diff mbox

[08/13] RTC: ds1307: Remove register "cache"

Message ID 1465970379-14703-9-git-send-email-andrew.smirnov@gmail.com
State Superseded
Headers show

Commit Message

Andrey Smirnov June 15, 2016, 5:59 a.m. UTC
Remove shared area used by many subroutines to store values of RTC's
registers. There wasn't very much caching or sharing going on in the
code and that register cache, being a semi-global variable, only created
additional implicit dependencies between function and made code more
confusing (there were a number of functions that defined a convenience
variable pointing to ds1307->regs, but failed to use it in the code
consistently).

Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
---
 drivers/rtc/rtc-ds1307.c | 229 ++++++++++++++++++++++++-----------------------
 1 file changed, 116 insertions(+), 113 deletions(-)
diff mbox

Patch

diff --git a/drivers/rtc/rtc-ds1307.c b/drivers/rtc/rtc-ds1307.c
index 5e7eb13..3c137ab 100644
--- a/drivers/rtc/rtc-ds1307.c
+++ b/drivers/rtc/rtc-ds1307.c
@@ -110,10 +110,10 @@  enum ds_type {
 #	define RX8025_BIT_VDET		0x40
 #	define RX8025_BIT_XST		0x20
 
+#define DS1307_REG_COUNT	11
 
 struct ds1307 {
 	u8			offset; /* register's offset */
-	u8			regs[11];
 	u16			nvram_offset;
 	struct bin_attribute	*nvram;
 	enum ds_type		type;
@@ -366,30 +366,31 @@  out:
 
 static int ds1307_get_time(struct device *dev, struct rtc_time *t)
 {
+	u8              regs[DS1307_REG_COUNT];
 	struct ds1307	*ds1307 = dev_get_drvdata(dev);
 	int		tmp;
 
 	/* read the RTC date and time registers all at once */
 	tmp = ds1307->read_block_data(ds1307->client,
-		ds1307->offset, 7, ds1307->regs);
+		ds1307->offset, 7, regs);
 	if (tmp != 7) {
 		dev_err(dev, "%s error %d\n", "read", tmp);
 		return -EIO;
 	}
 
-	dev_dbg(dev, "%s: %7ph\n", "read", ds1307->regs);
+	dev_dbg(dev, "%s: %7ph\n", "read", regs);
 
-	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_sec = bcd2bin(regs[DS1307_REG_SECS] & 0x7f);
+	t->tm_min = bcd2bin(regs[DS1307_REG_MIN] & 0x7f);
+	tmp = 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_wday = bcd2bin(regs[DS1307_REG_WDAY] & 0x07) - 1;
+	t->tm_mday = bcd2bin(regs[DS1307_REG_MDAY] & 0x3f);
+	tmp = 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;
+	t->tm_year = bcd2bin(regs[DS1307_REG_YEAR]) + 100;
 
 	dev_dbg(dev, "%s secs=%d, mins=%d, "
 		"hours=%d, mday=%d, mon=%d, year=%d, wday=%d\n",
@@ -406,7 +407,7 @@  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;
+	u8		regs[DS1307_REG_COUNT];
 
 	dev_dbg(dev, "%s secs=%d, mins=%d, "
 		"hours=%d, mday=%d, mon=%d, year=%d, wday=%d\n",
@@ -414,26 +415,26 @@  static int ds1307_set_time(struct device *dev, struct rtc_time *t)
 		t->tm_hour, t->tm_mday,
 		t->tm_mon, t->tm_year, t->tm_wday);
 
-	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);
+	regs[DS1307_REG_SECS]  = bin2bcd(t->tm_sec);
+	regs[DS1307_REG_MIN]   = bin2bcd(t->tm_min);
+	regs[DS1307_REG_HOUR]  = bin2bcd(t->tm_hour);
+	regs[DS1307_REG_WDAY]  = bin2bcd(t->tm_wday + 1);
+	regs[DS1307_REG_MDAY]  = bin2bcd(t->tm_mday);
+	regs[DS1307_REG_MONTH] = bin2bcd(t->tm_mon + 1);
 
