drivers/rtc/rtc-s35390a.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0-or-later
 /*
  * Seiko Instruments S-35390A RTC Driver
  *
  * Copyright (c) 2007 Byron Bradley
  */

 #include <linux/module.h>
 #include <linux/rtc.h>
 #include <linux/i2c.h>
 #include <linux/bitrev.h>
 #include <linux/bcd.h>
 #include <linux/slab.h>
 #include <linux/delay.h>

 #define S35390A_CMD_STATUS1	0
 #define S35390A_CMD_STATUS2	1
 #define S35390A_CMD_TIME1	2
 #define S35390A_CMD_TIME2	3
 #define S35390A_CMD_INT2_REG1	5

 #define S35390A_BYTE_YEAR	0
 #define S35390A_BYTE_MONTH	1
 #define S35390A_BYTE_DAY	2
 #define S35390A_BYTE_WDAY	3
 #define S35390A_BYTE_HOURS	4
 #define S35390A_BYTE_MINS	5
 #define S35390A_BYTE_SECS	6

 #define S35390A_ALRM_BYTE_WDAY	0
 #define S35390A_ALRM_BYTE_HOURS	1
 #define S35390A_ALRM_BYTE_MINS	2

 /* flags for STATUS1 */
 #define S35390A_FLAG_POC	BIT(0)
 #define S35390A_FLAG_BLD	BIT(1)
 #define S35390A_FLAG_INT2	BIT(2)
 #define S35390A_FLAG_24H	BIT(6)
 #define S35390A_FLAG_RESET	BIT(7)

 /* flag for STATUS2 */
 #define S35390A_FLAG_TEST	BIT(0)

 /* INT2 pin output mode */
 #define S35390A_INT2_MODE_MASK		0x0E
 #define S35390A_INT2_MODE_NOINTR	0x00
 #define S35390A_INT2_MODE_ALARM		BIT(1) /* INT2AE */
 #define S35390A_INT2_MODE_PMIN_EDG	BIT(2) /* INT2ME */
 #define S35390A_INT2_MODE_FREQ		BIT(3) /* INT2FE */
 #define S35390A_INT2_MODE_PMIN		(BIT(3) | BIT(2)) /* INT2FE | INT2ME */

 static const struct i2c_device_id s35390a_id[] = {
 	{ "s35390a", 0 },
 	{ }
 };
 MODULE_DEVICE_TABLE(i2c, s35390a_id);

 static const struct of_device_id s35390a_of_match[] = {
 	{ .compatible = "s35390a" },
 	{ .compatible = "sii,s35390a" },
 	{ }
 };
 MODULE_DEVICE_TABLE(of, s35390a_of_match);

 struct s35390a {
 	struct i2c_client *client[8];
 	struct rtc_device *rtc;
 	int twentyfourhour;
 };

 static int s35390a_set_reg(struct s35390a *s35390a, int reg, char *buf, int len)
 {
 	struct i2c_client *client = s35390a->client[reg];
 	struct i2c_msg msg[] = {
 		{
 			.addr = client->addr,
 			.len = len,
 			.buf = buf
 		},
 	};

 	if ((i2c_transfer(client->adapter, msg, 1)) != 1)
 		return -EIO;

 	return 0;
 }

 static int s35390a_get_reg(struct s35390a *s35390a, int reg, char *buf, int len)
 {
 	struct i2c_client *client = s35390a->client[reg];
 	struct i2c_msg msg[] = {
 		{
 			.addr = client->addr,
 			.flags = I2C_M_RD,
 			.len = len,
 			.buf = buf
 		},
 	};

 	if ((i2c_transfer(client->adapter, msg, 1)) != 1)
 		return -EIO;

 	return 0;
 }

 static int s35390a_init(struct s35390a *s35390a)
 {
 	u8 buf;
 	int ret;
 	unsigned initcount = 0;

 	/*
 	 * At least one of POC and BLD are set, so reinitialise chip. Keeping
 	 * this information in the hardware to know later that the time isn't
 	 * valid is unfortunately not possible because POC and BLD are cleared
 	 * on read. So the reset is best done now.
 	 *
 	 * The 24H bit is kept over reset, so set it already here.
 	 */
 initialize:
 	buf = S35390A_FLAG_RESET | S35390A_FLAG_24H;
 	ret = s35390a_set_reg(s35390a, S35390A_CMD_STATUS1, &buf, 1);

 	if (ret < 0)
 		return ret;

 	ret = s35390a_get_reg(s35390a, S35390A_CMD_STATUS1, &buf, 1);
 	if (ret < 0)
 		return ret;

 	if (buf & (S35390A_FLAG_POC | S35390A_FLAG_BLD)) {
 		/* Try up to five times to reset the chip */
 		if (initcount < 5) {
 			++initcount;
 			goto initialize;
 		} else
 			return -EIO;
 	}

