[PATCH 1/8 v3] i2c: i801: refactor use of LAST_BYTE i801_block_transaction_byte_by_byte

Daniel Kurtz
2012-06-27T13:55:01Z

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@chromium.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