 	/* assume 20YY not 19YY */
 	tmp = t->tm_year - 100;
-	buf[DS1307_REG_YEAR] = bin2bcd(tmp);
+	regs[DS1307_REG_YEAR] = bin2bcd(tmp);
 
 	switch (ds1307->type) {
 	case ds_1337:
 	case ds_1339:
 	case ds_3231:
 	case ds_1341:
-		buf[DS1307_REG_MONTH] |= DS1337_BIT_CENTURY;
+		regs[DS1307_REG_MONTH] |= DS1337_BIT_CENTURY;
 		break;
 	case ds_1340:
-		buf[DS1307_REG_HOUR] |= DS1340_BIT_CENTURY_EN
+		regs[DS1307_REG_HOUR] |= DS1340_BIT_CENTURY_EN
 				| DS1340_BIT_CENTURY;
 		break;
 	case mcp794xx:
@@ -442,17 +443,17 @@  static int ds1307_set_time(struct device *dev, struct rtc_time *t)
 		 * values and need to be set again before writing the
 		 * buffer out to the device.
 		 */
-		buf[DS1307_REG_SECS] |= MCP794XX_BIT_ST;
-		buf[DS1307_REG_WDAY] |= MCP794XX_BIT_VBATEN;
+		regs[DS1307_REG_SECS] |= MCP794XX_BIT_ST;
+		regs[DS1307_REG_WDAY] |= MCP794XX_BIT_VBATEN;
 		break;
 	default:
 		break;
 	}
 
-	dev_dbg(dev, "%s: %7ph\n", "write", buf);
+	dev_dbg(dev, "%s: %7ph\n", "write", regs);
 
 	result = ds1307->write_block_data(ds1307->client,
-		ds1307->offset, 7, buf);
+		ds1307->offset, 7, regs);
 	if (result < 0) {
 		dev_err(dev, "%s error %d\n", "write", result);
 		return result;
@@ -465,29 +466,30 @@  static int ds1337_read_alarm(struct device *dev, struct rtc_wkalrm *t)
 	struct i2c_client       *client = to_i2c_client(dev);
 	struct ds1307		*ds1307 = i2c_get_clientdata(client);
 	int			ret;
+	u8			regs[DS1307_REG_COUNT];
 
 	if (!test_bit(HAS_ALARM, &ds1307->flags))
 		return -EINVAL;
 
 	/* read all ALARM1, ALARM2, and status registers at once */
 	ret = ds1307->read_block_data(client,
-			DS1339_REG_ALARM1_SECS, 9, ds1307->regs);
+			DS1339_REG_ALARM1_SECS, 9, regs);
 	if (ret != 9) {
 		dev_err(dev, "%s error %d\n", "alarm read", ret);
 		return -EIO;
 	}
 
 	dev_dbg(dev, "%s: %4ph, %3ph, %2ph\n", "alarm read",
-		&ds1307->regs[0], &ds1307->regs[4], &ds1307->regs[7]);
+		&regs[0], &regs[4], &regs[7]);
 
 	/*
 	 * report alarm time (ALARM1); assume 24 hour and day-of-month modes,
 	 * and that all four fields are checked matches
 	 */
-	t->time.tm_sec = bcd2bin(ds1307->regs[0] & 0x7f);
-	t->time.tm_min = bcd2bin(ds1307->regs[1] & 0x7f);
-	t->time.tm_hour = bcd2bin(ds1307->regs[2] & 0x3f);
-	t->time.tm_mday = bcd2bin(ds1307->regs[3] & 0x3f);
+	t->time.tm_sec = bcd2bin(regs[0] & 0x7f);
+	t->time.tm_min = bcd2bin(regs[1] & 0x7f);
+	t->time.tm_hour = bcd2bin(regs[2] & 0x3f);
+	t->time.tm_mday = bcd2bin(regs[3] & 0x3f);
 	t->time.tm_mon = -1;
 	t->time.tm_year = -1;
 	t->time.tm_wday = -1;
@@ -495,8 +497,8 @@  static int ds1337_read_alarm(struct device *dev, struct rtc_wkalrm *t)
 	t->time.tm_isdst = -1;
 
