rtc: add support for DS3232 RTC

Add a driver for the DS3232 RTC chip via the I2C bus.  Alarms are not
supported in this version of the driver.

[akpm@linux-foundation.org: fix Kconfig help text]
Signed-off-by: Mingkai Hu <Mingkai.hu@freescale.com>
Signed-off-by: Jingchang Lu <b22599@freescale.com>
Signed-off-by: Srikanth Srinivasan <srikanth.srinivasan@freescale.com>
Signed-off-by: Roy Zang <tie-fei.zang@freescale.com>
Acked-by: Wan ZongShun <mcuos.com@gmail.com>
Cc: Kumar Gala <kumar.gala@freescale.com>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/rtc/Kconfig

@@ -166,6 +166,16 @@ config RTC_DRV_DS1672
 	  This driver can also be built as a module. If so, the module
 	  will be called rtc-ds1672.
 
+config RTC_DRV_DS3232
+	tristate "Dallas/Maxim DS3232"
+	depends on RTC_CLASS && I2C
+	help
+	  If you say yes here you get support for Dallas Semiconductor
+	  DS3232 real-time clock chips.
+
+	  This driver can also be built as a module.  If so, the module
+	  will be called rtc-ds3232.
+
 config RTC_DRV_MAX6900
 	tristate "Maxim MAX6900"
 	help

drivers/rtc/Makefile

@@ -41,6 +41,7 @@ obj-$(CONFIG_RTC_DRV_DS1511)	+= rtc-ds1511.o
 obj-$(CONFIG_RTC_DRV_DS1553)	+= rtc-ds1553.o
 obj-$(CONFIG_RTC_DRV_DS1672)	+= rtc-ds1672.o
 obj-$(CONFIG_RTC_DRV_DS1742)	+= rtc-ds1742.o
+obj-$(CONFIG_RTC_DRV_DS3232)	+= rtc-ds3232.o
 obj-$(CONFIG_RTC_DRV_DS3234)	+= rtc-ds3234.o
 obj-$(CONFIG_RTC_DRV_EFI)	+= rtc-efi.o
 obj-$(CONFIG_RTC_DRV_EP93XX)	+= rtc-ep93xx.o

