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/openbmc/linux/Documentation/hwmon/ |
H A D | ftsteutates.rst | ca8fd8c1 Fri Dec 23 22:18:53 CST 2022 Armin Wolf <W_Armin@gmx.de> hwmon: (ftsteutates) Fix scaling of measurements
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>
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/openbmc/linux/drivers/hwmon/ |
H A D | ftsteutates.c | ca8fd8c1 Fri Dec 23 22:18:53 CST 2022 Armin Wolf <W_Armin@gmx.de> hwmon: (ftsteutates) Fix scaling of measurements
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>
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