drivers/rtc/rtc-rx6110.c - linux - Git at Google

 /*
  * Driver for the Epson RTC module RX-6110 SA
  *
  * Copyright(C) 2015 Pengutronix, Steffen Trumtrar <kernel@pengutronix.de>
  * Copyright(C) SEIKO EPSON CORPORATION 2013. All rights reserved.
  *
  * This driver software is distributed as is, without any warranty of any kind,
  * either express or implied as further specified in the GNU Public License.
  * This software may be used and distributed according to the terms of the GNU
  * Public License, version 2 as published by the Free Software Foundation.
  * See the file COPYING in the main directory of this archive for more details.
  *
  * You should have received a copy of the GNU General Public License along with
  * this program. If not, see <http://www.gnu.org/licenses/>.
  */

 #include <linux/bcd.h>
 #include <linux/init.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/of_gpio.h>
 #include <linux/regmap.h>
 #include <linux/rtc.h>
 #include <linux/spi/spi.h>

 /* RX-6110 Register definitions */
 #define RX6110_REG_SEC		0x10
 #define RX6110_REG_MIN		0x11
 #define RX6110_REG_HOUR		0x12
 #define RX6110_REG_WDAY		0x13
 #define RX6110_REG_MDAY		0x14
 #define RX6110_REG_MONTH	0x15
 #define RX6110_REG_YEAR		0x16
 #define RX6110_REG_RES1		0x17
 #define RX6110_REG_ALMIN	0x18
 #define RX6110_REG_ALHOUR	0x19
 #define RX6110_REG_ALWDAY	0x1A
 #define RX6110_REG_TCOUNT0	0x1B
 #define RX6110_REG_TCOUNT1	0x1C
 #define RX6110_REG_EXT		0x1D
 #define RX6110_REG_FLAG		0x1E
 #define RX6110_REG_CTRL		0x1F
 #define RX6110_REG_USER0	0x20
 #define RX6110_REG_USER1	0x21
 #define RX6110_REG_USER2	0x22
 #define RX6110_REG_USER3	0x23
 #define RX6110_REG_USER4	0x24
 #define RX6110_REG_USER5	0x25
 #define RX6110_REG_USER6	0x26
 #define RX6110_REG_USER7	0x27
 #define RX6110_REG_USER8	0x28
 #define RX6110_REG_USER9	0x29
 #define RX6110_REG_USERA	0x2A
 #define RX6110_REG_USERB	0x2B
 #define RX6110_REG_USERC	0x2C
 #define RX6110_REG_USERD	0x2D
 #define RX6110_REG_USERE	0x2E
 #define RX6110_REG_USERF	0x2F
 #define RX6110_REG_RES2		0x30
 #define RX6110_REG_RES3		0x31
 #define RX6110_REG_IRQ		0x32

 #define RX6110_BIT_ALARM_EN		BIT(7)

 /* Extension Register (1Dh) bit positions */
 #define RX6110_BIT_EXT_TSEL0		BIT(0)
 #define RX6110_BIT_EXT_TSEL1		BIT(1)
 #define RX6110_BIT_EXT_TSEL2		BIT(2)
 #define RX6110_BIT_EXT_WADA		BIT(3)
 #define RX6110_BIT_EXT_TE		BIT(4)
 #define RX6110_BIT_EXT_USEL		BIT(5)
 #define RX6110_BIT_EXT_FSEL0		BIT(6)
 #define RX6110_BIT_EXT_FSEL1		BIT(7)

 /* Flag Register (1Eh) bit positions */
 #define RX6110_BIT_FLAG_VLF		BIT(1)
 #define RX6110_BIT_FLAG_AF		BIT(3)
 #define RX6110_BIT_FLAG_TF		BIT(4)
 #define RX6110_BIT_FLAG_UF		BIT(5)

