linux-kernel - [PATCH v2 2/2] thermal: power allocator: change how estimation code is called

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Date:   Thu,  8 Oct 2020 18:04:26 +0100
From:   Lukasz Luba <lukasz.luba@....com>
To:     linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org
Cc:     daniel.lezcano@...aro.org, amitk@...nel.org,
        Dietmar.Eggemann@....com, lukasz.luba@....com,
        ionela.voinescu@....com
Subject: [PATCH v2 2/2] thermal: power allocator: change how estimation code is called

The sustainable power value might come from the Device Tree or can be
estimated in run time. There is no need to estimate every time when the
governor is called and temperature is high. Instead, store the estimated
value and make it available via standard sysfs interface so it can be
checked from the user-space. Re-invoke the estimation only in case the
sustainable power was set to 0. Apart from that the PID coefficients
are not going to be force updated thus can better handle sysfs settings.

Signed-off-by: Lukasz Luba <lukasz.luba@....com>
---
 drivers/thermal/gov_power_allocator.c | 56 +++++++++++++--------------
 1 file changed, 26 insertions(+), 30 deletions(-)

diff --git a/drivers/thermal/gov_power_allocator.c b/drivers/thermal/gov_power_allocator.c
index aa35aa6c561c..1ad8d9c2685f 100644
--- a/drivers/thermal/gov_power_allocator.c
+++ b/drivers/thermal/gov_power_allocator.c
@@ -96,6 +96,9 @@ static u32 estimate_sustainable_power(struct thermal_zone_device *tz)
 		if (instance->trip != params->trip_max_desired_temperature)
 			continue;
 
+		if (!cdev_is_power_actor(cdev))
+			continue;
+
 		if (cdev->ops->state2power(cdev, tz, instance->upper,
 					   &min_power))
 			continue;
@@ -109,31 +112,28 @@ static u32 estimate_sustainable_power(struct thermal_zone_device *tz)
 /**
  * estimate_pid_constants() - Estimate the constants for the PID controller
  * @tz:		thermal zone for which to estimate the constants
- * @sustainable_power:	sustainable power for the thermal zone
  * @trip_switch_on:	trip point number for the switch on temperature
  * @control_temp:	target temperature for the power allocator governor
- * @force:	whether to force the update of the constants
  *
  * This function is used to update the estimation of the PID
  * controller constants in struct thermal_zone_parameters.
- * Sustainable power is provided in case it was estimated.  The
- * estimated sustainable_power should not be stored in the
- * thermal_zone_parameters so it has to be passed explicitly to this
- * function.
- *
- * If @force is not set, the values in the thermal zone's parameters
- * are preserved if they are not zero.  If @force is set, the values
- * in thermal zone's parameters are overwritten.
+ * Sustainable power is going to be estimated in case it is 0.
  */
 static void estimate_pid_constants(struct thermal_zone_device *tz,
-				   u32 sustainable_power, int trip_switch_on,
-				   int control_temp, bool force)
+				   int trip_switch_on, int control_temp)
 {
-	int ret;
-	int switch_on_temp;
+	u32 sustainable_power = tz->tzp->sustainable_power;
 	u32 temperature_threshold;
+	int switch_on_temp;
+	int ret;
 	s32 k_i;
 
+	if (!sustainable_power) {
+		sustainable_power = estimate_sustainable_power(tz);
+		/* Make the estimation available in sysfs */
+		tz->tzp->sustainable_power = sustainable_power;
+	}
+
 	ret = tz->ops->get_trip_temp(tz, trip_switch_on, &switch_on_temp);
 	if (ret)
 		switch_on_temp = 0;
@@ -150,15 +150,15 @@ static void estimate_pid_constants(struct thermal_zone_device *tz,
 	if (!temperature_threshold)
 		return;
 
-	if (!tz->tzp->k_po || force)
+	if (!tz->tzp->k_po)
 		tz->tzp->k_po = int_to_frac(sustainable_power) /
 			temperature_threshold;
 
-	if (!tz->tzp->k_pu || force)
+	if (!tz->tzp->k_pu)
 		tz->tzp->k_pu = int_to_frac(2 * sustainable_power) /
 			temperature_threshold;
 
-	if (!tz->tzp->k_i || force) {
+	if (!tz->tzp->k_i) {
 		k_i = tz->tzp->k_pu / 10;
 		tz->tzp->k_i = k_i > 0 ? k_i : 1;
 	}
@@ -198,14 +198,11 @@ static u32 pid_controller(struct thermal_zone_device *tz,
 
 	max_power_frac = int_to_frac(max_allocatable_power);
 
-	if (tz->tzp->sustainable_power) {
-		sustainable_power = tz->tzp->sustainable_power;
-	} else {
-		sustainable_power = estimate_sustainable_power(tz);
-		estimate_pid_constants(tz, sustainable_power,
-				       params->trip_switch_on, control_temp,
-				       true);
-	}
+	if (!tz->tzp->sustainable_power)
+		estimate_pid_constants(tz, params->trip_switch_on,
+				       control_temp);
+
+	sustainable_power = tz->tzp->sustainable_power;
 
 	err = control_temp - tz->temperature;
 	err = int_to_frac(err);
@@ -603,20 +600,19 @@ static int power_allocator_bind(struct thermal_zone_device *tz)
 
 	get_governor_trips(tz, params);
 
+	tz->governor_data = params;
+
 	if (tz->trips > 0) {
 		ret = tz->ops->get_trip_temp(tz,
 					params->trip_max_desired_temperature,
 					&control_temp);
 		if (!ret)
-			estimate_pid_constants(tz, tz->tzp->sustainable_power,
-					       params->trip_switch_on,
-					       control_temp, false);
+			estimate_pid_constants(tz, params->trip_switch_on,
+					       control_temp);
 	}
 
 	reset_pid_controller(params);
 
-	tz->governor_data = params;
-
 	return 0;
 
 free_params:
-- 
2.17.1