[PATCH v2 1/4] thermal: power_allocator: relax the requirement of a sustainable_power in tzp

[Javi Merino]

The power allocator governor currently requires that a sustainable power
is passed as part of the thermal zone's thermal zone parameters.  If
that parameter is not provided, it doesn't register with the thermal
zone.

While this parameter is strongly recommended for optimal performance, it
doesn't need to be mandatory.  Relax the requirement and allow the
governor to bind to thermal zones that don't provide it by estimating it
from the cooling devices' power model.

Cc: Zhang Rui <rui.zhang@xxxxxxxxx>
Cc: Eduardo Valentin <edubezval@xxxxxxxxx>
Signed-off-by: Javi Merino <javi.merino@xxxxxxx>
---
 drivers/thermal/power_allocator.c | 62 +++++++++++++++++++++++++++++++++------
 drivers/thermal/thermal_core.c    | 28 ++++++++++++++++++
 include/linux/thermal.h           |  6 ++++
 3 files changed, 87 insertions(+), 9 deletions(-)

diff --git a/drivers/thermal/power_allocator.c b/drivers/thermal/power_allocator.c
index 63a448f9d93b..f78836c2da26 100644
--- a/drivers/thermal/power_allocator.c
+++ b/drivers/thermal/power_allocator.c
@@ -73,6 +73,39 @@ struct power_allocator_params {
 };
 
 /**
+ * estimate_sustainable_power() - Estimate the sustainable power of a thermal zone
+ * @tz: thermal zone we are operating in
+ *
+ * For thermal zones that don't provide a sustainable_power in their
+ * thermal_zone_params, estimate one.  Calculate it using the minimum
+ * power of all the cooling devices as that gives a valid value that
+ * can give some degree of functionality.  For optimal performance of
+ * this governor, provide a sustainable_power in the thermal zone's
+ * thermal_zone_params.
+ */
+static u32 estimate_sustainable_power(struct thermal_zone_device *tz)
+{
+	u32 sustainable_power = 0;
+	struct thermal_instance *instance;
+	struct power_allocator_params *params = tz->governor_data;
+
+	list_for_each_entry(instance, &tz->thermal_instances, tz_node) {
+		struct thermal_cooling_device *cdev = instance->cdev;
+		u32 min_power;
+
+		if (instance->trip != params->trip_max_desired_temperature)
+			continue;
+
+		if (power_actor_get_min_power(cdev, tz, &min_power))
+			continue;
+
+		sustainable_power += min_power;
+	}
+
+	return sustainable_power;
+}
+
+/**
  * pid_controller() - PID controller
  * @tz:	thermal zone we are operating in
  * @current_temp:	the current temperature in millicelsius
@@ -98,6 +131,7 @@ static u32 pid_controller(struct thermal_zone_device *tz,
 {
 	s64 p, i, d, power_range;
 	s32 err, max_power_frac;
+	u32 sustainable_power;
 	struct power_allocator_params *params = tz->governor_data;
 
 	max_power_frac = int_to_frac(max_allocatable_power);
@@ -138,8 +172,11 @@ static u32 pid_controller(struct thermal_zone_device *tz,
 
 	power_range = p + i + d;
 
+	sustainable_power = tz->tzp->sustainable_power ?:
+		estimate_sustainable_power(tz);
+
 	/* feed-forward the known sustainable dissipatable power */
-	power_range = tz->tzp->sustainable_power + frac_to_int(power_range);
+	power_range = sustainable_power + frac_to_int(power_range);
 
 	power_range = clamp(power_range, (s64)0, (s64)max_allocatable_power);
 
@@ -418,18 +455,18 @@ 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;
+	u32 sustainable_power, temperature_threshold;
 
-	if (!tz->tzp || !tz->tzp->sustainable_power) {
-		dev_err(&tz->device,
-			"power_allocator: missing sustainable_power\n");
+	if (!tz->tzp)
 		return -EINVAL;
-	}
 
 	params = devm_kzalloc(&tz->device, sizeof(*params), GFP_KERNEL);
 	if (!params)
 		return -ENOMEM;
 
