Thermal: Introduce simple arbitrator for setting device cooling state

This fixes the problem that a cooling device may be referenced by
by multiple trip points in multiple thermal zones.

With this patch, we have two stages for updating a thermal zone,
1. check if a thermal_instance needs to be updated or not
2. update the cooling device, based on the target cooling state
   of all its instances.

Note that, currently, the cooling device is set to the deepest
cooling state required.

Signed-off-by: Zhang Rui <rui.zhang@intel.com>
Reviewed-by: Rafael J. Wysocki <rjw@sisk.pl>
Reviewed-by: Eduardo Valentin <eduardo.valentin@ti.com>

drivers/thermal/thermal_sys.c

@@ -41,6 +41,7 @@ MODULE_AUTHOR("Zhang Rui");
 MODULE_DESCRIPTION("Generic thermal management sysfs support");
 MODULE_LICENSE("GPL");
 
+#define THERMAL_NO_TARGET -1UL
 /*
  * This structure is used to describe the behavior of
  * a certain cooling device on a certain trip point
@@ -54,6 +55,7 @@ struct thermal_instance {
 	int trip;
 	unsigned long upper;	/* Highest cooling state for this trip point */
 	unsigned long lower;	/* Lowest cooling state for this trip point */
+	unsigned long target;	/* expected cooling state */
 	char attr_name[THERMAL_NAME_LENGTH];
 	struct device_attribute attr;
 	struct list_head tz_node; /* node in tz->thermal_instances */
@@ -853,6 +855,7 @@ int thermal_zone_bind_cooling_device(struct thermal_zone_device *tz,
 	dev->trip = trip;
 	dev->upper = upper;
 	dev->lower = lower;
+	dev->target = THERMAL_NO_TARGET;
 
 	result = get_idr(&tz->idr, &tz->lock, &dev->id);
 	if (result)
@@ -990,6 +993,7 @@ thermal_cooling_device_register(char *type, void *devdata,
 	strcpy(cdev->type, type);
 	INIT_LIST_HEAD(&cdev->thermal_instances);
 	cdev->ops = ops;
+	cdev->updated = true;
 	cdev->device.class = &thermal_class;
 	cdev->devdata = devdata;
 	dev_set_name(&cdev->device, "cooling_device%d", cdev->id);
@@ -1081,6 +1085,34 @@ void thermal_cooling_device_unregister(struct
 }
 EXPORT_SYMBOL(thermal_cooling_device_unregister);
 
+static void thermal_cdev_do_update(struct thermal_cooling_device *cdev)
+{
+	struct thermal_instance *instance;
+	unsigned long target = 0;
+
+	/* cooling device is updated*/
+	if (cdev->updated)
+		return;
+
+	/* Make sure cdev enters the deepest cooling state */
+	list_for_each_entry(instance, &cdev->thermal_instances, cdev_node) {
+		if (instance->target == THERMAL_NO_TARGET)
+			continue;
+		if (instance->target > target)
+			target = instance->target;
+	}
+	cdev->ops->set_cur_state(cdev, target);
+	cdev->updated = true;
+}
+
+static void thermal_zone_do_update(struct thermal_zone_device *tz)
+{
+	struct thermal_instance *instance;
+
+	list_for_each_entry(instance, &tz->thermal_instances, tz_node)
+		thermal_cdev_do_update(instance->cdev);
+}
+
 /*
  * Cooling algorithm for active trip points
  *
@@ -1138,19 +1170,24 @@ static void thermal_zone_trip_update(struct thermal_zone_device *tz,
 				cur_state = cur_state > instance->lower ?
 				    (cur_state - 1) : instance->lower;
 			}
-			cdev->ops->set_cur_state(cdev, cur_state);
+			instance->target = cur_state;
+			cdev->updated = false; /* cooling device needs update */
 		}
 	} else {	/* below trip */
 		list_for_each_entry(instance, &tz->thermal_instances, tz_node) {
 			if (instance->trip != trip)
 				continue;
 
+			/* Do not use the inactive thermal instance */
+			if (instance->target == THERMAL_NO_TARGET)
+				continue;
 			cdev = instance->cdev;
 			cdev->ops->get_cur_state(cdev, &cur_state);
 
 			cur_state = cur_state > instance->lower ?
-				    (cur_state - 1) : instance->lower;
-			cdev->ops->set_cur_state(cdev, cur_state);
+				    (cur_state - 1) : THERMAL_NO_TARGET;
+			instance->target = cur_state;
+			cdev->updated = false; /* cooling device needs update */
 		}
 	}
 
@@ -1211,6 +1248,7 @@ void thermal_zone_device_update(struct thermal_zone_device *tz)
 		}
 	}
 
+	thermal_zone_do_update(tz);
 	if (tz->forced_passive)
 		thermal_zone_device_passive(tz, temp, tz->forced_passive,
 					    THERMAL_TRIPS_NONE);

include/linux/thermal.h

@@ -94,6 +94,7 @@ struct thermal_cooling_device {
 	struct device device;
 	void *devdata;
 	const struct thermal_cooling_device_ops *ops;
+	bool updated; /* true if the cooling device does not need update */
 	struct list_head thermal_instances;
 	struct list_head node;
 };