 /* Control Register (1Fh) bit positions */
 #define RX6110_BIT_CTRL_TBKE		BIT(0)
 #define RX6110_BIT_CTRL_TBKON		BIT(1)
 #define RX6110_BIT_CTRL_TSTP		BIT(2)
 #define RX6110_BIT_CTRL_AIE		BIT(3)
 #define RX6110_BIT_CTRL_TIE		BIT(4)
 #define RX6110_BIT_CTRL_UIE		BIT(5)
 #define RX6110_BIT_CTRL_STOP		BIT(6)
 #define RX6110_BIT_CTRL_TEST		BIT(7)

 enum {
 	RTC_SEC = 0,
 	RTC_MIN,
 	RTC_HOUR,
 	RTC_WDAY,
 	RTC_MDAY,
 	RTC_MONTH,
 	RTC_YEAR,
 	RTC_NR_TIME
 };

 #define RX6110_DRIVER_NAME		"rx6110"

 struct rx6110_data {
 	struct rtc_device *rtc;
 	struct regmap *regmap;
 };

 /**
  * rx6110_rtc_tm_to_data - convert rtc_time to native time encoding
  *
  * @tm: holds date and time
  * @data: holds the encoding in rx6110 native form
  */
 static int rx6110_rtc_tm_to_data(struct rtc_time *tm, u8 *data)
 {
 	pr_debug("%s: date %ds %dm %dh %dmd %dm %dy\n", __func__,
 		 tm->tm_sec, tm->tm_min, tm->tm_hour,
 		 tm->tm_mday, tm->tm_mon, tm->tm_year);

 	/*
 	 * The year in the RTC is a value between 0 and 99.
 	 * Assume that this represents the current century
 	 * and disregard all other values.
 	 */
 	if (tm->tm_year < 100 || tm->tm_year >= 200)
 		return -EINVAL;

 	data[RTC_SEC] = bin2bcd(tm->tm_sec);
 	data[RTC_MIN] = bin2bcd(tm->tm_min);
 	data[RTC_HOUR] = bin2bcd(tm->tm_hour);
 	data[RTC_WDAY] = BIT(bin2bcd(tm->tm_wday));
 	data[RTC_MDAY] = bin2bcd(tm->tm_mday);
 	data[RTC_MONTH] = bin2bcd(tm->tm_mon + 1);
 	data[RTC_YEAR] = bin2bcd(tm->tm_year % 100);

 	return 0;
 }

 /**
  * rx6110_data_to_rtc_tm - convert native time encoding to rtc_time
  *
  * @data: holds the encoding in rx6110 native form
  * @tm: holds date and time
  */
 static int rx6110_data_to_rtc_tm(u8 *data, struct rtc_time *tm)
 {
 	tm->tm_sec = bcd2bin(data[RTC_SEC] & 0x7f);
 	tm->tm_min = bcd2bin(data[RTC_MIN] & 0x7f);
 	/* only 24-hour clock */
 	tm->tm_hour = bcd2bin(data[RTC_HOUR] & 0x3f);
 	tm->tm_wday = ffs(data[RTC_WDAY] & 0x7f);
 	tm->tm_mday = bcd2bin(data[RTC_MDAY] & 0x3f);
 	tm->tm_mon = bcd2bin(data[RTC_MONTH] & 0x1f) - 1;
 	tm->tm_year = bcd2bin(data[RTC_YEAR]) + 100;

 	pr_debug("%s: date %ds %dm %dh %dmd %dm %dy\n", __func__,
 		 tm->tm_sec, tm->tm_min, tm->tm_hour,
 		 tm->tm_mday, tm->tm_mon, tm->tm_year);

