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Date: Mon, 2 Feb 2015 16:51:20 -0700
From: Lina Iyer <lina.iyer@...aro.org>
To: Javi Merino <javi.merino@....com>
Cc: linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
punit.agrawal@....com, broonie@...nel.org,
Zhang Rui <rui.zhang@...el.com>,
Eduardo Valentin <edubezval@...il.com>
Subject: Re: [PATCH v1 4/7] thermal: introduce the Power Allocator governor
On Wed, Jan 28 2015 at 14:42 -0700, Javi Merino wrote:
>The power allocator governor is a thermal governor that controls system
>and device power allocation to control temperature. Conceptually, the
>implementation divides the sustainable power of a thermal zone among
>all the heat sources in that zone.
>
>This governor relies on "power actors", entities that represent heat
>sources. They can report current and maximum power consumption and
>can set a given maximum power consumption, usually via a cooling
>device.
>
>The governor uses a Proportional Integral Derivative (PID) controller
>driven by the temperature of the thermal zone. The output of the
>controller is a power budget that is then allocated to each power
>actor that can have bearing on the temperature we are trying to
>control. It decides how much power to give each cooling device based
>on the performance they are requesting. The PID controller ensures
>that the total power budget does not exceed the control temperature.
>
>Cc: Zhang Rui <rui.zhang@...el.com>
>Cc: Eduardo Valentin <edubezval@...il.com>
>Signed-off-by: Punit Agrawal <punit.agrawal@....com>
>Signed-off-by: Javi Merino <javi.merino@....com>
>---
> Documentation/thermal/power_allocator.txt | 241 +++++++++++++++
> drivers/thermal/Kconfig | 15 +
> drivers/thermal/Makefile | 1 +
> drivers/thermal/power_allocator.c | 478 ++++++++++++++++++++++++++++++
> drivers/thermal/thermal_core.c | 9 +-
> drivers/thermal/thermal_core.h | 8 +
> include/linux/thermal.h | 37 ++-
> 7 files changed, 782 insertions(+), 7 deletions(-)
> create mode 100644 Documentation/thermal/power_allocator.txt
> create mode 100644 drivers/thermal/power_allocator.c
>
>diff --git a/Documentation/thermal/power_allocator.txt b/Documentation/thermal/power_allocator.txt
>new file mode 100644
>index 000000000000..c9604e76c544
>--- /dev/null
>+++ b/Documentation/thermal/power_allocator.txt
>@@ -0,0 +1,241 @@
>+Power allocator governor tunables
>+=================================
>+
>+Trip points
>+-----------
>+
>+The governor requires the following two passive trip points:
>+
>+1. "switch on" trip point: temperature above which the governor
>+ control loop starts operating.
>+2. "desired temperature" trip point: it should be higher than the
>+ "switch on" trip point. This the target temperature the governor
>+ is controlling for.
>+
>+PID Controller
>+--------------
>+
>+The power allocator governor implements a
>+Proportional-Integral-Derivative controller (PID controller) with
>+temperature as the control input and power as the controlled output:
>+
>+ 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
>+
>+Sustainable power
>+-----------------
>+
>+An estimate of the sustainable dissipatable power (in mW) should be
>+provided while registering the thermal zone. This estimates the
>+sustained power that can be dissipated at the desired control
>+temperature. This is the maximum sustained power for allocation at
>+the desired maximum temperature. The actual sustained power can vary
>+for a number of reasons. The closed loop controller will take care of
>+variations such as environmental conditions, and some factors related
>+to the speed-grade of the silicon. `sustainable_power` is therefore
>+simply an estimate, and may be tuned to affect the aggressiveness of
>+the thermal ramp. For reference, the sustainable power of a 4" phone
>+is typically 2000mW, while on a 10" tablet is around 4500mW (may vary
>+depending on screen size).
>+
>+If you are using device tree, do add it as a property of the
>+thermal-zone. For example:
>+
>+ thermal-zones {
>+ soc_thermal {
>+ polling-delay = <1000>;
>+ polling-delay-passive = <100>;
>+ sustainable-power = <2500>;
>+ ...
