[PATCH] I2C: add ST M41T00 I2C RTC chip driver

This patch adds support for the ST M41T00 I2C RTC chip.

This rtc chip has no mechanism to freeze it's registers while being
read; however, it will delay updating the external values of the
registers for 250ms after a register is read.  To ensure that a sane
time value is read, the driver verifies that the same registers values
were read twice before returning.

Also, when setting the rtc from an interrupt handler, a tasklet is used
to provide the context required by the i2c core code.
Signed-off-by: Mark A. Greer <mgreer@mvista.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/i2c/chips/Kconfig

@@ -382,4 +382,13 @@ config ISP1301_OMAP
 	  This driver can also be built as a module.  If so, the module
 	  will be called isp1301_omap.
 
+config SENSORS_M41T00
+	tristate "ST M41T00 RTC chip"
+	depends on I2C && PPC32
+	help
+	  If you say yes here you get support for the ST M41T00 RTC chip.
+
+	  This driver can also be built as a module.  If so, the module
+	  will be called m41t00.
+
 endmenu

drivers/i2c/chips/Makefile

@@ -27,6 +27,7 @@ obj-$(CONFIG_SENSORS_LM85)	+= lm85.o
 obj-$(CONFIG_SENSORS_LM87)	+= lm87.o
 obj-$(CONFIG_SENSORS_LM90)	+= lm90.o
 obj-$(CONFIG_SENSORS_MAX1619)	+= max1619.o
+obj-$(CONFIG_SENSORS_M41T00)	+= m41t00.o
 obj-$(CONFIG_SENSORS_PC87360)	+= pc87360.o
 obj-$(CONFIG_SENSORS_PCF8574)	+= pcf8574.o
 obj-$(CONFIG_SENSORS_PCF8591)	+= pcf8591.o

