[PATCH] "RTC-framework" driver for DS1307 and similar RTC chips

This is an "RTC-framework" driver for DS1307 and similar RTC chips,

It should be a full replacement for the existing ds1337.c driver (using the
older RTC glue), giving a net increase in the number of RTC chips that work
out-of-the-box.  There's a whole cluster of RTCs that are very similar, but
the 1337 driver was a bit too picky to work with most of them.

Still no support for RTC alarm IRQs (on chips that support them).

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: James Chapman <jchapman@katalix.com>
Signed-off-by: Alessandro Zummo <a.zummo@towertech.it>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

drivers/rtc/Kconfig

@@ -86,6 +86,24 @@ config RTC_DRV_X1205
 	  This driver can also be built as a module. If so, the module
 	  will be called rtc-x1205.
 
+config RTC_DRV_DS1307
+	tristate "Dallas/Maxim DS1307 and similar I2C RTC chips"
+	depends on RTC_CLASS && I2C
+	help
+	  If you say yes here you get support for various compatible RTC
+	  chips (often with battery backup) connected with I2C.  This driver
+	  should handle DS1307, DS1337, DS1338, DS1339, DS1340, ST M41T00,
+	  and probably other chips.  In some cases the RTC must already
+	  have been initialized (by manufacturing or a bootloader).
+
+	  The first seven registers on these chips hold an RTC, and other
+	  registers may add features such as NVRAM, a trickle charger for
+	  the RTC/NVRAM backup power, and alarms.  This driver may not
+	  expose all those available chip features.
+
+	  This driver can also be built as a module. If so, the module
+	  will be called rtc-ds1307.
+
 config RTC_DRV_DS1672
 	tristate "Dallas/Maxim DS1672"
 	depends on RTC_CLASS && I2C

drivers/rtc/Makefile

@@ -13,6 +13,7 @@ obj-$(CONFIG_RTC_INTF_DEV)	+= rtc-dev.o
 
 obj-$(CONFIG_RTC_DRV_X1205)	+= rtc-x1205.o
 obj-$(CONFIG_RTC_DRV_TEST)	+= rtc-test.o
+obj-$(CONFIG_RTC_DRV_DS1307)	+= rtc-ds1307.o
 obj-$(CONFIG_RTC_DRV_DS1672)	+= rtc-ds1672.o
 obj-$(CONFIG_RTC_DRV_PCF8563)	+= rtc-pcf8563.o
 obj-$(CONFIG_RTC_DRV_RS5C372)	+= rtc-rs5c372.o

