- =======================
- INTEL POWERCLAMP DRIVER
- =======================
-By: Arjan van de Ven <arjan@linux.intel.com>
- Jacob Pan <jacob.jun.pan@linux.intel.com>
+=======================
+Intel Powerclamp Driver
+=======================
+
+By:
+ - Arjan van de Ven <arjan@linux.intel.com>
+ - Jacob Pan <jacob.jun.pan@linux.intel.com>
+
+.. Contents:
-Contents:
(*) Introduction
- Goals and Objectives
- Generic Thermal Layer (sysfs)
- Kernel APIs (TBD)
-============
INTRODUCTION
============
shown over taking the CPU offline or modulating the CPU clock.
-===================
THEORY OF OPERATION
===================
On modern Intel processors (Nehalem or later), package level C-state
residency is available in MSRs, thus also available to the kernel.
-These MSRs are:
- #define MSR_PKG_C2_RESIDENCY 0x60D
- #define MSR_PKG_C3_RESIDENCY 0x3F8
- #define MSR_PKG_C6_RESIDENCY 0x3F9
- #define MSR_PKG_C7_RESIDENCY 0x3FA
+These MSRs are::
+
+ #define MSR_PKG_C2_RESIDENCY 0x60D
+ #define MSR_PKG_C3_RESIDENCY 0x3F8
+ #define MSR_PKG_C6_RESIDENCY 0x3F9
+ #define MSR_PKG_C7_RESIDENCY 0x3FA
If the kernel can also inject idle time to the system, then a
closed-loop control system can be established that manages package
have a dramatic impact on the effectiveness of the powerclamp driver
on large scale systems (Westmere system with 80 processors).
-CPU0
- ____________ ____________
-kidle_inject/0 | sleep | mwait | sleep |
- _________| |________| |_______
- duration
-CPU1
- ____________ ____________
-kidle_inject/1 | sleep | mwait | sleep |
- _________| |________| |_______
- ^
- |
- |
- roundup(jiffies, interval)
+::
+
+ CPU0
+ ____________ ____________
+ kidle_inject/0 | sleep | mwait | sleep |
+ _________| |________| |_______
+ duration
+ CPU1
+ ____________ ____________
+ kidle_inject/1 | sleep | mwait | sleep |
+ _________| |________| |_______
+ ^
+ |
+ |
+ roundup(jiffies, interval)
Only one CPU is allowed to collect statistics and update global
control parameters. This CPU is referred to as the controlling CPU in
Compensation to each target ratio consists of two parts:
- a) steady state error compensation
+ a) steady state error compensation
This is to offset the error occurring when the system can
enter idle without extra wakeups (such as external interrupts).
slowing down CPU activities.
A debugfs file is provided for the user to examine compensation
-progress and results, such as on a Westmere system.
-[jacob@nex01 ~]$ cat
-/sys/kernel/debug/intel_powerclamp/powerclamp_calib
-controlling cpu: 0
-pct confidence steady dynamic (compensation)
-0 0 0 0
-1 1 0 0
-2 1 1 0
-3 3 1 0
-4 3 1 0
-5 3 1 0
-6 3 1 0
-7 3 1 0
-8 3 1 0
-...
-30 3 2 0
-31 3 2 0
-32 3 1 0
-33 3 2 0
-34 3 1 0
-35 3 2 0
-36 3 1 0
-37 3 2 0
-38 3 1 0
-39 3 2 0
-40 3 3 0
-41 3 1 0
-42 3 2 0
-43 3 1 0
-44 3 1 0
-45 3 2 0
-46 3 3 0
-47 3 0 0
-48 3 2 0
-49 3 3 0
+progress and results, such as on a Westmere system::
+
+ [jacob@nex01 ~]$ cat
+ /sys/kernel/debug/intel_powerclamp/powerclamp_calib
+ controlling cpu: 0
+ pct confidence steady dynamic (compensation)
+ 0 0 0 0
+ 1 1 0 0
+ 2 1 1 0
+ 3 3 1 0
+ 4 3 1 0
+ 5 3 1 0
+ 6 3 1 0
+ 7 3 1 0
+ 8 3 1 0
+ ...
+ 30 3 2 0
+ 31 3 2 0
+ 32 3 1 0
+ 33 3 2 0
+ 34 3 1 0
+ 35 3 2 0
+ 36 3 1 0
+ 37 3 2 0
+ 38 3 1 0
+ 39 3 2 0
+ 40 3 3 0
+ 41 3 1 0
+ 42 3 2 0
+ 43 3 1 0
+ 44 3 1 0
+ 45 3 2 0
+ 46 3 3 0
+ 47 3 0 0
+ 48 3 2 0
+ 49 3 3 0
Calibration occurs during runtime. No offline method is available.
