driver-api/thermal/power_allocator.rst

6 -----------
20 --------------
23 Proportional-Integral-Derivative controller (PID controller) with
29    -  e = desired_temperature - current_temperature
30    -  err_integral is the sum of previous errors
31    -  diff_err = e - previous_error
39        |              +----------+   +---+
40        |       +----->| diff_err |-->| X |------+
41        |       |      +----------+   +---+      |
47      +---+     |      +-------+      +---+    +---+   +---+   +----------+
48      | S |-----+----->| sum e |----->| X |--->| S |-->| S |-->|power     |
49      +---+     |      +-------+      +---+    +---+   +---+   |allocation|
50        ^       |                                ^             +----------+
52        |       |        +---+                   |                |     |
53        |       +------->| X |-------------------+                v     v
54        |                +---+                               granted performance
61 -----------------
70 to the speed-grade of the silicon.  `sustainable_power` is therefore
76 If you are using device tree, do add it as a property of the
77 thermal-zone.  For example::
79 	thermal-zones {
81 			polling-delay = <1000>;
82 			polling-delay-passive = <100>;
83 			sustainable-power = <2500>;
99 -------------
118     2 * sustainable_power / (desired_temperature - switch_on_temp)
124     sustainable_power / (desired_temperature - switch_on_temp)
136 an estimate, which is the reason for closed-loop control such as this.
140     P_max = 2 * sustainable_power * (T_set - T) / (T_set - T_on) +
145     - T_set is the desired temperature
146     - T is the current temperature
147     - T_on is the switch on temperature
152     P_max = 2 * sustainable_power * (T_set - T_on) / (T_set - T_on) +
161 -----------------------
165 the quantized nature of the output control: cooling devices can't set
173 ---
178 Cooling device power API
181 Cooling devices controlled by this governor must supply the additional
197 `get_requested_power()` calculates the power requested by the device
199 success, -E* on failure.  This is currently used by the power
200 allocator governor to calculate how much power to give to each cooling
201 device.
214 	A cooling device state
218 Convert cooling device state @state into power consumption in
219 milliwatts and store it in @power.  It should return 0 on success, -E*
235 Calculate a cooling device state that would make the device consume at
237 -E* on failure.  This is currently used by the thermal core to convert
239 cooling device can set.  It is a function because this conversion may
243 Cooling device weights
244 ----------------------
246 Weights are a mechanism to bias the allocation among cooling
248 cooling devices.  Higher weight can be used to express higher power
249 efficiency.  Weighting is relative such that if each cooling device
251 useful in heterogeneous systems where two cooling devices may perform
258 If the platform is registered using device tree, then they are passed
259 as the `contribution` property of each map in the `cooling-maps` node.
269 governor, step-wise will also misbehave if you call its throttle()