[PATCH V5] thermal/core/power_allocator: reset thermal governor when trip point is changed

[Di Shen]

When the thermal trip point is changed, the governor should
be reset so that the policy algorithm can be updated to adapt
to the new trip point.

1.Thermal governor is working for the passive trip point or active
trip point. Therefore, when the trip point is changed it should
reset the governor only for passic/active trip points.

2.For "power_allocator" governor reset, the parameters of pid
controller and the states of power cooling devices should be reset.

2.1
The IPA controls temperature using PID mechanism. It is a closed-
loop feedback monitoring system. It uses the gap between target
temperature and current temperature which says "error" as the
input of the PID controller:

err = desired_temperature - current_temperature
P_max =
k_p * err + k_i * err_integral + k_d * diff_err + sustainable_power

That algorithm can 'learn' from the 'observed' in the past reaction
for it's control decisions and accumulates that information in the
I(Integral) part so that it can conpensate for those 'learned'
mistakes.

Based on the above, the most important is the desired temperature
comes from the trip point. When the trip point is changed, all the
previous learned errors won't help for the IPA. So the pid parameters
should be reset for IPA governor reset.

2.2
Other wise, the cooling devices should also be reset when the trip
point is changed.

This patch adds an ops for the thermal_governor structure to reset
the governor and give the 'reset' function definition for power
allocator. The ops is called when the trip points are changed via
sysfs interface.

Signed-off-by: Di Shen <di.shen@xxxxxxxxxx>
---
 drivers/thermal/gov_power_allocator.c | 9 +++++++++
 drivers/thermal/thermal_trip.c        | 5 +++++
 include/linux/thermal.h               | 3 +++
 3 files changed, 17 insertions(+)

diff --git a/drivers/thermal/gov_power_allocator.c b/drivers/thermal/gov_power_allocator.c
index 8642f1096b91..8d17a10671e4 100644
--- a/drivers/thermal/gov_power_allocator.c
+++ b/drivers/thermal/gov_power_allocator.c
@@ -729,10 +729,19 @@ static int power_allocator_throttle(struct thermal_zone_device *tz, int trip_id)
 	return allocate_power(tz, trip.temperature);
 }
 
+static void power_allocator_reset(struct thermal_zone_device *tz)
+{
+	struct power_allocator_params *params = tz->governor_data;
+
+	reset_pid_controller(params);
+	allow_maximum_power(tz, true);
+}
+
 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,
+	.reset		= power_allocator_reset,
 };
 THERMAL_GOVERNOR_DECLARE(thermal_gov_power_allocator);
diff --git a/drivers/thermal/thermal_trip.c b/drivers/thermal/thermal_trip.c
index 907f3a4d7bc8..13bbe029c6ab 100644
--- a/drivers/thermal/thermal_trip.c
+++ b/drivers/thermal/thermal_trip.c
@@ -173,6 +173,11 @@ int thermal_zone_set_trip(struct thermal_zone_device *tz, int trip_id,
 	if (tz->trips && (t.temperature != trip->temperature || t.hysteresis != trip->hysteresis))
 		tz->trips[trip_id] = *trip;
 
+	/* Reset the governor only when the trip type is active or passive. */
+	ret = (trip->type == THERMAL_TRIP_PASSIVE || trip->type == THERMAL_TRIP_ACTIVE);
+	if (ret && t.temperature != trip->temperature && tz->governor && tz->governor->reset)
+		tz->governor->reset(tz);
+
 	thermal_notify_tz_trip_change(tz->id, trip_id, trip->type,
 				      trip->temperature, trip->hysteresis);
 
diff --git a/include/linux/thermal.h b/include/linux/thermal.h
index 87837094d549..d27d053319bf 100644
--- a/include/linux/thermal.h
+++ b/include/linux/thermal.h
@@ -197,6 +197,8 @@ struct thermal_zone_device {
  *			thermal zone.
  * @throttle:	callback called for every trip point even if temperature is
  *		below the trip point temperature
+ * @reset:	callback called for governor reset
+ *
  * @governor_list:	node in thermal_governor_list (in thermal_core.c)
  */
 struct thermal_governor {
@@ -204,6 +206,7 @@ struct thermal_governor {
 	int (*bind_to_tz)(struct thermal_zone_device *tz);
 	void (*unbind_from_tz)(struct thermal_zone_device *tz);
 	int (*throttle)(struct thermal_zone_device *tz, int trip);
+	void (*reset)(struct thermal_zone_device *tz);
 	struct list_head	governor_list;
 };
 
-- 
2.17.1