rtc: RTC class driver for the ds1374

This patch adds an RTC class driver for the Maxim/Dallas 1374 RTC chip,
based on drivers/i2c/chips/ds1374.c.  It supports alarm functionality.

Signed-off-by: Scott Wood <scottwood@freescale.com>
Acked-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>

drivers/rtc/Kconfig

@@ -139,6 +139,17 @@ config RTC_DRV_DS1307
 	  This driver can also be built as a module. If so, the module
 	  will be called rtc-ds1307.
 
+config RTC_DRV_DS1374
+	tristate "Maxim/Dallas Semiconductor DS1374 Real Time Clock"
+	depends on RTC_CLASS && I2C
+	help
+	  If you say yes here you get support for Dallas Semiconductor
+	  DS1374 real-time clock chips.  If an interrupt is associated
+	  with the device, the alarm functionality is supported.
+
+	  This driver can also be built as a module.  If so, the module
+	  will be called rtc-ds1374.
+
 config RTC_DRV_DS1672
 	tristate "Dallas/Maxim DS1672"
 	help

drivers/rtc/Makefile

@@ -23,6 +23,7 @@ obj-$(CONFIG_RTC_DRV_BFIN)	+= rtc-bfin.o
 obj-$(CONFIG_RTC_DRV_CMOS)	+= rtc-cmos.o
 obj-$(CONFIG_RTC_DRV_DS1216)	+= rtc-ds1216.o
 obj-$(CONFIG_RTC_DRV_DS1307)	+= rtc-ds1307.o
+obj-$(CONFIG_RTC_DRV_DS1374)	+= rtc-ds1374.o
 obj-$(CONFIG_RTC_DRV_DS1553)	+= rtc-ds1553.o
 obj-$(CONFIG_RTC_DRV_DS1672)	+= rtc-ds1672.o
 obj-$(CONFIG_RTC_DRV_DS1742)	+= rtc-ds1742.o