drivers/rtc/rtc-ds3232.c

@@ -0,0 +1,326 @@
+/*
+ * RTC client/driver for the Maxim/Dallas DS3232 Real-Time Clock over I2C
+ *
+ * Copyright (C) 2009-2010 Freescale Semiconductor.
+ *
+ * This program is free software; you can redistribute  it and/or modify it
+ * under  the terms of  the GNU General  Public License as published by the
+ * Free Software Foundation;  either version 2 of the  License, or (at your
+ * option) any later version.
+ */
+/*
+ * It would be more efficient to use i2c msgs/i2c_transfer directly but, as
+ * recommened in .../Documentation/i2c/writing-clients section
+ * "Sending and receiving", using SMBus level communication is preferred.
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/interrupt.h>
+#include <linux/i2c.h>
+#include <linux/rtc.h>
+#include <linux/bcd.h>
+#include <linux/workqueue.h>
+#include <linux/slab.h>
+
+#define DS3232_REG_SECONDS	0x00
+#define DS3232_REG_MINUTES	0x01
+#define DS3232_REG_HOURS	0x02
+#define DS3232_REG_AMPM		0x02
+#define DS3232_REG_DAY		0x03
+#define DS3232_REG_DATE		0x04
+#define DS3232_REG_MONTH	0x05
+#define DS3232_REG_CENTURY	0x05
+#define DS3232_REG_YEAR		0x06
+#define DS3232_REG_ALARM1         0x07	/* Alarm 1 BASE */
+#define DS3232_REG_ALARM2         0x0B	/* Alarm 2 BASE */
+#define DS3232_REG_CR		0x0E	/* Control register */
+#	define DS3232_REG_CR_nEOSC        0x80
+#       define DS3232_REG_CR_INTCN        0x04
+#       define DS3232_REG_CR_A2IE        0x02
+#       define DS3232_REG_CR_A1IE        0x01
+
+#define DS3232_REG_SR	0x0F	/* control/status register */
+#	define DS3232_REG_SR_OSF   0x80
+#       define DS3232_REG_SR_BSY   0x04
+#       define DS3232_REG_SR_A2F   0x02
+#       define DS3232_REG_SR_A1F   0x01
+
+struct ds3232 {
+	struct i2c_client *client;
+	struct rtc_device *rtc;
+	struct work_struct work;
+
+	/* The mutex protects alarm operations, and prevents a race
+	 * between the enable_irq() in the workqueue and the free_irq()
+	 * in the remove function.
+	 */
+	struct mutex mutex;
+	int exiting;
+};
+
+static struct i2c_driver ds3232_driver;
+
+static int ds3232_check_rtc_status(struct i2c_client *client)
+{
+	int ret = 0;
+	int control, stat;
+
+	stat = i2c_smbus_read_byte_data(client, DS3232_REG_SR);
+	if (stat < 0)
+		return stat;
+
+	if (stat & DS3232_REG_SR_OSF)
+		dev_warn(&client->dev,
+				"oscillator discontinuity flagged, "
+				"time unreliable\n");
+
+	stat &= ~(DS3232_REG_SR_OSF | DS3232_REG_SR_A1F | DS3232_REG_SR_A2F);
+
+	ret = i2c_smbus_write_byte_data(client, DS3232_REG_SR, stat);
+	if (ret < 0)
+		return ret;
+
+	/* If the alarm is pending, clear it before requesting
+	 * the interrupt, so an interrupt event isn't reported
+	 * before everything is initialized.
+	 */
+
+	control = i2c_smbus_read_byte_data(client, DS3232_REG_CR);
+	if (control < 0)
+		return control;
+
+	control &= ~(DS3232_REG_CR_A1IE | DS3232_REG_CR_A2IE);
+	control |= DS3232_REG_CR_INTCN;
+
+	return i2c_smbus_write_byte_data(client, DS3232_REG_CR, control);
+}
+
+static int ds3232_read_time(struct device *dev, struct rtc_time *time)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	int ret;
+	u8 buf[7];
+	unsigned int year, month, day, hour, minute, second;
+	unsigned int week, twelve_hr, am_pm;
+	unsigned int century, add_century = 0;
+
+	ret = i2c_smbus_read_i2c_block_data(client, DS3232_REG_SECONDS, 7, buf);
+
+	if (ret < 0)
+		return ret;
+	if (ret < 7)
+		return -EIO;
+
+	second = buf[0];
+	minute = buf[1];
+	hour = buf[2];
+	week = buf[3];
+	day = buf[4];
+	month = buf[5];
+	year = buf[6];
+
+	/* Extract additional information for AM/PM and century */
+
+	twelve_hr = hour & 0x40;
+	am_pm = hour & 0x20;
+	century = month & 0x80;
+
+	/* Write to rtc_time structure */
+
+	time->tm_sec = bcd2bin(second);
+	time->tm_min = bcd2bin(minute);
+	if (twelve_hr) {
+		/* Convert to 24 hr */
+		if (am_pm)
+			time->tm_hour = bcd2bin(hour & 0x1F) + 12;
+		else
+			time->tm_hour = bcd2bin(hour & 0x1F);
+	} else {
+		time->tm_hour = bcd2bin(hour);
+	}
+
+	time->tm_wday = bcd2bin(week);
+	time->tm_mday = bcd2bin(day);
+	time->tm_mon = bcd2bin(month & 0x7F);
+	if (century)
+		add_century = 100;
+
