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Commit e4879e28 authored by Jean Delvare's avatar Jean Delvare
Browse files

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: default avatarJean Delvare <khali@linux-fr.org>
Cc: Aurelien Jarno <aurelien@aurel32.net>
parent 594592dc

drivers/hwmon/ds1621.c

+9 −6
Original line number Diff line number Diff line
@@ -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);