>+
>+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:
>+
>+ static const struct thermal_zone_params tz_params = {
>+ .sustainable_power = 3500,
>+ };
>+
>+and then pass `tz_params` as the 5th parameter to
>+`thermal_zone_device_register()`
>+
>+k_po and k_pu
>+-------------
>+
>+The implementation of the PID controller in the power allocator
>+thermal governor allows the configuration of two proportional term
>+constants: `k_po` and `k_pu`. `k_po` is the proportional term
>+constant during temperature overshoot periods (current temperature is
>+above "desired temperature" trip point). Conversely, `k_pu` is the
>+proportional term constant during temperature undershoot periods
>+(current temperature below "desired temperature" trip point).
>+
>+These controls are intended as the primary mechanism for configuring
>+the permitted thermal "ramp" of the system. For instance, a lower
>+`k_pu` value will provide a slower ramp, at the cost of capping
>+available capacity at a low temperature. On the other hand, a high
>+value of `k_pu` will result in the governor granting very high power
>+whilst temperature is low, and may lead to temperature overshooting.
>+
>+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:
>+
>+ sustainable_power / (desired_temperature - switch_on_temp)
>+
>+Focusing on the proportional and feed forward values of the PID
>+controller equation we have:
>+
>+ P_max = k_p * e + sustainable_power
>+
>+The proportional term is proportional to the difference between the
>+desired temperature and the current one. When the current temperature
>+is the desired one, then the proportional component is zero and
>+`P_max` = `sustainable_power`. That is, the system should operate in
>+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:
>+ P_max = 2 * sustainable_power * (T_set - T) / (T_set - T_on) +
>+ sustainable_power
>+
>+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:
>+
>+ P_max = 2 * sustainable_power * (T_set - T_on) / (T_set - T_on) +
>+ 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
>+rises from the switch on temperature to the desired temperature.
>+
>+k_i and integral_cutoff
>+-----------------------
>+
>+`k_i` configures the PID loop's integral term constant. This term
>+allows the PID controller to compensate for long term drift and for
>+the quantized nature of the output control: cooling devices can't set
>+the exact power that the governor requests. When the temperature
>+error is below `integral_cutoff`, errors are accumulated in the
>+integral term. This term is then multiplied by `k_i` and the result
>+added to the output of the controller. Typically `k_i` is set low (1
>+or 2) and `integral_cutoff` is 0.
>+
>+k_d
>+---
>+
>+`k_d` configures the PID loop's derivative term constant. It's
>+recommended to leave it as the default: 0.
>+
>+Cooling device power API
>+========================
>+
>+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);
>+@...v: The `struct thermal_cooling_device` pointer
>+@tz: thermal zone in which we are currently operating
>+@...er: 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
>+success, -E* on failure. This is currently used by the power
>+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);
>+@...v: The `struct thermal_cooling_device` pointer
>+@tz: thermal zone in which we are currently operating
>+@...te: A cooling device state
>+@...er: 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);
>+@...v: The `struct thermal_cooling_device` pointer
>+@...er: power in milliwatts
>+@...te: 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,
>+-E* on failure. This is currently used by the thermal core to convert
>+a given power set by the power allocator governor to a state that the
>+cooling device can set. It is a function because this conversion may
>+depend on external factors that may change so this function should the
>+best conversion given "current circumstances".
>+
>+Cooling device weights
>+----------------------
>+
>+Weights are a mechanism to bias the allocation among cooling
>+devices. They express the relative power efficiency of different
>+cooling devices. Higher weight can be used to express higher power
>+efficiency. Weighting is relative such that if each cooling device
>+has a weight of one they are considered equal. This is particularly
>+useful in heterogeneous systems where two cooling devices may perform
>+the same kind of compute, but with different efficiency. For example,
>+a system with two different types of processors.
>+
>+Weights are passed as part of the thermal zone's
>+`thermal_bind_parameters`.
>+
>+Limitations of the power allocator governor
>+===========================================
>+
>+The power allocator governor's PID controller works best if there is a
>+periodic tick. If you have a driver that calls
>+`thermal_zone_device_update()` (or anything that ends up calling the
>+governor's `throttle()` function) repetitively, the governor response
>+won't be very good. Note that this is not particular to this
>+governor, step-wise will also misbehave if you call its throttle()
>+faster than the normal thermal framework tick (due to interrupts for
>+example) as it will overreact.
>diff --git a/drivers/thermal/Kconfig b/drivers/thermal/Kconfig
>index af40db0df58e..98a46383b19f 100644
>--- a/drivers/thermal/Kconfig
>+++ b/drivers/thermal/Kconfig
>@@ -71,6 +71,14 @@ config THERMAL_DEFAULT_GOV_USER_SPACE
> Select this if you want to let the user space manage the
> platform thermals.
