linux/drivers/thermal/step_wise.c
Daniel Lezcano 07209fcf33 thermal/drivers/step_wise: Fix temperature regulation misbehavior
There is a particular situation when the cooling device is cpufreq and the heat
dissipation is not efficient enough where the temperature increases little by
little until reaching the critical threshold and leading to a SoC reset.

The behavior is reproducible on a hikey6220 with bad heat dissipation (eg.
stacked with other boards).

Running a simple C program doing while(1); for each CPU of the SoC makes the
temperature to reach the passive regulation trip point and ends up to the
maximum allowed temperature followed by a reset.

This issue has been also reported by running the libhugetlbfs test suite.

What is observed is a ping pong between two cpu frequencies, 1.2GHz and 900MHz
while the temperature continues to grow.

It appears the step wise governor calls get_target_state() the first time with
the throttle set to true and the trend to 'raising'. The code selects logically
the next state, so the cpu frequency decreases from 1.2GHz to 900MHz, so far so
good. The temperature decreases immediately but still stays greater than the
trip point, then get_target_state() is called again, this time with the
throttle set to true *and* the trend to 'dropping'. From there the algorithm
assumes we have to step down the state and the cpu frequency jumps back to
1.2GHz. But the temperature is still higher than the trip point, so
get_target_state() is called with throttle=1 and trend='raising' again, we jump
to 900MHz, then get_target_state() is called with throttle=1 and
trend='dropping', we jump to 1.2GHz, etc ... but the temperature does not
stabilizes and continues to increase.

[  237.922654] thermal thermal_zone0: Trip0[type=1,temp=65000]:trend=1,throttle=1
[  237.922678] thermal thermal_zone0: Trip1[type=1,temp=75000]:trend=1,throttle=1
[  237.922690] thermal cooling_device0: cur_state=0
[  237.922701] thermal cooling_device0: old_target=0, target=1
[  238.026656] thermal thermal_zone0: Trip0[type=1,temp=65000]:trend=2,throttle=1
[  238.026680] thermal thermal_zone0: Trip1[type=1,temp=75000]:trend=2,throttle=1
[  238.026694] thermal cooling_device0: cur_state=1
[  238.026707] thermal cooling_device0: old_target=1, target=0
[  238.134647] thermal thermal_zone0: Trip0[type=1,temp=65000]:trend=1,throttle=1
[  238.134667] thermal thermal_zone0: Trip1[type=1,temp=75000]:trend=1,throttle=1
[  238.134679] thermal cooling_device0: cur_state=0
[  238.134690] thermal cooling_device0: old_target=0, target=1

In this situation the temperature continues to increase while the trend is
oscillating between 'dropping' and 'raising'. We need to keep the current state
untouched if the throttle is set, so the temperature can decrease or a higher
state could be selected, thus preventing this oscillation.

Keeping the next_target untouched when 'throttle' is true at 'dropping' time
fixes the issue.

The following traces show the governor does not change the next state if
trend==2 (dropping) and throttle==1.

[ 2306.127987] thermal thermal_zone0: Trip0[type=1,temp=65000]:trend=1,throttle=1
[ 2306.128009] thermal thermal_zone0: Trip1[type=1,temp=75000]:trend=1,throttle=1
[ 2306.128021] thermal cooling_device0: cur_state=0
[ 2306.128031] thermal cooling_device0: old_target=0, target=1
[ 2306.231991] thermal thermal_zone0: Trip0[type=1,temp=65000]:trend=2,throttle=1
[ 2306.232016] thermal thermal_zone0: Trip1[type=1,temp=75000]:trend=2,throttle=1
[ 2306.232030] thermal cooling_device0: cur_state=1
[ 2306.232042] thermal cooling_device0: old_target=1, target=1
[ 2306.335982] thermal thermal_zone0: Trip0[type=1,temp=65000]:trend=0,throttle=1
[ 2306.336006] thermal thermal_zone0: Trip1[type=1,temp=75000]:trend=0,throttle=1
[ 2306.336021] thermal cooling_device0: cur_state=1
[ 2306.336034] thermal cooling_device0: old_target=1, target=1
[ 2306.439984] thermal thermal_zone0: Trip0[type=1,temp=65000]:trend=2,throttle=1
[ 2306.440008] thermal thermal_zone0: Trip1[type=1,temp=75000]:trend=2,throttle=0
[ 2306.440022] thermal cooling_device0: cur_state=1
[ 2306.440034] thermal cooling_device0: old_target=1, target=0

