On Fri, Feb 15, 2013 at 05:57:15PM +0100, Lars-Peter Clausen wrote: > Currently each time the temperature register is read the driver also reads the > threshold and hysteresis registers. This increases the amount of I2C traffic and > time needed to read the temperature by a factor of ~5. Neither the threshold nor > the hysteresis change on their own, so once we've read them, we should be able > to just use the cached value of the registers. This patch modifies the code > accordingly and only reads the threshold and hysteresis registers once during > probe. > > Signed-off-by: Lars-Peter Clausen <lars@xxxxxxxxxx> > --- > drivers/hwmon/adt7410.c | 89 +++++++++++++++++++++++++++++++------------------ > 1 file changed, 56 insertions(+), 33 deletions(-) > > diff --git a/drivers/hwmon/adt7410.c b/drivers/hwmon/adt7410.c > index 99a7290..5de0376 100644 > --- a/drivers/hwmon/adt7410.c > +++ b/drivers/hwmon/adt7410.c > @@ -119,45 +119,31 @@ static int adt7410_temp_ready(struct i2c_client *client) > return -ETIMEDOUT; > } > > -static struct adt7410_data *adt7410_update_device(struct device *dev) > +static int adt7410_update_temp(struct device *dev) > { > struct i2c_client *client = to_i2c_client(dev); > struct adt7410_data *data = i2c_get_clientdata(client); > - struct adt7410_data *ret = data; > + int ret = 0; > + > mutex_lock(&data->update_lock); > > if (time_after(jiffies, data->last_updated + HZ + HZ / 2) > || !data->valid) { > - int i, status; > > dev_dbg(&client->dev, "Starting update\n"); > > - status = adt7410_temp_ready(client); /* check for new value */ > - if (unlikely(status)) { > - ret = ERR_PTR(status); > + ret = adt7410_temp_ready(client); /* check for new value */ > + if (ret) > goto abort; > - } > - for (i = 0; i < ARRAY_SIZE(data->temp); i++) { > - status = i2c_smbus_read_word_swapped(client, > - ADT7410_REG_TEMP[i]); > - if (unlikely(status < 0)) { > - dev_dbg(dev, > - "Failed to read value: reg %d, error %d\n", > - ADT7410_REG_TEMP[i], status); > - ret = ERR_PTR(status); > - goto abort; > - } > - data->temp[i] = status; > - } > - status = i2c_smbus_read_byte_data(client, ADT7410_T_HYST); > - if (unlikely(status < 0)) { > - dev_dbg(dev, > - "Failed to read value: reg %d, error %d\n", > - ADT7410_T_HYST, status); > - ret = ERR_PTR(status); > + > + ret = i2c_smbus_read_word_swapped(client, ADT7410_REG_TEMP[0]); > + if (ret) { Should be if (ret < 0) { or non-zero temperatures always create an error condition. > + dev_dbg(dev, "Failed to read value: reg %d, error %d\n", > + ADT7410_REG_TEMP[0], ret); > goto abort; > } > - data->hyst = status; > + data->temp[0] = ret; > + > data->last_updated = jiffies; > data->valid = true; > } > @@ -167,6 +153,35 @@ abort: > return ret; ret can be > 0 as no-error return. So you'll either have to change the no-error return case to always return 0, or change the return value check when the function is called. > } > > +static int adt7410_fill_cache(struct i2c_client *client) > +{ > + struct adt7410_data *data = i2c_get_clientdata(client); > + int ret; > + int i; > + > + for (i = 1; i < 3; i++) { I think using ARRAY_SIZE would be better here. With "i < 3" you don't read the critical temperature, which proves the point (unless I am missing something). > + ret = i2c_smbus_read_word_swapped(client, ADT7410_REG_TEMP[i]); > + if (ret) { ret < 0 > + dev_dbg(&client->dev, > + "Failed to read value: reg %d, error %d\n", > + ADT7410_REG_TEMP[0], ret); > + return ret; > + } > + data->temp[i] = ret; > + } > + > + ret = i2c_smbus_read_byte_data(client, ADT7410_T_HYST); > + if (ret) { ret < 0 > + dev_dbg(&client->dev, > + "Failed to read value: hyst reg, error %d\n", > + ret); > + return ret; > + } > + data->hyst = ret; > + > + return 0; > +} > + > static s16 ADT7410_TEMP_TO_REG(long temp) > { > return DIV_ROUND_CLOSEST(clamp_val(temp, ADT7410_TEMP_MIN, > @@ -193,10 +208,16 @@ static ssize_t adt7410_show_temp(struct device *dev, > struct device_attribute *da, char *buf) > { > struct sensor_device_attribute *attr = to_sensor_dev_attr(da); > - struct adt7410_data *data = adt7410_update_device(dev); > + struct i2c_client *client = to_i2c_client(dev); > + struct adt7410_data *data = i2c_get_clientdata(client); > > - if (IS_ERR(data)) > - return PTR_ERR(data); > + if (attr->index == 0) { > + int ret; > + > + ret = adt7410_update_temp(dev); > + if (ret) Problematic; see above. > + return ret; > + } > > return sprintf(buf, "%d\n", ADT7410_REG_TO_TEMP(data, > data->temp[attr->index])); > @@ -232,13 +253,11 @@ static ssize_t adt7410_show_t_hyst(struct device *dev, > char *buf) > { > struct sensor_device_attribute *attr = to_sensor_dev_attr(da); > - struct adt7410_data *data; > + struct i2c_client *client = to_i2c_client(dev); > + struct adt7410_data *data = i2c_get_clientdata(client); > int nr = attr->index; > int hyst; > > - data = adt7410_update_device(dev); > - if (IS_ERR(data)) > - return PTR_ERR(data); > hyst = (data->hyst & ADT7410_T_HYST_MASK) * 1000; > > /* > @@ -371,6 +390,10 @@ static int adt7410_probe(struct i2c_client *client, > } > dev_dbg(&client->dev, "Config %02x\n", data->config); > > + ret = adt7410_fill_cache(client); > + if (ret) > + goto exit_restore; > + > /* Register sysfs hooks */ > ret = sysfs_create_group(&client->dev.kobj, &adt7410_group); > if (ret) > -- > 1.8.0 > > -- To unsubscribe from this list: send the line "unsubscribe linux-iio" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html