 	/*
 	 * The year in the RTC is a value between 0 and 99.
 	 * Assume that this represents the current century
 	 * and disregard all other values.
 	 */
 	if (tm->tm_year < 100 || tm->tm_year >= 200)
 		return -EINVAL;

 	return 0;
 }

 /**
  * rx6110_set_time - set the current time in the rx6110 registers
  *
  * @dev: the rtc device in use
  * @tm: holds date and time
  *
  * BUG: The HW assumes every year that is a multiple of 4 to be a leap
  * year. Next time this is wrong is 2100, which will not be a leap year
  *
  * Note: If STOP is not set/cleared, the clock will start when the seconds
  *       register is written
  *
  */
 static int rx6110_set_time(struct device *dev, struct rtc_time *tm)
 {
 	struct rx6110_data *rx6110 = dev_get_drvdata(dev);
 	u8 data[RTC_NR_TIME];
 	int ret;

 	ret = rx6110_rtc_tm_to_data(tm, data);
 	if (ret < 0)
 		return ret;

 	/* set STOP bit before changing clock/calendar */
 	ret = regmap_update_bits(rx6110->regmap, RX6110_REG_CTRL,
 				 RX6110_BIT_CTRL_STOP, RX6110_BIT_CTRL_STOP);
 	if (ret)
 		return ret;

 	ret = regmap_bulk_write(rx6110->regmap, RX6110_REG_SEC, data,
 				RTC_NR_TIME);
 	if (ret)
 		return ret;

 	/* The time in the RTC is valid. Be sure to have VLF cleared. */
 	ret = regmap_update_bits(rx6110->regmap, RX6110_REG_FLAG,
 				 RX6110_BIT_FLAG_VLF, 0);
 	if (ret)
 		return ret;

 	/* clear STOP bit after changing clock/calendar */
 	ret = regmap_update_bits(rx6110->regmap, RX6110_REG_CTRL,
 				 RX6110_BIT_CTRL_STOP, 0);

 	return ret;
 }

 /**
  * rx6110_get_time - get the current time from the rx6110 registers
  * @dev: the rtc device in use
  * @tm: holds date and time
  */
 static int rx6110_get_time(struct device *dev, struct rtc_time *tm)
 {
 	struct rx6110_data *rx6110 = dev_get_drvdata(dev);
 	u8 data[RTC_NR_TIME];
 	int flags;
 	int ret;

 	ret = regmap_read(rx6110->regmap, RX6110_REG_FLAG, &flags);
 	if (ret)
 		return -EINVAL;

 	/* check for VLF Flag (set at power-on) */
 	if ((flags & RX6110_BIT_FLAG_VLF)) {
 		dev_warn(dev, "Voltage low, data is invalid.\n");
 		return -EINVAL;
 	}

 	/* read registers to date */
 	ret = regmap_bulk_read(rx6110->regmap, RX6110_REG_SEC, data,
 			       RTC_NR_TIME);
 	if (ret)
 		return ret;

 	ret = rx6110_data_to_rtc_tm(data, tm);
 	if (ret)
 		return ret;

 	dev_dbg(dev, "%s: date %ds %dm %dh %dmd %dm %dy\n", __func__,
 		tm->tm_sec, tm->tm_min, tm->tm_hour,
 		tm->tm_mday, tm->tm_mon, tm->tm_year);

 	return rtc_valid_tm(tm);
 }

 static const struct reg_sequence rx6110_default_regs[] = {
 	{ RX6110_REG_RES1,   0xB8 },
 	{ RX6110_REG_RES2,   0x00 },
 	{ RX6110_REG_RES3,   0x10 },
 	{ RX6110_REG_IRQ,    0x00 },
 	{ RX6110_REG_ALMIN,  0x00 },
 	{ RX6110_REG_ALHOUR, 0x00 },
 	{ RX6110_REG_ALWDAY, 0x00 },
 };

 /**
  * rx6110_init - initialize the rx6110 registers
  *
  * @rx6110: pointer to the rx6110 struct in use
  *
  */
 static int rx6110_init(struct rx6110_data *rx6110)
 {
 	struct rtc_device *rtc = rx6110->rtc;
 	int flags;
 	int ret;

 	ret = regmap_update_bits(rx6110->regmap, RX6110_REG_EXT,
 				 RX6110_BIT_EXT_TE, 0);
 	if (ret)
 		return ret;

 	ret = regmap_register_patch(rx6110->regmap, rx6110_default_regs,
 				    ARRAY_SIZE(rx6110_default_regs));
 	if (ret)
 		return ret;

 	ret = regmap_read(rx6110->regmap, RX6110_REG_FLAG, &flags);
 	if (ret)
 		return ret;

