Thermal: Introduce fair_share thermal governor

This patch introduces a simple 'weight' based
governor named fair_share governor. Whenever the
thermal framework gets notified of the trip point
violation, this governor (if configured), throttles
the cooling devices associated with a thermal zone.

This mapping between a thermal zone and a cooling device
and the effectiveness of cooling are provided in the
platform layer.

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

3 files changed, 140 insertions, 0 deletions

diff --git a/drivers/thermal/Kconfig b/drivers/thermal/Kconfig
index e1cb6bd75f60..84b0f0382e5d 100644
--- a/drivers/thermal/Kconfig
+++ b/drivers/thermal/Kconfig
@@ -55,3 +55,9 @@ config EXYNOS_THERMAL
         help
           If you say yes here you get support for TMU (Thermal Managment
           Unit) on SAMSUNG EXYNOS series of SoC.
+
+config FAIR_SHARE
+        bool "Fair-share thermal governor"
+        depends on THERMAL
+        help
+          Enable this to manage platform thermals using fair-share governor.
diff --git a/drivers/thermal/Makefile b/drivers/thermal/Makefile
index 885550dc64b7..30540dde4080 100644
--- a/drivers/thermal/Makefile
+++ b/drivers/thermal/Makefile
@@ -7,3 +7,4 @@ obj-$(CONFIG_CPU_THERMAL)		+= cpu_cooling.o
 obj-$(CONFIG_SPEAR_THERMAL)             += spear_thermal.o
 obj-$(CONFIG_RCAR_THERMAL)      += rcar_thermal.o
 obj-$(CONFIG_EXYNOS_THERMAL)            += exynos_thermal.o
+obj-$(CONFIG_FAIR_SHARE)                += fair_share.o
diff --git a/drivers/thermal/fair_share.c b/drivers/thermal/fair_share.c
new file mode 100644
index 000000000000..5d3a7a3e6a7a
--- /dev/null
+++ b/drivers/thermal/fair_share.c
@@ -0,0 +1,133 @@
+/*
+ *  fair_share.c - A simple weight based Thermal 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"
+
+/**
+ * get_trip_level: - obtains the current trip level for a zone
+ * @tz:         thermal zone device
+ */
+static int get_trip_level(struct thermal_zone_device *tz)
+{
+        int count = 0;
+        unsigned long trip_temp;
+
+        if (tz->trips == 0 || !tz->ops->get_trip_temp)
+                return 0;
+
+        for (count = 0; count < tz->trips; count++) {
+                tz->ops->get_trip_temp(tz, count, &trip_temp);
+                if (tz->temperature < trip_temp)
+                        break;
+        }
+        return count;
+}
+
+static long get_target_state(struct thermal_zone_device *tz,
+                struct thermal_cooling_device *cdev, int weight, int level)
+{
+        unsigned long max_state;
+
+        cdev->ops->get_max_state(cdev, &max_state);
+
+        return (long)(weight * level * max_state) / (100 * tz->trips);
+}
+
+/**
+ * fair_share_throttle - throttles devices asscciated with the given zone
+ * @tz - thermal_zone_device
+ *
+ * Throttling Logic: This uses three parameters to calculate the new
+ * throttle state of the cooling devices associated with the given zone.
+ *
+ * Parameters used for Throttling:
+ * P1. max_state: Maximum throttle state exposed by the cooling device.
+ * P2. weight[i]/100:
+ *      How 'effective' the 'i'th device is, in cooling the given zone.
+ * P3. cur_trip_level/max_no_of_trips:
+ *      This describes the extent to which the devices should be throttled.
+ *      We do not want to throttle too much when we trip a lower temperature,
+ *      whereas the throttling is at full swing if we trip critical levels.
+ *      (Heavily assumes the trip points are in ascending order)
+ * new_state of cooling device = P3 * P2 * P1
+ */
+int fair_share_throttle(struct thermal_zone_device *tz, int trip)
+{
+        const struct thermal_zone_params *tzp;
+        struct thermal_cooling_device *cdev;
+        struct thermal_instance *instance;
+        int i;
+        int cur_trip_level = get_trip_level(tz);
+
+        if (!tz->tzp || !tz->tzp->tbp)
+                return -EINVAL;
+
+        tzp = tz->tzp;
+
+        for (i = 0; i < tzp->num_tbps; i++) {
+                if (!tzp->tbp[i].cdev)
+                        continue;
+
+                cdev = tzp->tbp[i].cdev;
+                instance = get_thermal_instance(tz, cdev, trip);
+                if (!instance)
+                        continue;
+
+                instance->target = get_target_state(tz, cdev,
+                                        tzp->tbp[i].weight, cur_trip_level);
+
+                instance->cdev->updated = false;
+                thermal_cdev_update(cdev);
+        }
+        return 0;
+}
+
+struct thermal_governor thermal_gov_fair_share = {
+        .name           = "fair_share",
+        .throttle       = fair_share_throttle,
+        .owner          = THIS_MODULE,
+};
+
+static int __init thermal_gov_fair_share_init(void)
+{
+        return thermal_register_governor(&thermal_gov_fair_share);
+}
+
+static void __exit thermal_gov_fair_share_exit(void)
+{
+        thermal_unregister_governor(&thermal_gov_fair_share);
+}
+
+/* This should load after thermal framework */
+fs_initcall(thermal_gov_fair_share_init);
+module_exit(thermal_gov_fair_share_exit);
+
+MODULE_AUTHOR("Durgadoss R");
+MODULE_DESCRIPTION("A simple weight based thermal throttling governor");
+MODULE_LICENSE("GPL");