rtc: add stand-alone driver for RX8025 chip

Add support for the Epson RX-8025SA/NB RTC chips.  It includes support for
alarms, periodic interrupts (1 Hz) and clock precision adjustment.

For clock precision adjustment, the SYSFS file "clock_adjust_ppb" gets
created in "/sys/class/rtc/rtcX/device".  It permits to set and get the
clock adjustment in ppb (parts per billion), e.g.:

  # echo -183000 > /sys/class/rtc/rtc0/device/clock_adjust_ppb
  # cat /sys/class/rtc/rtc0/device/clock_adjust_ppb
  -183000

This allows to compensate temperature dependent clock drifts.  According
to the RX8025 SA/NB application manual the frequency and temperature
characteristics can be approximated using the following equation:

  df = a * (ut - t)**2

  df: Frequency deviation in any temperature
  a : Coefficient = (-35 +-5) * 10**-9
  ut: Ultimate temperature in degree = +25 +-5 degree
  t : Any temperature in degree

Signed-off-by: Wolfgang Grandegger <wg@grandegger.com>
Signed-off-by: Sergei Poselenov <sposelenov@emcraft.com>
Signed-off-by: Yuri Tikhonov <yur@emcraft.com>
Signed-off-by: Dmitry Rakhchev <rda@emcraft.com>
Signed-off-by: Matthias Fuchs <matthias.fuchs@esd.eu>
Acked-by: Jean Delvare <khali@linux-fr.org>
Signed-off-by: Alessandro Zummo <a.zummo@towertech.it>
Cc: David Brownell <david-b@pacbell.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

3 files changed, 698 insertions, 0 deletions

diff --git a/drivers/rtc/Kconfig b/drivers/rtc/Kconfig
index 277d35d..81adbdb 100644
--- a/drivers/rtc/Kconfig
+++ b/drivers/rtc/Kconfig
@@ -296,6 +296,15 @@ config RTC_DRV_RX8581
 	  This driver can also be built as a module. If so the module
 	  will be called rtc-rx8581.
 
+config RTC_DRV_RX8025
+	tristate "Epson RX-8025SA/NB"
+	help
+	  If you say yes here you get support for the Epson
+	  RX-8025SA/NB RTC chips.
+
+	  This driver can also be built as a module. If so, the module
+	  will be called rtc-rx8025.
+
 endif # I2C
 
 comment "SPI RTC drivers"
diff --git a/drivers/rtc/Makefile b/drivers/rtc/Makefile
index 6c0639a..3c0f2b2 100644
--- a/drivers/rtc/Makefile
+++ b/drivers/rtc/Makefile
@@ -62,6 +62,7 @@ obj-$(CONFIG_RTC_DRV_R9701)	+= rtc-r9701.o
 obj-$(CONFIG_RTC_DRV_RS5C313)	+= rtc-rs5c313.o
 obj-$(CONFIG_RTC_DRV_RS5C348)	+= rtc-rs5c348.o
 obj-$(CONFIG_RTC_DRV_RS5C372)	+= rtc-rs5c372.o
+obj-$(CONFIG_RTC_DRV_RX8025)	+= rtc-rx8025.o
 obj-$(CONFIG_RTC_DRV_RX8581)	+= rtc-rx8581.o
 obj-$(CONFIG_RTC_DRV_S35390A)	+= rtc-s35390a.o
 obj-$(CONFIG_RTC_DRV_S3C)	+= rtc-s3c.o
diff --git a/drivers/rtc/rtc-rx8025.c b/drivers/rtc/rtc-rx8025.c
new file mode 100644
index 0000000..b1a29bc
--- /dev/null
+++ b/drivers/rtc/rtc-rx8025.c
@@ -0,0 +1,688 @@
+/*
+ * Driver for Epson's RTC module RX-8025 SA/NB
+ *
+ * Copyright (C) 2009 Wolfgang Grandegger <wg@grandegger.com>
+ *
+ * Copyright (C) 2005 by Digi International Inc.
+ * All rights reserved.
