diff options
| -rw-r--r-- | Documentation/hwmon/lm77 | 20 | ||||
| -rw-r--r-- | drivers/hwmon/lm77.c | 6 |
2 files changed, 18 insertions, 8 deletions
diff --git a/Documentation/hwmon/lm77 b/Documentation/hwmon/lm77 index 57c3a46d6370..bfc915fe3639 100644 --- a/Documentation/hwmon/lm77 +++ b/Documentation/hwmon/lm77 @@ -18,5 +18,21 @@ sensor incorporates a band-gap type temperature sensor, 10-bit ADC, and a digital comparator with user-programmable upper and lower limit values. -Limits can be set through the Overtemperature Shutdown register and -Hysteresis register. +The LM77 implements 3 limits: low (temp1_min), high (temp1_max) and +critical (temp1_crit.) It also implements an hysteresis mechanism which +applies to all 3 limits. The relative difference is stored in a single +register on the chip, which means that the relative difference between +the limit and its hysteresis is always the same for all 3 limits. + +This implementation detail implies the following: +* When setting a limit, its hysteresis will automatically follow, the + difference staying unchanged. For example, if the old critical limit + was 80 degrees C, and the hysteresis was 75 degrees C, and you change + the critical limit to 90 degrees C, then the hysteresis will + automatically change to 85 degrees C. +* All 3 hysteresis can't be set independently. We decided to make + temp1_crit_hyst writable, while temp1_min_hyst and temp1_max_hyst are + read-only. Setting temp1_crit_hyst writes the difference between + temp1_crit_hyst and temp1_crit into the chip, and the same relative + hysteresis applies automatically to the low and high limits. +* The limits should be set before the hysteresis. diff --git a/drivers/hwmon/lm77.c b/drivers/hwmon/lm77.c index 4cd8a513c47b..85e5b3355be4 100644 --- a/drivers/hwmon/lm77.c +++ b/drivers/hwmon/lm77.c @@ -216,13 +216,11 @@ static ssize_t set_temp_crit_hyst(struct device *dev, return count; } -/* preserve hysteresis when setting T_crit */ static ssize_t set_temp_crit(struct device *dev, struct device_attribute *attr, const char *buf, size_t count) { struct i2c_client *client = to_i2c_client(dev); struct lm77_data *data = i2c_get_clientdata(client); - int oldcrithyst; unsigned long val; int err; @@ -231,13 +229,9 @@ static ssize_t set_temp_crit(struct device *dev, struct device_attribute *attr, return err; mutex_lock(&data->update_lock); - oldcrithyst = data->temp_crit - data->temp_hyst; data->temp_crit = val; - data->temp_hyst = data->temp_crit - oldcrithyst; lm77_write_value(client, LM77_REG_TEMP_CRIT, LM77_TEMP_TO_REG(data->temp_crit)); - lm77_write_value(client, LM77_REG_TEMP_HYST, - LM77_TEMP_TO_REG(data->temp_hyst)); mutex_unlock(&data->update_lock); return count; } |