Steady state compensation is used only when confidence levels of all
to other CPUs, after a CPU offline event.
-=====================
Performance Analysis
-=====================
+====================
This section describes the general performance data collected on
multiple systems, including Westmere (80P) and Ivy Bridge (4P, 8P).
counter summed over per CPU counting threads spawned for all running
CPUs).
-====================
Usage and Interfaces
====================
The powerclamp driver is registered to the generic thermal layer as a
-cooling device. Currently, it’s not bound to any thermal zones.
+cooling device. Currently, it’s not bound to any thermal zones::
-jacob@chromoly:/sys/class/thermal/cooling_device14$ grep . *
-cur_state:0
-max_state:50
-type:intel_powerclamp
+ jacob@chromoly:/sys/class/thermal/cooling_device14$ grep . *
+ cur_state:0
+ max_state:50
+ type:intel_powerclamp
cur_state allows user to set the desired idle percentage. Writing 0 to
cur_state will stop idle injection. Writing a value between 1 and
100% busy state with the disabled state.
Example usage:
-- To inject 25% idle time
-$ sudo sh -c "echo 25 > /sys/class/thermal/cooling_device80/cur_state
-"
+- To inject 25% idle time::
+
+ $ sudo sh -c "echo 25 > /sys/class/thermal/cooling_device80/cur_state
If the system is not busy and has more than 25% idle time already,
then the powerclamp driver will not start idle injection. Using Top
taken as the idle task.
In this example, 24.1% idle is shown. This helps the system admin or
-user determine the cause of slowdown, when a powerclamp driver is in action.
-
-
-Tasks: 197 total, 1 running, 196 sleeping, 0 stopped, 0 zombie
-Cpu(s): 71.2%us, 4.7%sy, 0.0%ni, 24.1%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st
-Mem: 3943228k total, 1689632k used, 2253596k free, 74960k buffers
-Swap: 4087804k total, 0k used, 4087804k free, 945336k cached
-
- PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
- 3352 jacob 20 0 262m 644 428 S 286 0.0 0:17.16 spin
- 3341 root -51 0 0 0 0 D 25 0.0 0:01.62 kidle_inject/0
- 3344 root -51 0 0 0 0 D 25 0.0 0:01.60 kidle_inject/3
- 3342 root -51 0 0 0 0 D 25 0.0 0:01.61 kidle_inject/1
- 3343 root -51 0 0 0 0 D 25 0.0 0:01.60 kidle_inject/2
- 2935 jacob 20 0 696m 125m 35m S 5 3.3 0:31.11 firefox
- 1546 root 20 0 158m 20m 6640 S 3 0.5 0:26.97 Xorg
- 2100 jacob 20 0 1223m 88m 30m S 3 2.3 0:23.68 compiz
+user determine the cause of slowdown, when a powerclamp driver is in action::
+
+
+ Tasks: 197 total, 1 running, 196 sleeping, 0 stopped, 0 zombie
+ Cpu(s): 71.2%us, 4.7%sy, 0.0%ni, 24.1%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st
+ Mem: 3943228k total, 1689632k used, 2253596k free, 74960k buffers
+ Swap: 4087804k total, 0k used, 4087804k free, 945336k cached
+
+ PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
+ 3352 jacob 20 0 262m 644 428 S 286 0.0 0:17.16 spin
+ 3341 root -51 0 0 0 0 D 25 0.0 0:01.62 kidle_inject/0
+ 3344 root -51 0 0 0 0 D 25 0.0 0:01.60 kidle_inject/3
+ 3342 root -51 0 0 0 0 D 25 0.0 0:01.61 kidle_inject/1
+ 3343 root -51 0 0 0 0 D 25 0.0 0:01.60 kidle_inject/2
+ 2935 jacob 20 0 696m 125m 35m S 5 3.3 0:31.11 firefox
+ 1546 root 20 0 158m 20m 6640 S 3 0.5 0:26.97 Xorg
+ 2100 jacob 20 0 1223m 88m 30m S 3 2.3 0:23.68 compiz
Tests have shown that by using the powerclamp driver as a cooling
device, a PID based userspace thermal controller can manage to
+=================================
Power allocator governor tunables
=================================
P_max = k_p * e + k_i * err_integral + k_d * diff_err + sustainable_power
where
- e = desired_temperature - current_temperature
- err_integral is the sum of previous errors
- diff_err = e - previous_error
-
-It is similar to the one depicted below:
-
- k_d
- |
-current_temp |
- | v
- | +----------+ +---+
- | +----->| diff_err |-->| X |------+
- | | +----------+ +---+ |
- | | | tdp actor
- | | k_i | | get_requested_power()
- | | | | | | |
- | | | | | | | ...
