1 files changed, 119 insertions, 0 deletions
diff --git a/drivers/thermal/gov_bang_bang.c b/drivers/thermal/gov_bang_bang.c
new file mode 100644
index 000000000..991a1c542
--- /dev/null
+++ b/drivers/thermal/gov_bang_bang.c
@@ -0,0 +1,119 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ *  gov_bang_bang.c - A simple thermal throttling governor using hysteresis
+ *
+ *  Copyright (C) 2014 Peter Kaestle <peter@piie.net>
+ *
+ *  Based on step_wise.c with following Copyrights:
+ *  Copyright (C) 2012 Intel Corp
+ *  Copyright (C) 2012 Durgadoss R <durgadoss.r@intel.com>
+ */
+
+#include <linux/thermal.h>
+
+#include "thermal_core.h"
+
+static void thermal_zone_trip_update(struct thermal_zone_device *tz, int trip)
+{
+	int trip_temp, trip_hyst;
+	struct thermal_instance *instance;
+
+	tz->ops->get_trip_temp(tz, trip, &trip_temp);
+
+	if (!tz->ops->get_trip_hyst) {
+		pr_warn_once("Undefined get_trip_hyst for thermal zone %s - "
+				"running with default hysteresis zero\n", tz->type);
+		trip_hyst = 0;
+	} else
+		tz->ops->get_trip_hyst(tz, trip, &trip_hyst);
+
+	dev_dbg(&tz->device, "Trip%d[temp=%d]:temp=%d:hyst=%d\n",
+				trip, trip_temp, tz->temperature,
+				trip_hyst);
+
+	mutex_lock(&tz->lock);
+
+	list_for_each_entry(instance, &tz->thermal_instances, tz_node) {
+		if (instance->trip != trip)
+			continue;
+
+		/* in case fan is in initial state, switch the fan off */
+		if (instance->target == THERMAL_NO_TARGET)
+			instance->target = 0;
+
+		/* in case fan is neither on nor off set the fan to active */
+		if (instance->target != 0 && instance->target != 1) {
+			pr_warn("Thermal instance %s controlled by bang-bang has unexpected state: %ld\n",
+					instance->name, instance->target);
+			instance->target = 1;
+		}
+
+		/*
+		 * enable fan when temperature exceeds trip_temp and disable
+		 * the fan in case it falls below trip_temp minus hysteresis
+		 */
+		if (instance->target == 0 && tz->temperature >= trip_temp)
+			instance->target = 1;
+		else if (instance->target == 1 &&
+				tz->temperature <= trip_temp - trip_hyst)
+			instance->target = 0;
+
+		dev_dbg(&instance->cdev->device, "target=%d\n",
+					(int)instance->target);
+
+		mutex_lock(&instance->cdev->lock);
+		instance->cdev->updated = false; /* cdev needs update */
+		mutex_unlock(&instance->cdev->lock);
+	}
+
+	mutex_unlock(&tz->lock);
+}
+
+/**
+ * bang_bang_control - controls devices associated with the given zone
+ * @tz: thermal_zone_device
+ * @trip: the trip point
+ *
+ * Regulation Logic: a two point regulation, deliver cooling state depending
+ * on the previous state shown in this diagram:
+ *
+ *                Fan:   OFF    ON
+ *
+ *                              |
+ *                              |
+ *          trip_temp:    +---->+
+ *                        |     |        ^
+ *                        |     |        |
+ *                        |     |   Temperature
+ * (trip_temp - hyst):    +<----+
+ *                        |
+ *                        |
+ *                        |
+ *
+ *   * If the fan is not running and temperature exceeds trip_temp, the fan
+ *     gets turned on.
+ *   * In case the fan is running, temperature must fall below
+ *     (trip_temp - hyst) so that the fan gets turned off again.
+ *
+ */
+static int bang_bang_control(struct thermal_zone_device *tz, int trip)
+{
+	struct thermal_instance *instance;
+
+	thermal_zone_trip_update(tz, trip);
+
+	mutex_lock(&tz->lock);
+
+	list_for_each_entry(instance, &tz->thermal_instances, tz_node)
+		thermal_cdev_update(instance->cdev);
+
+	mutex_unlock(&tz->lock);
+
+	return 0;
+}
+
+static struct thermal_governor thermal_gov_bang_bang = {
+	.name		= "bang_bang",
+	.throttle	= bang_bang_control,
+};
+THERMAL_GOVERNOR_DECLARE(thermal_gov_bang_bang);