>
>+config THERMAL_DEFAULT_GOV_POWER_ALLOCATOR
>+ bool "power_allocator"
>+ select THERMAL_GOV_POWER_ALLOCATOR
>+ help
>+ Select this if you want to control temperature based on
>+ system and device power allocation. This governor can only
>+ operate on cooling devices that implement the power API.
>+
> endchoice
>
> config THERMAL_GOV_FAIR_SHARE
>@@ -99,6 +107,13 @@ config THERMAL_GOV_USER_SPACE
> help
> Enable this to let the user space manage the platform thermals.
>
>+config THERMAL_GOV_POWER_ALLOCATOR
>+ bool "Power allocator thermal governor"
>+ select THERMAL_POWER_ACTOR
>+ help
>+ Enable this to manage platform thermals by dynamically
>+ allocating and limiting power to devices.
>+
> config CPU_THERMAL
> bool "generic cpu cooling support"
> depends on CPU_FREQ
>diff --git a/drivers/thermal/Makefile b/drivers/thermal/Makefile
>index fa0dc486790f..cd769ab06cbb 100644
>--- a/drivers/thermal/Makefile
>+++ b/drivers/thermal/Makefile
>@@ -14,6 +14,7 @@ thermal_sys-$(CONFIG_THERMAL_GOV_FAIR_SHARE) += fair_share.o
> thermal_sys-$(CONFIG_THERMAL_GOV_BANG_BANG) += gov_bang_bang.o
> thermal_sys-$(CONFIG_THERMAL_GOV_STEP_WISE) += step_wise.o
> thermal_sys-$(CONFIG_THERMAL_GOV_USER_SPACE) += user_space.o
>+thermal_sys-$(CONFIG_THERMAL_GOV_POWER_ALLOCATOR) += power_allocator.o
>
> # cpufreq cooling
> thermal_sys-$(CONFIG_CPU_THERMAL) += cpu_cooling.o
>diff --git a/drivers/thermal/power_allocator.c b/drivers/thermal/power_allocator.c
>new file mode 100644
>index 000000000000..c929143aee67
>--- /dev/null
>+++ b/drivers/thermal/power_allocator.c
>@@ -0,0 +1,478 @@
>+/*
>+ * A power allocator to manage temperature
>+ *
>+ * Copyright (C) 2014 ARM Ltd.
>+ *
>+ * This program is free software; you can redistribute it and/or modify
>+ * it under the terms of the GNU General Public License version 2 as
>+ * published by the Free Software Foundation.
>+ *
>+ * This program is distributed "as is" WITHOUT ANY WARRANTY of any
>+ * kind, whether express or implied; without even the implied warranty
>+ * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
>+ * GNU General Public License for more details.
>+ */
>+
>+#define pr_fmt(fmt) "Power allocator: " fmt
>+
>+#include <linux/rculist.h>
>+#include <linux/slab.h>
>+#include <linux/thermal.h>
>+
>+#include "thermal_core.h"
>+
>+#define FRAC_BITS 10
>+#define int_to_frac(x) ((x) << FRAC_BITS)
>+#define frac_to_int(x) ((x) >> FRAC_BITS)
>+
>+/**
>+ * mul_frac() - multiply two fixed-point numbers
>+ * @x: first multiplicand
>+ * @y: second multiplicand
>+ *
>+ * Return: the result of multiplying two fixed-point numbers. The
>+ * result is also a fixed-point number.
>+ */
>+static inline s64 mul_frac(s64 x, s64 y)
>+{
>+ return (x * y) >> FRAC_BITS;
>+}
>+
>+enum power_allocator_trip_levels {
>+ TRIP_SWITCH_ON = 0, /* Switch on PID controller */
>+ TRIP_MAX_DESIRED_TEMPERATURE, /* Temperature we are controlling for */
>+
>+ THERMAL_TRIP_NUM,
>+};
This has to be exported for tz's to respond to the request. See below.
>+
>+/**
>+ * struct power_allocator_params - parameters for the power allocator governor
>+ * @err_integral: accumulated error in the PID controller.
>+ * @prev_err: error in the previous iteration of the PID controller.
>+ * Used to calculate the derivative term.