+ *
+ * Modified by fengjh at rising.com.cn
+ * <http://lists.lm-sensors.org/mailman/listinfo/lm-sensors>
+ * 2006.11
+ *
+ * Code cleanup by Sergei Poselenov, <sposelenov@emcraft.com>
+ * Converted to new style by Wolfgang Grandegger <wg@grandegger.com>
+ * Alarm and periodic interrupt added by Dmitry Rakhchev <rda@emcraft.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/kernel.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/bcd.h>
+#include <linux/i2c.h>
+#include <linux/list.h>
+#include <linux/rtc.h>
+
+/* Register definitions */
+#define RX8025_REG_SEC		0x00
+#define RX8025_REG_MIN		0x01
+#define RX8025_REG_HOUR		0x02
+#define RX8025_REG_WDAY		0x03
+#define RX8025_REG_MDAY		0x04
+#define RX8025_REG_MONTH	0x05
+#define RX8025_REG_YEAR		0x06
+#define RX8025_REG_DIGOFF	0x07
+#define RX8025_REG_ALWMIN	0x08
+#define RX8025_REG_ALWHOUR	0x09
+#define RX8025_REG_ALWWDAY	0x0a
+#define RX8025_REG_ALDMIN	0x0b
+#define RX8025_REG_ALDHOUR	0x0c
+/* 0x0d is reserved */
+#define RX8025_REG_CTRL1	0x0e
+#define RX8025_REG_CTRL2	0x0f
+
+#define RX8025_BIT_CTRL1_CT	(7 << 0)
+/* 1 Hz periodic level irq */
+#define RX8025_BIT_CTRL1_CT_1HZ	4
+#define RX8025_BIT_CTRL1_TEST	(1 << 3)
+#define RX8025_BIT_CTRL1_1224	(1 << 5)
+#define RX8025_BIT_CTRL1_DALE	(1 << 6)
+#define RX8025_BIT_CTRL1_WALE	(1 << 7)
+
+#define RX8025_BIT_CTRL2_DAFG	(1 << 0)
+#define RX8025_BIT_CTRL2_WAFG	(1 << 1)
+#define RX8025_BIT_CTRL2_CTFG	(1 << 2)
+#define RX8025_BIT_CTRL2_PON	(1 << 4)
+#define RX8025_BIT_CTRL2_XST	(1 << 5)
+#define RX8025_BIT_CTRL2_VDET	(1 << 6)
+
+/* Clock precision adjustment */
+#define RX8025_ADJ_RESOLUTION	3050 /* in ppb */
+#define RX8025_ADJ_DATA_MAX	62
+#define RX8025_ADJ_DATA_MIN	-62
+
+static const struct i2c_device_id rx8025_id[] = {
+	{ "rx8025", 0 },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, rx8025_id);
+
+struct rx8025_data {
+	struct i2c_client *client;
+	struct rtc_device *rtc;
+	struct work_struct work;
+	u8 ctrl1;
+	unsigned exiting:1;
+};
+
+static int rx8025_read_reg(struct i2c_client *client, int number, u8 *value)
+{
+	int ret = i2c_smbus_read_byte_data(client, (number << 4) | 0x08);
+
+	if (ret < 0) {
+		dev_err(&client->dev, "Unable to read register #%d\n", number);
+		return ret;
+	}
+
+	*value = ret;
+	return 0;
+}
+
+static int rx8025_read_regs(struct i2c_client *client,
+			    int number, u8 length, u8 *values)
+{
+	int ret = i2c_smbus_read_i2c_block_data(client, (number << 4) | 0x08,
+						length, values);
+
+	if (ret != length) {
+		dev_err(&client->dev, "Unable to read registers #%d..#%d\n",
+			number, number + length - 1);
+		return ret < 0 ? ret : -EIO;
+	}
+
+	return 0;
+}
+
+static int rx8025_write_reg(struct i2c_client *client, int number, u8 value)
+{
+	int ret = i2c_smbus_write_byte_data(client, number << 4, value);
+
+	if (ret)
+		dev_err(&client->dev, "Unable to write register #%d\n",
+			number);
+
+	return ret;
+}
+
+static int rx8025_write_regs(struct i2c_client *client,
+			     int number, u8 length, u8 *values)
+{