drivers/rtc/rtc-ds1374.c

@@ -0,0 +1,449 @@
+/*
+ * RTC client/driver for the Maxim/Dallas DS1374 Real-Time Clock over I2C
+ *
+ * Based on code by Randy Vinson <rvinson@mvista.com>,
+ * which was based on the m41t00.c by Mark Greer <mgreer@mvista.com>.
+ *
+ * Copyright (C) 2006-2007 Freescale Semiconductor
+ *
+ * 2005 (c) MontaVista Software, Inc. This file is licensed under
+ * the terms of the GNU General Public License version 2. This program
+ * is licensed "as is" without any warranty of any kind, whether express
+ * or implied.
+ */
+/*
+ * 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>
+
+#define DS1374_REG_TOD0		0x00 /* Time of Day */
+#define DS1374_REG_TOD1		0x01
+#define DS1374_REG_TOD2		0x02
+#define DS1374_REG_TOD3		0x03
+#define DS1374_REG_WDALM0	0x04 /* Watchdog/Alarm */
+#define DS1374_REG_WDALM1	0x05
+#define DS1374_REG_WDALM2	0x06
+#define DS1374_REG_CR		0x07 /* Control */
+#define DS1374_REG_CR_AIE	0x01 /* Alarm Int. Enable */
+#define DS1374_REG_CR_WDALM	0x20 /* 1=Watchdog, 0=Alarm */
+#define DS1374_REG_CR_WACE	0x40 /* WD/Alarm counter enable */
+#define DS1374_REG_SR		0x08 /* Status */
+#define DS1374_REG_SR_OSF	0x80 /* Oscillator Stop Flag */
+#define DS1374_REG_SR_AF	0x01 /* Alarm Flag */
+#define DS1374_REG_TCR		0x09 /* Trickle Charge */
+
+struct ds1374 {
+	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 ds1374_driver;
+
+static int ds1374_read_rtc(struct i2c_client *client, u32 *time,
+                           int reg, int nbytes)
+{
+	u8 buf[4];
+	int ret;
+	int i;
+
+	if (nbytes > 4) {
+		WARN_ON(1);
+		return -EINVAL;
+	}
+
+	ret = i2c_smbus_read_i2c_block_data(client, reg, nbytes, buf);
+
+	if (ret < 0)
+		return ret;
+	if (ret < nbytes)
+		return -EIO;
+
+	for (i = nbytes - 1, *time = 0; i >= 0; i--)
+		*time = (*time << 8) | buf[i];
+
+	return 0;
+}
+
+static int ds1374_write_rtc(struct i2c_client *client, u32 time,
+                            int reg, int nbytes)
+{
+	u8 buf[4];
+	int i;
+
+	if (nbytes > 4) {
+		WARN_ON(1);
+		return -EINVAL;
+	}
+
+	for (i = 0; i < nbytes; i++) {
+		buf[i] = time & 0xff;
+		time >>= 8;
+	}
+
+	return i2c_smbus_write_i2c_block_data(client, reg, nbytes, buf);
+}
+
+static int ds1374_check_rtc_status(struct i2c_client *client)
+{
+	int ret = 0;
+	int control, stat;
+
+	stat = i2c_smbus_read_byte_data(client, DS1374_REG_SR);
+	if (stat < 0)
+		return stat;
+
+	if (stat & DS1374_REG_SR_OSF)
+		dev_warn(&client->dev,
+		         "oscillator discontinuity flagged, "
+		         "time unreliable\n");
+
+	stat &= ~(DS1374_REG_SR_OSF | DS1374_REG_SR_AF);
+
+	ret = i2c_smbus_write_byte_data(client, DS1374_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, DS1374_REG_CR);
+	if (control < 0)
+		return control;
+
+	control &= ~(DS1374_REG_CR_WACE | DS1374_REG_CR_AIE);
+	return i2c_smbus_write_byte_data(client, DS1374_REG_CR, control);
+}
+
+static int ds1374_read_time(struct device *dev, struct rtc_time *time)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	u32 itime;
+	int ret;
+
+	ret = ds1374_read_rtc(client, &itime, DS1374_REG_TOD0, 4);
+	if (!ret)
+		rtc_time_to_tm(itime, time);
+
+	return ret;
+}
+
+static int ds1374_set_time(struct device *dev, struct rtc_time *time)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	unsigned long itime;
+
+	rtc_tm_to_time(time, &itime);
+	return ds1374_write_rtc(client, itime, DS1374_REG_TOD0, 4);
+}
+
