thermal: introduce the Power Allocator governor

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@intel.com>
Cc: Eduardo Valentin <edubezval@gmail.com>
Signed-off-by: Punit Agrawal <punit.agrawal@arm.com>
Signed-off-by: Javi Merino <javi.merino@arm.com>
Signed-off-by: Eduardo Valentin <edubezval@gmail.com>

1 files changed, 32 insertions, 5 deletions

diff --git a/include/linux/thermal.h b/include/linux/thermal.h
index bf3c55f405c2..6bbe11c97cea 100644
--- a/include/linux/thermal.h
+++ b/include/linux/thermal.h
@@ -59,6 +59,8 @@
 #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;
@@ -154,8 +156,7 @@ 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)
@@ -165,7 +166,6 @@ 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.
@@ -197,7 +197,7 @@ 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;
@@ -275,6 +275,33 @@ 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 {
@@ -350,7 +377,7 @@ 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,