 	/* ... and status */
-	t->enabled = !!(ds1307->regs[7] & DS1337_BIT_A1IE);
-	t->pending = !!(ds1307->regs[8] & DS1337_BIT_A1I);
+	t->enabled = !!(regs[7] & DS1337_BIT_A1IE);
+	t->pending = !!(regs[8] & DS1337_BIT_A1I);
 
 	dev_dbg(dev, "%s secs=%d, mins=%d, "
 		"hours=%d, mday=%d, enabled=%d, pending=%d\n",
@@ -511,7 +513,7 @@  static int ds1337_set_alarm(struct device *dev, struct rtc_wkalrm *t)
 {
 	struct i2c_client	*client = to_i2c_client(dev);
 	struct ds1307		*ds1307 = i2c_get_clientdata(client);
-	unsigned char		*buf = ds1307->regs;
+	u8			regs[DS1307_REG_COUNT];
 	u8			control, status;
 	int			ret;
 
@@ -526,34 +528,34 @@  static int ds1337_set_alarm(struct device *dev, struct rtc_wkalrm *t)
 
 	/* read current status of both alarms and the chip */
 	ret = ds1307->read_block_data(client,
-			DS1339_REG_ALARM1_SECS, 9, buf);
+			DS1339_REG_ALARM1_SECS, 9, regs);
 	if (ret != 9) {
 		dev_err(dev, "%s error %d\n", "alarm write", ret);
 		return -EIO;
 	}
-	control = ds1307->regs[7];
-	status = ds1307->regs[8];
+	control = regs[7];
+	status  = regs[8];
 
 	dev_dbg(dev, "%s: %4ph, %3ph, %02x %02x\n", "alarm set (old status)",
-		&ds1307->regs[0], &ds1307->regs[4], control, status);
+		&regs[0], &regs[4], control, status);
 
 	/* set ALARM1, using 24 hour and day-of-month modes */
-	buf[0] = bin2bcd(t->time.tm_sec);
-	buf[1] = bin2bcd(t->time.tm_min);
-	buf[2] = bin2bcd(t->time.tm_hour);
-	buf[3] = bin2bcd(t->time.tm_mday);
+	regs[0] = bin2bcd(t->time.tm_sec);
+	regs[1] = bin2bcd(t->time.tm_min);
+	regs[2] = bin2bcd(t->time.tm_hour);
+	regs[3] = bin2bcd(t->time.tm_mday);
 
 	/* set ALARM2 to non-garbage */
-	buf[4] = 0;
-	buf[5] = 0;
-	buf[6] = 0;
+	regs[4] = 0;
+	regs[5] = 0;
+	regs[6] = 0;
 
 	/* disable alarms */
-	buf[7] = control & ~(DS1337_BIT_A1IE | DS1337_BIT_A2IE);
-	buf[8] = status & ~(DS1337_BIT_A1I | DS1337_BIT_A2I);
+	regs[7] = control & ~(DS1337_BIT_A1IE | DS1337_BIT_A2IE);
+	regs[8] = status & ~(DS1337_BIT_A1I | DS1337_BIT_A2I);
 
 	ret = ds1307->write_block_data(client,
-			DS1339_REG_ALARM1_SECS, 9, buf);
+			DS1339_REG_ALARM1_SECS, 9, regs);
 	if (ret < 0) {
 		dev_err(dev, "can't set alarm time\n");
 		return ret;
@@ -562,8 +564,8 @@  static int ds1337_set_alarm(struct device *dev, struct rtc_wkalrm *t)
 	/* optionally enable ALARM1 */
 	if (t->enabled) {
 		dev_dbg(dev, "alarm IRQ armed\n");
-		buf[7] |= DS1337_BIT_A1IE;	/* only ALARM1 is used */
-		i2c_smbus_write_byte_data(client, DS1337_REG_CONTROL, buf[7]);
+		regs[7] |= DS1337_BIT_A1IE;	/* only ALARM1 is used */
+		i2c_smbus_write_byte_data(client, DS1337_REG_CONTROL, regs[7]);
 	}
 