>+ */
>+struct power_allocator_params {
>+ s64 err_integral;
>+ s32 prev_err;
>+};
>+
>+/**
>+ * pid_controller() - PID controller
>+ * @tz: thermal zone we are operating in
>+ * @current_temp: the current temperature in millicelsius
>+ * @control_temp: the target temperature in millicelsius
>+ * @max_allocatable_power: maximum allocatable power for this thermal zone
>+ *
>+ * This PID controller increases the available power budget so that the
>+ * temperature of the thermal zone gets as close as possible to
>+ * @control_temp and limits the power if it exceeds it. k_po is the
>+ * proportional term when we are overshooting, k_pu is the
>+ * proportional term when we are undershooting. integral_cutoff is a
>+ * threshold below which we stop accumulating the error. The
>+ * accumulated error is only valid if the requested power will make
>+ * the system warmer. If the system is mostly idle, there's no point
>+ * in accumulating positive error.
>+ *
>+ * Return: The power budget for the next period.
>+ */
>+static u32 pid_controller(struct thermal_zone_device *tz,
>+ unsigned long current_temp,
>+ unsigned long control_temp,
>+ u32 max_allocatable_power)
>+{
>+ s64 p, i, d, power_range;
>+ s32 err, max_power_frac;
>+ struct power_allocator_params *params = tz->governor_data;
>+
>+ max_power_frac = int_to_frac(max_allocatable_power);
>+
>+ err = ((s32)control_temp - (s32)current_temp);
>+ err = int_to_frac(err);
>+
>+ /* Calculate the proportional term */
>+ p = mul_frac(err < 0 ? tz->tzp->k_po : tz->tzp->k_pu, err);
>+
>+ /*
>+ * Calculate the integral term
>+ *
>+ * if the error is less than cut off allow integration (but
>+ * the integral is limited to max power)
>+ */
>+ i = mul_frac(tz->tzp->k_i, params->err_integral);
>+
>+ if (err < int_to_frac(tz->tzp->integral_cutoff)) {
>+ s64 i_next = i + mul_frac(tz->tzp->k_i, err);
>+
>+ if (abs64(i_next) < max_power_frac) {
>+ i = i_next;
>+ params->err_integral += err;
>+ }
>+ }
>+
>+ /*
>+ * Calculate the derivative term
>+ *
>+ * We do err - prev_err, so with a positive k_d, a decreasing
>+ * error (i.e. driving closer to the line) results in less
>+ * power being applied, slowing down the controller)
>+ */
>+ d = mul_frac(tz->tzp->k_d, err - params->prev_err);
>+ params->prev_err = err;
>+
>+ power_range = p + i + d;
>+
>+ /* feed-forward the known sustainable dissipatable power */
>+ power_range = tz->tzp->sustainable_power + frac_to_int(power_range);
>+
>+ return clamp(power_range, (s64)0, (s64)max_allocatable_power);
>+}
>+
>+/**
>+ * divvy_up_power() - divvy the allocated power between the actors
>+ * @req_power: each actor's requested power
>+ * @max_power: each actor's maximum available power
>+ * @num_actors: size of the @req_power, @max_power and @granted_power's array
>+ * @total_req_power: sum of @req_power
>+ * @power_range: total allocated power
>+ * @granted_power: output array: each actor's granted power
>+ *
>+ * This function divides the total allocated power (@power_range)
>+ * fairly between the actors. It first tries to give each actor a
>+ * share of the @power_range according to how much power it requested
>+ * compared to the rest of the actors. For example, if only one actor
>+ * requests power, then it receives all the @power_range. If
>+ * three actors each requests 1mW, each receives a third of the
>+ * @power_range.
>+ *
>+ * If any actor received more than their maximum power, then that
>+ * surplus is re-divvied among the actors based on how far they are
>+ * from their respective maximums.
>+ *
>+ * Granted power for each actor is written to @granted_power, which
>+ * should've been allocated by the calling function.
>+ */
>+static void divvy_up_power(u32 *req_power, u32 *max_power, int num_actors,
>+ u32 total_req_power, u32 power_range,
>+ u32 *granted_power)
>+{
>+ u32 extra_power, capped_extra_power, extra_actor_power[num_actors];
>+ int i;
>+
>+ /*
>+ * Prevent division by 0 if none of the actors request power.
