i2c-i801: Use usleep_range to wait for command completion

Use usleep_range instead of msleep when waiting for command
completion. Most SMBus commands complete in less than 2 jiffies so
this brings a pleasant performance boost.

Strongly inspired from a similar change by Olivier Sobrie to the
i2c-isch driver.
Signed-off-by: Jean Delvare <khali@linux-fr.org>
Cc: Olivier Sobrie <olivier@sobrie.be>

drivers/i2c/busses/i2c-i801.c

@@ -2,7 +2,7 @@
     Copyright (c) 1998 - 2002  Frodo Looijaard <frodol@dds.nl>,
     Philip Edelbrock <phil@netroedge.com>, and Mark D. Studebaker
     <mdsxyz123@yahoo.com>
-    Copyright (C) 2007, 2008   Jean Delvare <khali@linux-fr.org>
+    Copyright (C) 2007 - 2012  Jean Delvare <khali@linux-fr.org>
     Copyright (C) 2010         Intel Corporation,
                                David Woodhouse <dwmw2@infradead.org>
 
@@ -106,7 +106,7 @@
 #define SMBHSTCNT_KILL		2
 
 /* Other settings */
-#define MAX_TIMEOUT		100
+#define MAX_RETRIES		400
 #define ENABLE_INT9		0	/* set to 0x01 to enable - untested */
 
 /* I801 command constants */
@@ -217,7 +217,7 @@ static int i801_check_post(struct i801_priv *priv, int status, int timeout)
 		dev_dbg(&priv->pci_dev->dev, "Terminating the current operation\n");
 		outb_p(inb_p(SMBHSTCNT(priv)) | SMBHSTCNT_KILL,
 		       SMBHSTCNT(priv));
-		msleep(1);
+		usleep_range(1000, 2000);
 		outb_p(inb_p(SMBHSTCNT(priv)) & (~SMBHSTCNT_KILL),
 		       SMBHSTCNT(priv));
 
@@ -274,11 +274,11 @@ static int i801_transaction(struct i801_priv *priv, int xact)
 
 	/* We will always wait for a fraction of a second! */
 	do {
-		msleep(1);
+		usleep_range(250, 500);
 		status = inb_p(SMBHSTSTS(priv));
-	} while ((status & SMBHSTSTS_HOST_BUSY) && (timeout++ < MAX_TIMEOUT));
+	} while ((status & SMBHSTSTS_HOST_BUSY) && (timeout++ < MAX_RETRIES));
 
-	result = i801_check_post(priv, status, timeout > MAX_TIMEOUT);
+	result = i801_check_post(priv, status, timeout > MAX_RETRIES);
 	if (result < 0)
 		return result;
 
@@ -293,12 +293,12 @@ static void i801_wait_hwpec(struct i801_priv *priv)
 	int status;
 
 	do {
-		msleep(1);
+		usleep_range(250, 500);
 		status = inb_p(SMBHSTSTS(priv));
 	} while ((!(status & SMBHSTSTS_INTR))
-		 && (timeout++ < MAX_TIMEOUT));
+		 && (timeout++ < MAX_RETRIES));
 
-	if (timeout > MAX_TIMEOUT)
+	if (timeout > MAX_RETRIES)
 		dev_dbg(&priv->pci_dev->dev, "PEC Timeout!\n");
 
 	outb_p(status, SMBHSTSTS(priv));
@@ -382,12 +382,12 @@ static int i801_block_transaction_byte_by_byte(struct i801_priv *priv,
 		/* We will always wait for a fraction of a second! */
 		timeout = 0;
 		do {
-			msleep(1);
+			usleep_range(250, 500);
 			status = inb_p(SMBHSTSTS(priv));
 		} while ((!(status & SMBHSTSTS_BYTE_DONE))
-			 && (timeout++ < MAX_TIMEOUT));
+			 && (timeout++ < MAX_RETRIES));
 
-		result = i801_check_post(priv, status, timeout > MAX_TIMEOUT);
+		result = i801_check_post(priv, status, timeout > MAX_RETRIES);
 		if (result < 0)
 			return result;