 	/* check for VLF Flag (set at power-on) */
 	if ((flags & RX6110_BIT_FLAG_VLF))
 		dev_warn(&rtc->dev, "Voltage low, data loss detected.\n");

 	/* check for Alarm Flag */
 	if (flags & RX6110_BIT_FLAG_AF)
 		dev_warn(&rtc->dev, "An alarm may have been missed.\n");

 	/* check for Periodic Timer Flag */
 	if (flags & RX6110_BIT_FLAG_TF)
 		dev_warn(&rtc->dev, "Periodic timer was detected\n");

 	/* check for Update Timer Flag */
 	if (flags & RX6110_BIT_FLAG_UF)
 		dev_warn(&rtc->dev, "Update timer was detected\n");

 	/* clear all flags BUT VLF */
 	ret = regmap_update_bits(rx6110->regmap, RX6110_REG_FLAG,
 				 RX6110_BIT_FLAG_AF |
 				 RX6110_BIT_FLAG_UF |
 				 RX6110_BIT_FLAG_TF,
 				 0);

 	return ret;
 }

 static const struct rtc_class_ops rx6110_rtc_ops = {
 	.read_time = rx6110_get_time,
 	.set_time = rx6110_set_time,
 };

 static struct regmap_config regmap_spi_config = {
 	.reg_bits = 8,
 	.val_bits = 8,
 	.max_register = RX6110_REG_IRQ,
 	.read_flag_mask = 0x80,
 };

 /**
  * rx6110_probe - initialize rtc driver
  * @spi: pointer to spi device
  */
 static int rx6110_probe(struct spi_device *spi)
 {
 	struct rx6110_data *rx6110;
 	int err;

 	if ((spi->bits_per_word && spi->bits_per_word != 8) ||
 	    (spi->max_speed_hz > 2000000) ||
 	    (spi->mode != (SPI_CS_HIGH | SPI_CPOL | SPI_CPHA))) {
 		dev_warn(&spi->dev, "SPI settings: bits_per_word: %d, max_speed_hz: %d, mode: %xh\n",
 			 spi->bits_per_word, spi->max_speed_hz, spi->mode);
 		dev_warn(&spi->dev, "driving device in an unsupported mode");
 	}

 	rx6110 = devm_kzalloc(&spi->dev, sizeof(*rx6110), GFP_KERNEL);
 	if (!rx6110)
 		return -ENOMEM;

 	rx6110->regmap = devm_regmap_init_spi(spi, &regmap_spi_config);
 	if (IS_ERR(rx6110->regmap)) {
 		dev_err(&spi->dev, "regmap init failed for rtc rx6110\n");
 		return PTR_ERR(rx6110->regmap);
 	}

 	spi_set_drvdata(spi, rx6110);

 	rx6110->rtc = devm_rtc_device_register(&spi->dev,
 					       RX6110_DRIVER_NAME,
 					       &rx6110_rtc_ops, THIS_MODULE);

 	if (IS_ERR(rx6110->rtc))
 		return PTR_ERR(rx6110->rtc);

 	err = rx6110_init(rx6110);
 	if (err)
 		return err;

 	rx6110->rtc->max_user_freq = 1;

 	return 0;
 }

 static int rx6110_remove(struct spi_device *spi)
 {
 	return 0;
 }

 static const struct spi_device_id rx6110_id[] = {
 	{ "rx6110", 0 },
 	{ }
 };
 MODULE_DEVICE_TABLE(spi, rx6110_id);

 static struct spi_driver rx6110_driver = {
 	.driver = {
 		.name = RX6110_DRIVER_NAME,
 	},
 	.probe		= rx6110_probe,
 	.remove		= rx6110_remove,
 	.id_table	= rx6110_id,
 };

 module_spi_driver(rx6110_driver);

