293 lines
11 KiB
Plaintext
293 lines
11 KiB
Plaintext
Generic Thermal Sysfs driver How To
|
|
===================================
|
|
|
|
Written by Sujith Thomas <sujith.thomas@intel.com>, Zhang Rui <rui.zhang@intel.com>
|
|
|
|
Updated: 2 January 2008
|
|
|
|
Copyright (c) 2008 Intel Corporation
|
|
|
|
|
|
0. Introduction
|
|
|
|
The generic thermal sysfs provides a set of interfaces for thermal zone
|
|
devices (sensors) and thermal cooling devices (fan, processor...) to register
|
|
with the thermal management solution and to be a part of it.
|
|
|
|
This how-to focuses on enabling new thermal zone and cooling devices to
|
|
participate in thermal management.
|
|
This solution is platform independent and any type of thermal zone devices
|
|
and cooling devices should be able to make use of the infrastructure.
|
|
|
|
The main task of the thermal sysfs driver is to expose thermal zone attributes
|
|
as well as cooling device attributes to the user space.
|
|
An intelligent thermal management application can make decisions based on
|
|
inputs from thermal zone attributes (the current temperature and trip point
|
|
temperature) and throttle appropriate devices.
|
|
|
|
[0-*] denotes any positive number starting from 0
|
|
[1-*] denotes any positive number starting from 1
|
|
|
|
1. thermal sysfs driver interface functions
|
|
|
|
1.1 thermal zone device interface
|
|
1.1.1 struct thermal_zone_device *thermal_zone_device_register(char *name,
|
|
int trips, void *devdata, struct thermal_zone_device_ops *ops)
|
|
|
|
This interface function adds a new thermal zone device (sensor) to
|
|
/sys/class/thermal folder as thermal_zone[0-*]. It tries to bind all the
|
|
thermal cooling devices registered at the same time.
|
|
|
|
name: the thermal zone name.
|
|
trips: the total number of trip points this thermal zone supports.
|
|
devdata: device private data
|
|
ops: thermal zone device call-backs.
|
|
.bind: bind the thermal zone device with a thermal cooling device.
|
|
.unbind: unbind the thermal zone device with a thermal cooling device.
|
|
.get_temp: get the current temperature of the thermal zone.
|
|
.get_mode: get the current mode (user/kernel) of the thermal zone.
|
|
- "kernel" means thermal management is done in kernel.
|
|
- "user" will prevent kernel thermal driver actions upon trip points
|
|
so that user applications can take charge of thermal management.
|
|
.set_mode: set the mode (user/kernel) of the thermal zone.
|
|
.get_trip_type: get the type of certain trip point.
|
|
.get_trip_temp: get the temperature above which the certain trip point
|
|
will be fired.
|
|
|
|
1.1.2 void thermal_zone_device_unregister(struct thermal_zone_device *tz)
|
|
|
|
This interface function removes the thermal zone device.
|
|
It deletes the corresponding entry form /sys/class/thermal folder and
|
|
unbind all the thermal cooling devices it uses.
|
|
|
|
1.2 thermal cooling device interface
|
|
1.2.1 struct thermal_cooling_device *thermal_cooling_device_register(char *name,
|
|
void *devdata, struct thermal_cooling_device_ops *)
|
|
|
|
This interface function adds a new thermal cooling device (fan/processor/...)
|
|
to /sys/class/thermal/ folder as cooling_device[0-*]. It tries to bind itself
|
|
to all the thermal zone devices register at the same time.
|
|
name: the cooling device name.
|
|
devdata: device private data.
|
|
ops: thermal cooling devices call-backs.
|
|
.get_max_state: get the Maximum throttle state of the cooling device.
|
|
.get_cur_state: get the Current throttle state of the cooling device.
|
|
.set_cur_state: set the Current throttle state of the cooling device.
|
|
|
|
1.2.2 void thermal_cooling_device_unregister(struct thermal_cooling_device *cdev)
|
|
|
|
This interface function remove the thermal cooling device.
|
|
It deletes the corresponding entry form /sys/class/thermal folder and
|
|
unbind itself from all the thermal zone devices using it.
|
|
|
|
1.3 interface for binding a thermal zone device with a thermal cooling device
|
|
1.3.1 int thermal_zone_bind_cooling_device(struct thermal_zone_device *tz,
|
|
int trip, struct thermal_cooling_device *cdev);
|
|
|
|
This interface function bind a thermal cooling device to the certain trip
|
|
point of a thermal zone device.