 	return 0;
@@ -665,7 +667,7 @@  static int mcp794xx_read_alarm(struct device *dev, struct rtc_wkalrm *t)
 {
 	struct i2c_client *client = to_i2c_client(dev);
 	struct ds1307 *ds1307 = i2c_get_clientdata(client);
-	u8 *regs = ds1307->regs;
+	u8  regs[DS1307_REG_COUNT];
 	int ret;
 
 	if (!test_bit(HAS_ALARM, &ds1307->flags))
@@ -679,12 +681,12 @@  static int mcp794xx_read_alarm(struct device *dev, struct rtc_wkalrm *t)
 	t->enabled = !!(regs[0] & MCP794XX_BIT_ALM0_EN);
 
 	/* Report alarm 0 time assuming 24-hour and day-of-month modes. */
-	t->time.tm_sec = bcd2bin(ds1307->regs[3] & 0x7f);
-	t->time.tm_min = bcd2bin(ds1307->regs[4] & 0x7f);
-	t->time.tm_hour = bcd2bin(ds1307->regs[5] & 0x3f);
-	t->time.tm_wday = bcd2bin(ds1307->regs[6] & 0x7) - 1;
-	t->time.tm_mday = bcd2bin(ds1307->regs[7] & 0x3f);
-	t->time.tm_mon = bcd2bin(ds1307->regs[8] & 0x1f) - 1;
+	t->time.tm_sec = bcd2bin(regs[3] & 0x7f);
+	t->time.tm_min = bcd2bin(regs[4] & 0x7f);
+	t->time.tm_hour = bcd2bin(regs[5] & 0x3f);
+	t->time.tm_wday = bcd2bin(regs[6] & 0x7) - 1;
+	t->time.tm_mday = bcd2bin(regs[7] & 0x3f);
+	t->time.tm_mon = bcd2bin(regs[8] & 0x1f) - 1;
 	t->time.tm_year = -1;
 	t->time.tm_yday = -1;
 	t->time.tm_isdst = -1;
@@ -693,9 +695,9 @@  static int mcp794xx_read_alarm(struct device *dev, struct rtc_wkalrm *t)
 		"enabled=%d polarity=%d irq=%d match=%d\n", __func__,
 		t->time.tm_sec, t->time.tm_min, t->time.tm_hour,
 		t->time.tm_wday, t->time.tm_mday, t->time.tm_mon, t->enabled,
-		!!(ds1307->regs[6] & MCP794XX_BIT_ALMX_POL),
-		!!(ds1307->regs[6] & MCP794XX_BIT_ALMX_IF),
-		(ds1307->regs[6] & MCP794XX_MSK_ALMX_MATCH) >> 4);
+		!!(regs[6] & MCP794XX_BIT_ALMX_POL),
+		!!(regs[6] & MCP794XX_BIT_ALMX_IF),
+		(regs[6] & MCP794XX_MSK_ALMX_MATCH) >> 4);
 
 	return 0;
 }
@@ -704,7 +706,7 @@  static int mcp794xx_set_alarm(struct device *dev, struct rtc_wkalrm *t)
 {
 	struct i2c_client *client = to_i2c_client(dev);
 	struct ds1307 *ds1307 = i2c_get_clientdata(client);
-	unsigned char *regs = ds1307->regs;
+	u8  regs[DS1307_REG_COUNT];
 	int ret;
 
 	if (!test_bit(HAS_ALARM, &ds1307->flags))
@@ -1274,11 +1276,9 @@  static bool ds1307_want_irq(const struct ds1307 *ds1307,
 static int ds1307_chip_configure(struct ds1307 *ds1307)
 {
 	int tmp;
-	unsigned char *buf;
+	u8  regs[DS1307_REG_COUNT];
 	struct i2c_client *client = ds1307->client;
 
-	buf = ds1307->regs;
-
 	switch (ds1307->type) {
 	case ds_1337:
 	case ds_1339:
@@ -1293,32 +1293,32 @@  static int ds1307_chip_configure(struct ds1307 *ds1307)
 