 	return 1;
 }

 /*
  * Returns <0 on error, 0 if rtc is setup fine and 1 if the chip was reset.
  * To keep the information if an irq is pending, pass the value read from
  * STATUS1 to the caller.
  */
 static int s35390a_read_status(struct s35390a *s35390a, char *status1)
 {
 	int ret;

 	ret = s35390a_get_reg(s35390a, S35390A_CMD_STATUS1, status1, 1);
 	if (ret < 0)
 		return ret;

 	if (*status1 & S35390A_FLAG_POC) {
 		/*
 		 * Do not communicate for 0.5 seconds since the power-on
 		 * detection circuit is in operation.
 		 */
 		msleep(500);
 		return 1;
 	} else if (*status1 & S35390A_FLAG_BLD)
 		return 1;
 	/*
 	 * If both POC and BLD are unset everything is fine.
 	 */
 	return 0;
 }

 static int s35390a_disable_test_mode(struct s35390a *s35390a)
 {
 	char buf[1];

 	if (s35390a_get_reg(s35390a, S35390A_CMD_STATUS2, buf, sizeof(buf)) < 0)
 		return -EIO;

 	if (!(buf[0] & S35390A_FLAG_TEST))
 		return 0;

 	buf[0] &= ~S35390A_FLAG_TEST;
 	return s35390a_set_reg(s35390a, S35390A_CMD_STATUS2, buf, sizeof(buf));
 }

 static char s35390a_hr2reg(struct s35390a *s35390a, int hour)
 {
 	if (s35390a->twentyfourhour)
 		return bin2bcd(hour);

 	if (hour < 12)
 		return bin2bcd(hour);

 	return 0x40 | bin2bcd(hour - 12);
 }

 static int s35390a_reg2hr(struct s35390a *s35390a, char reg)
 {
 	unsigned hour;

 	if (s35390a->twentyfourhour)
 		return bcd2bin(reg & 0x3f);

 	hour = bcd2bin(reg & 0x3f);
 	if (reg & 0x40)
 		hour += 12;

 	return hour;
 }

 static int s35390a_rtc_set_time(struct device *dev, struct rtc_time *tm)
 {
 	struct i2c_client *client = to_i2c_client(dev);
 	struct s35390a	*s35390a = i2c_get_clientdata(client);
 	int i, err;
 	char buf[7], status;

 	dev_dbg(&client->dev, "%s: tm is secs=%d, mins=%d, hours=%d mday=%d, "
 		"mon=%d, year=%d, wday=%d\n", __func__, tm->tm_sec,
 		tm->tm_min, tm->tm_hour, tm->tm_mday, tm->tm_mon, tm->tm_year,
 		tm->tm_wday);

 	if (s35390a_read_status(s35390a, &status) == 1)
 		s35390a_init(s35390a);

 	buf[S35390A_BYTE_YEAR] = bin2bcd(tm->tm_year - 100);
 	buf[S35390A_BYTE_MONTH] = bin2bcd(tm->tm_mon + 1);
 	buf[S35390A_BYTE_DAY] = bin2bcd(tm->tm_mday);
 	buf[S35390A_BYTE_WDAY] = bin2bcd(tm->tm_wday);
 	buf[S35390A_BYTE_HOURS] = s35390a_hr2reg(s35390a, tm->tm_hour);
 	buf[S35390A_BYTE_MINS] = bin2bcd(tm->tm_min);
 	buf[S35390A_BYTE_SECS] = bin2bcd(tm->tm_sec);

 	/* This chip expects the bits of each byte to be in reverse order */
 	for (i = 0; i < 7; ++i)
 		buf[i] = bitrev8(buf[i]);

 	err = s35390a_set_reg(s35390a, S35390A_CMD_TIME1, buf, sizeof(buf));

 	return err;
 }

 static int s35390a_rtc_read_time(struct device *dev, struct rtc_time *tm)
 {
 	struct i2c_client *client = to_i2c_client(dev);
 	struct s35390a *s35390a = i2c_get_clientdata(client);
 	char buf[7], status;
 	int i, err;

 	if (s35390a_read_status(s35390a, &status) == 1)
 		return -EINVAL;

 	err = s35390a_get_reg(s35390a, S35390A_CMD_TIME1, buf, sizeof(buf));
 	if (err < 0)
 		return err;

