[PATCH] i2c: Extend ds1337 initialization

Add code to handle case where board firmware does not start the
RTC.

Signed-off-by: Jean Delvare <khali@linux-fr.org>
CC: James Chapman <jchapman@katalix.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/i2c/chips/ds1337.c

@@ -337,13 +337,38 @@ exit:
 
 static void ds1337_init_client(struct i2c_client *client)
 {
-	s32 val;
+	u8 status, control;
 
-	/* Ensure that device is set in 24-hour mode */
-	val = i2c_smbus_read_byte_data(client, DS1337_REG_HOUR);
-	if ((val >= 0) && (val & (1 << 6)))
-		i2c_smbus_write_byte_data(client, DS1337_REG_HOUR,
-					  val & 0x3f);
+	/* On some boards, the RTC isn't configured by boot firmware.
+	 * Handle that case by starting/configuring the RTC now.
+	 */
+	status = i2c_smbus_read_byte_data(client, DS1337_REG_STATUS);
+	control = i2c_smbus_read_byte_data(client, DS1337_REG_CONTROL);
+
+	if ((status & 0x80) || (control & 0x80)) {
+		/* RTC not running */
+		u8 buf[16];
+		struct i2c_msg msg[1];
+
+		dev_dbg(&client->dev, "%s: RTC not running!\n", __FUNCTION__);
+
+		/* Initialize all, including STATUS and CONTROL to zero */
+		memset(buf, 0, sizeof(buf));
+		msg[0].addr = client->addr;
+		msg[0].flags = 0;
+		msg[0].len = sizeof(buf);
+		msg[0].buf = &buf[0];
+
+		i2c_transfer(client->adapter, msg, 1);
+	} else {
+		/* Running: ensure that device is set in 24-hour mode */
+		s32 val;
+
+		val = i2c_smbus_read_byte_data(client, DS1337_REG_HOUR);
+		if ((val >= 0) && (val & (1 << 6)))
+			i2c_smbus_write_byte_data(client, DS1337_REG_HOUR,
+						  val & 0x3f);
+	}
 }
 
 static int ds1337_detach_client(struct i2c_client *client)