 		/* get registers that the "rtc" read below won't read... */
 		tmp = ds1307->read_block_data(client,
-					      DS1337_REG_CONTROL, 2, buf);
+					      DS1337_REG_CONTROL, 2, regs);
 		if (tmp != 2) {
 			dev_dbg(&ds1307->client->dev, "read error %d\n", tmp);
 			return -EIO;
 		}
 
 		/* oscillator off?  turn it on, so clock can tick. */
-		if (ds1307->regs[0] & DS1337_BIT_nEOSC)
-			ds1307->regs[0] &= ~DS1337_BIT_nEOSC;
+		if (regs[0] & DS1337_BIT_nEOSC)
+			regs[0] &= ~DS1337_BIT_nEOSC;
 
 		if (ds1307->type == ds_1341) {
 			/* Make sure we are not generating square wave
 			 * output */
-			ds1307->regs[1] &= ~DS1341_BIT_ECLK;
+			regs[1] &= ~DS1341_BIT_ECLK;
 
 			if (of_property_read_bool(client->dev.of_node,
 						  "disable-oscillator-stop-flag"))
-				ds1307->regs[1] |= DS1341_BIT_DOSF;
+				regs[1] |= DS1341_BIT_DOSF;
 			else
-				ds1307->regs[1] &= ~DS1341_BIT_DOSF;
+				regs[1] &= ~DS1341_BIT_DOSF;
 
 			if (of_property_read_bool(client->dev.of_node,
 						  "enable-glitch-filter"))
-				ds1307->regs[0] |= DS1341_BIT_EGFIL;
+				regs[0] |= DS1341_BIT_EGFIL;
 			else
-				ds1307->regs[0] &= ~DS1341_BIT_EGFIL;
+				regs[0] &= ~DS1341_BIT_EGFIL;
 
 			/*
 			 * Write status register. Control register
@@ -1326,7 +1326,7 @@  static int ds1307_chip_configure(struct ds1307 *ds1307)
 			 */
 			i2c_smbus_write_byte_data(client,
 						  DS1337_REG_STATUS,
-						  ds1307->regs[1]);
+						  regs[1]);
 		}
 
 		/*
@@ -1334,19 +1334,19 @@  static int ds1307_chip_configure(struct ds1307 *ds1307)
 		 * For some variants, be sure alarms can trigger when we're
 		 * running on Vbackup (BBSQI/BBSQW)
 		 */
-		ds1307->regs[0] |= DS1337_BIT_INTCN
+		regs[0] |= DS1337_BIT_INTCN
 			| bbsqi_bitpos[ds1307->type];
-		ds1307->regs[0] &= ~(DS1337_BIT_A2IE | DS1337_BIT_A1IE);
+		regs[0] &= ~(DS1337_BIT_A2IE | DS1337_BIT_A1IE);
 
 		i2c_smbus_write_byte_data(client,
 					  DS1337_REG_CONTROL,
-					  ds1307->regs[0]);
+					  regs[0]);
 
 		/* oscillator fault?  clear flag, and warn */
-		if (ds1307->regs[1] & DS1337_BIT_OSF) {
+		if (regs[1] & DS1337_BIT_OSF) {
 			i2c_smbus_write_byte_data(client,
 						  DS1337_REG_STATUS,
-						  ds1307->regs[1] & ~DS1337_BIT_OSF);
+						  regs[1] & ~DS1337_BIT_OSF);
 			dev_warn(&ds1307->client->dev, "SET TIME!\n");
 		}
 		break;
@@ -1354,60 +1354,60 @@  static int ds1307_chip_configure(struct ds1307 *ds1307)
 	case rx_8025:
 		tmp = i2c_smbus_read_i2c_block_data(client,
 						    RX8025_REG_CTRL1 << 4 | 0x08,
-						    2, buf);
+						    2, regs);
 		if (tmp != 2) {
 			dev_dbg(&client->dev, "read error %d\n", tmp);
 			return -EIO;
 		}
 