+	time->tm_year = bcd2bin(year) + add_century;
+
+	return rtc_valid_tm(time);
+}
+
+static int ds3232_set_time(struct device *dev, struct rtc_time *time)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	u8 buf[7];
+
+	/* Extract time from rtc_time and load into ds3232*/
+
+	buf[0] = bin2bcd(time->tm_sec);
+	buf[1] = bin2bcd(time->tm_min);
+	buf[2] = bin2bcd(time->tm_hour);
+	buf[3] = bin2bcd(time->tm_wday); /* Day of the week */
+	buf[4] = bin2bcd(time->tm_mday); /* Date */
+	buf[5] = bin2bcd(time->tm_mon);
+	if (time->tm_year >= 100) {
+		buf[5] |= 0x80;
+		buf[6] = bin2bcd(time->tm_year - 100);
+	} else {
+		buf[6] = bin2bcd(time->tm_year);
+	}
+
+	return i2c_smbus_write_i2c_block_data(client,
+					      DS3232_REG_SECONDS, 7, buf);
+}
+
+static irqreturn_t ds3232_irq(int irq, void *dev_id)
+{
+	struct i2c_client *client = dev_id;
+	struct ds3232 *ds3232 = i2c_get_clientdata(client);
+
+	disable_irq_nosync(irq);
+	schedule_work(&ds3232->work);
+	return IRQ_HANDLED;
+}
+
+static void ds3232_work(struct work_struct *work)
+{
+	struct ds3232 *ds3232 = container_of(work, struct ds3232, work);
+	struct i2c_client *client = ds3232->client;
+	int stat, control;
+
+	mutex_lock(&ds3232->mutex);
+
+	stat = i2c_smbus_read_byte_data(client, DS3232_REG_SR);
+	if (stat < 0)
+		goto unlock;
+
+	if (stat & DS3232_REG_SR_A1F) {
+		control = i2c_smbus_read_byte_data(client, DS3232_REG_CR);
+		if (control < 0)
+			goto out;
+		/* disable alarm1 interrupt */
+		control &= ~(DS3232_REG_CR_A1IE);
+		i2c_smbus_write_byte_data(client, DS3232_REG_CR, control);
+
+		/* clear the alarm pend flag */
+		stat &= ~DS3232_REG_SR_A1F;
+		i2c_smbus_write_byte_data(client, DS3232_REG_SR, stat);
+
+		rtc_update_irq(ds3232->rtc, 1, RTC_AF | RTC_IRQF);
+	}
+
+out:
+	if (!ds3232->exiting)
+		enable_irq(client->irq);
+unlock:
+	mutex_unlock(&ds3232->mutex);
+}
+
+static const struct rtc_class_ops ds3232_rtc_ops = {
+	.read_time = ds3232_read_time,
+	.set_time = ds3232_set_time,
+};
+
+static int __devinit ds3232_probe(struct i2c_client *client,
+		const struct i2c_device_id *id)
+{
+	struct ds3232 *ds3232;
+	int ret;
+
+	ds3232 = kzalloc(sizeof(struct ds3232), GFP_KERNEL);
+	if (!ds3232)
+		return -ENOMEM;
+
+	ds3232->client = client;
+	i2c_set_clientdata(client, ds3232);
+
+	INIT_WORK(&ds3232->work, ds3232_work);
+	mutex_init(&ds3232->mutex);
+
+	ret = ds3232_check_rtc_status(client);
+	if (ret)
+		goto out_free;
+
+	ds3232->rtc = rtc_device_register(client->name, &client->dev,
+					  &ds3232_rtc_ops, THIS_MODULE);
+	if (IS_ERR(ds3232->rtc)) {
+		ret = PTR_ERR(ds3232->rtc);
+		dev_err(&client->dev, "unable to register the class device\n");
+		goto out_irq;
+	}
+
+	if (client->irq >= 0) {
+		ret = request_irq(client->irq, ds3232_irq, 0,
+				 "ds3232", client);
+		if (ret) {
+			dev_err(&client->dev, "unable to request IRQ\n");
+			goto out_free;
+		}
+	}
+
+	return 0;
+
+out_irq:
+	if (client->irq >= 0)
+		free_irq(client->irq, client);
+
+out_free:
+	i2c_set_clientdata(client, NULL);
+	kfree(ds3232);
+	return ret;
+}
+
+static int __devexit ds3232_remove(struct i2c_client *client)
+{
+	struct ds3232 *ds3232 = i2c_get_clientdata(client);
+
+	if (client->irq >= 0) {
+		mutex_lock(&ds3232->mutex);
+		ds3232->exiting = 1;
+		mutex_unlock(&ds3232->mutex);
+
+		free_irq(client->irq, client);
+		flush_scheduled_work();
+	}
+
+	rtc_device_unregister(ds3232->rtc);
+	i2c_set_clientdata(client, NULL);
+	kfree(ds3232);
+	return 0;
+}
+
+static const struct i2c_device_id ds3232_id[] = {
+	{ "ds3232", 0 },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, ds3232_id);
+
+static struct i2c_driver ds3232_driver = {
+	.driver = {
+		.name = "rtc-ds3232",
+		.owner = THIS_MODULE,
+	},
+	.probe = ds3232_probe,
+	.remove = __devexit_p(ds3232_remove),
+	.id_table = ds3232_id,
+};
+
+static int __init ds3232_init(void)
+{
+	return i2c_add_driver(&ds3232_driver);
+}
+
+static void __exit ds3232_exit(void)
+{
+	i2c_del_driver(&ds3232_driver);
+}
+
+module_init(ds3232_init);
+module_exit(ds3232_exit);
+
+MODULE_AUTHOR("Srikanth Srinivasan <srikanth.srinivasan@freescale.com>");
+MODULE_DESCRIPTION("Maxim/Dallas DS3232 RTC Driver");
+MODULE_LICENSE("GPL");