|
|
This function is usually called in the thermal zone device .bind callback.
|
|
tz: the thermal zone device
|
|
cdev: thermal cooling device
|
|
trip: indicates which trip point the cooling devices is associated with
|
|
in this thermal zone.
|
|
|
|
1.3.2 int thermal_zone_unbind_cooling_device(struct thermal_zone_device *tz,
|
|
int trip, struct thermal_cooling_device *cdev);
|
|
|
|
This interface function unbind a thermal cooling device from the certain
|
|
trip point of a thermal zone device. This function is usually called in
|
|
the thermal zone device .unbind callback.
|
|
tz: the thermal zone device
|
|
cdev: thermal cooling device
|
|
trip: indicates which trip point the cooling devices is associated with
|
|
in this thermal zone.
|
|
|
|
2. sysfs attributes structure
|
|
|
|
RO read only value
|
|
RW read/write value
|
|
|
|
Thermal sysfs attributes will be represented under /sys/class/thermal.
|
|
Hwmon sysfs I/F extension is also available under /sys/class/hwmon
|
|
if hwmon is compiled in or built as a module.
|
|
|
|
Thermal zone device sys I/F, created once it's registered:
|
|
/sys/class/thermal/thermal_zone[0-*]:
|
|
|---type: Type of the thermal zone
|
|
|---temp: Current temperature
|
|
|---mode: Working mode of the thermal zone
|
|
|---trip_point_[0-*]_temp: Trip point temperature
|
|
|---trip_point_[0-*]_type: Trip point type
|
|
|
|
Thermal cooling device sys I/F, created once it's registered:
|
|
/sys/class/thermal/cooling_device[0-*]:
|
|
|---type: Type of the cooling device(processor/fan/...)
|
|
|---max_state: Maximum cooling state of the cooling device
|
|
|---cur_state: Current cooling state of the cooling device
|
|
|
|
|
|
Then next two dynamic attributes are created/removed in pairs. They represent
|
|
the relationship between a thermal zone and its associated cooling device.
|
|
They are created/removed for each successful execution of
|
|
thermal_zone_bind_cooling_device/thermal_zone_unbind_cooling_device.
|
|
|
|
/sys/class/thermal/thermal_zone[0-*]:
|
|
|---cdev[0-*]: [0-*]th cooling device in current thermal zone
|
|
|---cdev[0-*]_trip_point: Trip point that cdev[0-*] is associated with
|
|
|
|
Besides the thermal zone device sysfs I/F and cooling device sysfs I/F,
|
|
the generic thermal driver also creates a hwmon sysfs I/F for each _type_
|
|
of thermal zone device. E.g. the generic thermal driver registers one hwmon
|
|
class device and build the associated hwmon sysfs I/F for all the registered
|
|
ACPI thermal zones.
|
|
|
|
/sys/class/hwmon/hwmon[0-*]:
|
|
|---name: The type of the thermal zone devices
|
|
|---temp[1-*]_input: The current temperature of thermal zone [1-*]
|
|
|---temp[1-*]_critical: The critical trip point of thermal zone [1-*]
|
|
|
|
Please read Documentation/hwmon/sysfs-interface for additional information.
|
|
|
|
***************************
|
|
* Thermal zone attributes *
|
|
***************************
|
|
|
|
type
|
|
Strings which represent the thermal zone type.
|
|
This is given by thermal zone driver as part of registration.
|
|
E.g: "acpitz" indicates it's an ACPI thermal device.
|
|
In order to keep it consistent with hwmon sys attribute; this should
|
|
be a short, lowercase string, not containing spaces nor dashes.
|
|
RO, Required
|
|
|
|
temp
|
|
Current temperature as reported by thermal zone (sensor).
|
|
Unit: millidegree Celsius
|
|
RO, Required
|
|
|
|
mode
|
|
One of the predefined values in [kernel, user].
|
|
This file gives information about the algorithm that is currently
|
|
managing the thermal zone. It can be either default kernel based
|
|
algorithm or user space application.
|
|
kernel = Thermal management in kernel thermal zone driver.
|
|
user = Preventing kernel thermal zone driver actions upon
|
|
trip points so that user application can take full
|
|
charge of the thermal management.
|
|
RW, Optional
|
|
|
|
trip_point_[0-*]_temp
|
|
The temperature above which trip point will be fired.
|
|
Unit: millidegree Celsius
|
|
RO, Optional
|
|
|
|
trip_point_[0-*]_type
|
|
Strings which indicate the type of the trip point.