 MODULE_AUTHOR("Val Krutov <val.krutov@erd.epson.com>");
 MODULE_DESCRIPTION("RX-6110 SA RTC driver");
 MODULE_LICENSE("GPL");
	/*
	* Driver for the Epson RTC module RX-6110 SA
	*
	* Copyright(C) 2015 Pengutronix, Steffen Trumtrar <kernel@pengutronix.de>
	* Copyright(C) SEIKO EPSON CORPORATION 2013. All rights reserved.
	*
	* This driver software is distributed as is, without any warranty of any kind,
	* either express or implied as further specified in the GNU Public License.
	* This software may be used and distributed according to the terms of the GNU
	* Public License, version 2 as published by the Free Software Foundation.
	* See the file COPYING in the main directory of this archive for more details.
	*
	* You should have received a copy of the GNU General Public License along with
	* this program. If not, see <http://www.gnu.org/licenses/>.
	*/

	#include <linux/bcd.h>
	#include <linux/init.h>
	#include <linux/kernel.h>
	#include <linux/module.h>
	#include <linux/of_gpio.h>
	#include <linux/regmap.h>
	#include <linux/rtc.h>
	#include <linux/spi/spi.h>

	/* RX-6110 Register definitions */
	#define RX6110_REG_SEC 0x10
	#define RX6110_REG_MIN 0x11
	#define RX6110_REG_HOUR 0x12
	#define RX6110_REG_WDAY 0x13
	#define RX6110_REG_MDAY 0x14
	#define RX6110_REG_MONTH 0x15
	#define RX6110_REG_YEAR 0x16
	#define RX6110_REG_RES1 0x17
	#define RX6110_REG_ALMIN 0x18
	#define RX6110_REG_ALHOUR 0x19
	#define RX6110_REG_ALWDAY 0x1A
	#define RX6110_REG_TCOUNT0 0x1B
	#define RX6110_REG_TCOUNT1 0x1C
	#define RX6110_REG_EXT 0x1D
	#define RX6110_REG_FLAG 0x1E
	#define RX6110_REG_CTRL 0x1F
	#define RX6110_REG_USER0 0x20
	#define RX6110_REG_USER1 0x21
	#define RX6110_REG_USER2 0x22
	#define RX6110_REG_USER3 0x23
	#define RX6110_REG_USER4 0x24
	#define RX6110_REG_USER5 0x25
	#define RX6110_REG_USER6 0x26
	#define RX6110_REG_USER7 0x27
	#define RX6110_REG_USER8 0x28
	#define RX6110_REG_USER9 0x29
	#define RX6110_REG_USERA 0x2A
	#define RX6110_REG_USERB 0x2B
	#define RX6110_REG_USERC 0x2C
	#define RX6110_REG_USERD 0x2D
	#define RX6110_REG_USERE 0x2E
	#define RX6110_REG_USERF 0x2F
	#define RX6110_REG_RES2 0x30
	#define RX6110_REG_RES3 0x31
	#define RX6110_REG_IRQ 0x32

	#define RX6110_BIT_ALARM_EN BIT(7)

	/* Extension Register (1Dh) bit positions */
	#define RX6110_BIT_EXT_TSEL0 BIT(0)
	#define RX6110_BIT_EXT_TSEL1 BIT(1)
	#define RX6110_BIT_EXT_TSEL2 BIT(2)
	#define RX6110_BIT_EXT_WADA BIT(3)
	#define RX6110_BIT_EXT_TE BIT(4)
	#define RX6110_BIT_EXT_USEL BIT(5)
	#define RX6110_BIT_EXT_FSEL0 BIT(6)
	#define RX6110_BIT_EXT_FSEL1 BIT(7)

	/* Flag Register (1Eh) bit positions */
	#define RX6110_BIT_FLAG_VLF BIT(1)
	#define RX6110_BIT_FLAG_AF BIT(3)
	#define RX6110_BIT_FLAG_TF BIT(4)
	#define RX6110_BIT_FLAG_UF BIT(5)