- v | v v v v v
- +---+ | +-------+ +---+ +---+ +---+ +----------+
- | S |-------+----->| sum e |----->| X |--->| S |-->| S |-->|power |
- +---+ | +-------+ +---+ +---+ +---+ |allocation|
- ^ | ^ +----------+
- | | | | |
- | | +---+ | | |
- | +------->| X |-------------------+ v v
- | +---+ granted performance
-desired_temperature ^
- |
- |
- k_po/k_pu
+ - e = desired_temperature - current_temperature
+ - err_integral is the sum of previous errors
+ - diff_err = e - previous_error
+
+It is similar to the one depicted below::
+
+ k_d
+ |
+ current_temp |
+ | v
+ | +----------+ +---+
+ | +----->| diff_err |-->| X |------+
+ | | +----------+ +---+ |
+ | | | tdp actor
+ | | k_i | | get_requested_power()
+ | | | | | | |
+ | | | | | | | ...
+ v | v v v v v
+ +---+ | +-------+ +---+ +---+ +---+ +----------+
+ | S |-----+----->| sum e |----->| X |--->| S |-->| S |-->|power |
+ +---+ | +-------+ +---+ +---+ +---+ |allocation|
+ ^ | ^ +----------+
+ | | | | |
+ | | +---+ | | |
+ | +------->| X |-------------------+ v v
+ | +---+ granted performance
+ desired_temperature ^
+ |
+ |
+ k_po/k_pu
Sustainable power
-----------------
depending on screen size).
If you are using device tree, do add it as a property of the
-thermal-zone. For example:
+thermal-zone. For example::
thermal-zones {
soc_thermal {
Instead, if the thermal zone is registered from the platform code, pass a
`thermal_zone_params` that has a `sustainable_power`. If no
`thermal_zone_params` were being passed, then something like below
-will suffice:
+will suffice::
static const struct thermal_zone_params tz_params = {
.sustainable_power = 3500,
value of `k_pu` will result in the governor granting very high power
while temperature is low, and may lead to temperature overshooting.
-The default value for `k_pu` is:
+The default value for `k_pu` is::
2 * sustainable_power / (desired_temperature - switch_on_temp)
This means that at `switch_on_temp` the output of the controller's
proportional term will be 2 * `sustainable_power`. The default value
-for `k_po` is:
+for `k_po` is::
sustainable_power / (desired_temperature - switch_on_temp)
Focusing on the proportional and feed forward values of the PID
-controller equation we have:
+controller equation we have::
P_max = k_p * e + sustainable_power
thermal equilibrium under constant load. `sustainable_power` is only
an estimate, which is the reason for closed-loop control such as this.
-Expanding `k_pu` we get:
+Expanding `k_pu` we get::
+
P_max = 2 * sustainable_power * (T_set - T) / (T_set - T_on) +
- sustainable_power
+ sustainable_power
-where
- T_set is the desired temperature
- T is the current temperature
- T_on is the switch on temperature
+where:
+
+ - T_set is the desired temperature
+ - T is the current temperature
+ - T_on is the switch on temperature
When the current temperature is the switch_on temperature, the above
-formula becomes:
+formula becomes::
P_max = 2 * sustainable_power * (T_set - T_on) / (T_set - T_on) +
- sustainable_power = 2 * sustainable_power + sustainable_power =
- 3 * sustainable_power
+ sustainable_power = 2 * sustainable_power + sustainable_power =
+ 3 * sustainable_power
Therefore, the proportional term alone linearly decreases power from
3 * `sustainable_power` to `sustainable_power` as the temperature
Cooling devices controlled by this governor must supply the additional
"power" API in their `cooling_device_ops`. It consists on three ops:
-1. int get_requested_power(struct thermal_cooling_device *cdev,
- struct thermal_zone_device *tz, u32 *power);
-@cdev: The `struct thermal_cooling_device` pointer
-@tz: thermal zone in which we are currently operating
-@power: pointer in which to store the calculated power
+1. ::
+
+ int get_requested_power(struct thermal_cooling_device *cdev,
+ struct thermal_zone_device *tz, u32 *power);
+
+
+@cdev:
+ The `struct thermal_cooling_device` pointer
+@tz:
+ thermal zone in which we are currently operating
+@power:
+ pointer in which to store the calculated power
`get_requested_power()` calculates the power requested by the device
in milliwatts and stores it in @power . It should return 0 on
allocator governor to calculate how much power to give to each cooling
device.
