rtc: add RTC class driver for the Maxim MAX6900

Signed-off-by: Dale Farnsworth.org <dale@farnsworth.org>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Cc: David Brownell <david-b@pacbell.net>
Cc: Jean Delvare <khali@linux-fr.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/rtc/Kconfig

@@ -334,6 +334,16 @@ config RTC_DRV_TEST
 	  This driver can also be built as a module. If so, the module
 	  will be called rtc-test.
 
+config RTC_DRV_MAX6900
+	tristate "Maxim 6900"
+	depends on RTC_CLASS && I2C
+	help
+	  If you say yes here you will get support for the
+	  Maxim MAX6900 I2C RTC chip.
+
+	  This driver can also be built as a module. If so, the module
+	  will be called rtc-max6900.
+
 config RTC_DRV_MAX6902
 	tristate "Maxim 6902"
 	depends on RTC_CLASS && SPI

drivers/rtc/Makefile

@@ -35,6 +35,7 @@ obj-$(CONFIG_RTC_DRV_EP93XX)	+= rtc-ep93xx.o
 obj-$(CONFIG_RTC_DRV_SA1100)	+= rtc-sa1100.o
 obj-$(CONFIG_RTC_DRV_VR41XX)	+= rtc-vr41xx.o
 obj-$(CONFIG_RTC_DRV_PL031)	+= rtc-pl031.o
+obj-$(CONFIG_RTC_DRV_MAX6900)	+= rtc-max6900.o
 obj-$(CONFIG_RTC_DRV_MAX6902)	+= rtc-max6902.o
 obj-$(CONFIG_RTC_DRV_V3020)	+= rtc-v3020.o
 obj-$(CONFIG_RTC_DRV_AT91RM9200)+= rtc-at91rm9200.o