 	/* This chip returns the bits of each byte in reverse order */
 	for (i = 0; i < 7; ++i)
 		buf[i] = bitrev8(buf[i]);

 	tm->tm_sec = bcd2bin(buf[S35390A_BYTE_SECS]);
 	tm->tm_min = bcd2bin(buf[S35390A_BYTE_MINS]);
 	tm->tm_hour = s35390a_reg2hr(s35390a, buf[S35390A_BYTE_HOURS]);
 	tm->tm_wday = bcd2bin(buf[S35390A_BYTE_WDAY]);
 	tm->tm_mday = bcd2bin(buf[S35390A_BYTE_DAY]);
 	tm->tm_mon = bcd2bin(buf[S35390A_BYTE_MONTH]) - 1;
 	tm->tm_year = bcd2bin(buf[S35390A_BYTE_YEAR]) + 100;

 	dev_dbg(&client->dev, "%s: tm is secs=%d, mins=%d, hours=%d, mday=%d, "
 		"mon=%d, year=%d, wday=%d\n", __func__, tm->tm_sec,
 		tm->tm_min, tm->tm_hour, tm->tm_mday, tm->tm_mon, tm->tm_year,
 		tm->tm_wday);

 	return 0;
 }

 static int s35390a_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alm)
 {
 	struct i2c_client *client = to_i2c_client(dev);
 	struct s35390a *s35390a = i2c_get_clientdata(client);
 	char buf[3], sts = 0;
 	int err, i;

 	dev_dbg(&client->dev, "%s: alm is secs=%d, mins=%d, hours=%d mday=%d, "\
 		"mon=%d, year=%d, wday=%d\n", __func__, alm->time.tm_sec,
 		alm->time.tm_min, alm->time.tm_hour, alm->time.tm_mday,
 		alm->time.tm_mon, alm->time.tm_year, alm->time.tm_wday);

 	if (alm->time.tm_sec != 0)
 		dev_warn(&client->dev, "Alarms are only supported on a per minute basis!\n");

 	/* disable interrupt (which deasserts the irq line) */
 	err = s35390a_set_reg(s35390a, S35390A_CMD_STATUS2, &sts, sizeof(sts));
 	if (err < 0)
 		return err;

 	/* clear pending interrupt (in STATUS1 only), if any */
 	err = s35390a_get_reg(s35390a, S35390A_CMD_STATUS1, &sts, sizeof(sts));
 	if (err < 0)
 		return err;

 	if (alm->enabled)
 		sts = S35390A_INT2_MODE_ALARM;
 	else
 		sts = S35390A_INT2_MODE_NOINTR;

 	/* set interupt mode*/
 	err = s35390a_set_reg(s35390a, S35390A_CMD_STATUS2, &sts, sizeof(sts));
 	if (err < 0)
 		return err;

 	if (alm->time.tm_wday != -1)
 		buf[S35390A_ALRM_BYTE_WDAY] = bin2bcd(alm->time.tm_wday) | 0x80;
 	else
 		buf[S35390A_ALRM_BYTE_WDAY] = 0;

 	buf[S35390A_ALRM_BYTE_HOURS] = s35390a_hr2reg(s35390a,
 			alm->time.tm_hour) | 0x80;
 	buf[S35390A_ALRM_BYTE_MINS] = bin2bcd(alm->time.tm_min) | 0x80;

 	if (alm->time.tm_hour >= 12)
 		buf[S35390A_ALRM_BYTE_HOURS] |= 0x40;

 	for (i = 0; i < 3; ++i)
 		buf[i] = bitrev8(buf[i]);

 	err = s35390a_set_reg(s35390a, S35390A_CMD_INT2_REG1, buf,
 								sizeof(buf));

 	return err;
 }

 static int s35390a_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alm)
 {
 	struct i2c_client *client = to_i2c_client(dev);
 	struct s35390a *s35390a = i2c_get_clientdata(client);
 	char buf[3], sts;
 	int i, err;

 	err = s35390a_get_reg(s35390a, S35390A_CMD_STATUS2, &sts, sizeof(sts));
 	if (err < 0)
 		return err;

 	if ((sts & S35390A_INT2_MODE_MASK) != S35390A_INT2_MODE_ALARM) {
 		/*
 		 * When the alarm isn't enabled, the register to configure
 		 * the alarm time isn't accessible.
 		 */
 		alm->enabled = 0;
 		return 0;
 	} else {
 		alm->enabled = 1;
 	}

 	err = s35390a_get_reg(s35390a, S35390A_CMD_INT2_REG1, buf, sizeof(buf));
 	if (err < 0)
 		return err;

 	/* This chip returns the bits of each byte in reverse order */
 	for (i = 0; i < 3; ++i)
 		buf[i] = bitrev8(buf[i]);

 	/*
 	 * B0 of the three matching registers is an enable flag. Iff it is set
 	 * the configured value is used for matching.
 	 */
 	if (buf[S35390A_ALRM_BYTE_WDAY] & 0x80)
 		alm->time.tm_wday =
 			bcd2bin(buf[S35390A_ALRM_BYTE_WDAY] & ~0x80);

 	if (buf[S35390A_ALRM_BYTE_HOURS] & 0x80)
 		alm->time.tm_hour =
 			s35390a_reg2hr(s35390a,
 				       buf[S35390A_ALRM_BYTE_HOURS] & ~0x80);

 	if (buf[S35390A_ALRM_BYTE_MINS] & 0x80)
 		alm->time.tm_min = bcd2bin(buf[S35390A_ALRM_BYTE_MINS] & ~0x80);