 		/* oscillator off?  turn it on, so clock can tick. */
-		if (!(ds1307->regs[1] & RX8025_BIT_XST)) {
-			ds1307->regs[1] |= RX8025_BIT_XST;
+		if (!(regs[1] & RX8025_BIT_XST)) {
+			regs[1] |= RX8025_BIT_XST;
 			i2c_smbus_write_byte_data(client,
 						  RX8025_REG_CTRL2 << 4 | 0x08,
-						  ds1307->regs[1]);
+						  regs[1]);
 			dev_warn(&client->dev,
 				 "oscillator stop detected - SET TIME!\n");
 		}
 
-		if (ds1307->regs[1] & RX8025_BIT_PON) {
-			ds1307->regs[1] &= ~RX8025_BIT_PON;
+		if (regs[1] & RX8025_BIT_PON) {
+			regs[1] &= ~RX8025_BIT_PON;
 			i2c_smbus_write_byte_data(client,
 						  RX8025_REG_CTRL2 << 4 | 0x08,
-						  ds1307->regs[1]);
+						  regs[1]);
 			dev_warn(&client->dev, "power-on detected\n");
 		}
 
-		if (ds1307->regs[1] & RX8025_BIT_VDET) {
-			ds1307->regs[1] &= ~RX8025_BIT_VDET;
+		if (regs[1] & RX8025_BIT_VDET) {
+			regs[1] &= ~RX8025_BIT_VDET;
 			i2c_smbus_write_byte_data(client,
 						  RX8025_REG_CTRL2 << 4 | 0x08,
-						  ds1307->regs[1]);
+						  regs[1]);
 			dev_warn(&client->dev, "voltage drop detected\n");
 		}
 
 		/* make sure we are running in 24hour mode */
-		if (!(ds1307->regs[0] & RX8025_BIT_2412)) {
+		if (!(regs[0] & RX8025_BIT_2412)) {
 			u8 hour;
 
 			/* switch to 24 hour mode */
 			i2c_smbus_write_byte_data(client,
 						  RX8025_REG_CTRL1 << 4 | 0x08,
-						  ds1307->regs[0] | RX8025_BIT_2412);
+						  regs[0] | RX8025_BIT_2412);
 
 			tmp = i2c_smbus_read_i2c_block_data(client,
 							    RX8025_REG_CTRL1 << 4 | 0x08,
-							    2, buf);
+							    2, regs);
 			if (tmp != 2) {
 				dev_dbg(&client->dev, "read error %d\n", tmp);
 				return -EIO;
 			}
 
 			/* correct hour */
-			hour = bcd2bin(ds1307->regs[DS1307_REG_HOUR]);
+			hour = bcd2bin(regs[DS1307_REG_HOUR]);
 			if (hour == 12)
 				hour = 0;
-			if (ds1307->regs[DS1307_REG_HOUR] & DS1307_BIT_PM)
+			if (regs[DS1307_REG_HOUR] & DS1307_BIT_PM)
 				hour += 12;
 
 			i2c_smbus_write_byte_data(client,
@@ -1425,14 +1425,12 @@  static int ds1307_chip_configure(struct ds1307 *ds1307)
 static int ds1307_chip_sanity_check(struct ds1307 *ds1307)
 {
 	int tmp;
-	unsigned char *buf;
+	u8  regs[DS1307_REG_COUNT];
 	struct i2c_client *client = ds1307->client;
 
-	buf = ds1307->regs;
-
 read_rtc:
 	/* read RTC registers */
-	tmp = ds1307->read_block_data(ds1307->client, ds1307->offset, 8, buf);
+	tmp = ds1307->read_block_data(ds1307->client, ds1307->offset, 8, regs);
 	if (tmp != 8) {
 		dev_dbg(&client->dev, "read error %d\n", tmp);
 		return -EIO;
@@ -1443,7 +1441,7 @@  read_rtc:
 	 * 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];
+	tmp = regs[DS1307_REG_SECS];
 	switch (ds1307->type) {
 	case ds_1307:
 	case m41t00:
@@ -1460,9 +1458,9 @@  read_rtc:
 			i2c_smbus_write_byte_data(client, DS1307_REG_SECS, 0);
 