	/* Control Register (1Fh) bit positions */
	#define RX6110_BIT_CTRL_TBKE BIT(0)
	#define RX6110_BIT_CTRL_TBKON BIT(1)
	#define RX6110_BIT_CTRL_TSTP BIT(2)
	#define RX6110_BIT_CTRL_AIE BIT(3)
	#define RX6110_BIT_CTRL_TIE BIT(4)
	#define RX6110_BIT_CTRL_UIE BIT(5)
	#define RX6110_BIT_CTRL_STOP BIT(6)
	#define RX6110_BIT_CTRL_TEST BIT(7)

	enum {
	RTC_SEC = 0,
	RTC_MIN,
	RTC_HOUR,
	RTC_WDAY,
	RTC_MDAY,
	RTC_MONTH,
	RTC_YEAR,
	RTC_NR_TIME
	};

	#define RX6110_DRIVER_NAME "rx6110"

	struct rx6110_data {
	struct rtc_device *rtc;
	struct regmap *regmap;
	};

	/**
	* rx6110_rtc_tm_to_data - convert rtc_time to native time encoding
	*
	* @tm: holds date and time
	* @data: holds the encoding in rx6110 native form
	*/
	static int rx6110_rtc_tm_to_data(struct rtc_time tm, u8 data)
	{
	pr_debug("%s: date %ds %dm %dh %dmd %dm %dy\n", __func__,
	tm->tm_sec, tm->tm_min, tm->tm_hour,
	tm->tm_mday, tm->tm_mon, tm->tm_year);

	/*
	* The year in the RTC is a value between 0 and 99.
	* Assume that this represents the current century
	* and disregard all other values.
	*/
	if (tm->tm_year < 100 \|\| tm->tm_year >= 200)
	return -EINVAL;

	data[RTC_SEC] = bin2bcd(tm->tm_sec);
	data[RTC_MIN] = bin2bcd(tm->tm_min);
	data[RTC_HOUR] = bin2bcd(tm->tm_hour);
	data[RTC_WDAY] = BIT(bin2bcd(tm->tm_wday));
	data[RTC_MDAY] = bin2bcd(tm->tm_mday);
	data[RTC_MONTH] = bin2bcd(tm->tm_mon + 1);
	data[RTC_YEAR] = bin2bcd(tm->tm_year % 100);

	return 0;
	}

	/**
	* rx6110_data_to_rtc_tm - convert native time encoding to rtc_time
	*
	* @data: holds the encoding in rx6110 native form
	* @tm: holds date and time
	*/
	static int rx6110_data_to_rtc_tm(u8 data, struct rtc_time tm)
	{
	tm->tm_sec = bcd2bin(data[RTC_SEC] & 0x7f);
	tm->tm_min = bcd2bin(data[RTC_MIN] & 0x7f);
	/* only 24-hour clock */
	tm->tm_hour = bcd2bin(data[RTC_HOUR] & 0x3f);
	tm->tm_wday = ffs(data[RTC_WDAY] & 0x7f);
	tm->tm_mday = bcd2bin(data[RTC_MDAY] & 0x3f);
	tm->tm_mon = bcd2bin(data[RTC_MONTH] & 0x1f) - 1;
	tm->tm_year = bcd2bin(data[RTC_YEAR]) + 100;

	pr_debug("%s: date %ds %dm %dh %dmd %dm %dy\n", __func__,
	tm->tm_sec, tm->tm_min, tm->tm_hour,
	tm->tm_mday, tm->tm_mon, tm->tm_year);