[ ... ]

After a while, if the temperature continues to increase, the next state becomes
2 which is 720MHz on the hikey. That results in the temperature stabilizing
around the trip point.

[ 2455.831982] thermal thermal_zone0: Trip0[type=1,temp=65000]:trend=1,throttle=1
[ 2455.832006] thermal thermal_zone0: Trip1[type=1,temp=75000]:trend=1,throttle=0
[ 2455.832019] thermal cooling_device0: cur_state=1
[ 2455.832032] thermal cooling_device0: old_target=1, target=1
[ 2455.935985] thermal thermal_zone0: Trip0[type=1,temp=65000]:trend=0,throttle=1
[ 2455.936013] thermal thermal_zone0: Trip1[type=1,temp=75000]:trend=0,throttle=0
[ 2455.936027] thermal cooling_device0: cur_state=1
[ 2455.936040] thermal cooling_device0: old_target=1, target=1
[ 2456.043984] thermal thermal_zone0: Trip0[type=1,temp=65000]:trend=0,throttle=1
[ 2456.044009] thermal thermal_zone0: Trip1[type=1,temp=75000]:trend=0,throttle=0
[ 2456.044023] thermal cooling_device0: cur_state=1
[ 2456.044036] thermal cooling_device0: old_target=1, target=1
[ 2456.148001] thermal thermal_zone0: Trip0[type=1,temp=65000]:trend=1,throttle=1
[ 2456.148028] thermal thermal_zone0: Trip1[type=1,temp=75000]:trend=1,throttle=1
[ 2456.148042] thermal cooling_device0: cur_state=1
[ 2456.148055] thermal cooling_device0: old_target=1, target=2
[ 2456.252009] thermal thermal_zone0: Trip0[type=1,temp=65000]:trend=2,throttle=1
[ 2456.252041] thermal thermal_zone0: Trip1[type=1,temp=75000]:trend=2,throttle=0
[ 2456.252058] thermal cooling_device0: cur_state=2
[ 2456.252075] thermal cooling_device0: old_target=2, target=1

IOW, this change is needed to keep the state for a cooling device if the
temperature trend is oscillating while the temperature increases slightly.

Without this change, the situation above leads to a catastrophic crash by a
hardware reset on hikey. This issue has been reported to happen on an OMAP
dra7xx also.

Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: Keerthy <j-keerthy@ti.com>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Leo Yan <leo.yan@linaro.org>
Tested-by: Keerthy <j-keerthy@ti.com>
Reviewed-by: Keerthy <j-keerthy@ti.com>
Signed-off-by: Eduardo Valentin <edubezval@gmail.com>
2017-10-31 19:32:17 -07:00

