From ed4dfa0cbdf6c3e910518dfa1ab9468cb8acb1b7 Mon Sep 17 00:00:00 2001
From: Jean Delvare <khali@linux-fr.org>
Date: Mon, 24 May 2004 18:40:07 +0000
Subject: [PATCH] Rework auto fan clock divider algorithm.

git-svn-id: http://lm-sensors.org/svn/lm-sensors/trunk@2563 7894878c-1315-0410-8ee3-d5d059ff63e0
---
 kernel/chips/pc87360.c | 25 ++++++++++++++-----------
 1 file changed, 14 insertions(+), 11 deletions(-)

diff --git a/kernel/chips/pc87360.c b/kernel/chips/pc87360.c
index c0bfc802..d8035609 100644
--- a/kernel/chips/pc87360.c
+++ b/kernel/chips/pc87360.c
@@ -853,6 +853,8 @@ static void pc87360_init_client(struct i2c_client *client, int use_thermistors)
 
 static void pc87360_autodiv(struct pc87360_data *data, int nr)
 {
+	u8 old_min = data->fan_min[nr];
+
 	/* Increase clock divider if needed and possible */
 	if ((data->fan_status[nr] & 0x04) /* overflow flag */
 	 || (data->fan[nr] >= 224)) { /* next to overflow */
@@ -860,9 +862,6 @@ static void pc87360_autodiv(struct pc87360_data *data, int nr)
 			data->fan_status[nr] += 0x20;
 			data->fan_min[nr] >>= 1;
 			data->fan[nr] >>= 1;
-			pc87360_write_value(data, LD_FAN, NO_BANK,
-					    PC87360_REG_FAN_MIN(nr),
-					    data->fan_min[nr]);
 #ifdef DEBUG
 			printk(KERN_DEBUG "pc87360.o: Increasing "
 			       "clock divider to %d for fan %d\n",
@@ -870,17 +869,14 @@ static void pc87360_autodiv(struct pc87360_data *data, int nr)
 			       nr+1);
 #endif
 		}
-	} else
-	/* Decrease clock divider if needed and possible */
-	if (data->fan[nr] < 85 /* bad accuracy */
-	 && !(data->fan_min[nr] & 0x80)) {
-		if ((data->fan_status[nr] & 0x60) != 0x00) {
+	} else {
+		/* Decrease clock divider if possible */
+		while (!(data->fan_min[nr] & 0x80) /* fan min "nails" divider */
+		 && data->fan[nr] < 85 /* bad accuracy */
+		 && (data->fan_status[nr] & 0x60) != 0x00) {
 			data->fan_status[nr] -= 0x20;
 			data->fan_min[nr] <<= 1;
 			data->fan[nr] <<= 1;
-			pc87360_write_value(data, LD_FAN, NO_BANK,
-					    PC87360_REG_FAN_MIN(nr),
-					    data->fan_min[nr]);
 #ifdef DEBUG
 			printk(KERN_DEBUG "pc87360.o: Decreasing "
 			       "clock divider to %d for fan %d\n",
@@ -889,6 +885,13 @@ static void pc87360_autodiv(struct pc87360_data *data, int nr)
 #endif
 		}
 	}
+
+	/* Write new fan min if it changed */
+	if (old_min != data->fan_min[nr]) {
+		pc87360_write_value(data, LD_FAN, NO_BANK,
+				    PC87360_REG_FAN_MIN(nr),
+				    data->fan_min[nr]);
+	}
 }
 
 static void pc87360_update_client(struct i2c_client *client)