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>
diff --git a/drivers/rtc/rtc-max6916.c b/drivers/rtc/rtc-max6916.c
new file mode 100644
index 0000000..623ab27
--- /dev/null
+++ b/drivers/rtc/rtc-max6916.c
@@ -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");
