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Documentation/admin-guide/acpi: Add documentation for fine grain control 

Add documentation for the newly added attributes:
fine_grain_control
fan_speed_rpm

Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
This commit is contained in:
Srinivas Pandruvada 2022-02-11 08:09:32 -08:00 committed by Rafael J. Wysocki
parent f1197343f0
commit 0750b8fcf3
1 changed files with 28 additions and 0 deletions
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28
Documentation/admin-guide/acpi/fan_performance_states.rst
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@ -60,3 +60,31 @@ For example::
When a given field is not populated or its value provided by the platform
firmware is invalid, the "not-defined" string is shown instead of the value.
ACPI Fan Fine Grain Control
=============================
When _FIF object specifies support for fine grain control, then fan speed
can be set from 0 to 100% with the recommended minimum "step size" via
_FSL object. User can adjust fan speed using thermal sysfs cooling device.
Here use can look at fan performance states for a reference speed (speed_rpm)
and set it by changing cooling device cur_state. If the fine grain control
is supported then user can also adjust to some other speeds which are
not defined in the performance states.
The support of fine grain control is presented via sysfs attribute
"fine_grain_control". If fine grain control is present, this attribute
will show "1" otherwise "0".
This sysfs attribute is presented in the same directory as performance states.
ACPI Fan Performance Feedback
=============================
The optional _FST object provides status information for the fan device.
This includes field to provide current fan speed in revolutions per minute
at which the fan is rotating.
This speed is presented in the sysfs using the attribute "fan_speed_rpm",
in the same directory as performance states.