drivers/rtc/rtc-ds1307.c

@@ -0,0 +1,388 @@
+/*
+ * rtc-ds1307.c - RTC driver for some mostly-compatible I2C chips.
+ *
+ *  Copyright (C) 2005 James Chapman (ds1337 core)
+ *  Copyright (C) 2006 David Brownell
+ *
+ * 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/module.h>
+#include <linux/init.h>
+#include <linux/slab.h>
+#include <linux/i2c.h>
+#include <linux/string.h>
+#include <linux/rtc.h>
+#include <linux/bcd.h>
+
+
+
+/* We can't determine type by probing, but if we expect pre-Linux code
+ * to have set the chip up as a clock (turning on the oscillator and
+ * setting the date and time), Linux can ignore the non-clock features.
+ * That's a natural job for a factory or repair bench.
+ *
+ * If the I2C "force" mechanism is used, we assume the chip is a ds1337.
+ * (Much better would be board-specific tables of I2C devices, along with
+ * the platform_data drivers would use to sort such issues out.)
+ */
+enum ds_type {
+	unknown = 0,
+	ds_1307,		/* or ds1338, ... */
+	ds_1337,		/* or ds1339, ... */
+	ds_1340,		/* or st m41t00, ... */
+	// rs5c372 too?  different address...
+};
+
+static unsigned short normal_i2c[] = { 0x68, I2C_CLIENT_END };
+
+I2C_CLIENT_INSMOD;
+
+
+
+/* RTC registers don't differ much, except for the century flag */
+#define DS1307_REG_SECS		0x00	/* 00-59 */
+#	define DS1307_BIT_CH		0x80
+#define DS1307_REG_MIN		0x01	/* 00-59 */
+#define DS1307_REG_HOUR		0x02	/* 00-23, or 1-12{am,pm} */
+#	define DS1340_BIT_CENTURY_EN	0x80	/* in REG_HOUR */
+#	define DS1340_BIT_CENTURY	0x40	/* in REG_HOUR */
+#define DS1307_REG_WDAY		0x03	/* 01-07 */
+#define DS1307_REG_MDAY		0x04	/* 01-31 */
+#define DS1307_REG_MONTH	0x05	/* 01-12 */
+#	define DS1337_BIT_CENTURY	0x80	/* in REG_MONTH */
+#define DS1307_REG_YEAR		0x06	/* 00-99 */
+
+/* Other registers (control, status, alarms, trickle charge, NVRAM, etc)
+ * start at 7, and they differ a lot. Only control and status matter for RTC;
+ * be careful using them.
+ */
+#define DS1307_REG_CONTROL	0x07
+#	define DS1307_BIT_OUT		0x80
+#	define DS1307_BIT_SQWE		0x10
+#	define DS1307_BIT_RS1		0x02
+#	define DS1307_BIT_RS0		0x01
+#define DS1337_REG_CONTROL	0x0e
+#	define DS1337_BIT_nEOSC		0x80
+#	define DS1337_BIT_RS2		0x10
+#	define DS1337_BIT_RS1		0x08
+#	define DS1337_BIT_INTCN		0x04
+#	define DS1337_BIT_A2IE		0x02
+#	define DS1337_BIT_A1IE		0x01
+#define DS1337_REG_STATUS	0x0f
+#	define DS1337_BIT_OSF		0x80
+#	define DS1337_BIT_A2I		0x02
+#	define DS1337_BIT_A1I		0x01
+#define DS1339_REG_TRICKLE	0x10
+
+
+
+struct ds1307 {
+	u8			reg_addr;
+	u8			regs[8];
+	enum ds_type		type;
+	struct i2c_msg		msg[2];
+	struct i2c_client	client;
+	struct rtc_device	*rtc;
+};
+
+
+static int ds1307_get_time(struct device *dev, struct rtc_time *t)
+{
+	struct ds1307	*ds1307 = dev_get_drvdata(dev);
+	int		tmp;
+
+	/* read the RTC registers all at once */
+	ds1307->msg[1].flags = I2C_M_RD;
+	ds1307->msg[1].len = 7;
+
+	tmp = i2c_transfer(ds1307->client.adapter, ds1307->msg, 2);
+	if (tmp != 2) {
+		dev_err(dev, "%s error %d\n", "read", tmp);
+		return -EIO;
+	}
+
+	dev_dbg(dev, "%s: %02x %02x %02x %02x %02x %02x %02x\n",
+			"read",
+			ds1307->regs[0], ds1307->regs[1],
+			ds1307->regs[2], ds1307->regs[3],
+			ds1307->regs[4], ds1307->regs[5],
+			ds1307->regs[6]);
+
+	t->tm_sec = BCD2BIN(ds1307->regs[DS1307_REG_SECS] & 0x7f);
+	t->tm_min = BCD2BIN(ds1307->regs[DS1307_REG_MIN] & 0x7f);
+	tmp = ds1307->regs[DS1307_REG_HOUR] & 0x3f;
+	t->tm_hour = BCD2BIN(tmp);