 	/* alarm triggers always at s=0 */
 	alm->time.tm_sec = 0;

 	dev_dbg(&client->dev, "%s: alm is mins=%d, hours=%d, wday=%d\n",
 			__func__, alm->time.tm_min, alm->time.tm_hour,
 			alm->time.tm_wday);

 	return 0;
 }

 static int s35390a_rtc_ioctl(struct device *dev, unsigned int cmd,
 			     unsigned long arg)
 {
 	struct i2c_client *client = to_i2c_client(dev);
 	struct s35390a *s35390a = i2c_get_clientdata(client);
 	char sts;
 	int err;

 	switch (cmd) {
 	case RTC_VL_READ:
 		/* s35390a_reset set lowvoltage flag and init RTC if needed */
 		err = s35390a_read_status(s35390a, &sts);
 		if (err < 0)
 			return err;
 		if (copy_to_user((void __user *)arg, &err, sizeof(int)))
 			return -EFAULT;
 		break;
 	case RTC_VL_CLR:
 		/* update flag and clear register */
 		err = s35390a_init(s35390a);
 		if (err < 0)
 			return err;
 		break;
 	default:
 		return -ENOIOCTLCMD;
 	}

 	return 0;
 }

 static const struct rtc_class_ops s35390a_rtc_ops = {
 	.read_time	= s35390a_rtc_read_time,
 	.set_time	= s35390a_rtc_set_time,
 	.set_alarm	= s35390a_rtc_set_alarm,
 	.read_alarm	= s35390a_rtc_read_alarm,
 	.ioctl          = s35390a_rtc_ioctl,
 };

 static int s35390a_probe(struct i2c_client *client,
 			 const struct i2c_device_id *id)
 {
 	int err, err_read;
 	unsigned int i;
 	struct s35390a *s35390a;
 	char buf, status1;
 	struct device *dev = &client->dev;

 	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
 		return -ENODEV;

 	s35390a = devm_kzalloc(dev, sizeof(struct s35390a), GFP_KERNEL);
 	if (!s35390a)
 		return -ENOMEM;

 	s35390a->client[0] = client;
 	i2c_set_clientdata(client, s35390a);

 	/* This chip uses multiple addresses, use dummy devices for them */
 	for (i = 1; i < 8; ++i) {
 		s35390a->client[i] = devm_i2c_new_dummy_device(dev,
 							       client->adapter,
 							       client->addr + i);
 		if (IS_ERR(s35390a->client[i])) {
 			dev_err(dev, "Address %02x unavailable\n",
 				client->addr + i);
 			return PTR_ERR(s35390a->client[i]);
 		}
 	}

 	s35390a->rtc = devm_rtc_allocate_device(dev);
 	if (IS_ERR(s35390a->rtc))
 		return PTR_ERR(s35390a->rtc);

 	err_read = s35390a_read_status(s35390a, &status1);
 	if (err_read < 0) {
 		dev_err(dev, "error resetting chip\n");
 		return err_read;
 	}

 	if (status1 & S35390A_FLAG_24H)
 		s35390a->twentyfourhour = 1;
 	else
 		s35390a->twentyfourhour = 0;

 	if (status1 & S35390A_FLAG_INT2) {
 		/* disable alarm (and maybe test mode) */
 		buf = 0;
 		err = s35390a_set_reg(s35390a, S35390A_CMD_STATUS2, &buf, 1);
 		if (err < 0) {
 			dev_err(dev, "error disabling alarm");
 			return err;
 		}
 	} else {
 		err = s35390a_disable_test_mode(s35390a);
 		if (err < 0) {
 			dev_err(dev, "error disabling test mode\n");
 			return err;
 		}
 	}

 	device_set_wakeup_capable(dev, 1);

 	s35390a->rtc->ops = &s35390a_rtc_ops;
 	s35390a->rtc->range_min = RTC_TIMESTAMP_BEGIN_2000;
 	s35390a->rtc->range_max = RTC_TIMESTAMP_END_2099;

 	/* supports per-minute alarms only, therefore set uie_unsupported */
 	s35390a->rtc->uie_unsupported = 1;

 	if (status1 & S35390A_FLAG_INT2)
 		rtc_update_irq(s35390a->rtc, 1, RTC_AF);

 	return devm_rtc_register_device(s35390a->rtc);
 }

 static struct i2c_driver s35390a_driver = {
 	.driver		= {
 		.name	= "rtc-s35390a",
 		.of_match_table = of_match_ptr(s35390a_of_match),
 	},
 	.probe		= s35390a_probe,
 	.id_table	= s35390a_id,
 };

 module_i2c_driver(s35390a_driver);

