Register access over SMBus isn't cheap, so avoid register access where
possible:
* Only write back the configuration register if it changed.
* Don't refresh the register cache when we don't have to.
Signed-off-by: Jean Delvare <khali at linux-fr.org>
Cc: Aurelien Jarno <aurelien at aurel32.net>
---
drivers/hwmon/ds1621.c | 15 +++++++++------
1 file changed, 9 insertions(+), 6 deletions(-)
--- linux-2.6.29-rc2.orig/drivers/hwmon/ds1621.c 2009-01-28 10:04:25.000000000 +0100
+++ linux-2.6.29-rc2/drivers/hwmon/ds1621.c 2009-01-28 10:06:50.000000000 +0100
@@ -101,17 +101,20 @@ static int ds1621_write_temp(struct i2c_
static void ds1621_init_client(struct i2c_client *client)
{
- int reg = i2c_smbus_read_byte_data(client, DS1621_REG_CONF);
+ u8 conf, new_conf;
+
+ new_conf = conf = i2c_smbus_read_byte_data(client, DS1621_REG_CONF);
/* switch to continuous conversion mode */
- reg &= ~ DS1621_REG_CONFIG_1SHOT;
+ new_conf &= ~DS1621_REG_CONFIG_1SHOT;
/* setup output polarity */
if (polarity == 0)
- reg &= ~DS1621_REG_CONFIG_POLARITY;
+ new_conf &= ~DS1621_REG_CONFIG_POLARITY;
else if (polarity == 1)
- reg |= DS1621_REG_CONFIG_POLARITY;
+ new_conf |= DS1621_REG_CONFIG_POLARITY;
- i2c_smbus_write_byte_data(client, DS1621_REG_CONF, reg);
+ if (conf != new_conf)
+ i2c_smbus_write_byte_data(client, DS1621_REG_CONF, new_conf);
/* start conversion */
i2c_smbus_write_byte(client, DS1621_COM_START);
@@ -170,7 +173,7 @@ static ssize_t set_temp(struct device *d
{
struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
struct i2c_client *client = to_i2c_client(dev);
- struct ds1621_data *data = ds1621_update_client(dev);
+ struct ds1621_data *data = i2c_get_clientdata(client);
u16 val = LM75_TEMP_TO_REG(simple_strtol(buf, NULL, 10));
mutex_lock(&data->update_lock);
--
Jean Delvare