+/* The ds1374 has a decrementer for an alarm, rather than a comparator.
+ * If the time of day is changed, then the alarm will need to be
+ * reset.
+ */
+static int ds1374_read_alarm(struct device *dev, struct rtc_wkalrm *alarm)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	struct ds1374 *ds1374 = i2c_get_clientdata(client);
+	u32 now, cur_alarm;
+	int cr, sr;
+	int ret = 0;
+
+	if (client->irq < 0)
+		return -EINVAL;
+
+	mutex_lock(&ds1374->mutex);
+
+	cr = ret = i2c_smbus_read_byte_data(client, DS1374_REG_CR);
+	if (ret < 0)
+		goto out;
+
+	sr = ret = i2c_smbus_read_byte_data(client, DS1374_REG_SR);
+	if (ret < 0)
+		goto out;
+
+	ret = ds1374_read_rtc(client, &now, DS1374_REG_TOD0, 4);
+	if (ret)
+		goto out;
+
+	ret = ds1374_read_rtc(client, &cur_alarm, DS1374_REG_WDALM0, 3);
+	if (ret)
+		goto out;
+
+	rtc_time_to_tm(now + cur_alarm, &alarm->time);
+	alarm->enabled = !!(cr & DS1374_REG_CR_WACE);
+	alarm->pending = !!(sr & DS1374_REG_SR_AF);
+
+out:
+	mutex_unlock(&ds1374->mutex);
+	return ret;
+}
+
+static int ds1374_set_alarm(struct device *dev, struct rtc_wkalrm *alarm)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	struct ds1374 *ds1374 = i2c_get_clientdata(client);
+	struct rtc_time now;
+	unsigned long new_alarm, itime;
+	int cr;
+	int ret = 0;
+
+	if (client->irq < 0)
+		return -EINVAL;
+
+	ret = ds1374_read_time(dev, &now);
+	if (ret < 0)
+		return ret;
+
+	rtc_tm_to_time(&alarm->time, &new_alarm);
+	rtc_tm_to_time(&now, &itime);
+
+	new_alarm -= itime;
+
+	/* This can happen due to races, in addition to dates that are
+	 * truly in the past.  To avoid requiring the caller to check for
+	 * races, dates in the past are assumed to be in the recent past
+	 * (i.e. not something that we'd rather the caller know about via
+	 * an error), and the alarm is set to go off as soon as possible.
+	 */
+	if (new_alarm <= 0)
+		new_alarm = 1;
+
+	mutex_lock(&ds1374->mutex);
+
+	ret = cr = i2c_smbus_read_byte_data(client, DS1374_REG_CR);
+	if (ret < 0)
+		goto out;
+
+	/* Disable any existing alarm before setting the new one
+	 * (or lack thereof). */
+	cr &= ~DS1374_REG_CR_WACE;
+
+	ret = i2c_smbus_write_byte_data(client, DS1374_REG_CR, cr);
+	if (ret < 0)
+		goto out;
+
+	ret = ds1374_write_rtc(client, new_alarm, DS1374_REG_WDALM0, 3);
+	if (ret)
+		goto out;
+
+	if (alarm->enabled) {
+		cr |= DS1374_REG_CR_WACE | DS1374_REG_CR_AIE;
+		cr &= ~DS1374_REG_CR_WDALM;
+
+		ret = i2c_smbus_write_byte_data(client, DS1374_REG_CR, cr);
+	}
+
+out:
+	mutex_unlock(&ds1374->mutex);
+	return ret;
+}
+
+static irqreturn_t ds1374_irq(int irq, void *dev_id)
+{
+	struct i2c_client *client = dev_id;
+	struct ds1374 *ds1374 = i2c_get_clientdata(client);
+
+	disable_irq_nosync(irq);
+	schedule_work(&ds1374->work);
+	return IRQ_HANDLED;
+}
+
+static void ds1374_work(struct work_struct *work)
+{
+	struct ds1374 *ds1374 = container_of(work, struct ds1374, work);
+	struct i2c_client *client = ds1374->client;
+	int stat, control;
+
+	mutex_lock(&ds1374->mutex);
+
+	stat = i2c_smbus_read_byte_data(client, DS1374_REG_SR);
+	if (stat < 0)
+		return;
+
+	if (stat & DS1374_REG_SR_AF) {
+		stat &= ~DS1374_REG_SR_AF;
+		i2c_smbus_write_byte_data(client, DS1374_REG_SR, stat);
+
+		control = i2c_smbus_read_byte_data(client, DS1374_REG_CR);
+		if (control < 0)
+			goto out;
+
+		control &= ~(DS1374_REG_CR_WACE | DS1374_REG_CR_AIE);
+		i2c_smbus_write_byte_data(client, DS1374_REG_CR, control);