+	if (!tz->tzp->sustainable_power)
+		dev_warn(&tz->device, "power_allocator: sustainable_power will be estimated\n");
+
 	ret = get_governor_trips(tz, params);
 	if (ret) {
 		dev_err(&tz->device,
@@ -448,13 +485,20 @@ static int power_allocator_bind(struct thermal_zone_device *tz)
 	if (ret)
 		goto free;
 
+	/*
+	 * Provide an arbitrary sustainable_power to set the default
+	 * values of k_po and k_pu.  We can estimate sustainable_power
+	 * at this point because no cooling devices have been
+	 * registered yet.  By providing an arbitrary value we get
+	 * better defaults that setting k_po and k_pu to 0.
+	 */
+	sustainable_power = tz->tzp->sustainable_power ?: 2500;
 	temperature_threshold = control_temp - switch_on_temp;
 
 	tz->tzp->k_po = tz->tzp->k_po ?:
-		int_to_frac(tz->tzp->sustainable_power) / temperature_threshold;
+		int_to_frac(sustainable_power) / temperature_threshold;
 	tz->tzp->k_pu = tz->tzp->k_pu ?:
-		int_to_frac(2 * tz->tzp->sustainable_power) /
-		temperature_threshold;
+		int_to_frac(2 * 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
diff --git a/drivers/thermal/thermal_core.c b/drivers/thermal/thermal_core.c
index 4ca211be4c0f..d26bc9e6f936 100644
--- a/drivers/thermal/thermal_core.c
+++ b/drivers/thermal/thermal_core.c
@@ -997,6 +997,34 @@ int power_actor_get_max_power(struct thermal_cooling_device *cdev,
 }
 
 /**
+ * power_actor_get_min_power() - get the mainimum power that a cdev can consume
+ * @cdev:	pointer to &thermal_cooling_device
+ * @tz:		a valid thermal zone device pointer
+ * @min_power:	pointer in which to store the minimum power
+ *
+ * Calculate the minimum power consumption in milliwats that the
+ * cooling device can currently consume and store it in @min_power.
+ *
+ * Return: 0 on success, -EINVAL if @cdev doesn't support the
+ * power_actor API or -E* on other error.
+ */
+int power_actor_get_min_power(struct thermal_cooling_device *cdev,
+			      struct thermal_zone_device *tz, u32 *min_power)
+{
+	unsigned long max_state;
+	int ret;
+
+	if (!cdev_is_power_actor(cdev))
+		return -EINVAL;
+
+	ret = cdev->ops->get_max_state(cdev, &max_state);
+	if (ret)
+		return ret;
+
+	return cdev->ops->state2power(cdev, tz, max_state, min_power);
+}
+
+/**
  * power_actor_set_power() - limit the maximum power that a cooling device can consume
  * @cdev:	pointer to &thermal_cooling_device
  * @instance:	thermal instance to update
diff --git a/include/linux/thermal.h b/include/linux/thermal.h
index 037e9df2f610..f99d934d373a 100644
--- a/include/linux/thermal.h
+++ b/include/linux/thermal.h
@@ -384,6 +384,8 @@ static inline bool cdev_is_power_actor(struct thermal_cooling_device *cdev)
 
 int power_actor_get_max_power(struct thermal_cooling_device *,
 			      struct thermal_zone_device *tz, u32 *max_power);
+int power_actor_get_min_power(struct thermal_cooling_device *,
+			      struct thermal_zone_device *tz, u32 *min_power);
 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,
@@ -419,6 +421,10 @@ static inline bool cdev_is_power_actor(struct thermal_cooling_device *cdev)
 static inline int power_actor_get_max_power(struct thermal_cooling_device *cdev,
 			      struct thermal_zone_device *tz, u32 *max_power)
 { return 0; }
+static inline int power_actor_get_min_power(struct thermal_cooling_device *cdev,
+					    struct thermal_zone_device *tz,
+					    u32 *min_power)
+{ return -ENODEV; }
 static inline int power_actor_set_power(struct thermal_cooling_device *cdev,
 			  struct thermal_instance *tz, u32 power)
 { return 0; }
-- 
1.9.1

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