+	int ret = i2c_smbus_write_i2c_block_data(client, (number << 4) | 0x08,
+						 length, values);
+
+	if (ret)
+		dev_err(&client->dev, "Unable to write registers #%d..#%d\n",
+			number, number + length - 1);
+
+	return ret;
+}
+
+static irqreturn_t rx8025_irq(int irq, void *dev_id)
+{
+	struct i2c_client *client = dev_id;
+	struct rx8025_data *rx8025 = i2c_get_clientdata(client);
+
+	disable_irq_nosync(irq);
+	schedule_work(&rx8025->work);
+	return IRQ_HANDLED;
+}
+
+static void rx8025_work(struct work_struct *work)
+{
+	struct rx8025_data *rx8025 = container_of(work, struct rx8025_data,
+						  work);
+	struct i2c_client *client = rx8025->client;
+	struct mutex *lock = &rx8025->rtc->ops_lock;
+	u8 status;
+
+	mutex_lock(lock);
+
+	if (rx8025_read_reg(client, RX8025_REG_CTRL2, &status))
+		goto out;
+
+	if (!(status & RX8025_BIT_CTRL2_XST))
+		dev_warn(&client->dev, "Oscillation stop was detected,"
+			 "you may have to readjust the clock\n");
+
+	if (status & RX8025_BIT_CTRL2_CTFG) {
+		/* periodic */
+		status &= ~RX8025_BIT_CTRL2_CTFG;
+		local_irq_disable();
+		rtc_update_irq(rx8025->rtc, 1, RTC_PF | RTC_IRQF);
+		local_irq_enable();
+	}
+
+	if (status & RX8025_BIT_CTRL2_DAFG) {
+		/* alarm */
+		status &= RX8025_BIT_CTRL2_DAFG;
+		if (rx8025_write_reg(client, RX8025_REG_CTRL1,
+				     rx8025->ctrl1 & ~RX8025_BIT_CTRL1_DALE))
+			goto out;
+		local_irq_disable();
+		rtc_update_irq(rx8025->rtc, 1, RTC_AF | RTC_IRQF);
+		local_irq_enable();
+	}
+
+	/* acknowledge IRQ */
+	rx8025_write_reg(client, RX8025_REG_CTRL2,
+			 status | RX8025_BIT_CTRL2_XST);
+
+out:
+	if (!rx8025->exiting)
+		enable_irq(client->irq);
+
+	mutex_unlock(lock);
+}
+
+static int rx8025_get_time(struct device *dev, struct rtc_time *dt)
+{
+	struct rx8025_data *rx8025 = dev_get_drvdata(dev);
+	u8 date[7];
+	int err;
+
+	err = rx8025_read_regs(rx8025->client, RX8025_REG_SEC, 7, date);
+	if (err)
+		return err;
+
+	dev_dbg(dev, "%s: read 0x%02x 0x%02x "
+		"0x%02x 0x%02x 0x%02x 0x%02x 0x%02x\n", __func__,
+		date[0], date[1], date[2], date[3], date[4],
+		date[5], date[6]);
+
+	dt->tm_sec = bcd2bin(date[RX8025_REG_SEC] & 0x7f);
+	dt->tm_min = bcd2bin(date[RX8025_REG_MIN] & 0x7f);
+	if (rx8025->ctrl1 & RX8025_BIT_CTRL1_1224)
+		dt->tm_hour = bcd2bin(date[RX8025_REG_HOUR] & 0x3f);
+	else
+		dt->tm_hour = bcd2bin(date[RX8025_REG_HOUR] & 0x1f) % 12
+			+ (date[RX8025_REG_HOUR] & 0x20 ? 12 : 0);
+
+	dt->tm_mday = bcd2bin(date[RX8025_REG_MDAY] & 0x3f);
+	dt->tm_mon = bcd2bin(date[RX8025_REG_MONTH] & 0x1f) - 1;
+	dt->tm_year = bcd2bin(date[RX8025_REG_YEAR]);
+
+	if (dt->tm_year < 70)
+		dt->tm_year += 100;
+
+	dev_dbg(dev, "%s: date %ds %dm %dh %dmd %dm %dy\n", __func__,
+		dt->tm_sec, dt->tm_min, dt->tm_hour,
+		dt->tm_mday, dt->tm_mon, dt->tm_year);
+
+	return rtc_valid_tm(dt);
+}
+
+static int rx8025_set_time(struct device *dev, struct rtc_time *dt)
+{
+	struct rx8025_data *rx8025 = dev_get_drvdata(dev);
+	u8 date[7];
+
+	/*
+	 * 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.