	/*
	* The year in the RTC is a value between 0 and 99.
	* Assume that this represents the current century
	* and disregard all other values.
	*/
	if (tm->tm_year < 100 \|\| tm->tm_year >= 200)
	return -EINVAL;

	return 0;
	}

	/**
	* rx6110_set_time - set the current time in the rx6110 registers
	*
	* @dev: the rtc device in use
	* @tm: holds date and time
	*
	* BUG: The HW assumes every year that is a multiple of 4 to be a leap
	* year. Next time this is wrong is 2100, which will not be a leap year
	*
	* Note: If STOP is not set/cleared, the clock will start when the seconds
	* register is written
	*
	*/
	static int rx6110_set_time(struct device dev, struct rtc_time tm)
	{
	struct rx6110_data *rx6110 = dev_get_drvdata(dev);
	u8 data[RTC_NR_TIME];
	int ret;

	ret = rx6110_rtc_tm_to_data(tm, data);
	if (ret < 0)
	return ret;

	/* set STOP bit before changing clock/calendar */
	ret = regmap_update_bits(rx6110->regmap, RX6110_REG_CTRL,
	RX6110_BIT_CTRL_STOP, RX6110_BIT_CTRL_STOP);
	if (ret)
	return ret;

	ret = regmap_bulk_write(rx6110->regmap, RX6110_REG_SEC, data,
	RTC_NR_TIME);
	if (ret)
	return ret;

	/* The time in the RTC is valid. Be sure to have VLF cleared. */
	ret = regmap_update_bits(rx6110->regmap, RX6110_REG_FLAG,
	RX6110_BIT_FLAG_VLF, 0);
	if (ret)
	return ret;

	/* clear STOP bit after changing clock/calendar */
	ret = regmap_update_bits(rx6110->regmap, RX6110_REG_CTRL,
	RX6110_BIT_CTRL_STOP, 0);

	return ret;
	}

	/**
	* rx6110_get_time - get the current time from the rx6110 registers
	* @dev: the rtc device in use
	* @tm: holds date and time
	*/
	static int rx6110_get_time(struct device dev, struct rtc_time tm)
	{
	struct rx6110_data *rx6110 = dev_get_drvdata(dev);
	u8 data[RTC_NR_TIME];
	int flags;
	int ret;

	ret = regmap_read(rx6110->regmap, RX6110_REG_FLAG, &flags);
	if (ret)
	return -EINVAL;

	/* check for VLF Flag (set at power-on) */
	if ((flags & RX6110_BIT_FLAG_VLF)) {
	dev_warn(dev, "Voltage low, data is invalid.\n");
	return -EINVAL;
	}

	/* read registers to date */
	ret = regmap_bulk_read(rx6110->regmap, RX6110_REG_SEC, data,
	RTC_NR_TIME);
	if (ret)
	return ret;

	ret = rx6110_data_to_rtc_tm(data, tm);
	if (ret)
	return ret;

	dev_dbg(dev, "%s: date %ds %dm %dh %dmd %dm %dy\n", __func__,
	tm->tm_sec, tm->tm_min, tm->tm_hour,
	tm->tm_mday, tm->tm_mon, tm->tm_year);

	return rtc_valid_tm(tm);
	}

	static const struct reg_sequence rx6110_default_regs[] = {
	{ RX6110_REG_RES1, 0xB8 },
	{ RX6110_REG_RES2, 0x00 },
	{ RX6110_REG_RES3, 0x10 },
	{ RX6110_REG_IRQ, 0x00 },
	{ RX6110_REG_ALMIN, 0x00 },
	{ RX6110_REG_ALHOUR, 0x00 },
	{ RX6110_REG_ALWDAY, 0x00 },
	};

	/**
	* rx6110_init - initialize the rx6110 registers
	*
	* @rx6110: pointer to the rx6110 struct in use
	*
	*/
	static int rx6110_init(struct rx6110_data *rx6110)
	{
	struct rtc_device *rtc = rx6110->rtc;
	int flags;
	int ret;

	ret = regmap_update_bits(rx6110->regmap, RX6110_REG_EXT,
	RX6110_BIT_EXT_TE, 0);
	if (ret)
	return ret;

	ret = regmap_register_patch(rx6110->regmap, rx6110_default_regs,
	ARRAY_SIZE(rx6110_default_regs));
	if (ret)
	return ret;

	ret = regmap_read(rx6110->regmap, RX6110_REG_FLAG, &flags);
	if (ret)
	return ret;