 MODULE_AUTHOR("Byron Bradley <byron.bbradley@gmail.com>");
 MODULE_DESCRIPTION("S35390A RTC driver");
 MODULE_LICENSE("GPL");
	// SPDX-License-Identifier: GPL-2.0-or-later
	/*
	* Seiko Instruments S-35390A RTC Driver
	*
	* Copyright (c) 2007 Byron Bradley
	*/

	#include <linux/module.h>
	#include <linux/rtc.h>
	#include <linux/i2c.h>
	#include <linux/bitrev.h>
	#include <linux/bcd.h>
	#include <linux/slab.h>
	#include <linux/delay.h>

	#define S35390A_CMD_STATUS1 0
	#define S35390A_CMD_STATUS2 1
	#define S35390A_CMD_TIME1 2
	#define S35390A_CMD_TIME2 3
	#define S35390A_CMD_INT2_REG1 5

	#define S35390A_BYTE_YEAR 0
	#define S35390A_BYTE_MONTH 1
	#define S35390A_BYTE_DAY 2
	#define S35390A_BYTE_WDAY 3
	#define S35390A_BYTE_HOURS 4
	#define S35390A_BYTE_MINS 5
	#define S35390A_BYTE_SECS 6

	#define S35390A_ALRM_BYTE_WDAY 0
	#define S35390A_ALRM_BYTE_HOURS 1
	#define S35390A_ALRM_BYTE_MINS 2

	/* flags for STATUS1 */
	#define S35390A_FLAG_POC BIT(0)
	#define S35390A_FLAG_BLD BIT(1)
	#define S35390A_FLAG_INT2 BIT(2)
	#define S35390A_FLAG_24H BIT(6)
	#define S35390A_FLAG_RESET BIT(7)

	/* flag for STATUS2 */
	#define S35390A_FLAG_TEST BIT(0)

	/* INT2 pin output mode */
	#define S35390A_INT2_MODE_MASK 0x0E
	#define S35390A_INT2_MODE_NOINTR 0x00
	#define S35390A_INT2_MODE_ALARM BIT(1) /* INT2AE */
	#define S35390A_INT2_MODE_PMIN_EDG BIT(2) /* INT2ME */
	#define S35390A_INT2_MODE_FREQ BIT(3) /* INT2FE */
	#define S35390A_INT2_MODE_PMIN (BIT(3) \| BIT(2)) /* INT2FE \| INT2ME */

	static const struct i2c_device_id s35390a_id[] = {
	{ "s35390a", 0 },
	{ }
	};
	MODULE_DEVICE_TABLE(i2c, s35390a_id);

	static const struct of_device_id s35390a_of_match[] = {
	{ .compatible = "s35390a" },
	{ .compatible = "sii,s35390a" },
	{ }
	};
	MODULE_DEVICE_TABLE(of, s35390a_of_match);

	struct s35390a {
	struct i2c_client *client[8];
	struct rtc_device *rtc;
	int twentyfourhour;
	};

	static int s35390a_set_reg(struct s35390a s35390a, int reg, char buf, int len)
	{
	struct i2c_client *client = s35390a->client[reg];
	struct i2c_msg msg[] = {
	{
	.addr = client->addr,
	.len = len,
	.buf = buf
	},
	};

	if ((i2c_transfer(client->adapter, msg, 1)) != 1)
	return -EIO;

	return 0;
	}

	static int s35390a_get_reg(struct s35390a s35390a, int reg, char buf, int len)
	{
	struct i2c_client *client = s35390a->client[reg];
	struct i2c_msg msg[] = {
	{
	.addr = client->addr,
	.flags = I2C_M_RD,
	.len = len,
	.buf = buf
	},
	};

	if ((i2c_transfer(client->adapter, msg, 1)) != 1)
	return -EIO;

	return 0;
	}

	static int s35390a_init(struct s35390a *s35390a)
	{
	u8 buf;
	int ret;
	unsigned initcount = 0;