>+ */
>+ if (!total_req_power)
>+ total_req_power = 1;
>+
>+ capped_extra_power = 0;
>+ extra_power = 0;
>+ for (i = 0; i < num_actors; i++) {
>+ u64 req_range = req_power[i] * power_range;
>+
>+ granted_power[i] = div_u64(req_range, total_req_power);
>+
>+ if (granted_power[i] > max_power[i]) {
>+ extra_power += granted_power[i] - max_power[i];
>+ granted_power[i] = max_power[i];
>+ }
>+
>+ extra_actor_power[i] = max_power[i] - granted_power[i];
>+ capped_extra_power += extra_actor_power[i];
>+ }
>+
>+ if (!extra_power)
>+ return;
>+
>+ /*
>+ * Re-divvy the reclaimed extra among actors based on
>+ * how far they are from the max
>+ */
>+ extra_power = min(extra_power, capped_extra_power);
>+ if (capped_extra_power > 0)
>+ for (i = 0; i < num_actors; i++)
>+ granted_power[i] += (extra_actor_power[i] *
>+ extra_power) / capped_extra_power;
>+}
>+
>+static int allocate_power(struct thermal_zone_device *tz,
>+ unsigned long current_temp,
>+ unsigned long control_temp)
>+{
>+ struct thermal_instance *instance;
>+ u32 *req_power, *max_power, *granted_power;
>+ u32 total_req_power, max_allocatable_power;
>+ u32 power_range;
>+ int i, num_actors, ret = 0;
>+
>+ mutex_lock(&tz->lock);
>+
>+ num_actors = 0;
>+ list_for_each_entry(instance, &tz->thermal_instances, tz_node)
>+ if ((instance->trip == TRIP_MAX_DESIRED_TEMPERATURE) &&
>+ cdev_is_power_actor(instance->cdev))
>+ num_actors++;
>+
>+ req_power = devm_kcalloc(&tz->device, num_actors, sizeof(*req_power),
>+ GFP_KERNEL);
>+ if (!req_power) {
>+ ret = -ENOMEM;
>+ goto unlock;
>+ }
>+
>+ max_power = devm_kcalloc(&tz->device, num_actors, sizeof(*max_power),
>+ GFP_KERNEL);
>+ if (!max_power) {
>+ ret = -ENOMEM;
>+ goto free_req_power;
>+ }
>+
>+ granted_power = devm_kcalloc(&tz->device, num_actors,
>+ sizeof(*granted_power), GFP_KERNEL);
>+ if (!granted_power) {
>+ ret = -ENOMEM;
>+ goto free_max_power;
>+ }
You could optimize this allocation by allocating them together and then
using an offset to get max_power and granted_power from req_power.
>+
>+ i = 0;
>+ total_req_power = 0;
>+ max_allocatable_power = 0;
>+
>+ list_for_each_entry(instance, &tz->thermal_instances, tz_node) {
>+ struct thermal_cooling_device *cdev = instance->cdev;
>+
>+ if (instance->trip != TRIP_MAX_DESIRED_TEMPERATURE)
>+ continue;
>+
>+ if (!cdev_is_power_actor(cdev))
>+ continue;
>+
>+ if (cdev->ops->get_requested_power(cdev, tz, &req_power[i]))
>+ continue;
>+
>+ req_power[i] = frac_to_int(instance->weight * req_power[i]);
>+
>+ if (power_actor_get_max_power(cdev, tz, &max_power[i]))
>+ continue;
>+
>+ total_req_power += req_power[i];
>+ max_allocatable_power += max_power[i];
>+
>+ i++;
>+ }
>+
>+ power_range = pid_controller(tz, current_temp, control_temp,
>+ max_allocatable_power);
>+
>+ divvy_up_power(req_power, max_power, num_actors, total_req_power,
>+ power_range, granted_power);
>+
>+ i = 0;
>+ list_for_each_entry(instance, &tz->thermal_instances, tz_node) {
>+ if (instance->trip != TRIP_MAX_DESIRED_TEMPERATURE)
>+ continue;
>+
>+ if (!cdev_is_power_actor(instance->cdev))
>+ continue;
>+
>+ power_actor_set_power(instance->cdev, instance,
>+ granted_power[i]);
>+
>+ i++;
>+ }
>+
>+ devm_kfree(&tz->device, granted_power);
>+free_max_power:
>+ devm_kfree(&tz->device, max_power);
>+free_req_power:
>+ devm_kfree(&tz->device, req_power);
>+unlock:
>+ mutex_unlock(&tz->lock);
>+
>+ return ret;
>+}
>+
>+static int check_trips(struct thermal_zone_device *tz)
>+{
>+ int ret;
>+ enum thermal_trip_type type;
>+
>+ if (tz->trips < THERMAL_TRIP_NUM)
>+ return -EINVAL;
>+
>+ ret = tz->ops->get_trip_type(tz, TRIP_SWITCH_ON, &type);
>+ if (ret)
>+ return ret;
TZ should be able to correctly enumerate the value of this definition in
their driver.