+	 */
+
+	/*
+	 * Here the read-only bits are written as "0".  I'm not sure if that
+	 * is sound.
+	 */
+	date[RX8025_REG_SEC] = bin2bcd(dt->tm_sec);
+	date[RX8025_REG_MIN] = bin2bcd(dt->tm_min);
+	if (rx8025->ctrl1 & RX8025_BIT_CTRL1_1224)
+		date[RX8025_REG_HOUR] = bin2bcd(dt->tm_hour);
+	else
+		date[RX8025_REG_HOUR] = (dt->tm_hour >= 12 ? 0x20 : 0)
+			| bin2bcd((dt->tm_hour + 11) % 12 + 1);
+
+	date[RX8025_REG_WDAY] = bin2bcd(dt->tm_wday);
+	date[RX8025_REG_MDAY] = bin2bcd(dt->tm_mday);
+	date[RX8025_REG_MONTH] = bin2bcd(dt->tm_mon + 1);
+	date[RX8025_REG_YEAR] = bin2bcd(dt->tm_year % 100);
+
+	dev_dbg(dev,
+		"%s: write 0x%02x 0x%02x 0x%02x 0x%02x 0x%02x 0x%02x 0x%02x\n",
+		__func__,
+		date[0], date[1], date[2], date[3], date[4], date[5], date[6]);
+
+	return rx8025_write_regs(rx8025->client, RX8025_REG_SEC, 7, date);
+}
+
+static int rx8025_init_client(struct i2c_client *client, int *need_reset)
+{
+	struct rx8025_data *rx8025 = i2c_get_clientdata(client);
+	u8 ctrl[2], ctrl2;
+	int need_clear = 0;
+	int err;
+
+	err = rx8025_read_regs(rx8025->client, RX8025_REG_CTRL1, 2, ctrl);
+	if (err)
+		goto out;
+
+	/* Keep test bit zero ! */
+	rx8025->ctrl1 = ctrl[0] & ~RX8025_BIT_CTRL1_TEST;
+
+	if (ctrl[1] & RX8025_BIT_CTRL2_PON) {
+		dev_warn(&client->dev, "power-on reset was detected, "
+			 "you may have to readjust the clock\n");
+		*need_reset = 1;
+	}
+
+	if (ctrl[1] & RX8025_BIT_CTRL2_VDET) {
+		dev_warn(&client->dev, "a power voltage drop was detected, "
+			 "you may have to readjust the clock\n");
+		*need_reset = 1;
+	}
+
+	if (!(ctrl[1] & RX8025_BIT_CTRL2_XST)) {
+		dev_warn(&client->dev, "Oscillation stop was detected,"
+			 "you may have to readjust the clock\n");
+		*need_reset = 1;
+	}
+
+	if (ctrl[1] & (RX8025_BIT_CTRL2_DAFG | RX8025_BIT_CTRL2_WAFG)) {
+		dev_warn(&client->dev, "Alarm was detected\n");
+		need_clear = 1;
+	}
+
+	if (!(ctrl[1] & RX8025_BIT_CTRL2_CTFG))
+		need_clear = 1;
+
+	if (*need_reset || need_clear) {
+		ctrl2 = ctrl[0];
+		ctrl2 &= ~(RX8025_BIT_CTRL2_PON | RX8025_BIT_CTRL2_VDET |
+			   RX8025_BIT_CTRL2_CTFG | RX8025_BIT_CTRL2_WAFG |
+			   RX8025_BIT_CTRL2_DAFG);
+		ctrl2 |= RX8025_BIT_CTRL2_XST;
+
+		err = rx8025_write_reg(client, RX8025_REG_CTRL2, ctrl2);
+	}
+out:
+	return err;
+}
+
+/* Alarm support */
+static int rx8025_read_alarm(struct device *dev, struct rtc_wkalrm *t)
+{
+	struct rx8025_data *rx8025 = dev_get_drvdata(dev);
+	struct i2c_client *client = rx8025->client;
+	u8 ctrl2, ald[2];
+	int err;
+
+	if (client->irq <= 0)
+		return -EINVAL;
+
+	err = rx8025_read_regs(client, RX8025_REG_ALDMIN, 2, ald);
+	if (err)
+		return err;
+
+	err = rx8025_read_reg(client, RX8025_REG_CTRL2, &ctrl2);
+	if (err)
+		return err;
+
+	dev_dbg(dev, "%s: read alarm 0x%02x 0x%02x ctrl2 %02x\n",
+		__func__, ald[0], ald[1], ctrl2);
+
