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author | Armin Wolf <W_Armin@gmx.de> | 2022-12-24 07:18:53 +0300 |
---|---|---|
committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2023-03-10 11:33:10 +0300 |
commit | 9aba03fb5146eadd1fcef4aaf58a0b6a0b688ef8 (patch) | |
tree | 2a0de18617ab794353ec53fd200b99bcb0391140 /Documentation/hwmon | |
parent | 41286a53e7f54202fd277cd516724de3ab7497c7 (diff) | |
download | linux-9aba03fb5146eadd1fcef4aaf58a0b6a0b688ef8.tar.xz |
hwmon: (ftsteutates) Fix scaling of measurements
[ 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>
Diffstat (limited to 'Documentation/hwmon')
-rw-r--r-- | Documentation/hwmon/ftsteutates.rst | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/Documentation/hwmon/ftsteutates.rst b/Documentation/hwmon/ftsteutates.rst index 58a2483d8d0d..198fa8e2819d 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:: |