	/*
	* At least one of POC and BLD are set, so reinitialise chip. Keeping
	* this information in the hardware to know later that the time isn't
	* valid is unfortunately not possible because POC and BLD are cleared
	* on read. So the reset is best done now.
	*
	* The 24H bit is kept over reset, so set it already here.
	*/
	initialize:
	buf = S35390A_FLAG_RESET \| S35390A_FLAG_24H;
	ret = s35390a_set_reg(s35390a, S35390A_CMD_STATUS1, &buf, 1);

	if (ret < 0)
	return ret;

	ret = s35390a_get_reg(s35390a, S35390A_CMD_STATUS1, &buf, 1);
	if (ret < 0)
	return ret;

	if (buf & (S35390A_FLAG_POC \| S35390A_FLAG_BLD)) {
	/* Try up to five times to reset the chip */
	if (initcount < 5) {
	++initcount;
	goto initialize;
	} else
	return -EIO;
	}

	return 1;
	}

	/*
	* Returns <0 on error, 0 if rtc is setup fine and 1 if the chip was reset.
	* To keep the information if an irq is pending, pass the value read from
	* STATUS1 to the caller.
	*/
	static int s35390a_read_status(struct s35390a s35390a, char status1)
	{
	int ret;

	ret = s35390a_get_reg(s35390a, S35390A_CMD_STATUS1, status1, 1);
	if (ret < 0)
	return ret;

	if (*status1 & S35390A_FLAG_POC) {
	/*
	* Do not communicate for 0.5 seconds since the power-on
	* detection circuit is in operation.
	*/
	msleep(500);
	return 1;
	} else if (*status1 & S35390A_FLAG_BLD)
	return 1;
	/*
	* If both POC and BLD are unset everything is fine.
	*/
	return 0;
	}

	static int s35390a_disable_test_mode(struct s35390a *s35390a)
	{
	char buf[1];

	if (s35390a_get_reg(s35390a, S35390A_CMD_STATUS2, buf, sizeof(buf)) < 0)
	return -EIO;

	if (!(buf[0] & S35390A_FLAG_TEST))
	return 0;

	buf[0] &= ~S35390A_FLAG_TEST;
	return s35390a_set_reg(s35390a, S35390A_CMD_STATUS2, buf, sizeof(buf));
	}

	static char s35390a_hr2reg(struct s35390a *s35390a, int hour)
	{
	if (s35390a->twentyfourhour)
	return bin2bcd(hour);

	if (hour < 12)
	return bin2bcd(hour);

	return 0x40 \| bin2bcd(hour - 12);
	}

	static int s35390a_reg2hr(struct s35390a *s35390a, char reg)
	{
	unsigned hour;

	if (s35390a->twentyfourhour)
	return bcd2bin(reg & 0x3f);

	hour = bcd2bin(reg & 0x3f);
	if (reg & 0x40)
	hour += 12;

	return hour;
	}

	static int s35390a_rtc_set_time(struct device dev, struct rtc_time tm)
	{
	struct i2c_client *client = to_i2c_client(dev);
	struct s35390a *s35390a = i2c_get_clientdata(client);
	int i, err;
	char buf[7], status;

	dev_dbg(&client->dev, "%s: tm is secs=%d, mins=%d, hours=%d mday=%d, "
	"mon=%d, year=%d, wday=%d\n", __func__, tm->tm_sec,
	tm->tm_min, tm->tm_hour, tm->tm_mday, tm->tm_mon, tm->tm_year,
	tm->tm_wday);

	if (s35390a_read_status(s35390a, &status) == 1)
	s35390a_init(s35390a);

	buf[S35390A_BYTE_YEAR] = bin2bcd(tm->tm_year - 100);
	buf[S35390A_BYTE_MONTH] = bin2bcd(tm->tm_mon + 1);
	buf[S35390A_BYTE_DAY] = bin2bcd(tm->tm_mday);
	buf[S35390A_BYTE_WDAY] = bin2bcd(tm->tm_wday);
	buf[S35390A_BYTE_HOURS] = s35390a_hr2reg(s35390a, tm->tm_hour);
	buf[S35390A_BYTE_MINS] = bin2bcd(tm->tm_min);
	buf[S35390A_BYTE_SECS] = bin2bcd(tm->tm_sec);

	/* This chip expects the bits of each byte to be in reverse order */
	for (i = 0; i < 7; ++i)
	buf[i] = bitrev8(buf[i]);

	err = s35390a_set_reg(s35390a, S35390A_CMD_TIME1, buf, sizeof(buf));

	return err;
	}

	static int s35390a_rtc_read_time(struct device dev, struct rtc_time tm)
	{
	struct i2c_client *client = to_i2c_client(dev);
	struct s35390a *s35390a = i2c_get_clientdata(client);
	char buf[7], status;
	int i, err;

	if (s35390a_read_status(s35390a, &status) == 1)
	return -EINVAL;

	err = s35390a_get_reg(s35390a, S35390A_CMD_TIME1, buf, sizeof(buf));
	if (err < 0)
	return err;