+
+		/* rtc_update_irq() assumes that it is called
+		 * from IRQ-disabled context.
+		 */
+		local_irq_disable();
+		rtc_update_irq(ds1374->rtc, 1, RTC_AF | RTC_IRQF);
+		local_irq_enable();
+	}
+
+out:
+	if (!ds1374->exiting)
+		enable_irq(client->irq);
+
+	mutex_unlock(&ds1374->mutex);
+}
+
+static int ds1374_ioctl(struct device *dev, unsigned int cmd, unsigned long arg)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	struct ds1374 *ds1374 = i2c_get_clientdata(client);
+	int ret = -ENOIOCTLCMD;
+
+	mutex_lock(&ds1374->mutex);
+
+	switch (cmd) {
+	case RTC_AIE_OFF:
+		ret = i2c_smbus_read_byte_data(client, DS1374_REG_CR);
+		if (ret < 0)
+			goto out;
+
+		ret &= ~DS1374_REG_CR_WACE;
+
+		ret = i2c_smbus_write_byte_data(client, DS1374_REG_CR, ret);
+		if (ret < 0)
+			goto out;
+
+		break;
+
+	case RTC_AIE_ON:
+		ret = i2c_smbus_read_byte_data(client, DS1374_REG_CR);
+		if (ret < 0)
+			goto out;
+
+		ret |= DS1374_REG_CR_WACE | DS1374_REG_CR_AIE;
+		ret &= ~DS1374_REG_CR_WDALM;
+
+		ret = i2c_smbus_write_byte_data(client, DS1374_REG_CR, ret);
+		if (ret < 0)
+			goto out;
+
+		break;
+	}
+
+out:
+	mutex_unlock(&ds1374->mutex);
+	return ret;
+}
+
+static const struct rtc_class_ops ds1374_rtc_ops = {
+	.read_time = ds1374_read_time,
+	.set_time = ds1374_set_time,
+	.read_alarm = ds1374_read_alarm,
+	.set_alarm = ds1374_set_alarm,
+	.ioctl = ds1374_ioctl,
+};
+
+static int ds1374_probe(struct i2c_client *client)
+{
+	struct ds1374 *ds1374;
+	int ret;
+
+	ds1374 = kzalloc(sizeof(struct ds1374), GFP_KERNEL);
+	if (!ds1374)
+		return -ENOMEM;
+
+	ds1374->client = client;
+	i2c_set_clientdata(client, ds1374);
+
+	INIT_WORK(&ds1374->work, ds1374_work);
+	mutex_init(&ds1374->mutex);
+
+	ret = ds1374_check_rtc_status(client);
+	if (ret)
+		goto out_free;
+
+	if (client->irq >= 0) {
+		ret = request_irq(client->irq, ds1374_irq, 0,
+		                  "ds1374", client);
+		if (ret) {
+			dev_err(&client->dev, "unable to request IRQ\n");
+			goto out_free;
+		}
+	}
+
+	ds1374->rtc = rtc_device_register(client->name, &client->dev,
+	                                  &ds1374_rtc_ops, THIS_MODULE);
+	if (IS_ERR(ds1374->rtc)) {
+		ret = PTR_ERR(ds1374->rtc);
+		dev_err(&client->dev, "unable to register the class device\n");
+		goto out_irq;
+	}
+
+	return 0;
+
+out_irq:
+	if (client->irq >= 0)
+		free_irq(client->irq, client);
+
+out_free:
+	i2c_set_clientdata(client, NULL);
+	kfree(ds1374);
+	return ret;
+}
+
+static int __devexit ds1374_remove(struct i2c_client *client)
+{
+	struct ds1374 *ds1374 = i2c_get_clientdata(client);
+
+	if (client->irq >= 0) {
+		mutex_lock(&ds1374->mutex);
+		ds1374->exiting = 1;
+		mutex_unlock(&ds1374->mutex);
+
+		free_irq(client->irq, client);
+		flush_scheduled_work();
+	}
+
+	rtc_device_unregister(ds1374->rtc);
+	i2c_set_clientdata(client, NULL);
+	kfree(ds1374);
+	return 0;
+}
+
+static struct i2c_driver ds1374_driver = {
+	.driver = {
+		.name = "rtc-ds1374",
+		.owner = THIS_MODULE,
+	},
+	.probe = ds1374_probe,
+	.remove = __devexit_p(ds1374_remove),
+};
+
+static int __init ds1374_init(void)
+{
+	return i2c_add_driver(&ds1374_driver);
+}
+
+static void __exit ds1374_exit(void)
+{
+	i2c_del_driver(&ds1374_driver);
+}
+
+module_init(ds1374_init);
+module_exit(ds1374_exit);
+
+MODULE_AUTHOR("Scott Wood <scottwood@freescale.com>");
+MODULE_DESCRIPTION("Maxim/Dallas DS1374 RTC Driver");
+MODULE_LICENSE("GPL");