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Date: Fri, 6 Jan 2012 18:58:20 +0800
From: Daniel Kurtz <djkurtz@...omium.org>
To: khali@...ux-fr.org, ben-linux@...ff.org, seth.heasley@...el.com,
ben@...adent.org.uk, David.Woodhouse@...el.com,
linux-i2c@...r.kernel.org, linux-kernel@...r.kernel.org
Cc: olofj@...omium.org, bleung@...omium.org,
Daniel Kurtz <djkurtz@...omium.org>
Subject: [PATCH 1/3] i2c: i801: refactor i801_block_transaction_byte_by_byte
1) As a slight optimization, pull some logic out of the byte 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.
2) Clear INTR after clearing BYTE_DONE per ICH10 datasheet [1] pg. 711:
When the last byte of a block message is received, the host controller
sets DS. However, it does not set the INTR bit (and generate another
interrupt) until DS is cleared. Thus, for a block message of n bytes,
the ICH10 will generate n+1 interrupts.
3) If DEV_ERR is set in polling loop, abort the transaction and return
-ENXIO to the caller. DEV_ERR is set if the device does not respond with
an acknowledge, and the SMBus controller times out (minimum 25ms).
[1] http://www.intel.com/content/dam/doc/datasheet/io-controller-hub-10-family-datasheet.pdf
Signed-off-by: Daniel Kurtz <djkurtz@...omium.org>
---
drivers/i2c/busses/i2c-i801.c | 45 ++++++++++++++++++++++++----------------
1 files changed, 27 insertions(+), 18 deletions(-)
diff --git a/drivers/i2c/busses/i2c-i801.c b/drivers/i2c/busses/i2c-i801.c
index ab26840d..f3418cf 100644
--- a/drivers/i2c/busses/i2c-i801.c
+++ b/drivers/i2c/busses/i2c-i801.c
@@ -116,8 +116,7 @@
#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 */
@@ -320,7 +319,7 @@ static int i801_block_transaction_by_block(struct i801_priv *priv,
}
status = i801_transaction(priv, I801_BLOCK_DATA | ENABLE_INT9 |
- I801_PEC_EN * hwpec);
+ (hwpec ? I801_PEC_EN : 0));
if (status)
return status;
@@ -336,6 +335,10 @@ static int i801_block_transaction_by_block(struct i801_priv *priv,
return 0;
}
+/*
+ * 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,
@@ -358,19 +361,15 @@ 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)
@@ -382,8 +381,9 @@ static int i801_block_transaction_byte_by_byte(struct i801_priv *priv,
do {
msleep(1);
status = inb_p(SMBHSTSTS(priv));
- } while ((!(status & SMBHSTSTS_BYTE_DONE))
- && (timeout++ < MAX_TIMEOUT));
+ } while (!(status & SMBHSTSTS_BYTE_DONE) &&
+ !(status & SMBHSTSTS_DEV_ERR) &&
+ timeout++ < MAX_TIMEOUT);
result = i801_check_post(priv, status, timeout > MAX_TIMEOUT);
if (result < 0)
@@ -414,8 +414,17 @@ static int i801_block_transaction_byte_by_byte(struct i801_priv *priv,
outb_p(data->block[i+1], SMBBLKDAT(priv));
/* signals SMBBLKDAT ready */
- outb_p(SMBHSTSTS_BYTE_DONE | SMBHSTSTS_INTR, SMBHSTSTS(priv));
+ outb_p(SMBHSTSTS_BYTE_DONE, SMBHSTSTS(priv));
+ }
+
+ /* Wait for command-completion interrupt so we can clear it */
+ timeout = 0;
+ status = inb_p(SMBHSTSTS(priv));
+ while (!(status & SMBHSTSTS_INTR) && timeout++ < MAX_TIMEOUT) {
+ msleep(1);
+ status = inb_p(SMBHSTSTS(priv));
}
+ outb_p(SMBHSTSTS_INTR, SMBHSTSTS(priv));
return 0;
}
--
1.7.3.1
--
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