drivers/rtc/rtc-max6900.c

+/*
+ * rtc class driver for the Maxim MAX6900 chip
+ *
+ * Author: Dale Farnsworth <dale@farnsworth.org>
+ *
+ * based on previously existing rtc class drivers
+ *
+ * 2007 (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.
+ */
+
+#include <linux/module.h>
+#include <linux/i2c.h>
+#include <linux/bcd.h>
+#include <linux/rtc.h>
+#include <linux/delay.h>
+
+#define DRV_NAME "max6900"
+#define DRV_VERSION "0.1"
+
+/*
+ * register indices
+ */
+#define MAX6900_REG_SC			0	/* seconds	00-59 */
+#define MAX6900_REG_MN			1	/* minutes	00-59 */
+#define MAX6900_REG_HR			2	/* hours	00-23 */
+#define MAX6900_REG_DT			3	/* day of month	00-31 */
+#define MAX6900_REG_MO			4	/* month	01-12 */
+#define MAX6900_REG_DW			5	/* day of week	 1-7  */
+#define MAX6900_REG_YR			6	/* year		00-99 */
+#define MAX6900_REG_CT			7	/* control */
+#define MAX6900_REG_LEN			8
+
+#define MAX6900_REG_CT_WP		(1 << 7)	/* Write Protect */
+
+/*
+ * register read/write commands
+ */
+#define MAX6900_REG_CONTROL_WRITE	0x8e
+#define MAX6900_REG_BURST_READ		0xbf
+#define MAX6900_REG_BURST_WRITE		0xbe
+#define MAX6900_REG_RESERVED_READ	0x96
+
+#define MAX6900_IDLE_TIME_AFTER_WRITE	3	/* specification says 2.5 mS */
+
+#define MAX6900_I2C_ADDR		0xa0
+
+static unsigned short normal_i2c[] = {
+	MAX6900_I2C_ADDR >> 1,
+	I2C_CLIENT_END
+};
+
+I2C_CLIENT_INSMOD;			/* defines addr_data */
+
+static int max6900_probe(struct i2c_adapter *adapter, int addr, int kind);
+
+static int max6900_i2c_read_regs(struct i2c_client *client, u8 *buf)
+{
+	u8 reg_addr[1] = { MAX6900_REG_BURST_READ };
+	struct i2c_msg msgs[2] = {
+		{
+			.addr	= client->addr,
+			.flags	= 0, /* write */
+			.len	= sizeof(reg_addr),
+			.buf	= reg_addr
+		},
+		{
+			.addr	= client->addr,
+			.flags	= I2C_M_RD,
+			.len	= MAX6900_REG_LEN,
+			.buf	= buf
+		}
+	};
+	int rc;
+
+	rc = i2c_transfer(client->adapter, msgs, ARRAY_SIZE(msgs));
+	if (rc != ARRAY_SIZE(msgs)) {
+		dev_err(&client->dev, "%s: register read failed\n",
+			__FUNCTION__);
+		return -EIO;
+	}
+	return 0;
+}
+
+static int max6900_i2c_write_regs(struct i2c_client *client, u8 const *buf)
+{
+	u8 i2c_buf[MAX6900_REG_LEN + 1] = { MAX6900_REG_BURST_WRITE };
+	struct i2c_msg msgs[1] = {
+		{
+			.addr	= client->addr,
+			.flags	= 0, /* write */
+			.len	= MAX6900_REG_LEN + 1,
+			.buf	= i2c_buf
+		}
+	};
+	int rc;
+
+	memcpy(&i2c_buf[1], buf, MAX6900_REG_LEN);
+
+	rc = i2c_transfer(client->adapter, msgs, ARRAY_SIZE(msgs));
+	if (rc != ARRAY_SIZE(msgs)) {
+		dev_err(&client->dev, "%s: register write failed\n",
+			__FUNCTION__);
+		return -EIO;
+	}
+	msleep(MAX6900_IDLE_TIME_AFTER_WRITE);
+	return 0;
+}
+
+static int max6900_i2c_validate_client(struct i2c_client *client)
+{
+	u8 regs[MAX6900_REG_LEN];
+	u8 zero_mask[MAX6900_REG_LEN] = {
+		0x80,	/* seconds */
+		0x80,	/* minutes */
+		0x40,	/* hours */
+		0xc0,	/* day of month */
+		0xe0,	/* month */
+		0xf8,	/* day of week */
+		0x00,	/* year */
+		0x7f,	/* control */
+	};
+	int i;
+	int rc;
+	int reserved;
+
+	reserved = i2c_smbus_read_byte_data(client, MAX6900_REG_RESERVED_READ);
+	if (reserved != 0x07)
+		return -ENODEV;
+
+	rc = max6900_i2c_read_regs(client, regs);
+	if (rc < 0)
+		return rc;
+
+	for (i = 0; i < MAX6900_REG_LEN; ++i) {
+		if (regs[i] & zero_mask[i])
+			return -ENODEV;
+	}
+
+	return 0;
+}
+
+static int max6900_i2c_read_time(struct i2c_client *client, struct rtc_time *tm)
+{
+	int rc;
+	u8 regs[MAX6900_REG_LEN];
+
+	rc = max6900_i2c_read_regs(client, regs);
+	if (rc < 0)
+		return rc;
+
+	tm->tm_sec = BCD2BIN(regs[MAX6900_REG_SC]);
+	tm->tm_min = BCD2BIN(regs[MAX6900_REG_MN]);