	/* check for VLF Flag (set at power-on) */
	if ((flags & RX6110_BIT_FLAG_VLF))
	dev_warn(&rtc->dev, "Voltage low, data loss detected.\n");

	/* check for Alarm Flag */
	if (flags & RX6110_BIT_FLAG_AF)
	dev_warn(&rtc->dev, "An alarm may have been missed.\n");

	/* check for Periodic Timer Flag */
	if (flags & RX6110_BIT_FLAG_TF)
	dev_warn(&rtc->dev, "Periodic timer was detected\n");

	/* check for Update Timer Flag */
	if (flags & RX6110_BIT_FLAG_UF)
	dev_warn(&rtc->dev, "Update timer was detected\n");

	/* clear all flags BUT VLF */
	ret = regmap_update_bits(rx6110->regmap, RX6110_REG_FLAG,
	RX6110_BIT_FLAG_AF \|
	RX6110_BIT_FLAG_UF \|
	RX6110_BIT_FLAG_TF,
	0);

	return ret;
	}

	static const struct rtc_class_ops rx6110_rtc_ops = {
	.read_time = rx6110_get_time,
	.set_time = rx6110_set_time,
	};

	static struct regmap_config regmap_spi_config = {
	.reg_bits = 8,
	.val_bits = 8,
	.max_register = RX6110_REG_IRQ,
	.read_flag_mask = 0x80,
	};

	/**
	* rx6110_probe - initialize rtc driver
	* @spi: pointer to spi device
	*/
	static int rx6110_probe(struct spi_device *spi)
	{
	struct rx6110_data *rx6110;
	int err;

	if ((spi->bits_per_word && spi->bits_per_word != 8) \|\|
	(spi->max_speed_hz > 2000000) \|\|
	(spi->mode != (SPI_CS_HIGH \| SPI_CPOL \| SPI_CPHA))) {
	dev_warn(&spi->dev, "SPI settings: bits_per_word: %d, max_speed_hz: %d, mode: %xh\n",
	spi->bits_per_word, spi->max_speed_hz, spi->mode);
	dev_warn(&spi->dev, "driving device in an unsupported mode");
	}

	rx6110 = devm_kzalloc(&spi->dev, sizeof(*rx6110), GFP_KERNEL);
	if (!rx6110)
	return -ENOMEM;

	rx6110->regmap = devm_regmap_init_spi(spi, &regmap_spi_config);
	if (IS_ERR(rx6110->regmap)) {
	dev_err(&spi->dev, "regmap init failed for rtc rx6110\n");
	return PTR_ERR(rx6110->regmap);
	}

	spi_set_drvdata(spi, rx6110);

	rx6110->rtc = devm_rtc_device_register(&spi->dev,
	RX6110_DRIVER_NAME,
	&rx6110_rtc_ops, THIS_MODULE);

	if (IS_ERR(rx6110->rtc))
	return PTR_ERR(rx6110->rtc);

	err = rx6110_init(rx6110);
	if (err)
	return err;

	rx6110->rtc->max_user_freq = 1;

	return 0;
	}

	static int rx6110_remove(struct spi_device *spi)
	{
	return 0;
	}

	static const struct spi_device_id rx6110_id[] = {
	{ "rx6110", 0 },
	{ }
	};
	MODULE_DEVICE_TABLE(spi, rx6110_id);

	static struct spi_driver rx6110_driver = {
	.driver = {
	.name = RX6110_DRIVER_NAME,
	},
	.probe = rx6110_probe,
	.remove = rx6110_remove,
	.id_table = rx6110_id,
	};

	module_spi_driver(rx6110_driver);

	MODULE_AUTHOR("Val Krutov <val.krutov@erd.epson.com>");
	MODULE_DESCRIPTION("RX-6110 SA RTC driver");
	MODULE_LICENSE("GPL");