-2. int state2power(struct thermal_cooling_device *cdev, struct
- thermal_zone_device *tz, unsigned long state, u32 *power);
-@cdev: The `struct thermal_cooling_device` pointer
-@tz: thermal zone in which we are currently operating
-@state: A cooling device state
-@power: pointer in which to store the equivalent power
+2. ::
+
+ int state2power(struct thermal_cooling_device *cdev, struct
+ thermal_zone_device *tz, unsigned long state,
+ u32 *power);
+
+@cdev:
+ The `struct thermal_cooling_device` pointer
+@tz:
+ thermal zone in which we are currently operating
+@state:
+ A cooling device state
+@power:
+ pointer in which to store the equivalent power
Convert cooling device state @state into power consumption in
milliwatts and store it in @power. It should return 0 on success, -E*
on failure. This is currently used by thermal core to calculate the
maximum power that an actor can consume.
-3. int power2state(struct thermal_cooling_device *cdev, u32 power,
- unsigned long *state);
-@cdev: The `struct thermal_cooling_device` pointer
-@power: power in milliwatts
-@state: pointer in which to store the resulting state
+3. ::
+
+ int power2state(struct thermal_cooling_device *cdev, u32 power,
+ unsigned long *state);
+
+@cdev:
+ The `struct thermal_cooling_device` pointer
+@power:
+ power in milliwatts
+@state:
+ pointer in which to store the resulting state
Calculate a cooling device state that would make the device consume at
most @power mW and store it in @state. It should return 0 on success,
+===================================
Generic Thermal Sysfs driver How To
===================================
0. Introduction
+===============
The generic thermal sysfs provides a set of interfaces for thermal zone
devices (sensors) and thermal cooling devices (fan, processor...) to register
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
+- `[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 *type,
- int trips, int mask, void *devdata,
- struct thermal_zone_device_ops *ops,
- const struct thermal_zone_params *tzp,
- int passive_delay, int polling_delay))
+---------------------------------
+
+ ::
+
+ struct thermal_zone_device
+ *thermal_zone_device_register(char *type,
+ int trips, int mask, void *devdata,
+ struct thermal_zone_device_ops *ops,
+ const struct thermal_zone_params *tzp,
+ int passive_delay, int polling_delay))
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
+ /sys/class/thermal folder as `thermal_zone[0-*]`. It tries to bind all the
thermal cooling devices registered at the same time.
- type: the thermal zone type.
- trips: the total number of trip points this thermal zone supports.
- mask: Bit string: If 'n'th bit is set, then trip point 'n' is writeable.
- 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.
- .set_trips: set the trip points window. Whenever the current temperature
+ type:
+ the thermal zone type.
+ trips:
+ the total number of trip points this thermal zone supports.
+ mask:
+ Bit string: If 'n'th bit is set, then trip point 'n' is writeable.
+ 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.
+ .set_trips:
+ set the trip points window. Whenever the current temperature
is updated, the trip points immediately below and above the
current temperature are found.
- .get_mode: get the current mode (enabled/disabled) of the thermal zone.
- - "enabled" means the kernel thermal management is enabled.
- - "disabled" will prevent kernel thermal driver action upon trip points
- so that user applications can take charge of thermal management.
- .set_mode: set the mode (enabled/disabled) 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
+ .get_mode:
+ get the current mode (enabled/disabled) of the thermal zone.
+
+ - "enabled" means the kernel thermal management is
+ enabled.
+ - "disabled" will prevent kernel thermal driver action
+ upon trip points so that user applications can take
+ charge of thermal management.
+ .set_mode:
+ set the mode (enabled/disabled) 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.
- .set_emul_temp: set the emulation temperature which helps in debugging
+ .set_emul_temp:
+ set the emulation temperature which helps in debugging
different threshold temperature points.
- tzp: thermal zone platform parameters.
- passive_delay: number of milliseconds to wait between polls when
+ tzp:
+ thermal zone platform parameters.
+ passive_delay:
+ number of milliseconds to wait between polls when
performing passive cooling.
- polling_delay: number of milliseconds to wait between polls when checking
+ polling_delay:
+ number of milliseconds to wait between polls when checking
whether trip points have been crossed (0 for interrupt driven systems).
+ ::
-1.1.2 void thermal_zone_device_unregister(struct thermal_zone_device *tz)
+ void thermal_zone_device_unregister(struct thermal_zone_device *tz)
This interface function removes the thermal zone device.
It deletes the corresponding entry from /sys/class/thermal folder and
unbinds all the thermal cooling devices it uses.