|
|
E.g. it can be one of critical, hot, passive, active[0-*] for ACPI
|
|
thermal zone.
|
|
RO, Optional
|
|
|
|
cdev[0-*]
|
|
Sysfs link to the thermal cooling device node where the sys I/F
|
|
for cooling device throttling control represents.
|
|
RO, Optional
|
|
|
|
cdev[0-*]_trip_point
|
|
The trip point with which cdev[0-*] is associated in this thermal
|
|
zone; -1 means the cooling device is not associated with any trip
|
|
point.
|
|
RO, Optional
|
|
|
|
passive
|
|
Attribute is only present for zones in which the passive cooling
|
|
policy is not supported by native thermal driver. Default is zero
|
|
and can be set to a temperature (in millidegrees) to enable a
|
|
passive trip point for the zone. Activation is done by polling with
|
|
an interval of 1 second.
|
|
Unit: millidegrees Celsius
|
|
Valid values: 0 (disabled) or greater than 1000
|
|
RW, Optional
|
|
|
|
*****************************
|
|
* Cooling device attributes *
|
|
*****************************
|
|
|
|
type
|
|
String which represents the type of device, e.g:
|
|
- for generic ACPI: should be "Fan", "Processor" or "LCD"
|
|
- for memory controller device on intel_menlow platform:
|
|
should be "Memory controller".
|
|
RO, Required
|
|
|
|
max_state
|
|
The maximum permissible cooling state of this cooling device.
|
|
RO, Required
|
|
|
|
cur_state
|
|
The current cooling state of this cooling device.
|
|
The value can any integer numbers between 0 and max_state:
|
|
- cur_state == 0 means no cooling
|
|
- cur_state == max_state means the maximum cooling.
|
|
RW, Required
|
|
|
|
3. A simple implementation
|
|
|
|
ACPI thermal zone may support multiple trip points like critical, hot,
|
|
passive, active. If an ACPI thermal zone supports critical, passive,
|
|
active[0] and active[1] at the same time, it may register itself as a
|
|
thermal_zone_device (thermal_zone1) with 4 trip points in all.
|
|
It has one processor and one fan, which are both registered as
|
|
thermal_cooling_device.
|
|
|
|
If the processor is listed in _PSL method, and the fan is listed in _AL0
|
|
method, the sys I/F structure will be built like this:
|
|
|
|
/sys/class/thermal:
|
|
|
|
|thermal_zone1:
|
|
|---type: acpitz
|
|
|---temp: 37000
|
|
|---mode: kernel
|
|
|---trip_point_0_temp: 100000
|
|
|---trip_point_0_type: critical
|
|
|---trip_point_1_temp: 80000
|
|
|---trip_point_1_type: passive
|
|
|---trip_point_2_temp: 70000
|
|
|---trip_point_2_type: active0
|
|
|---trip_point_3_temp: 60000
|
|
|---trip_point_3_type: active1
|
|
|---cdev0: --->/sys/class/thermal/cooling_device0
|
|
|---cdev0_trip_point: 1 /* cdev0 can be used for passive */
|
|
|---cdev1: --->/sys/class/thermal/cooling_device3
|
|
|---cdev1_trip_point: 2 /* cdev1 can be used for active[0]*/
|
|
|
|
|cooling_device0:
|
|
|---type: Processor
|
|
|---max_state: 8
|
|
|---cur_state: 0
|
|
|
|
|cooling_device3:
|
|
|---type: Fan
|
|
|---max_state: 2
|
|
|---cur_state: 0
|
|
|
|
/sys/class/hwmon:
|
|
|
|
|hwmon0:
|
|
|---name: acpitz
|
|
|---temp1_input: 37000
|
|
|---temp1_crit: 100000
|
|
|
|
4. Event Notification
|
|
|
|
The framework includes a simple notification mechanism, in the form of a
|
|
netlink event. Netlink socket initialization is done during the _init_
|
|
of the framework. Drivers which intend to use the notification mechanism
|
|
just need to call thermal_generate_netlink_event() with two arguments viz
|
|
(originator, event). Typically the originator will be an integer assigned
|
|
to a thermal_zone_device when it registers itself with the framework. The
|
|
event will be one of:{THERMAL_AUX0, THERMAL_AUX1, THERMAL_CRITICAL,
|
|
THERMAL_DEV_FAULT}. Notification can be sent when the current temperature
|
|
crosses any of the configured thresholds.
|