+	t->tm_wday = BCD2BIN(ds1307->regs[DS1307_REG_WDAY] & 0x07) - 1;
+	t->tm_mday = BCD2BIN(ds1307->regs[DS1307_REG_MDAY] & 0x3f);
+	tmp = ds1307->regs[DS1307_REG_MONTH] & 0x1f;
+	t->tm_mon = BCD2BIN(tmp) - 1;
+
+	/* assume 20YY not 19YY, and ignore DS1337_BIT_CENTURY */
+	t->tm_year = BCD2BIN(ds1307->regs[DS1307_REG_YEAR]) + 100;
+
+	dev_dbg(dev, "%s secs=%d, mins=%d, "
+		"hours=%d, mday=%d, mon=%d, year=%d, wday=%d\n",
+		"read", t->tm_sec, t->tm_min,
+		t->tm_hour, t->tm_mday,
+		t->tm_mon, t->tm_year, t->tm_wday);
+
+	return 0;
+}
+
+static int ds1307_set_time(struct device *dev, struct rtc_time *t)
+{
+	struct ds1307	*ds1307 = dev_get_drvdata(dev);
+	int		result;
+	int		tmp;
+	u8		*buf = ds1307->regs;
+
+	dev_dbg(dev, "%s secs=%d, mins=%d, "
+		"hours=%d, mday=%d, mon=%d, year=%d, wday=%d\n",
+		"write", dt->tm_sec, dt->tm_min,
+		dt->tm_hour, dt->tm_mday,
+		dt->tm_mon, dt->tm_year, dt->tm_wday);
+
+	*buf++ = 0;		/* first register addr */
+	buf[DS1307_REG_SECS] = BIN2BCD(t->tm_sec);
+	buf[DS1307_REG_MIN] = BIN2BCD(t->tm_min);
+	buf[DS1307_REG_HOUR] = BIN2BCD(t->tm_hour);
+	buf[DS1307_REG_WDAY] = BIN2BCD(t->tm_wday + 1);
+	buf[DS1307_REG_MDAY] = BIN2BCD(t->tm_mday);
+	buf[DS1307_REG_MONTH] = BIN2BCD(t->tm_mon + 1);
+
+	/* assume 20YY not 19YY */
+	tmp = t->tm_year - 100;
+	buf[DS1307_REG_YEAR] = BIN2BCD(tmp);
+
+	if (ds1307->type == ds_1337)
+		buf[DS1307_REG_MONTH] |= DS1337_BIT_CENTURY;
+	else if (ds1307->type == ds_1340)
+		buf[DS1307_REG_HOUR] |= DS1340_BIT_CENTURY_EN
+				| DS1340_BIT_CENTURY;
+
+	ds1307->msg[1].flags = 0;
+	ds1307->msg[1].len = 8;
+
+	dev_dbg(dev, "%s: %02x %02x %02x %02x %02x %02x %02x\n",
+		"write", buf[0], buf[1], buf[2], buf[3],
+		buf[4], buf[5], buf[6]);
+
+	result = i2c_transfer(ds1307->client.adapter, &ds1307->msg[1], 1);
+	if (result != 1) {
+		dev_err(dev, "%s error %d\n", "write", tmp);
+		return -EIO;
+	}
+	return 0;
+}
+
+static struct rtc_class_ops ds13xx_rtc_ops = {
+	.read_time	= ds1307_get_time,
+	.set_time	= ds1307_set_time,
+};
+
+static struct i2c_driver ds1307_driver;
+
+static int __devinit
+ds1307_detect(struct i2c_adapter *adapter, int address, int kind)
+{
+	struct ds1307		*ds1307;
+	int			err = -ENODEV;
+	struct i2c_client	*client;
+	int			tmp;
+
+	if (!(ds1307 = kzalloc(sizeof(struct ds1307), GFP_KERNEL))) {
+		err = -ENOMEM;
+		goto exit;
+	}
+
+	client = &ds1307->client;
+	client->addr = address;
+	client->adapter = adapter;
+	client->driver = &ds1307_driver;
+	client->flags = 0;
+
+	i2c_set_clientdata(client, ds1307);
+
+	ds1307->msg[0].addr = client->addr;
+	ds1307->msg[0].flags = 0;
+	ds1307->msg[0].len = 1;
+	ds1307->msg[0].buf = &ds1307->reg_addr;
+
+	ds1307->msg[1].addr = client->addr;
+	ds1307->msg[1].flags = I2C_M_RD;
+	ds1307->msg[1].len = sizeof(ds1307->regs);
+	ds1307->msg[1].buf = ds1307->regs;
+
+	/* HACK: "force" implies "needs ds1337-style-oscillator setup" */
+	if (kind >= 0) {
+		ds1307->type = ds_1337;
+
+		ds1307->reg_addr = DS1337_REG_CONTROL;
+		ds1307->msg[1].len = 2;
+
+		tmp = i2c_transfer(client->adapter, ds1307->msg, 2);
+		if (tmp != 2) {
+			pr_debug("read error %d\n", tmp);
+			err = -EIO;
+			goto exit_free;
+		}
+
+		ds1307->reg_addr = 0;
+		ds1307->msg[1].len = sizeof(ds1307->regs);
+
+		/* oscillator is off; need to turn it on */
+		if ((ds1307->regs[0] & DS1337_BIT_nEOSC)
+				|| (ds1307->regs[1] & DS1337_BIT_OSF)) {
+			printk(KERN_ERR "no ds1337 oscillator code\n");
+			goto exit_free;
+		}
+	} else
+		ds1307->type = ds_1307;
+
+read_rtc:
+	/* read RTC registers */
+
+	tmp = i2c_transfer(client->adapter, ds1307->msg, 2);
+	if (tmp != 2) {
+		pr_debug("read error %d\n", tmp);
+		err = -EIO;
+		goto exit_free;
+	}
+
+	/* minimal sanity checking; some chips (like DS1340) don't
+	 * specify the extra bits as must-be-zero, but there are
+	 * still a few values that are clearly out-of-range.
+	 */
+	tmp = ds1307->regs[DS1307_REG_SECS];
+	if (tmp & DS1307_BIT_CH) {
+		if (ds1307->type && ds1307->type != ds_1307) {
+			pr_debug("not a ds1307?\n");
+			goto exit_free;
+		}
+		ds1307->type = ds_1307;
+
+		/* this partial initialization should work for ds1307,
+		 * ds1338, ds1340, st m41t00, and more.
+		 */
+		dev_warn(&client->dev, "oscillator started; SET TIME!\n");
+		i2c_smbus_write_byte_data(client, 0, 0);
+		goto read_rtc;
+	}
+	tmp = BCD2BIN(tmp & 0x7f);
+	if (tmp > 60)
+		goto exit_free;
+	tmp = BCD2BIN(ds1307->regs[DS1307_REG_MIN] & 0x7f);
+	if (tmp > 60)
+		goto exit_free;
+
+	tmp = BCD2BIN(ds1307->regs[DS1307_REG_MDAY] & 0x3f);
+	if (tmp == 0 || tmp > 31)
+		goto exit_free;
+
+	tmp = BCD2BIN(ds1307->regs[DS1307_REG_MONTH] & 0x1f);
+	if (tmp == 0 || tmp > 12)
+		goto exit_free;
+
+	/* force into in 24 hour mode (most chips) or
+	 * disable century bit (ds1340)
+	 */
+	tmp = ds1307->regs[DS1307_REG_HOUR];
+	if (tmp & (1 << 6)) {
+		if (tmp & (1 << 5))
+			tmp = BCD2BIN(tmp & 0x1f) + 12;
+		else
+			tmp = BCD2BIN(tmp);
+		i2c_smbus_write_byte_data(client,
+				DS1307_REG_HOUR,
+				BIN2BCD(tmp));
+	}
+
+	/* FIXME chips like 1337 can generate alarm irqs too; those are
+	 * worth exposing through the API (especially when the irq is
+	 * wakeup-capable).
+	 */
+
+	switch (ds1307->type) {
+	case unknown:
+		strlcpy(client->name, "unknown", I2C_NAME_SIZE);
+		break;
+	case ds_1307:
+		strlcpy(client->name, "ds1307", I2C_NAME_SIZE);
+		break;
+	case ds_1337:
+		strlcpy(client->name, "ds1337", I2C_NAME_SIZE);
+		break;
+	case ds_1340:
+		strlcpy(client->name, "ds1340", I2C_NAME_SIZE);
+		break;
+	}
+
+	/* Tell the I2C layer a new client has arrived */
+	if ((err = i2c_attach_client(client)))
+		goto exit_free;
+
+	ds1307->rtc = rtc_device_register(client->name, &client->dev,
+				&ds13xx_rtc_ops, THIS_MODULE);
+	if (IS_ERR(ds1307->rtc)) {
+		err = PTR_ERR(ds1307->rtc);
+		dev_err(&client->dev,
+			"unable to register the class device\n");
+		goto exit_detach;
+	}
+
+	return 0;
+
+exit_detach:
+	i2c_detach_client(client);
+exit_free:
+	kfree(ds1307);
+exit:
+	return err;
+}
+
+static int __devinit
+ds1307_attach_adapter(struct i2c_adapter *adapter)
+{
+	if (!i2c_check_functionality(adapter, I2C_FUNC_I2C))
+		return 0;
+	return i2c_probe(adapter, &addr_data, ds1307_detect);
+}
+
+static int __devexit ds1307_detach_client(struct i2c_client *client)
+{
+	int		err;
+	struct ds1307	*ds1307 = i2c_get_clientdata(client);
+
+	rtc_device_unregister(ds1307->rtc);
+	if ((err = i2c_detach_client(client)))
+		return err;
+	kfree(ds1307);
+	return 0;
+}
+
+static struct i2c_driver ds1307_driver = {
+	.driver = {
+		.name	= "ds1307",
+		.owner	= THIS_MODULE,
+	},
+	.attach_adapter	= ds1307_attach_adapter,
+	.detach_client	= __devexit_p(ds1307_detach_client),
+};
+
+static int __init ds1307_init(void)
+{
+	return i2c_add_driver(&ds1307_driver);
+}
+module_init(ds1307_init);
+
+static void __exit ds1307_exit(void)
+{
+	i2c_del_driver(&ds1307_driver);
+}
+module_exit(ds1307_exit);
+
+MODULE_DESCRIPTION("RTC driver for DS1307 and similar chips");
+MODULE_LICENSE("GPL");