drivers/i2c/chips/m41t00.c

+/*
+ * drivers/i2c/chips/m41t00.c
+ *
+ * I2C client/driver for the ST M41T00 Real-Time Clock chip.
+ *
+ * Author: Mark A. Greer <mgreer@mvista.com>
+ *
+ * 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.
+ */
+/*
+ * This i2c client/driver wedges between the drivers/char/genrtc.c RTC
+ * interface and the SMBus interface of the i2c subsystem.
+ * 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 <asm/time.h>
+#include <asm/rtc.h>
+
+#define	M41T00_DRV_NAME		"m41t00"
+
+static DECLARE_MUTEX(m41t00_mutex);
+
+static struct i2c_driver m41t00_driver;
+static struct i2c_client *save_client;
+
+static unsigned short ignore[] = { I2C_CLIENT_END };
+static unsigned short normal_addr[] = { 0x68, I2C_CLIENT_END };
+
+static struct i2c_client_address_data addr_data = {
+	.normal_i2c		= normal_addr,
+	.normal_i2c_range	= ignore,
+	.probe			= ignore,
+	.probe_range		= ignore,
+	.ignore			= ignore,
+	.ignore_range		= ignore,
+	.force			= ignore,
+};
+
+ulong
+m41t00_get_rtc_time(void)
+{
+	s32	sec, min, hour, day, mon, year;
+	s32	sec1, min1, hour1, day1, mon1, year1;
+	ulong	limit = 10;
+
+	sec = min = hour = day = mon = year = 0;
+	sec1 = min1 = hour1 = day1 = mon1 = year1 = 0;
+
+	down(&m41t00_mutex);
+	do {
+		if (((sec = i2c_smbus_read_byte_data(save_client, 0)) >= 0)
+			&& ((min = i2c_smbus_read_byte_data(save_client, 1))
+				>= 0)
+			&& ((hour = i2c_smbus_read_byte_data(save_client, 2))
+				>= 0)
+			&& ((day = i2c_smbus_read_byte_data(save_client, 4))
+				>= 0)
+			&& ((mon = i2c_smbus_read_byte_data(save_client, 5))
+				>= 0)
+			&& ((year = i2c_smbus_read_byte_data(save_client, 6))
+				>= 0)
+			&& ((sec == sec1) && (min == min1) && (hour == hour1)
+				&& (day == day1) && (mon == mon1)
+				&& (year == year1)))
+
+				break;
+
+		sec1 = sec;
+		min1 = min;
+		hour1 = hour;
+		day1 = day;
+		mon1 = mon;
+		year1 = year;
+	} while (--limit > 0);
+	up(&m41t00_mutex);
+
+	if (limit == 0) {
+		dev_warn(&save_client->dev,
+			"m41t00: can't read rtc chip\n");
+		sec = min = hour = day = mon = year = 0;
+	}
+
+	sec &= 0x7f;
+	min &= 0x7f;
+	hour &= 0x3f;
+	day &= 0x3f;
+	mon &= 0x1f;
+	year &= 0xff;
+
+	BCD_TO_BIN(sec);
+	BCD_TO_BIN(min);
+	BCD_TO_BIN(hour);
+	BCD_TO_BIN(day);
+	BCD_TO_BIN(mon);
+	BCD_TO_BIN(year);
+
+	year += 1900;
+	if (year < 1970)
+		year += 100;
+
+	return mktime(year, mon, day, hour, min, sec);
+}
+
+static void
+m41t00_set_tlet(ulong arg)
+{
+	struct rtc_time	tm;
+	ulong	nowtime = *(ulong *)arg;
+
+	to_tm(nowtime, &tm);
+	tm.tm_year = (tm.tm_year - 1900) % 100;
+
+	BIN_TO_BCD(tm.tm_sec);
+	BIN_TO_BCD(tm.tm_min);
+	BIN_TO_BCD(tm.tm_hour);
+	BIN_TO_BCD(tm.tm_mon);
+	BIN_TO_BCD(tm.tm_mday);
+	BIN_TO_BCD(tm.tm_year);
+
+	down(&m41t00_mutex);
+	if ((i2c_smbus_write_byte_data(save_client, 0, tm.tm_sec & 0x7f) < 0)
+		|| (i2c_smbus_write_byte_data(save_client, 1, tm.tm_min & 0x7f)
+			< 0)
+		|| (i2c_smbus_write_byte_data(save_client, 2, tm.tm_hour & 0x7f)
+			< 0)
+		|| (i2c_smbus_write_byte_data(save_client, 4, tm.tm_mday & 0x7f)
+			< 0)
+		|| (i2c_smbus_write_byte_data(save_client, 5, tm.tm_mon & 0x7f)
+			< 0)
+		|| (i2c_smbus_write_byte_data(save_client, 6, tm.tm_year & 0x7f)
+			< 0))
+
+		dev_warn(&save_client->dev,"m41t00: can't write to rtc chip\n");
+
+	up(&m41t00_mutex);
+	return;
+}
+
+ulong	new_time;
+
+DECLARE_TASKLET_DISABLED(m41t00_tasklet, m41t00_set_tlet, (ulong)&new_time);
+
+int
+m41t00_set_rtc_time(ulong nowtime)
+{
+	new_time = nowtime;
+
+	if (in_interrupt())
+		tasklet_schedule(&m41t00_tasklet);
+	else
+		m41t00_set_tlet((ulong)&new_time);
+
+	return 0;
+}
+
+/*
+ *****************************************************************************
+ *
+ *	Driver Interface
+ *
+ *****************************************************************************
+ */
+static int
+m41t00_probe(struct i2c_adapter *adap, int addr, int kind)
+{
+	struct i2c_client *client;
+	int rc;
+
+	client = kmalloc(sizeof(struct i2c_client), GFP_KERNEL);
+	if (!client)
+		return -ENOMEM;
+
+	memset(client, 0, sizeof(struct i2c_client));
+	strncpy(client->name, M41T00_DRV_NAME, I2C_NAME_SIZE);
+	client->id = m41t00_driver.id;
+	client->flags = I2C_DF_NOTIFY;
+	client->addr = addr;
+	client->adapter = adap;
+	client->driver = &m41t00_driver;
+
+	if ((rc = i2c_attach_client(client)) != 0) {
+		kfree(client);
+		return rc;
+	}
+
+	save_client = client;
+	return 0;
+}
+
+static int
+m41t00_attach(struct i2c_adapter *adap)
+{
+	return i2c_probe(adap, &addr_data, m41t00_probe);
+}
+
+static int
+m41t00_detach(struct i2c_client *client)
+{
+	int	rc;
+
+	if ((rc = i2c_detach_client(client)) == 0) {
+		kfree(i2c_get_clientdata(client));
+		tasklet_kill(&m41t00_tasklet);
+	}
+	return rc;
+}
+
+static struct i2c_driver m41t00_driver = {
+	.owner		= THIS_MODULE,
+	.name		= M41T00_DRV_NAME,
+	.id		= I2C_DRIVERID_STM41T00,
+	.flags		= I2C_DF_NOTIFY,
+	.attach_adapter	= m41t00_attach,
+	.detach_client	= m41t00_detach,
+};
+
+static int __init
+m41t00_init(void)
+{
+	return i2c_add_driver(&m41t00_driver);
+}
+
+static void __exit
+m41t00_exit(void)
+{
+	i2c_del_driver(&m41t00_driver);
+	return;
+}
+
+module_init(m41t00_init);
+module_exit(m41t00_exit);
+
+MODULE_AUTHOR("Mark A. Greer <mgreer@mvista.com>");
+MODULE_DESCRIPTION("ST Microelectronics M41T00 RTC I2C Client Driver");
+MODULE_LICENSE("GPL");