	/* This chip returns the bits of each byte in reverse order */
	for (i = 0; i < 7; ++i)
	buf[i] = bitrev8(buf[i]);

	tm->tm_sec = bcd2bin(buf[S35390A_BYTE_SECS]);
	tm->tm_min = bcd2bin(buf[S35390A_BYTE_MINS]);
	tm->tm_hour = s35390a_reg2hr(s35390a, buf[S35390A_BYTE_HOURS]);
	tm->tm_wday = bcd2bin(buf[S35390A_BYTE_WDAY]);
	tm->tm_mday = bcd2bin(buf[S35390A_BYTE_DAY]);
	tm->tm_mon = bcd2bin(buf[S35390A_BYTE_MONTH]) - 1;
	tm->tm_year = bcd2bin(buf[S35390A_BYTE_YEAR]) + 100;

	dev_dbg(&client->dev, "%s: tm is secs=%d, mins=%d, hours=%d, mday=%d, "
	"mon=%d, year=%d, wday=%d\n", __func__, tm->tm_sec,
	tm->tm_min, tm->tm_hour, tm->tm_mday, tm->tm_mon, tm->tm_year,
	tm->tm_wday);

	return 0;
	}

	static int s35390a_rtc_set_alarm(struct device dev, struct rtc_wkalrm alm)
	{
	struct i2c_client *client = to_i2c_client(dev);
	struct s35390a *s35390a = i2c_get_clientdata(client);
	char buf[3], sts = 0;
	int err, i;

	dev_dbg(&client->dev, "%s: alm is secs=%d, mins=%d, hours=%d mday=%d, "\
	"mon=%d, year=%d, wday=%d\n", __func__, alm->time.tm_sec,
	alm->time.tm_min, alm->time.tm_hour, alm->time.tm_mday,
	alm->time.tm_mon, alm->time.tm_year, alm->time.tm_wday);

	if (alm->time.tm_sec != 0)
	dev_warn(&client->dev, "Alarms are only supported on a per minute basis!\n");

	/* disable interrupt (which deasserts the irq line) */
	err = s35390a_set_reg(s35390a, S35390A_CMD_STATUS2, &sts, sizeof(sts));
	if (err < 0)
	return err;

	/* clear pending interrupt (in STATUS1 only), if any */
	err = s35390a_get_reg(s35390a, S35390A_CMD_STATUS1, &sts, sizeof(sts));
	if (err < 0)
	return err;

	if (alm->enabled)
	sts = S35390A_INT2_MODE_ALARM;
	else
	sts = S35390A_INT2_MODE_NOINTR;

	/* set interupt mode*/
	err = s35390a_set_reg(s35390a, S35390A_CMD_STATUS2, &sts, sizeof(sts));
	if (err < 0)
	return err;

	if (alm->time.tm_wday != -1)
	buf[S35390A_ALRM_BYTE_WDAY] = bin2bcd(alm->time.tm_wday) \| 0x80;
	else
	buf[S35390A_ALRM_BYTE_WDAY] = 0;

	buf[S35390A_ALRM_BYTE_HOURS] = s35390a_hr2reg(s35390a,
	alm->time.tm_hour) \| 0x80;
	buf[S35390A_ALRM_BYTE_MINS] = bin2bcd(alm->time.tm_min) \| 0x80;

	if (alm->time.tm_hour >= 12)
	buf[S35390A_ALRM_BYTE_HOURS] \|= 0x40;

	for (i = 0; i < 3; ++i)
	buf[i] = bitrev8(buf[i]);

	err = s35390a_set_reg(s35390a, S35390A_CMD_INT2_REG1, buf,
	sizeof(buf));

	return err;
	}

	static int s35390a_rtc_read_alarm(struct device dev, struct rtc_wkalrm alm)
	{
	struct i2c_client *client = to_i2c_client(dev);
	struct s35390a *s35390a = i2c_get_clientdata(client);
	char buf[3], sts;
	int i, err;

	err = s35390a_get_reg(s35390a, S35390A_CMD_STATUS2, &sts, sizeof(sts));
	if (err < 0)
	return err;

	if ((sts & S35390A_INT2_MODE_MASK) != S35390A_INT2_MODE_ALARM) {
	/*
	* When the alarm isn't enabled, the register to configure
	* the alarm time isn't accessible.
	*/
	alm->enabled = 0;
	return 0;
	} else {
	alm->enabled = 1;
	}

	err = s35390a_get_reg(s35390a, S35390A_CMD_INT2_REG1, buf, sizeof(buf));
	if (err < 0)
	return err;

	/* This chip returns the bits of each byte in reverse order */
	for (i = 0; i < 3; ++i)
	buf[i] = bitrev8(buf[i]);

	/*
	* B0 of the three matching registers is an enable flag. Iff it is set
	* the configured value is used for matching.
	*/
	if (buf[S35390A_ALRM_BYTE_WDAY] & 0x80)
	alm->time.tm_wday =
	bcd2bin(buf[S35390A_ALRM_BYTE_WDAY] & ~0x80);

	if (buf[S35390A_ALRM_BYTE_HOURS] & 0x80)
	alm->time.tm_hour =
	s35390a_reg2hr(s35390a,
	buf[S35390A_ALRM_BYTE_HOURS] & ~0x80);

	if (buf[S35390A_ALRM_BYTE_MINS] & 0x80)
	alm->time.tm_min = bcd2bin(buf[S35390A_ALRM_BYTE_MINS] & ~0x80);