I dont think anymore, this should be a enum thermal_trip_type, but it has to be
generic across governors.
Thanks,
Lina
>+
>+ if (type != THERMAL_TRIP_PASSIVE)
>+ return -EINVAL;
>+
>+ ret = tz->ops->get_trip_type(tz, TRIP_MAX_DESIRED_TEMPERATURE, &type);
>+ if (ret)
>+ return ret;
>+
>+ if (type != THERMAL_TRIP_PASSIVE)
>+ return -EINVAL;
>+
>+ return ret;
>+}
>+
>+static void reset_pid_controller(struct power_allocator_params *params)
>+{
>+ params->err_integral = 0;
>+ params->prev_err = 0;
>+}
>+
>+static void allow_maximum_power(struct thermal_zone_device *tz)
>+{
>+ struct thermal_instance *instance;
>+
>+ list_for_each_entry(instance, &tz->thermal_instances, tz_node) {
>+ if ((instance->trip != TRIP_MAX_DESIRED_TEMPERATURE) ||
>+ (!cdev_is_power_actor(instance->cdev)))
>+ continue;
>+
>+ instance->target = 0;
>+ instance->cdev->updated = false;
>+ thermal_cdev_update(instance->cdev);
>+ }
>+}
>+
>+/**
>+ * power_allocator_bind() - bind the power_allocator governor to a thermal zone
>+ * @tz: thermal zone to bind it to
>+ *
>+ * Check that the thermal zone is valid for this governor, that is, it
>+ * has two thermal trips. If so, initialize the PID controller
>+ * parameters and bind it to the thermal zone.
>+ *
>+ * Return: 0 on success, -EINVAL if the trips were invalid or -ENOMEM
>+ * if we ran out of memory.
>+ */
>+static int power_allocator_bind(struct thermal_zone_device *tz)
>+{
>+ int ret;
>+ struct power_allocator_params *params;
>+ unsigned long switch_on_temp, control_temp;
>+ u32 temperature_threshold;
>+
>+ ret = check_trips(tz);
>+ if (ret) {
>+ dev_err(&tz->device,
>+ "thermal zone %s has wrong trip setup for power allocator\n",
>+ tz->type);
>+ return ret;
>+ }
>+
>+ if (!tz->tzp || !tz->tzp->sustainable_power) {
>+ dev_err(&tz->device,
>+ "power_allocator: missing sustainable_power\n");
>+ return -EINVAL;
>+ }
>+
>+ params = devm_kzalloc(&tz->device, sizeof(*params), GFP_KERNEL);
>+ if (!params)
>+ return -ENOMEM;
>+
>+ ret = tz->ops->get_trip_temp(tz, TRIP_SWITCH_ON, &switch_on_temp);
>+ if (ret)
>+ goto free;
>+
>+ ret = tz->ops->get_trip_temp(tz, TRIP_MAX_DESIRED_TEMPERATURE,
>+ &control_temp);
>+ if (ret)
>+ goto free;
>+
>+ temperature_threshold = control_temp - switch_on_temp;
>+
>+ tz->tzp->k_po = tz->tzp->k_po ?:
>+ int_to_frac(tz->tzp->sustainable_power) / temperature_threshold;
>+ tz->tzp->k_pu = tz->tzp->k_pu ?:
>+ int_to_frac(2 * tz->tzp->sustainable_power) /
>+ temperature_threshold;
>+ tz->tzp->k_i = tz->tzp->k_i ?: int_to_frac(10) / 1000;
>+ /*
>+ * The default for k_d and integral_cutoff is 0, so we can
>+ * leave them as they are.
