91 lines · plain
1.. SPDX-License-Identifier: GPL-2.02 3===========================4ACPI Fan Performance States5===========================6 7When the optional _FPS object is present under an ACPI device representing a8fan (for example, PNP0C0B or INT3404), the ACPI fan driver creates additional9"state*" attributes in the sysfs directory of the ACPI device in question.10These attributes list properties of fan performance states.11 12For more information on _FPS refer to the ACPI specification at:13 14http://uefi.org/specifications15 16For instance, the contents of the INT3404 ACPI device sysfs directory17may look as follows::18 19 $ ls -l /sys/bus/acpi/devices/INT3404:00/20 total 021 ...22 -r--r--r-- 1 root root 4096 Dec 13 20:38 state023 -r--r--r-- 1 root root 4096 Dec 13 20:38 state124 -r--r--r-- 1 root root 4096 Dec 13 20:38 state1025 -r--r--r-- 1 root root 4096 Dec 13 20:38 state1126 -r--r--r-- 1 root root 4096 Dec 13 20:38 state227 -r--r--r-- 1 root root 4096 Dec 13 20:38 state328 -r--r--r-- 1 root root 4096 Dec 13 20:38 state429 -r--r--r-- 1 root root 4096 Dec 13 20:38 state530 -r--r--r-- 1 root root 4096 Dec 13 20:38 state631 -r--r--r-- 1 root root 4096 Dec 13 20:38 state732 -r--r--r-- 1 root root 4096 Dec 13 20:38 state833 -r--r--r-- 1 root root 4096 Dec 13 20:38 state934 -r--r--r-- 1 root root 4096 Dec 13 01:00 status35 ...36 37where each of the "state*" files represents one performance state of the fan38and contains a colon-separated list of 5 integer numbers (fields) with the39following interpretation::40 41 control_percent:trip_point_index:speed_rpm:noise_level_mdb:power_mw42 43* ``control_percent``: The percent value to be used to set the fan speed to a44 specific level using the _FSL object (0-100).45 46* ``trip_point_index``: The active cooling trip point number that corresponds47 to this performance state (0-9).48 49* ``speed_rpm``: Speed of the fan in rotations per minute.50 51* ``noise_level_mdb``: Audible noise emitted by the fan in this state in52 millidecibels.53 54* ``power_mw``: Power draw of the fan in this state in milliwatts.55 56For example::57 58 $cat /sys/bus/acpi/devices/INT3404:00/state159 25:0:3200:12500:125060 61When a given field is not populated or its value provided by the platform62firmware is invalid, the "not-defined" string is shown instead of the value.63 64ACPI Fan Fine Grain Control65=============================66 67When _FIF object specifies support for fine grain control, then fan speed68can be set from 0 to 100% with the recommended minimum "step size" via69_FSL object. User can adjust fan speed using thermal sysfs cooling device.70 71Here use can look at fan performance states for a reference speed (speed_rpm)72and set it by changing cooling device cur_state. If the fine grain control73is supported then user can also adjust to some other speeds which are74not defined in the performance states.75 76The support of fine grain control is presented via sysfs attribute77"fine_grain_control". If fine grain control is present, this attribute78will show "1" otherwise "0".79 80This sysfs attribute is presented in the same directory as performance states.81 82ACPI Fan Performance Feedback83=============================84 85The optional _FST object provides status information for the fan device.86This includes field to provide current fan speed in revolutions per minute87at which the fan is rotating.88 89This speed is presented in the sysfs using the attribute "fan_speed_rpm",90in the same directory as performance states.91