-1.1.3 struct thermal_zone_device *thermal_zone_of_sensor_register(
- struct device *dev, int sensor_id, void *data,
- const struct thermal_zone_of_device_ops *ops)
+ ::
+
+ struct thermal_zone_device
+ *thermal_zone_of_sensor_register(struct device *dev, int sensor_id,
+ void *data,
+ const struct thermal_zone_of_device_ops *ops)
This interface adds a new sensor to a DT thermal zone.
This function will search the list of thermal zones described in
thermal zone device.
The parameters for this interface are:
- dev: Device node of sensor containing valid node pointer in
+
+ dev:
+ Device node of sensor containing valid node pointer in
dev->of_node.
- sensor_id: a sensor identifier, in case the sensor IP has more
+ sensor_id:
+ a sensor identifier, in case the sensor IP has more
than one sensors
- data: a private pointer (owned by the caller) that will be
+ data:
+ a private pointer (owned by the caller) that will be
passed back, when a temperature reading is needed.
- ops: struct thermal_zone_of_device_ops *.
+ ops:
+ `struct thermal_zone_of_device_ops *`.
- get_temp: a pointer to a function that reads the
+ ============== =======================================
+ get_temp a pointer to a function that reads the
sensor temperature. This is mandatory
callback provided by sensor driver.
- set_trips: a pointer to a function that sets a
+ set_trips a pointer to a function that sets a
temperature window. When this window is
left the driver must inform the thermal
core via thermal_zone_device_update.
- get_trend: a pointer to a function that reads the
+ get_trend a pointer to a function that reads the
sensor temperature trend.
- set_emul_temp: a pointer to a function that sets
+ set_emul_temp a pointer to a function that sets
sensor emulated temperature.
+ ============== =======================================
+
The thermal zone temperature is provided by the get_temp() function
pointer of thermal_zone_of_device_ops. When called, it will
have the private pointer @data back.
handle. Caller should check the return handle with IS_ERR() for finding
whether success or not.
-1.1.4 void thermal_zone_of_sensor_unregister(struct device *dev,
- struct thermal_zone_device *tzd)
+ ::
+
+ void thermal_zone_of_sensor_unregister(struct device *dev,
+ struct thermal_zone_device *tzd)
This interface unregisters a sensor from a DT thermal zone which was
successfully added by interface thermal_zone_of_sensor_register().
interface. It will also silent the zone by remove the .get_temp() and
get_trend() thermal zone device callbacks.
-1.1.5 struct thermal_zone_device *devm_thermal_zone_of_sensor_register(
- struct device *dev, int sensor_id,
- void *data, const struct thermal_zone_of_device_ops *ops)
+ ::
+
+ struct thermal_zone_device
+ *devm_thermal_zone_of_sensor_register(struct device *dev,
+ int sensor_id,
+ void *data,
+ const struct thermal_zone_of_device_ops *ops)
This interface is resource managed version of
thermal_zone_of_sensor_register().
+
All details of thermal_zone_of_sensor_register() described in
section 1.1.3 is applicable here.
+
The benefit of using this interface to register sensor is that it
is not require to explicitly call thermal_zone_of_sensor_unregister()
in error path or during driver unbinding as this is done by driver
resource manager.
-1.1.6 void devm_thermal_zone_of_sensor_unregister(struct device *dev,
- struct thermal_zone_device *tzd)
+ ::
+
+ void devm_thermal_zone_of_sensor_unregister(struct device *dev,
+ struct thermal_zone_device *tzd)
This interface is resource managed version of
thermal_zone_of_sensor_unregister().
Normally this function will not need to be called and the resource
management code will ensure that the resource is freed.
-1.1.7 int thermal_zone_get_slope(struct thermal_zone_device *tz)
+ ::
+
+ int thermal_zone_get_slope(struct thermal_zone_device *tz)
This interface is used to read the slope attribute value
for the thermal zone device, which might be useful for platform
drivers for temperature calculations.
-1.1.8 int thermal_zone_get_offset(struct thermal_zone_device *tz)
+ ::
+
+ int thermal_zone_get_offset(struct thermal_zone_device *tz)
This interface is used to read the offset attribute value
for the thermal zone device, which might be useful for platform
drivers for temperature calculations.
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 *)
+------------------------------------
+
+
+ ::
+
+ 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 /sys/class/thermal/ folder as `cooling_device[0-*]`. It tries to bind itself
to all the thermal zone devices registered 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 Currently requested 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)
+ 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 Currently requested throttle state of the
+ cooling device.
