Lines Matching refs:the
7 The governor works optimally with the following two passive trip points:
9 1. "switch on" trip point: temperature above which the governor
10 control loop starts operating. This is the first passive trip
11 point of the thermal zone.
13 2. "desired temperature" trip point: it should be higher than the
14 "switch on" trip point. This the target temperature the governor
15 is controlling for. This is the last passive trip point of the
23 temperature as the control input and power as the controlled output:
29 err_integral is the sum of previous errors
32 It is similar to the one depicted below:
62 An estimate of the sustainable dissipatable power (in mW) should be
63 provided while registering the thermal zone. This estimates the
64 sustained power that can be dissipated at the desired control
65 temperature. This is the maximum sustained power for allocation at
66 the desired maximum temperature. The actual sustained power can vary
69 to the speed-grade of the silicon. `sustainable_power` is therefore
70 simply an estimate, and may be tuned to affect the aggressiveness of
71 the thermal ramp. For reference, the sustainable power of a 4" phone
75 If you are using device tree, do add it as a property of the
85 Instead, if the thermal zone is registered from the platform code, pass a
94 and then pass `tz_params` as the 5th parameter to
100 The implementation of the PID controller in the power allocator
101 thermal governor allows the configuration of two proportional term
102 constants: `k_po` and `k_pu`. `k_po` is the proportional term
104 above "desired temperature" trip point). Conversely, `k_pu` is the
108 These controls are intended as the primary mechanism for configuring
109 the permitted thermal "ramp" of the system. For instance, a lower
110 `k_pu` value will provide a slower ramp, at the cost of capping
111 available capacity at a low temperature. On the other hand, a high
112 value of `k_pu` will result in the governor granting very high power
119 This means that at `switch_on_temp` the output of the controller's
125 Focusing on the proportional and feed forward values of the PID
130 The proportional term is proportional to the difference between the
131 desired temperature and the current one. When the current temperature
132 is the desired one, then the proportional component is zero and
133 `P_max` = `sustainable_power`. That is, the system should operate in
135 an estimate, which is the reason for closed-loop control such as this.
142 T_set is the desired temperature
143 T is the current temperature
144 T_on is the switch on temperature
146 When the current temperature is the switch_on temperature, the above
153 Therefore, the proportional term alone linearly decreases power from
154 3 * `sustainable_power` to `sustainable_power` as the temperature
155 rises from the switch on temperature to the desired temperature.
160 `k_i` configures the PID loop's integral term constant. This term
161 allows the PID controller to compensate for long term drift and for
162 the quantized nature of the output control: cooling devices can't set
163 the exact power that the governor requests. When the temperature
164 error is below `integral_cutoff`, errors are accumulated in the
165 integral term. This term is then multiplied by `k_i` and the result
166 added to the output of the controller. Typically `k_i` is set low (1
172 `k_d` configures the PID loop's derivative term constant. It's
173 recommended to leave it as the default: 0.
178 Cooling devices controlled by this governor must supply the additional
185 @power: pointer in which to store the calculated power
187 `get_requested_power()` calculates the power requested by the device
189 success, -E* on failure. This is currently used by the power
198 @power: pointer in which to store the equivalent power
202 on failure. This is currently used by thermal core to calculate the
209 @state: pointer in which to store the resulting state
211 Calculate a cooling device state that would make the device consume at
213 -E* on failure. This is currently used by the thermal core to convert
214 a given power set by the power allocator governor to a state that the
216 depend on external factors that may change so this function should the
222 Weights are a mechanism to bias the allocation among cooling
223 devices. They express the relative power efficiency of different
228 the same kind of compute, but with different efficiency. For example,
231 If the thermal zone is registered using
233 are passed as part of the thermal zone's `thermal_bind_parameters`.
234 If the platform is registered using device tree, then they are passed
235 as the `contribution` property of each map in the `cooling-maps` node.
237 Limitations of the power allocator governor
242 `thermal_zone_device_update()` (or anything that ends up calling the
243 governor's `throttle()` function) repetitively, the governor response
246 faster than the normal thermal framework tick (due to interrupts for