231 lines
6.7 KiB
C

/*
* 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.
*
* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
*/
#include <linux/thermal.h>
#include <trace/events/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, do nothing
* c. if the trend is THERMAL_TREND_RAISE_FULL, use upper limit
* for this trip point
* d. if the trend is THERMAL_TREND_DROP_FULL, use lower limit
* for this trip point
* If the temperature is lower than a trip point,
* a. if the trend is THERMAL_TREND_RAISING, do nothing
* b. if the trend is THERMAL_TREND_DROPPING, use lower cooling
* state for this trip point, if the cooling state already
* equals lower limit, deactivate the thermal instance
* c. if the trend is THERMAL_TREND_RAISE_FULL, do nothing
* d. if the trend is THERMAL_TREND_DROP_FULL, use lower limit,
* if the cooling state already equals lower limit,
* deactivate the thermal instance
*/
static unsigned long get_target_state(struct thermal_instance *instance,
enum thermal_trend trend, bool throttle)
{
struct thermal_cooling_device *cdev = instance->cdev;
unsigned long cur_state;
unsigned long next_target;
/*
* We keep this instance the way it is by default.
* Otherwise, we use the current state of the
* cdev in use to determine the next_target.
*/
cdev->ops->get_cur_state(cdev, &cur_state);
next_target = instance->target;
dev_dbg(&cdev->device, "cur_state=%ld\n", cur_state);
if (!instance->initialized) {
if (throttle) {
next_target = (cur_state + 1) >= instance->upper ?
instance->upper :
((cur_state + 1) < instance->lower ?
instance->lower : (cur_state + 1));
} else {
next_target = THERMAL_NO_TARGET;
}
return next_target;
}
switch (trend) {
case THERMAL_TREND_RAISING:
if (throttle) {
next_target = cur_state < instance->upper ?
(cur_state + 1) : instance->upper;
if (next_target < instance->lower)
next_target = instance->lower;
}
break;
case THERMAL_TREND_RAISE_FULL:
if (throttle)
next_target = instance->upper;
break;
case THERMAL_TREND_DROPPING:
if (cur_state <= instance->lower) {
if (!throttle)
next_target = THERMAL_NO_TARGET;
} else {
if (!throttle) {
next_target = cur_state - 1;
if (next_target > instance->upper)
next_target = instance->upper;
}
}
break;
case THERMAL_TREND_DROP_FULL:
if (cur_state == instance->lower) {
if (!throttle)
next_target = THERMAL_NO_TARGET;
} else
next_target = instance->lower;
break;
default:
break;
}
return next_target;
}
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 thermal_zone_trip_update(struct thermal_zone_device *tz, int trip)
{
int trip_temp;
enum thermal_trip_type trip_type;
enum thermal_trend trend;
struct thermal_instance *instance;
bool throttle = false;
int old_target;
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);
if (tz->temperature >= trip_temp) {
throttle = true;
trace_thermal_zone_trip(tz, trip, trip_type);
}
dev_dbg(&tz->device, "Trip%d[type=%d,temp=%d]:trend=%d,throttle=%d\n",
trip, trip_type, trip_temp, trend, throttle);
mutex_lock(&tz->lock);
list_for_each_entry(instance, &tz->thermal_instances, tz_node) {
if (instance->trip != trip)
continue;
old_target = instance->target;
instance->target = get_target_state(instance, trend, throttle);
dev_dbg(&instance->cdev->device, "old_target=%d, target=%d\n",
old_target, (int)instance->target);
if (instance->initialized && old_target == instance->target)
continue;
/* Activate a passive thermal instance */
if (old_target == THERMAL_NO_TARGET &&
instance->target != THERMAL_NO_TARGET)
update_passive_instance(tz, trip_type, 1);
/* Deactivate a passive thermal instance */
else if (old_target != THERMAL_NO_TARGET &&
instance->target == THERMAL_NO_TARGET)
update_passive_instance(tz, trip_type, -1);
instance->initialized = true;
mutex_lock(&instance->cdev->lock);
instance->cdev->updated = false; /* cdev needs update */
mutex_unlock(&instance->cdev->lock);
}
mutex_unlock(&tz->lock);
}
/**
* step_wise_throttle - throttles devices associated with the given zone
* @tz - thermal_zone_device
* @trip - trip point index
*
* 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.
*/
static 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;
}
static struct thermal_governor thermal_gov_step_wise = {
.name = "step_wise",
.throttle = step_wise_throttle,
};
int thermal_gov_step_wise_register(void)
{
return thermal_register_governor(&thermal_gov_step_wise);
}
void thermal_gov_step_wise_unregister(void)
{
thermal_unregister_governor(&thermal_gov_step_wise);
}