+ .set_cur_state:
+ set the Current throttle state of the cooling device.
+
+ ::
+
+ void thermal_cooling_device_unregister(struct thermal_cooling_device *cdev)
This interface function removes the thermal cooling device.
It deletes the corresponding entry from /sys/class/thermal folder and
unbinds 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,
- unsigned long upper, unsigned long lower, unsigned int weight);
+-----------------------------------------------------------------------------
+
+ ::
+
+ int thermal_zone_bind_cooling_device(struct thermal_zone_device *tz,
+ int trip, struct thermal_cooling_device *cdev,
+ unsigned long upper, unsigned long lower, unsigned int weight);
This interface function binds a thermal cooling device to a particular 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 in this thermal zone the cooling device
- is associated with.
- upper:the Maximum cooling state for this trip point.
- THERMAL_NO_LIMIT means no upper limit,
+
+ tz:
+ the thermal zone device
+ cdev:
+ thermal cooling device
+ trip:
+ indicates which trip point in this thermal zone the cooling device
+ is associated with.
+ upper:
+ the Maximum cooling state for this trip point.
+ THERMAL_NO_LIMIT means no upper limit,
and the cooling device can be in max_state.
- lower:the Minimum cooling state can be used for this trip point.
- THERMAL_NO_LIMIT means no lower limit,
+ lower:
+ the Minimum cooling state can be used for this trip point.
+ THERMAL_NO_LIMIT means no lower limit,
and the cooling device can be in cooling state 0.
- weight: the influence of this cooling device in this thermal
- zone. See 1.4.1 below for more information.
+ weight:
+ the influence of this cooling device in this thermal
+ zone. See 1.4.1 below for more information.
-1.3.2 int thermal_zone_unbind_cooling_device(struct thermal_zone_device *tz,
- int trip, struct thermal_cooling_device *cdev);
+ ::
+
+ int thermal_zone_unbind_cooling_device(struct thermal_zone_device *tz,
+ int trip, struct thermal_cooling_device *cdev);
This interface function unbinds a thermal cooling device from a particular
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 in this thermal zone the cooling device
- is associated with.
+
+ tz:
+ the thermal zone device
+ cdev:
+ thermal cooling device
+ trip:
+ indicates which trip point in this thermal zone the cooling device
+ is associated with.
1.4 Thermal Zone Parameters
-1.4.1 struct thermal_bind_params
+---------------------------
+
+ ::
+
+ struct thermal_bind_params
+
This structure defines the following parameters that are used to bind
a zone with a cooling device for a particular trip point.
- .cdev: The cooling device pointer
- .weight: The 'influence' of a particular cooling device on this
- zone. This is relative to the rest of the cooling
- devices. For example, if all cooling devices have a
- weight of 1, then they all contribute the same. You can
- use percentages if you want, but it's not mandatory. A
- weight of 0 means that this cooling device doesn't
- contribute to the cooling of this zone unless all cooling
- devices have a weight of 0. If all weights are 0, then
- they all contribute the same.
- .trip_mask:This is a bit mask that gives the binding relation between
- this thermal zone and cdev, for a particular trip point.
- If nth bit is set, then the cdev and thermal zone are bound
- for trip point n.
- .binding_limits: This is an array of cooling state limits. Must have
- exactly 2 * thermal_zone.number_of_trip_points. It is an
- array consisting of tuples <lower-state upper-state> of
- state limits. Each trip will be associated with one state
- limit tuple when binding. A NULL pointer means
- <THERMAL_NO_LIMITS THERMAL_NO_LIMITS> on all trips.
- These limits are used when binding a cdev to a trip point.
- .match: This call back returns success(0) if the 'tz and cdev' need to
+
+ .cdev:
+ The cooling device pointer
+ .weight:
+ The 'influence' of a particular cooling device on this
+ zone. This is relative to the rest of the cooling
+ devices. For example, if all cooling devices have a
+ weight of 1, then they all contribute the same. You can
+ use percentages if you want, but it's not mandatory. A
+ weight of 0 means that this cooling device doesn't
+ contribute to the cooling of this zone unless all cooling
+ devices have a weight of 0. If all weights are 0, then
+ they all contribute the same.
+ .trip_mask:
+ This is a bit mask that gives the binding relation between
+ this thermal zone and cdev, for a particular trip point.
+ If nth bit is set, then the cdev and thermal zone are bound
+ for trip point n.
+ .binding_limits:
+ This is an array of cooling state limits. Must have
+ exactly 2 * thermal_zone.number_of_trip_points. It is an
+ array consisting of tuples <lower-state upper-state> of
+ state limits. Each trip will be associated with one state
+ limit tuple when binding. A NULL pointer means
+ <THERMAL_NO_LIMITS THERMAL_NO_LIMITS> on all trips.