 		/* oscillator fault?  clear flag, and warn */
-		if (ds1307->regs[DS1307_REG_CONTROL] & DS1338_BIT_OSF) {
+		if (regs[DS1307_REG_CONTROL] & DS1338_BIT_OSF) {
 			i2c_smbus_write_byte_data(client, DS1307_REG_CONTROL,
-					ds1307->regs[DS1307_REG_CONTROL]
+					regs[DS1307_REG_CONTROL]
 					& ~DS1338_BIT_OSF);
 			dev_warn(&client->dev, "SET TIME!\n");
 			goto read_rtc;
@@ -1487,9 +1485,9 @@  read_rtc:
 		break;
 	case mcp794xx:
 		/* make sure that the backup battery is enabled */
-		if (!(ds1307->regs[DS1307_REG_WDAY] & MCP794XX_BIT_VBATEN)) {
+		if (!(regs[DS1307_REG_WDAY] & MCP794XX_BIT_VBATEN)) {
 			i2c_smbus_write_byte_data(client, DS1307_REG_WDAY,
-					ds1307->regs[DS1307_REG_WDAY]
+					regs[DS1307_REG_WDAY]
 					| MCP794XX_BIT_VBATEN);
 		}
 
@@ -1514,10 +1512,10 @@  static int ds1307_probe(struct i2c_client *client,
 {
 	struct ds1307		*ds1307;
 	int			err = -ENODEV;
-	int			tmp;
+	int			reg;
+	u8			hour;
 	struct chip_desc	*chip = &chips[id->driver_data];
 	struct i2c_adapter	*adapter = to_i2c_adapter(client->dev.parent);
-	unsigned char		*buf;
 	struct ds1307_platform_data *pdata = dev_get_platdata(&client->dev);
 	irq_handler_t	irq_handler = ds1307_irq;
 
@@ -1550,7 +1548,6 @@  static int ds1307_probe(struct i2c_client *client,
 		    chip->trickle_charger_setup);
 	}
 
-	buf = ds1307->regs;
 	if (i2c_check_functionality(adapter, I2C_FUNC_SMBUS_I2C_BLOCK)) {
 		ds1307->read_block_data = ds1307_native_smbus_read_block_data;
 		ds1307->write_block_data = ds1307_native_smbus_write_block_data;
@@ -1579,7 +1576,14 @@  static int ds1307_probe(struct i2c_client *client,
 	if (err < 0)
 		return err;
 
-	tmp = ds1307->regs[DS1307_REG_HOUR];
+	reg = i2c_smbus_read_byte_data(client,
+				       ds1307->offset + DS1307_REG_HOUR);
+	if (reg < 0) {
+		dev_err(&client->dev,
+			"failed to read HOUR register\n");
+		return reg;
+	}
+
 	switch (ds1307->type) {
 	case ds_1340:
 	case m41t00:
@@ -1591,21 +1595,21 @@  static int ds1307_probe(struct i2c_client *client,
 	case rx_8025:
 		break;
 	default:
-		if (!(tmp & DS1307_BIT_12HR))
+		if (!(reg & DS1307_BIT_12HR))
 			break;
 
 		/*
 		 * Be sure we're in 24 hour mode.  Multi-master systems
 		 * take note...
 		 */
-		tmp = bcd2bin(tmp & 0x1f);
-		if (tmp == 12)
-			tmp = 0;
-		if (ds1307->regs[DS1307_REG_HOUR] & DS1307_BIT_PM)
-			tmp += 12;
+		hour = bcd2bin(reg & 0x1f);
+		if (hour == 12)
+			hour = 0;
+		if (reg & DS1307_BIT_PM)
+			hour += 12;
 		i2c_smbus_write_byte_data(client,
 				ds1307->offset + DS1307_REG_HOUR,
-				bin2bcd(tmp));
+				bin2bcd(hour));
 	}
 
 	if (ds1307_want_irq(ds1307, chip)) {
@@ -1620,7 +1624,6 @@  static int ds1307_probe(struct i2c_client *client,
 
 	if (ds1307_can_wakeup_device(ds1307) &&
 	    ds1307->client->irq <= 0) {
-		/* Disable request for an IRQ */
 		dev_info(&client->dev,
 			 "'wakeup-source' is set, request for an IRQ is disabled!\n");
 		/* We cannot support UIE mode if we do not have an IRQ line */