Commit e4dbf98f authored by Peter Feuerer's avatar Peter Feuerer Committed by Zhang Rui

thermal: Added Bang-bang thermal governor

The bang-bang thermal governor uses a hysteresis to switch abruptly on
or off a cooling device.  It is intended to control fans, which can
not be throttled but just switched on or off.
Bang-bang cannot be set as default governor as it is intended for
special devices only.  For those special devices the driver needs to
explicitely request it.

Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Zhang Rui <rui.zhang@intel.com>
Cc: Andreas Mohr <andi@lisas.de>
Cc: Borislav Petkov <bp@suse.de>
Cc: Javi Merino <javi.merino@arm.com>
Cc: linux-pm@vger.kernel.org
Signed-off-by: default avatarPeter Feuerer <peter@piie.net>
Signed-off-by: default avatarZhang Rui <rui.zhang@intel.com>
parent 52addcf9
......@@ -84,6 +84,16 @@ config THERMAL_GOV_STEP_WISE
Enable this to manage platform thermals using a simple linear
governor.
config THERMAL_GOV_BANG_BANG
bool "Bang Bang thermal governor"
default n
help
Enable this to manage platform thermals using bang bang governor.
Say 'Y' here if you want to use two point temperature regulation
used for fans without throttling. Some fan drivers depend on this
governor to be enabled (e.g. acerhdf).
config THERMAL_GOV_USER_SPACE
bool "User_space thermal governor"
help
......
......@@ -11,6 +11,7 @@ thermal_sys-$(CONFIG_THERMAL_OF) += of-thermal.o
# governors
thermal_sys-$(CONFIG_THERMAL_GOV_FAIR_SHARE) += fair_share.o
thermal_sys-$(CONFIG_THERMAL_GOV_BANG_BANG) += gov_bang_bang.o
thermal_sys-$(CONFIG_THERMAL_GOV_STEP_WISE) += step_wise.o
thermal_sys-$(CONFIG_THERMAL_GOV_USER_SPACE) += user_space.o
......
/*
* gov_bang_bang.c - A simple thermal throttling governor using hysteresis
*
* Copyright (C) 2014 Peter Feuerer <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>
*
*
* 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.
*
* 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.
*
*/
#include <linux/thermal.h>
#include "thermal_core.h"
static void thermal_zone_trip_update(struct thermal_zone_device *tz, int trip)
{
long trip_temp;
unsigned long trip_hyst;
struct thermal_instance *instance;
tz->ops->get_trip_temp(tz, trip, &trip_temp);
tz->ops->get_trip_hyst(tz, trip, &trip_hyst);
dev_dbg(&tz->device, "Trip%d[temp=%ld]:temp=%d:hyst=%ld\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);
instance->cdev->updated = false; /* cdev needs update */
}
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,
};
int thermal_gov_bang_bang_register(void)
{
return thermal_register_governor(&thermal_gov_bang_bang);
}
void thermal_gov_bang_bang_unregister(void)
{
thermal_unregister_governor(&thermal_gov_bang_bang);
}
......@@ -1790,6 +1790,10 @@ static int __init thermal_register_governors(void)
if (result)
return result;
result = thermal_gov_bang_bang_register();
if (result)
return result;
return thermal_gov_user_space_register();
}
......@@ -1797,6 +1801,7 @@ static void thermal_unregister_governors(void)
{
thermal_gov_step_wise_unregister();
thermal_gov_fair_share_unregister();
thermal_gov_bang_bang_unregister();
thermal_gov_user_space_unregister();
}
......
......@@ -69,6 +69,14 @@ static inline int thermal_gov_fair_share_register(void) { return 0; }
static inline void thermal_gov_fair_share_unregister(void) {}
#endif /* CONFIG_THERMAL_GOV_FAIR_SHARE */
#ifdef CONFIG_THERMAL_GOV_BANG_BANG
int thermal_gov_bang_bang_register(void);
void thermal_gov_bang_bang_unregister(void);
#else
static inline int thermal_gov_bang_bang_register(void) { return 0; }
static inline void thermal_gov_bang_bang_unregister(void) {}
#endif /* CONFIG_THERMAL_GOV_BANG_BANG */
#ifdef CONFIG_THERMAL_GOV_USER_SPACE
int thermal_gov_user_space_register(void);
void thermal_gov_user_space_unregister(void);
......
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