docs/designs/thermal-control-modes.md

1 # Control.ThermalMode dbus interface with Supported and Current properties
7 Created: 2019-02-06
11 An issue was discovered where the exhaust heat from the system GPUs causes
12 overtemp warnings on optical cables on certain system configurations. The issue
13 can be resolved by altering the fan control application's floor table,
17 optical cables plugged into a card downwind from the GPUs' exhaust, an end-user
22 The witherspoon system supports pci cards that could have optical cables plugged
30 exhaust temp and include that within the fan control algorithm. A similar issue
31 exists on other system where mathematical calculations are done based on the
35 https://github.com/openbmc/dbus-sensors/blob/master/src/ExitAirTempSensor.cpp
39 Create the ability for an end-user to enable the use of a thermal control mode
40 other than the default. In this use-case, the mode is specific to an
42 standardized profile/modes such "Acoustic" and "Performance". Once the end-user
43 selects a documented mode for the platform, the thermal control application
44 alters its control algorithm according to the defined mode, which is
49 Create a Control.ThermalMode dbus interface containing a supported list of
50 available thermal control modes along with what current mode is in use.
54 As one implementation, phosphor-fan-presence/control would be updated to extend
56 its fan control configuration for the platform. Once the fan control application
58 queried for supported modes or update the current mode. An end-user may set the
60 persisted each time it is updated. This is to ensure each time the fan control
61 application zone objects are started, the last set control mode is used.
73 The thermal control application used must be configured to provide what thermal
74 control modes are supported/available on the interface as well as perform the
75 associated control changes when a mode is set.
79 Trigger the use of an alternative fan floor table based on the thermal control
80 mode selected on a witherspoon system.