Thermal: Introduce a step_wise thermal governor

This patch adds a simple step_wise governor to the
generic thermal layer. This algorithm throttles the
cooling devices in a linear fashion. If the 'trend'
is heating, it throttles by one step. And if the
thermal trend is cooling it de-throttles by one step.

This actually moves the throttling logic from thermal_sys.c
and puts inside step_wise.c, without any change.

Signed-off-by: Durgadoss R <durgadoss.r@intel.com>
Signed-off-by: Zhang Rui <rui.zhang@intel.com>

1 files changed, 194 insertions, 0 deletions

diff --git a/drivers/thermal/step_wise.c b/drivers/thermal/step_wise.c
new file mode 100644
index 000000000000..3f9cfcf66ccd
--- /dev/null
+++ b/drivers/thermal/step_wise.c
@@ -0,0 +1,194 @@
+/*
+ *  step_wise.c - A step-by-step Thermal throttling governor
+ *
+ *  Copyright (C) 2012 Intel Corp
+ *  Copyright (C) 2012 Durgadoss R <durgadoss.r@intel.com>
+ *
+ *  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; version 2 of the License.
+ *
+ *  This program is distributed in the hope that it will be useful, but
+ *  WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ *  General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License along
+ *  with this program; if not, write to the Free Software Foundation, Inc.,
+ *  59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
+ *
+ * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/module.h>
+#include <linux/thermal.h>
+
+#include "thermal_core.h"
+
+/*
+ * If the temperature is higher than a trip point,
+ *    a. if the trend is THERMAL_TREND_RAISING, use higher cooling
+ *       state for this trip point
+ *    b. if the trend is THERMAL_TREND_DROPPING, use lower cooling
+ *       state for this trip point
+ */
+static unsigned long get_target_state(struct thermal_instance *instance,
+					enum thermal_trend trend)
+{
+	struct thermal_cooling_device *cdev = instance->cdev;
+	unsigned long cur_state;
+
+	cdev->ops->get_cur_state(cdev, &cur_state);
+
+	if (trend == THERMAL_TREND_RAISING) {
+		cur_state = cur_state < instance->upper ?
+			    (cur_state + 1) : instance->upper;
+	} else if (trend == THERMAL_TREND_DROPPING) {
+		cur_state = cur_state > instance->lower ?
+			    (cur_state - 1) : instance->lower;
+	}
+
+	return cur_state;
+}
+
+static void update_passive_instance(struct thermal_zone_device *tz,
+				enum thermal_trip_type type, int value)
+{
+	/*
+	 * If value is +1, activate a passive instance.
+	 * If value is -1, deactivate a passive instance.
+	 */
+	if (type == THERMAL_TRIP_PASSIVE || type == THERMAL_TRIPS_NONE)
+		tz->passive += value;
+}
+
+static void update_instance_for_throttle(struct thermal_zone_device *tz,
+				int trip, enum thermal_trip_type trip_type,
+				enum thermal_trend trend)
+{
+	struct thermal_instance *instance;
+
+	list_for_each_entry(instance, &tz->thermal_instances, tz_node) {
+		if (instance->trip != trip)
+			continue;
+
+		instance->target = get_target_state(instance, trend);
+
+		/* Activate a passive thermal instance */
+		if (instance->target == THERMAL_NO_TARGET)
+			update_passive_instance(tz, trip_type, 1);
+
+		instance->cdev->updated = false; /* cdev needs update */
+	}
+}
+
+static void update_instance_for_dethrottle(struct thermal_zone_device *tz,
+				int trip, enum thermal_trip_type trip_type)
+{
+	struct thermal_instance *instance;
+	struct thermal_cooling_device *cdev;
+	unsigned long cur_state;
+
+	list_for_each_entry(instance, &tz->thermal_instances, tz_node) {
+		if (instance->trip != trip ||
+			instance->target == THERMAL_NO_TARGET)
+			continue;
+
+		cdev = instance->cdev;
+		cdev->ops->get_cur_state(cdev, &cur_state);
+
+		instance->target = cur_state > instance->lower ?
+			    (cur_state - 1) : THERMAL_NO_TARGET;
+
+		/* Deactivate a passive thermal instance */
+		if (instance->target == THERMAL_NO_TARGET)
+			update_passive_instance(tz, trip_type, -1);
+
+		cdev->updated = false; /* cdev needs update */
+	}
+}
+
+static void thermal_zone_trip_update(struct thermal_zone_device *tz, int trip)
+{
+	long trip_temp;
+	enum thermal_trip_type trip_type;
+	enum thermal_trend trend;
+
+	if (trip == THERMAL_TRIPS_NONE) {
+		trip_temp = tz->forced_passive;
+		trip_type = THERMAL_TRIPS_NONE;
+	} else {
+		tz->ops->get_trip_temp(tz, trip, &trip_temp);
+		tz->ops->get_trip_type(tz, trip, &trip_type);
+	}
+
+	trend = get_tz_trend(tz, trip);
+
+	mutex_lock(&tz->lock);
+
+	if (tz->temperature >= trip_temp)
+		update_instance_for_throttle(tz, trip, trip_type, trend);
+	else
+		update_instance_for_dethrottle(tz, trip, trip_type);
+
+	mutex_unlock(&tz->lock);
+}
+
+/**
+ * step_wise_throttle - throttles devices asscciated with the given zone
+ * @tz - thermal_zone_device
+ * @trip - the trip point
+ * @trip_type - type of the trip point
+ *
+ * Throttling Logic: This uses the trend of the thermal zone to throttle.
+ * If the thermal zone is 'heating up' this throttles all the cooling
+ * devices associated with the zone and its particular trip point, by one
+ * step. If the zone is 'cooling down' it brings back the performance of
+ * the devices by one step.
+ */
+int step_wise_throttle(struct thermal_zone_device *tz, int trip)
+{
+	struct thermal_instance *instance;
+
+	thermal_zone_trip_update(tz, trip);
+
+	if (tz->forced_passive)
+		thermal_zone_trip_update(tz, THERMAL_TRIPS_NONE);
+
+	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;
+}
+
+struct thermal_governor thermal_gov_step_wise = {
+	.name		= DEFAULT_THERMAL_GOVERNOR,
+	.throttle	= step_wise_throttle,
+	.owner		= THIS_MODULE,
+};
+
+static int __init thermal_gov_step_wise_init(void)
+{
+	return thermal_register_governor(&thermal_gov_step_wise);
+}
+
+static void __exit thermal_gov_step_wise_exit(void)
+{
+	thermal_unregister_governor(&thermal_gov_step_wise);
+}
+
+/* This should load after thermal framework */
+fs_initcall(thermal_gov_step_wise_init);
+module_exit(thermal_gov_step_wise_exit);
+
+MODULE_AUTHOR("Durgadoss R");
+MODULE_DESCRIPTION("A step-by-step thermal throttling governor");
+MODULE_LICENSE("GPL");