+ These limits are used when binding a cdev to a trip point.
+ .match:
+ This call back returns success(0) if the 'tz and cdev' need to
be bound, as per platform data.
-1.4.2 struct thermal_zone_params
+
+ ::
+
+ struct thermal_zone_params
+
This structure defines the platform level parameters for a thermal zone.
This data, for each thermal zone should come from the platform layer.
This is an optional feature where some platforms can choose not to
provide this data.
- .governor_name: Name of the thermal governor used for this zone
- .no_hwmon: a boolean to indicate if the thermal to hwmon sysfs interface
- is required. when no_hwmon == false, a hwmon sysfs interface
- will be created. when no_hwmon == true, nothing will be done.
- In case the thermal_zone_params is NULL, the hwmon interface
- will be created (for backward compatibility).
- .num_tbps: Number of thermal_bind_params entries for this zone
- .tbp: thermal_bind_params entries
+
+ .governor_name:
+ Name of the thermal governor used for this zone
+ .no_hwmon:
+ a boolean to indicate if the thermal to hwmon sysfs interface
+ is required. when no_hwmon == false, a hwmon sysfs interface
+ will be created. when no_hwmon == true, nothing will be done.
+ In case the thermal_zone_params is NULL, the hwmon interface
+ will be created (for backward compatibility).
+ .num_tbps:
+ Number of thermal_bind_params entries for this zone
+ .tbp:
+ thermal_bind_params entries
2. sysfs attributes structure
+=============================
+== ================
RO read only value
WO write 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-*]:
+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
|---slope: Slope constant applied as linear extrapolation
|---offset: Offset constant applied as linear extrapolation
-Thermal cooling device sys I/F, created once it's registered:
-/sys/class/thermal/cooling_device[0-*]:
+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
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-*]:
+::
+
+ /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
|---cdev[0-*]_weight: Influence of the cooling device in
- this thermal zone
+ this thermal zone
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_
class device and build the associated hwmon sysfs I/F for all the registered
ACPI thermal zones.
-/sys/class/hwmon/hwmon[0-*]:
+::
+
+ /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.rst for additional information.
-***************************
-* Thermal zone attributes *
-***************************
+Thermal zone attributes
+-----------------------
type
Strings which represent the thermal zone type.
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.
- enabled = enable Kernel Thermal management.
- disabled = Preventing kernel thermal zone driver actions upon
+
+ enabled
+ enable Kernel Thermal management.
+ disabled
+ Preventing kernel thermal zone driver actions upon
trip points so that user application can take full
charge of the thermal management.
+
RW, Optional
policy
One of the various thermal governors used for a particular zone.
+
RW, Required
available_policies
Available thermal governors which can be used for a particular zone.
+
RO, Required
-trip_point_[0-*]_temp
+`trip_point_[0-*]_temp`
The temperature above which trip point will be fired.
+
Unit: millidegree Celsius
+
RO, Optional
-trip_point_[0-*]_type
+`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
+
+ E.g. it can be one of critical, hot, passive, `active[0-*]` for ACPI
thermal zone.
+
RO, Optional
-trip_point_[0-*]_hyst
+`trip_point_[0-*]_hyst`
The hysteresis value for a trip point, represented as an integer
Unit: Celsius
RW, Optional
-cdev[0-*]
+`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 in this thermal zone which cdev[0-*] is associated
+`cdev[0-*]_trip_point`
+ The trip point in this thermal zone which `cdev[0-*]` is associated
with; -1 means the cooling device is not associated with any trip
point.
+
RO, Optional
-cdev[0-*]_weight
- The influence of cdev[0-*] in this thermal zone. This value
- is relative to the rest of cooling devices in the thermal
- zone. For example, if a cooling device has a weight double
- than that of other, it's twice as effective in cooling the
- thermal zone.
- RW, Optional
+`cdev[0-*]_weight`
+ The influence of `cdev[0-*]` in this thermal zone. This value
+ is relative to the rest of cooling devices in the thermal
+ zone. For example, if a cooling device has a weight double
+ than that of other, it's twice as effective in cooling the
+ thermal zone.
+
+ RW, Optional
passive
Attribute is only present for zones in which the passive cooling
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
emul_temp
threshold and its associated cooling action. This is write only node
and writing 0 on this node should disable emulation.
Unit: millidegree Celsius
+
WO, Optional
- WARNING: Be careful while enabling this option on production systems,
- because userland can easily disable the thermal policy by simply
- flooding this sysfs node with low temperature values.
