From: Armin Wolf W_Armin@gmx.de
[ Upstream commit ca8fd8c16a8b77dfcf7f6ce52d2c863220693a78 ]
A user complained that the ftsteutates driver was displaying bogus values since its introduction. This happens because the sensor measurements need to be scaled in order to produce meaningful results: - the fan speed needs to be multiplied by 60 since its in RPS - the temperature is in degrees celsius and needs an offset of 64 - the voltage is in 1/256 of 3.3V
The offical datasheet says the voltage needs to be divided by 256, but this is likely an off-by-one-error, since even the BIOS devides by 255 (otherwise 3.3V could not be measured).
The voltage channels additionally need a board-specific multiplier, however this can be done by the driver since its board-specific.
The reason the missing scaling of measurements is the way Fujitsu used this driver when it was still out-of-tree. Back then, all scaling was done in userspace by libsensors, even the generic one.
Tested on a Fujitsu DS3401-B1.
Fixes: 08426eda58e0 ("hwmon: Add driver for FTS BMC chip "Teutates"") Signed-off-by: Armin Wolf W_Armin@gmx.de Link: https://lore.kernel.org/r/20221224041855.83981-2-W_Armin@gmx.de Signed-off-by: Guenter Roeck linux@roeck-us.net Signed-off-by: Sasha Levin sashal@kernel.org --- Documentation/hwmon/ftsteutates.rst | 4 ++++ drivers/hwmon/ftsteutates.c | 19 +++++++++++++------ 2 files changed, 17 insertions(+), 6 deletions(-)
diff --git a/Documentation/hwmon/ftsteutates.rst b/Documentation/hwmon/ftsteutates.rst index 58a2483d8d0da..198fa8e2819da 100644 --- a/Documentation/hwmon/ftsteutates.rst +++ b/Documentation/hwmon/ftsteutates.rst @@ -22,6 +22,10 @@ enhancements. It can monitor up to 4 voltages, 16 temperatures and 8 fans. It also contains an integrated watchdog which is currently implemented in this driver.
+The 4 voltages require a board-specific multiplier, since the BMC can +only measure voltages up to 3.3V and thus relies on voltage dividers. +Consult your motherboard manual for details. + To clear a temperature or fan alarm, execute the following command with the correct path to the alarm file::
diff --git a/drivers/hwmon/ftsteutates.c b/drivers/hwmon/ftsteutates.c index ceffc76a0c515..2998d8cdce006 100644 --- a/drivers/hwmon/ftsteutates.c +++ b/drivers/hwmon/ftsteutates.c @@ -12,6 +12,7 @@ #include <linux/i2c.h> #include <linux/init.h> #include <linux/jiffies.h> +#include <linux/math.h> #include <linux/module.h> #include <linux/mutex.h> #include <linux/slab.h> @@ -347,13 +348,15 @@ static ssize_t in_value_show(struct device *dev, { struct fts_data *data = dev_get_drvdata(dev); int index = to_sensor_dev_attr(devattr)->index; - int err; + int value, err;
err = fts_update_device(data); if (err < 0) return err;
- return sprintf(buf, "%u\n", data->volt[index]); + value = DIV_ROUND_CLOSEST(data->volt[index] * 3300, 255); + + return sprintf(buf, "%d\n", value); }
static ssize_t temp_value_show(struct device *dev, @@ -361,13 +364,15 @@ static ssize_t temp_value_show(struct device *dev, { struct fts_data *data = dev_get_drvdata(dev); int index = to_sensor_dev_attr(devattr)->index; - int err; + int value, err;
err = fts_update_device(data); if (err < 0) return err;
- return sprintf(buf, "%u\n", data->temp_input[index]); + value = (data->temp_input[index] - 64) * 1000; + + return sprintf(buf, "%d\n", value); }
static ssize_t temp_fault_show(struct device *dev, @@ -436,13 +441,15 @@ static ssize_t fan_value_show(struct device *dev, { struct fts_data *data = dev_get_drvdata(dev); int index = to_sensor_dev_attr(devattr)->index; - int err; + int value, err;
err = fts_update_device(data); if (err < 0) return err;
- return sprintf(buf, "%u\n", data->fan_input[index]); + value = data->fan_input[index] * 60; + + return sprintf(buf, "%d\n", value); }
static ssize_t fan_source_show(struct device *dev,