From e4879e28abd67b894fb9d2db0afd08f1945670ba Mon Sep 17 00:00:00 2001 From: Jean Delvare Date: Mon, 30 Mar 2009 21:46:40 +0200 Subject: hwmon: (ds1621) Avoid unneeded register access 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 Cc: Aurelien Jarno --- drivers/hwmon/ds1621.c | 15 +++++++++------ 1 file changed, 9 insertions(+), 6 deletions(-) (limited to 'drivers') diff --git a/drivers/hwmon/ds1621.c b/drivers/hwmon/ds1621.c index fe160c54b959..53f88f511816 100644 --- a/drivers/hwmon/ds1621.c +++ b/drivers/hwmon/ds1621.c @@ -101,17 +101,20 @@ static int ds1621_write_temp(struct i2c_client *client, u8 reg, u16 value) 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 *dev, struct device_attribute *da, { 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); -- cgit v1.2.3-59-g8ed1b