+ WARNING:
+ Be careful while enabling this option on production systems,
+ because userland can easily disable the thermal policy by simply
+ flooding this sysfs node with low temperature values.
sustainable_power
An estimate of the sustained power that can be dissipated by
the thermal zone. Used by the power allocator governor. For
- more information see Documentation/thermal/power_allocator.txt
+ more information see Documentation/thermal/power_allocator.rst
+
Unit: milliwatts
+
RW, Optional
k_po
controller during temperature overshoot. Temperature overshoot
is when the current temperature is above the "desired
temperature" trip point. For more information see
- Documentation/thermal/power_allocator.txt
+ Documentation/thermal/power_allocator.rst
+
RW, Optional
k_pu
controller during temperature undershoot. Temperature undershoot
is when the current temperature is below the "desired
temperature" trip point. For more information see
- Documentation/thermal/power_allocator.txt
+ Documentation/thermal/power_allocator.rst
+
RW, Optional
k_i
The integral term of the power allocator governor's PID
controller. This term allows the PID controller to compensate
for long term drift. For more information see
- Documentation/thermal/power_allocator.txt
+ Documentation/thermal/power_allocator.rst
+
RW, Optional
k_d
The derivative term of the power allocator governor's PID
controller. For more information see
- Documentation/thermal/power_allocator.txt
+ Documentation/thermal/power_allocator.rst
+
RW, Optional
integral_cutoff
example, if integral_cutoff is 0, then the integral term only
accumulates error when temperature is above the desired
temperature trip point. For more information see
- Documentation/thermal/power_allocator.txt
+ Documentation/thermal/power_allocator.rst
+
Unit: millidegree Celsius
+
RW, Optional
slope
to determine a hotspot temperature based off the sensor's
raw readings. It is up to the device driver to determine
the usage of these values.
+
RW, Optional
offset
to determine a hotspot temperature based off the sensor's
raw readings. It is up to the device driver to determine
the usage of these values.
+
RW, Optional
-*****************************
-* Cooling device attributes *
-*****************************
+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
stats/reset
units here is 10mS (similar to other time exported in /proc).
RO, Required
+
stats/total_trans:
A single positive value showing the total number of times the state of a
cooling device is changed.
+
RO, Required
stats/trans_table:
RO, 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,
effectiveness in cooling the thermal zone.
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:
+method, the sys I/F structure will be built like this::
-/sys/class/thermal:
-
-|thermal_zone1:
+ /sys/class/thermal:
+ |thermal_zone1:
|---type: acpitz
|---temp: 37000
|---mode: enabled
|---cdev1_trip_point: 2 /* cdev1 can be used for active[0]*/
|---cdev1_weight: 1024
-|cooling_device0:
+ |cooling_device0:
|---type: Processor
|---max_state: 8
|---cur_state: 0
-|cooling_device3:
+ |cooling_device3:
|---type: Fan
|---max_state: 2
|---cur_state: 0
-/sys/class/hwmon:
-
-|hwmon0:
+ /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_
THERMAL_DEV_FAULT}. Notification can be sent when the current temperature
crosses any of the configured thresholds.
-5. Export Symbol APIs:
+5. Export Symbol APIs
+=====================
+
+5.1. get_tz_trend
+-----------------
-5.1: get_tz_trend:
This function returns the trend of a thermal zone, i.e the rate of change
of temperature of the thermal zone. Ideally, the thermal sensor drivers
are supposed to implement the callback. If they don't, the thermal
framework calculated the trend by comparing the previous and the current
temperature values.
-5.2:get_thermal_instance:
+5.2. get_thermal_instance
+-------------------------
+
This function returns the thermal_instance corresponding to a given
{thermal_zone, cooling_device, trip_point} combination. Returns NULL
if such an instance does not exist.
-5.3:thermal_notify_framework:
+5.3. thermal_notify_framework
+-----------------------------
+
This function handles the trip events from sensor drivers. It starts
throttling the cooling devices according to the policy configured.
For CRITICAL and HOT trip points, this notifies the respective drivers,
The throttling policy is based on the configured platform data; if no
platform data is provided, this uses the step_wise throttling policy.
-5.4:thermal_cdev_update:
+5.4. thermal_cdev_update
+------------------------
+
This function serves as an arbitrator to set the state of a cooling
device. It sets the cooling device to the deepest cooling state if
possible.
-6. thermal_emergency_poweroff:
+6. thermal_emergency_poweroff
+=============================
On an event of critical trip temperature crossing. Thermal framework
allows the system to shutdown gracefully by calling orderly_poweroff().
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