linux-kernel - [PATCH 1/8 v3] i2c: i801: refactor use of LAST_BYTE i801_block_transaction_byte_by

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Date:	Wed, 27 Jun 2012 21:54:08 +0800
From:	Daniel Kurtz <djkurtz@...omium.org>
To:	Jean Delvare <khali@...ux-fr.org>, Ben Dooks <ben-linux@...ff.org>,
	Wolfram Sang <w.sang@...gutronix.de>,
	Seth Heasley <seth.heasley@...el.com>
Cc:	Olof Johansson <olof@...om.net>,
	Benson Leung <bleung@...omium.org>, linux-i2c@...r.kernel.org,
	linux-kernel@...r.kernel.org, Daniel Kurtz <djkurtz@...omium.org>
Subject: [PATCH 1/8 v3] i2c: i801: refactor use of LAST_BYTE i801_block_transaction_byte_by_byte

As a slight optimization, pull some logic out of the polling loop during
byte-by-byte transactions by just setting the I801_LAST_BYTE bit, as
defined in the i801 (PCH) datasheet, when reading the last byte of a
byte-by-byte I2C_SMBUS_READ.

Signed-off-by: Daniel Kurtz <djkurtz@...omium.org>
---
 drivers/i2c/busses/i2c-i801.c |   28 ++++++++++++++--------------
 1 files changed, 14 insertions(+), 14 deletions(-)

diff --git a/drivers/i2c/busses/i2c-i801.c b/drivers/i2c/busses/i2c-i801.c
index ae2945a..51e11eb 100644
--- a/drivers/i2c/busses/i2c-i801.c
+++ b/drivers/i2c/busses/i2c-i801.c
@@ -117,8 +117,7 @@
 #define I801_PROC_CALL		0x10	/* unimplemented */
 #define I801_BLOCK_DATA		0x14
 #define I801_I2C_BLOCK_DATA	0x18	/* ICH5 and later */
-#define I801_BLOCK_LAST		0x34
-#define I801_I2C_BLOCK_LAST	0x38	/* ICH5 and later */
+#define I801_LAST_BYTE		0x20
 #define I801_START		0x40
 #define I801_PEC_EN		0x80	/* ICH3 and later */
 
@@ -338,6 +337,11 @@ static int i801_block_transaction_by_block(struct i801_priv *priv,
 	return 0;
 }
 
+/*
+ * For "byte-by-byte" block transactions:
+ *   I2C write uses cmd=I801_BLOCK_DATA, I2C_EN=1
+ *   I2C read uses cmd=I801_I2C_BLOCK_DATA
+ */
 static int i801_block_transaction_byte_by_byte(struct i801_priv *priv,
 					       union i2c_smbus_data *data,
 					       char read_write, int command,
@@ -360,19 +364,15 @@ static int i801_block_transaction_byte_by_byte(struct i801_priv *priv,
 		outb_p(data->block[1], SMBBLKDAT(priv));
 	}
 
+	if (command == I2C_SMBUS_I2C_BLOCK_DATA &&
+	    read_write == I2C_SMBUS_READ)
+		smbcmd = I801_I2C_BLOCK_DATA;
+	else
+		smbcmd = I801_BLOCK_DATA;
+
 	for (i = 1; i <= len; i++) {
-		if (i == len && read_write == I2C_SMBUS_READ) {
-			if (command == I2C_SMBUS_I2C_BLOCK_DATA)
-				smbcmd = I801_I2C_BLOCK_LAST;
-			else
-				smbcmd = I801_BLOCK_LAST;
-		} else {
-			if (command == I2C_SMBUS_I2C_BLOCK_DATA
-			 && read_write == I2C_SMBUS_READ)
-				smbcmd = I801_I2C_BLOCK_DATA;
-			else
-				smbcmd = I801_BLOCK_DATA;
-		}
+		if (i == len && read_write == I2C_SMBUS_READ)
+			smbcmd |= I801_LAST_BYTE;
 		outb_p(smbcmd | ENABLE_INT9, SMBHSTCNT(priv));
 
 		if (i == 1)
-- 
1.7.7.3

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