+	/* Hardware alarms precision is 1 minute! */
+	t->time.tm_sec = 0;
+	t->time.tm_min = bcd2bin(ald[0] & 0x7f);
+	if (rx8025->ctrl1 & RX8025_BIT_CTRL1_1224)
+		t->time.tm_hour = bcd2bin(ald[1] & 0x3f);
+	else
+		t->time.tm_hour = bcd2bin(ald[1] & 0x1f) % 12
+			+ (ald[1] & 0x20 ? 12 : 0);
+
+	t->time.tm_wday = -1;
+	t->time.tm_mday = -1;
+	t->time.tm_mon = -1;
+	t->time.tm_year = -1;
+
+	dev_dbg(dev, "%s: date: %ds %dm %dh %dmd %dm %dy\n",
+		__func__,
+		t->time.tm_sec, t->time.tm_min, t->time.tm_hour,
+		t->time.tm_mday, t->time.tm_mon, t->time.tm_year);
+	t->enabled = !!(rx8025->ctrl1 & RX8025_BIT_CTRL1_DALE);
+	t->pending = (ctrl2 & RX8025_BIT_CTRL2_DAFG) && t->enabled;
+
+	return err;
+}
+
+static int rx8025_set_alarm(struct device *dev, struct rtc_wkalrm *t)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	struct rx8025_data *rx8025 = dev_get_drvdata(dev);
+	u8 ald[2];
+	int err;
+
+	if (client->irq <= 0)
+		return -EINVAL;
+
+	/* Hardware alarm precision is 1 minute! */
+	ald[0] = bin2bcd(t->time.tm_min);
+	if (rx8025->ctrl1 & RX8025_BIT_CTRL1_1224)
+		ald[1] = bin2bcd(t->time.tm_hour);
+	else
+		ald[1] = (t->time.tm_hour >= 12 ? 0x20 : 0)
+			| bin2bcd((t->time.tm_hour + 11) % 12 + 1);
+
+	dev_dbg(dev, "%s: write 0x%02x 0x%02x\n", __func__, ald[0], ald[1]);
+
+	if (rx8025->ctrl1 & RX8025_BIT_CTRL1_DALE) {
+		rx8025->ctrl1 &= ~RX8025_BIT_CTRL1_DALE;
+		err = rx8025_write_reg(rx8025->client, RX8025_REG_CTRL1,
+				       rx8025->ctrl1);
+		if (err)
+			return err;
+	}
+	err = rx8025_write_regs(rx8025->client, RX8025_REG_ALDMIN, 2, ald);
+	if (err)
+		return err;
+
+	if (t->enabled) {
+		rx8025->ctrl1 |= RX8025_BIT_CTRL1_DALE;
+		err = rx8025_write_reg(rx8025->client, RX8025_REG_CTRL1,
+				       rx8025->ctrl1);
+		if (err)
+			return err;
+	}
+
+	return 0;
+}
+
+static int rx8025_alarm_irq_enable(struct device *dev, unsigned int enabled)
+{
+	struct rx8025_data *rx8025 = dev_get_drvdata(dev);
+	u8 ctrl1;
+	int err;
+
+	ctrl1 = rx8025->ctrl1;
+	if (enabled)
+		ctrl1 |= RX8025_BIT_CTRL1_DALE;
+	else
+		ctrl1 &= ~RX8025_BIT_CTRL1_DALE;
+
+	if (ctrl1 != rx8025->ctrl1) {
+		rx8025->ctrl1 = ctrl1;
+		err = rx8025_write_reg(rx8025->client, RX8025_REG_CTRL1,
+				       rx8025->ctrl1);
+		if (err)
+			return err;
+	}
+	return 0;
+}
+
+static int rx8025_irq_set_state(struct device *dev, int enabled)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	struct rx8025_data *rx8025 = i2c_get_clientdata(client);
+	int ctrl1;
+	int err;
+
+	if (client->irq <= 0)
+		return -ENXIO;
+
+	ctrl1 = rx8025->ctrl1 & ~RX8025_BIT_CTRL1_CT;
+	if (enabled)
+		ctrl1 |= RX8025_BIT_CTRL1_CT_1HZ;
+	if (ctrl1 != rx8025->ctrl1) {
+		rx8025->ctrl1 = ctrl1;
+		err = rx8025_write_reg(rx8025->client, RX8025_REG_CTRL1,
+				       rx8025->ctrl1);
+		if (err)
+			return err;
+	}
+
+	return 0;
+}
+
+static struct rtc_class_ops rx8025_rtc_ops = {