+	tm->tm_hour = BCD2BIN(regs[MAX6900_REG_HR] & 0x3f);
+	tm->tm_mday = BCD2BIN(regs[MAX6900_REG_DT]);
+	tm->tm_mon = BCD2BIN(regs[MAX6900_REG_MO]) - 1;
+	tm->tm_year = BCD2BIN(regs[MAX6900_REG_YR]) + 100;
+	tm->tm_wday = BCD2BIN(regs[MAX6900_REG_DW]);
+
+	return 0;
+}
+
+static int max6900_i2c_clear_write_protect(struct i2c_client *client)
+{
+	int rc;
+	rc = i2c_smbus_write_byte_data (client, MAX6900_REG_CONTROL_WRITE, 0);
+	if (rc < 0) {
+		dev_err(&client->dev, "%s: control register write failed\n",
+			__FUNCTION__);
+		return -EIO;
+	}
+	return 0;
+}
+
+static int max6900_i2c_set_time(struct i2c_client *client,
+				struct rtc_time const *tm)
+{
+	u8 regs[MAX6900_REG_LEN];
+	int rc;
+
+	rc = max6900_i2c_clear_write_protect(client);
+	if (rc < 0)
+		return rc;
+
+	regs[MAX6900_REG_SC] = BIN2BCD(tm->tm_sec);
+	regs[MAX6900_REG_MN] = BIN2BCD(tm->tm_min);
+	regs[MAX6900_REG_HR] = BIN2BCD(tm->tm_hour);
+	regs[MAX6900_REG_DT] = BIN2BCD(tm->tm_mday);
+	regs[MAX6900_REG_MO] = BIN2BCD(tm->tm_mon + 1);
+	regs[MAX6900_REG_YR] = BIN2BCD(tm->tm_year - 100);
+	regs[MAX6900_REG_DW] = BIN2BCD(tm->tm_wday);
+	regs[MAX6900_REG_CT] = MAX6900_REG_CT_WP;	/* set write protect */
+
+	rc = max6900_i2c_write_regs(client, regs);
+	if (rc < 0)
+		return rc;
+
+	return 0;
+}
+
+static int max6900_rtc_read_time(struct device *dev, struct rtc_time *tm)
+{
+	return max6900_i2c_read_time(to_i2c_client(dev), tm);
+}
+
+static int max6900_rtc_set_time(struct device *dev, struct rtc_time *tm)
+{
+	return max6900_i2c_set_time(to_i2c_client(dev), tm);
+}
+
+static int max6900_attach_adapter(struct i2c_adapter *adapter)
+{
+	return i2c_probe(adapter, &addr_data, max6900_probe);
+}
+
+static int max6900_detach_client(struct i2c_client *client)
+{
+	struct rtc_device *const rtc = i2c_get_clientdata(client);
+
+	if (rtc)
+		rtc_device_unregister(rtc);
+
+	return i2c_detach_client(client);
+}
+
+static struct i2c_driver max6900_driver = {
+	.driver		= {
+		.name	= DRV_NAME,
+	},
+	.id		= I2C_DRIVERID_MAX6900,
+	.attach_adapter = max6900_attach_adapter,
+	.detach_client	= max6900_detach_client,
+};
+
+static const struct rtc_class_ops max6900_rtc_ops = {
+	.read_time	= max6900_rtc_read_time,
+	.set_time	= max6900_rtc_set_time,
+};
+
+static int max6900_probe(struct i2c_adapter *adapter, int addr, int kind)
+{
+	int rc = 0;
+	struct i2c_client *client = NULL;
+	struct rtc_device *rtc = NULL;
+
+	if (!i2c_check_functionality(adapter, I2C_FUNC_I2C)) {
+		rc = -ENODEV;
+		goto failout;
+	}
+
+	client = kzalloc(sizeof(struct i2c_client), GFP_KERNEL);
+	if (client == NULL) {
+		rc = -ENOMEM;
+		goto failout;
+	}
+
+	client->addr = addr;
+	client->adapter = adapter;
+	client->driver = &max6900_driver;
+	strlcpy(client->name, DRV_NAME, I2C_NAME_SIZE);
+
+	if (kind < 0) {
+		rc = max6900_i2c_validate_client(client);
+		if (rc < 0)
+			goto failout;
+	}
+
+	rc = i2c_attach_client(client);
+	if (rc < 0)
+		goto failout;
+
+	dev_info(&client->dev,
+		 "chip found, driver version " DRV_VERSION "\n");
+
+	rtc = rtc_device_register(max6900_driver.driver.name,
+				  &client->dev,
+				  &max6900_rtc_ops, THIS_MODULE);
+	if (IS_ERR(rtc)) {
+		rc = PTR_ERR(rtc);
+		goto failout_detach;
+	}
+
+	i2c_set_clientdata(client, rtc);
+
+	return 0;
+
+failout_detach:
+	i2c_detach_client(client);
+failout:
+	kfree(client);
+	return rc;
+}
+
+static int __init max6900_init(void)
+{
+	return i2c_add_driver(&max6900_driver);
+}
+
+static void __exit max6900_exit(void)
+{
+	i2c_del_driver(&max6900_driver);
+}
+
+MODULE_DESCRIPTION("Maxim MAX6900 RTC driver");
+MODULE_LICENSE("GPL");
+MODULE_VERSION(DRV_VERSION);
+
+module_init(max6900_init);
+module_exit(max6900_exit);