>+ */
>+
>+ reset_pid_controller(params);
>+
>+ tz->governor_data = params;
>+
>+ return 0;
>+
>+free:
>+ devm_kfree(&tz->device, params);
>+ return ret;
>+}
>+
>+static void power_allocator_unbind(struct thermal_zone_device *tz)
>+{
>+ dev_dbg(&tz->device, "Unbinding from thermal zone %d\n", tz->id);
>+ devm_kfree(&tz->device, tz->governor_data);
>+ tz->governor_data = NULL;
>+}
>+
>+static int power_allocator_throttle(struct thermal_zone_device *tz, int trip)
>+{
>+ int ret;
>+ unsigned long switch_on_temp, control_temp, current_temp;
>+ struct power_allocator_params *params = tz->governor_data;
>+
>+ /*
>+ * We get called for every trip point but we only need to do
>+ * our calculations once
>+ */
>+ if (trip != TRIP_MAX_DESIRED_TEMPERATURE)
>+ return 0;
>+
>+ ret = thermal_zone_get_temp(tz, ¤t_temp);
>+ if (ret) {
>+ dev_warn(&tz->device, "Failed to get temperature: %d\n", ret);
>+ return ret;
>+ }
>+
>+ ret = tz->ops->get_trip_temp(tz, TRIP_SWITCH_ON, &switch_on_temp);
>+ if (ret) {
>+ dev_warn(&tz->device,
>+ "Failed to get switch on temperature: %d\n", ret);
>+ return ret;
>+ }
>+
>+ if (current_temp < switch_on_temp) {
>+ tz->passive = 0;
>+ reset_pid_controller(params);
>+ allow_maximum_power(tz);
>+ return 0;
>+ }
>+
>+ tz->passive = 1;
>+
>+ ret = tz->ops->get_trip_temp(tz, TRIP_MAX_DESIRED_TEMPERATURE,
>+ &control_temp);
>+ if (ret) {
>+ dev_warn(&tz->device,
>+ "Failed to get the maximum desired temperature: %d\n",
>+ ret);
>+ return ret;
>+ }
>+
>+ return allocate_power(tz, current_temp, control_temp);
>+}
>+
>+static struct thermal_governor thermal_gov_power_allocator = {
>+ .name = "power_allocator",
>+ .bind_to_tz = power_allocator_bind,
>+ .unbind_from_tz = power_allocator_unbind,
>+ .throttle = power_allocator_throttle,
>+};
>+
>+int thermal_gov_power_allocator_register(void)
>+{
>+ return thermal_register_governor(&thermal_gov_power_allocator);
>+}
>+
>+void thermal_gov_power_allocator_unregister(void)
>+{
>+ thermal_unregister_governor(&thermal_gov_power_allocator);
>+}
>diff --git a/drivers/thermal/thermal_core.c b/drivers/thermal/thermal_core.c
>index a01d4a72bd93..b77b5416929c 100644
>--- a/drivers/thermal/thermal_core.c
>+++ b/drivers/thermal/thermal_core.c
>@@ -1567,7 +1567,7 @@ static void remove_trip_attrs(struct thermal_zone_device *tz)
> struct thermal_zone_device *thermal_zone_device_register(const char *type,
> int trips, int mask, void *devdata,
> struct thermal_zone_device_ops *ops,
>- const struct thermal_zone_params *tzp,
>+ struct thermal_zone_params *tzp,
> int passive_delay, int polling_delay)
> {
> struct thermal_zone_device *tz;
>@@ -1923,7 +1923,11 @@ static int __init thermal_register_governors(void)
> if (result)
> return result;
>
>- return thermal_gov_user_space_register();
>+ result = thermal_gov_user_space_register();
>+ if (result)
>+ return result;
>+
>+ return thermal_gov_power_allocator_register();
> }
>
> static void thermal_unregister_governors(void)
>@@ -1932,6 +1936,7 @@ static void thermal_unregister_governors(void)
> thermal_gov_fair_share_unregister();
> thermal_gov_bang_bang_unregister();
> thermal_gov_user_space_unregister();
>+ thermal_gov_power_allocator_unregister();
> }
>
> static int __init thermal_init(void)
>diff --git a/drivers/thermal/thermal_core.h b/drivers/thermal/thermal_core.h
>index 0531c752fbbb..28aa326806eb 100644
>--- a/drivers/thermal/thermal_core.h
>+++ b/drivers/thermal/thermal_core.h
>@@ -85,6 +85,14 @@ static inline int thermal_gov_user_space_register(void) { return 0; }
> static inline void thermal_gov_user_space_unregister(void) {}