+	.read_time = rx8025_get_time,
+	.set_time = rx8025_set_time,
+	.read_alarm = rx8025_read_alarm,
+	.set_alarm = rx8025_set_alarm,
+	.alarm_irq_enable = rx8025_alarm_irq_enable,
+	.irq_set_state  = rx8025_irq_set_state,
+};
+
+/*
+ * Clock precision adjustment support
+ *
+ * According to the RX8025 SA/NB application manual the frequency and
+ * temperature charateristics can be approximated using the following
+ * equation:
+ *
+ *   df = a * (ut - t)**2
+ *
+ *   df: Frequency deviation in any temperature
+ *   a : Coefficient = (-35 +-5) * 10**-9
+ *   ut: Ultimate temperature in degree = +25 +-5 degree
+ *   t : Any temperature in degree
+ *
+ * Note that the clock adjustment in ppb must be entered (which is
+ * the negative value of the deviation).
+ */
+static int rx8025_get_clock_adjust(struct device *dev, int *adj)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	u8 digoff;
+	int err;
+
+	err = rx8025_read_reg(client, RX8025_REG_DIGOFF, &digoff);
+	if (err)
+		return err;
+
+	*adj = digoff >= 64 ? digoff - 128 : digoff;
+	if (*adj > 0)
+		(*adj)--;
+	*adj *= -RX8025_ADJ_RESOLUTION;
+
+	return 0;
+}
+
+static int rx8025_set_clock_adjust(struct device *dev, int adj)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	u8 digoff;
+	int err;
+
+	adj /= -RX8025_ADJ_RESOLUTION;
+	if (adj > RX8025_ADJ_DATA_MAX)
+		adj = RX8025_ADJ_DATA_MAX;
+	else if (adj < RX8025_ADJ_DATA_MIN)
+		adj = RX8025_ADJ_DATA_MIN;
+	else if (adj > 0)
+		adj++;
+	else if (adj < 0)
+		adj += 128;
+	digoff = adj;
+
+	err = rx8025_write_reg(client, RX8025_REG_DIGOFF, digoff);
+	if (err)
+		return err;
+
+	dev_dbg(dev, "%s: write 0x%02x\n", __func__, digoff);
+
+	return 0;
+}
+
+static ssize_t rx8025_sysfs_show_clock_adjust(struct device *dev,
+					      struct device_attribute *attr,
+					      char *buf)
+{
+	int err, adj;
+
+	err = rx8025_get_clock_adjust(dev, &adj);
+	if (err)
+		return err;
+
+	return sprintf(buf, "%d\n", adj);
+}
+
+static ssize_t rx8025_sysfs_store_clock_adjust(struct device *dev,
+					       struct device_attribute *attr,
+					       const char *buf, size_t count)
+{
+	int adj, err;
+
+	if (sscanf(buf, "%i", &adj) != 1)
+		return -EINVAL;
+
+	err = rx8025_set_clock_adjust(dev, adj);
+
+	return err ? err : count;
+}
+
+static DEVICE_ATTR(clock_adjust_ppb, S_IRUGO | S_IWUSR,
+		   rx8025_sysfs_show_clock_adjust,
+		   rx8025_sysfs_store_clock_adjust);
+
+static int rx8025_sysfs_register(struct device *dev)
+{
+	return device_create_file(dev, &dev_attr_clock_adjust_ppb);
+}
+
+static void rx8025_sysfs_unregister(struct device *dev)
+{
+	device_remove_file(dev, &dev_attr_clock_adjust_ppb);
+}
+
+static int __devinit rx8025_probe(struct i2c_client *client,
+				  const struct i2c_device_id *id)
+{
+	struct i2c_adapter *adapter = to_i2c_adapter(client->dev.parent);