	/* alarm triggers always at s=0 */
	alm->time.tm_sec = 0;

	dev_dbg(&client->dev, "%s: alm is mins=%d, hours=%d, wday=%d\n",
	__func__, alm->time.tm_min, alm->time.tm_hour,
	alm->time.tm_wday);

	return 0;
	}

	static int s35390a_rtc_ioctl(struct device *dev, unsigned int cmd,
	unsigned long arg)
	{
	struct i2c_client *client = to_i2c_client(dev);
	struct s35390a *s35390a = i2c_get_clientdata(client);
	char sts;
	int err;

	switch (cmd) {
	case RTC_VL_READ:
	/* s35390a_reset set lowvoltage flag and init RTC if needed */
	err = s35390a_read_status(s35390a, &sts);
	if (err < 0)
	return err;
	if (copy_to_user((void __user *)arg, &err, sizeof(int)))
	return -EFAULT;
	break;
	case RTC_VL_CLR:
	/* update flag and clear register */
	err = s35390a_init(s35390a);
	if (err < 0)
	return err;
	break;
	default:
	return -ENOIOCTLCMD;
	}

	return 0;
	}

	static const struct rtc_class_ops s35390a_rtc_ops = {
	.read_time = s35390a_rtc_read_time,
	.set_time = s35390a_rtc_set_time,
	.set_alarm = s35390a_rtc_set_alarm,
	.read_alarm = s35390a_rtc_read_alarm,
	.ioctl = s35390a_rtc_ioctl,
	};

	static int s35390a_probe(struct i2c_client *client,
	const struct i2c_device_id *id)
	{
	int err, err_read;
	unsigned int i;
	struct s35390a *s35390a;
	char buf, status1;
	struct device *dev = &client->dev;

	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
	return -ENODEV;

	s35390a = devm_kzalloc(dev, sizeof(struct s35390a), GFP_KERNEL);
	if (!s35390a)
	return -ENOMEM;

	s35390a->client[0] = client;
	i2c_set_clientdata(client, s35390a);

	/* This chip uses multiple addresses, use dummy devices for them */
	for (i = 1; i < 8; ++i) {
	s35390a->client[i] = devm_i2c_new_dummy_device(dev,
	client->adapter,
	client->addr + i);
	if (IS_ERR(s35390a->client[i])) {
	dev_err(dev, "Address %02x unavailable\n",
	client->addr + i);
	return PTR_ERR(s35390a->client[i]);
	}
	}

	s35390a->rtc = devm_rtc_allocate_device(dev);
	if (IS_ERR(s35390a->rtc))
	return PTR_ERR(s35390a->rtc);

	err_read = s35390a_read_status(s35390a, &status1);
	if (err_read < 0) {
	dev_err(dev, "error resetting chip\n");
	return err_read;
	}

	if (status1 & S35390A_FLAG_24H)
	s35390a->twentyfourhour = 1;
	else
	s35390a->twentyfourhour = 0;

	if (status1 & S35390A_FLAG_INT2) {
	/* disable alarm (and maybe test mode) */
	buf = 0;
	err = s35390a_set_reg(s35390a, S35390A_CMD_STATUS2, &buf, 1);
	if (err < 0) {
	dev_err(dev, "error disabling alarm");
	return err;
	}
	} else {
	err = s35390a_disable_test_mode(s35390a);
	if (err < 0) {
	dev_err(dev, "error disabling test mode\n");
	return err;
	}
	}

	device_set_wakeup_capable(dev, 1);

	s35390a->rtc->ops = &s35390a_rtc_ops;
	s35390a->rtc->range_min = RTC_TIMESTAMP_BEGIN_2000;
	s35390a->rtc->range_max = RTC_TIMESTAMP_END_2099;

	/* supports per-minute alarms only, therefore set uie_unsupported */
	s35390a->rtc->uie_unsupported = 1;

	if (status1 & S35390A_FLAG_INT2)
	rtc_update_irq(s35390a->rtc, 1, RTC_AF);

	return devm_rtc_register_device(s35390a->rtc);
	}

	static struct i2c_driver s35390a_driver = {
	.driver = {
	.name = "rtc-s35390a",
	.of_match_table = of_match_ptr(s35390a_of_match),
	},
	.probe = s35390a_probe,
	.id_table = s35390a_id,
	};

	module_i2c_driver(s35390a_driver);

	MODULE_AUTHOR("Byron Bradley <byron.bbradley@gmail.com>");
	MODULE_DESCRIPTION("S35390A RTC driver");
	MODULE_LICENSE("GPL");