6916.c
index e69de29..ced341a 100644
--- a/driver/rtc/rtc-max6916.c
+++ b/driver/rtc/rtc-max6916.c
@@ -0,0 +1,162 @@
+#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
+#define MAX6916_REG_MAP_ADDRESS 0x1B
+
+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, int MAX6916_CONTROL_REG = 0x08, &data);
+ data = data & ~(1<<7);
+ max6916_write_reg(&spi->dev, int MAX6916_CONTROL_REG = 0x08, data);
+
+ /*Enable the oscillator,disable the oscillator stop flag, and glitch filter to reduce current consumption*/
+ max6916_read_reg(&spi->dev, int MAX6916_STATUS_REG = 0X0C, &data);
+ data = data & MAX6916_REG_MAP_ADDRESS;
+ max6916_write_reg(&spi->dev, int MAX6916_STATUS_REG = 0x0C, data);
+
+ /* display the settings */
+ max6916_read_reg(&spi->dev, int MAX6916_CONTROL_REG = 0x08, &data);
+ dev_info(&spi->dev, "MAX6916 RTC CTRL Reg = 0x%02x\n", data);
+
+ max6916_read_reg(&spi->dev, int MAX6916_STATUS_REG = 0X0C, &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@xxxxxxxxx>");
+MODULE_LICENSE("GPL v2");
+
+
+
+
+
+
+
+
+
--
1.9.2