+	struct rx8025_data *rx8025;
+	int err, need_reset = 0;
+
+	if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE_DATA
+				     | I2C_FUNC_SMBUS_I2C_BLOCK)) {
+		dev_err(&adapter->dev,
+			"doesn't support required functionality\n");
+		err = -EIO;
+		goto errout;
+	}
+
+	rx8025 = kzalloc(sizeof(*rx8025), GFP_KERNEL);
+	if (!rx8025) {
+		dev_err(&adapter->dev, "failed to alloc memory\n");
+		err = -ENOMEM;
+		goto errout;
+	}
+
+	rx8025->client = client;
+	i2c_set_clientdata(client, rx8025);
+	INIT_WORK(&rx8025->work, rx8025_work);
+
+	err = rx8025_init_client(client, &need_reset);
+	if (err)
+		goto errout_free;
+
+	if (need_reset) {
+		struct rtc_time tm;
+		dev_info(&client->dev,
+			 "bad conditions detected, resetting date\n");
+		rtc_time_to_tm(0, &tm);	/* 1970/1/1 */
+		rx8025_set_time(&client->dev, &tm);
+	}
+
+	rx8025->rtc = rtc_device_register(client->name, &client->dev,
+					  &rx8025_rtc_ops, THIS_MODULE);
+	if (IS_ERR(rx8025->rtc)) {
+		err = PTR_ERR(rx8025->rtc);
+		dev_err(&client->dev, "unable to register the class device\n");
+		goto errout_free;
+	}
+
+	if (client->irq > 0) {
+		dev_info(&client->dev, "IRQ %d supplied\n", client->irq);
+		err = request_irq(client->irq, rx8025_irq,
+				  0, "rx8025", client);
+		if (err) {
+			dev_err(&client->dev, "unable to request IRQ\n");
+			goto errout_reg;
+		}
+	}
+
+	rx8025->rtc->irq_freq = 1;
+	rx8025->rtc->max_user_freq = 1;
+
+	err = rx8025_sysfs_register(&client->dev);
+	if (err)
+		goto errout_irq;
+
+	return 0;
+
+errout_irq:
+	if (client->irq > 0)
+		free_irq(client->irq, client);
+
+errout_reg:
+	rtc_device_unregister(rx8025->rtc);
+
+errout_free:
+	i2c_set_clientdata(client, NULL);
+	kfree(rx8025);
+
+errout:
+	dev_err(&adapter->dev, "probing for rx8025 failed\n");
+	return err;
+}
+
+static int __devexit rx8025_remove(struct i2c_client *client)
+{
+	struct rx8025_data *rx8025 = i2c_get_clientdata(client);
+	struct mutex *lock = &rx8025->rtc->ops_lock;
+
+	if (client->irq > 0) {
+		mutex_lock(lock);
+		rx8025->exiting = 1;
+		mutex_unlock(lock);
+
+		free_irq(client->irq, client);
+		flush_scheduled_work();
+	}
+
+	rx8025_sysfs_unregister(&client->dev);
+	rtc_device_unregister(rx8025->rtc);
+	i2c_set_clientdata(client, NULL);
+	kfree(rx8025);
+	return 0;
+}
+
+static struct i2c_driver rx8025_driver = {
+	.driver = {
+		.name = "rtc-rx8025",
+		.owner = THIS_MODULE,
+	},
+	.probe		= rx8025_probe,
+	.remove		= __devexit_p(rx8025_remove),
+	.id_table	= rx8025_id,
+};
+
+static int __init rx8025_init(void)
+{
+	return i2c_add_driver(&rx8025_driver);
+}
+
+static void __exit rx8025_exit(void)
+{
+	i2c_del_driver(&rx8025_driver);
+}
+
+MODULE_AUTHOR("Wolfgang Grandegger <wg@grandegger.com>");
+MODULE_DESCRIPTION("RX-8025 SA/NB RTC driver");
+MODULE_LICENSE("GPL");
+
+module_init(rx8025_init);
+module_exit(rx8025_exit);