> #endif /* CONFIG_THERMAL_GOV_USER_SPACE */
>
>+#ifdef CONFIG_THERMAL_GOV_POWER_ALLOCATOR
>+int thermal_gov_power_allocator_register(void);
>+void thermal_gov_power_allocator_unregister(void);
>+#else
>+static inline int thermal_gov_power_allocator_register(void) { return 0; }
>+static inline void thermal_gov_power_allocator_unregister(void) {}
>+#endif /* CONFIG_THERMAL_GOV_POWER_ALLOCATOR */
>+
> /* device tree support */
> #ifdef CONFIG_THERMAL_OF
> int of_parse_thermal_zones(void);
>diff --git a/include/linux/thermal.h b/include/linux/thermal.h
>index 288ac6fd743d..b42f790bb23c 100644
>--- a/include/linux/thermal.h
>+++ b/include/linux/thermal.h
>@@ -56,6 +56,8 @@
> #define DEFAULT_THERMAL_GOVERNOR "fair_share"
> #elif defined(CONFIG_THERMAL_DEFAULT_GOV_USER_SPACE)
> #define DEFAULT_THERMAL_GOVERNOR "user_space"
>+#elif defined(CONFIG_THERMAL_DEFAULT_GOV_POWER_ALLOCATOR)
>+#define DEFAULT_THERMAL_GOVERNOR "power_allocator"
> #endif
>
> struct thermal_zone_device;
>@@ -151,8 +153,7 @@ struct thermal_attr {
> * @devdata: private pointer for device private data
> * @trips: number of trip points the thermal zone supports
> * @passive_delay: number of milliseconds to wait between polls when
>- * performing passive cooling. Currenty only used by the
>- * step-wise governor
>+ * performing passive cooling.
> * @polling_delay: number of milliseconds to wait between polls when
> * checking whether trip points have been crossed (0 for
> * interrupt driven systems)
>@@ -162,7 +163,6 @@ struct thermal_attr {
> * @last_temperature: previous temperature read
> * @emul_temperature: emulated temperature when using CONFIG_THERMAL_EMULATION
> * @passive: 1 if you've crossed a passive trip point, 0 otherwise.
>- * Currenty only used by the step-wise governor.
> * @forced_passive: If > 0, temperature at which to switch on all ACPI
> * processor cooling devices. Currently only used by the
> * step-wise governor.
>@@ -194,7 +194,7 @@ struct thermal_zone_device {
> int passive;
> unsigned int forced_passive;
> struct thermal_zone_device_ops *ops;
>- const struct thermal_zone_params *tzp;
>+ struct thermal_zone_params *tzp;
> struct thermal_governor *governor;
> void *governor_data;
> struct list_head thermal_instances;
>@@ -269,6 +269,33 @@ struct thermal_zone_params {
>
> int num_tbps; /* Number of tbp entries */
> struct thermal_bind_params *tbp;
>+
>+ /*
>+ * Sustainable power (heat) that this thermal zone can dissipate in
>+ * mW
>+ */
>+ u32 sustainable_power;
>+
>+ /*
>+ * Proportional parameter of the PID controller when
>+ * overshooting (i.e., when temperature is below the target)
>+ */
>+ s32 k_po;
>+
>+ /*
>+ * Proportional parameter of the PID controller when
>+ * undershooting
>+ */
>+ s32 k_pu;
>+
>+ /* Integral parameter of the PID controller */
>+ s32 k_i;
>+
>+ /* Derivative parameter of the PID controller */
>+ s32 k_d;
>+
>+ /* threshold below which the error is no longer accumulated */
>+ s32 integral_cutoff;
> };
>
> struct thermal_genl_event {
>@@ -343,7 +370,7 @@ int power_actor_set_power(struct thermal_cooling_device *,
> struct thermal_instance *, u32);
> struct thermal_zone_device *thermal_zone_device_register(const char *, int, int,
> void *, struct thermal_zone_device_ops *,
>- const struct thermal_zone_params *, int, int);
>+ struct thermal_zone_params *, int, int);
> void thermal_zone_device_unregister(struct thermal_zone_device *);
>
> int thermal_zone_bind_cooling_device(struct thermal_zone_device *, int,
>--
>1.9.1
>
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