kernel/drivers/thermal/step_wise.c, branch linux-5.1.y

thermal/drivers/step_wise: Fix temperature regulation misbehavior

2017-11-01T02:32:17Z

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 Cc: Keerthy Cc: John Stultz Cc: Leo Yan Tested-by: Keerthy Reviewed-by: Keerthy Signed-off-by: Eduardo Valentin

thermal: fix source code documentation for parameters

2017-06-29T02:46:31Z

Some parameters are not documented, or not present at all, in thermal governors code. Signed-off-by: Willy Wolff Signed-off-by: Zhang Rui

thermal: fix race condition when updating cooling device

2016-08-08T02:57:39Z

When multiple thermal zones are bound to the same cooling device, multiple kernel threads may want to update the cooling device state by calling thermal_cdev_update(). Having cdev not protected by a mutex can lead to a race condition. Consider the following situation with two kernel threads k1 and k2: Thread k1 Thread k2 || || call thermal_cdev_update() || ... || set_cur_state(cdev, target); call power_actor_set_power() || ... || instance->target = state; || cdev->updated = false; || || cdev->updated = true; || // completes execution call thermal_cdev_update() || // cdev->updated == true || return; || \/ time k2 has already looped through the thermal instances looking for the deepest cooling device state and is preempted right before setting cdev->updated to true. Now, k1 runs, modifies the thermal instance state and sets cdev->updated to false. Then, k1 is preempted and k2 continues the execution by setting cdev->updated to true, therefore preventing k1 from performing the update. Notice that this is not an issue if k2 looks at the instance->target modified by k1 "after" it is assigned by k1. In fact, in this case the update will happen anyway and k1 can safely return immediately from thermal_cdev_update(). This may lead to a situation where a thermal governor never updates the cooling device. For example, this is the case for the step_wise governor: when calling the function thermal_zone_trip_update(), the governor may always get a new state equal to the old one (which, however, wasn't notified to the cooling device) and will therefore skip the update. CC: Zhang Rui CC: Eduardo Valentin CC: Peter Feuerer Reported-by: Toby Huang Signed-off-by: Michele Di Giorgio Reviewed-by: Javi Merino Signed-off-by: Zhang Rui

Thermal: initialize thermal zone device correctly

2015-12-29T07:59:44Z

After thermal zone device registered, as we have not read any temperature before, thus tz->temperature should not be 0, which actually means 0C, and thermal trend is not available. In this case, we need specially handling for the first thermal_zone_device_update(). Both thermal core framework and step_wise governor is enhanced to handle this. And since the step_wise governor is the only one that uses trends, so it's the only thermal governor that needs to be updated. CC: #3.18+ Tested-by: Manuel Krause Tested-by: szegad Tested-by: prash Tested-by: amish Tested-by: Matthias Reviewed-by: Javi Merino Signed-off-by: Zhang Rui Signed-off-by: Chen Yu

thermal: consistently use int for temperatures

2015-08-03T15:15:50Z

The thermal code uses int, long and unsigned long for temperatures in different places. Using an unsigned type limits the thermal framework to positive temperatures without need. Also several drivers currently will report temperatures near UINT_MAX for temperatures below 0°C. This will probably immediately shut the machine down due to overtemperature if started below 0°C. 'long' is 64bit on several architectures. This is not needed since INT_MAX °mC is above the melting point of all known materials. Consistently use a plain 'int' for temperatures throughout the thermal code and the drivers. This only changes the places in the drivers where the temperature is passed around as pointer, when drivers internally use another type this is not changed. Signed-off-by: Sascha Hauer Acked-by: Geert Uytterhoeven Reviewed-by: Jean Delvare Reviewed-by: Lukasz Majewski Reviewed-by: Darren Hart Reviewed-by: Heiko Stuebner Reviewed-by: Peter Feuerer Cc: Punit Agrawal Cc: Zhang Rui Cc: Eduardo Valentin Cc: linux-pm@vger.kernel.org Cc: linux-kernel@vger.kernel.org Cc: Jean Delvare Cc: Peter Feuerer Cc: Heiko Stuebner Cc: Lukasz Majewski Cc: Stephen Warren Cc: Thierry Reding Cc: linux-acpi@vger.kernel.org Cc: platform-driver-x86@vger.kernel.org Cc: linux-arm-kernel@lists.infradead.org Cc: linux-omap@vger.kernel.org Cc: linux-samsung-soc@vger.kernel.org Cc: Guenter Roeck Cc: Rafael J. Wysocki Cc: Maxime Ripard Cc: Darren Hart Cc: lm-sensors@lm-sensors.org Signed-off-by: Zhang Rui

thermal: step_wise: spelling fixes

2015-02-06T08:35:00Z

Signed-off-by: Brian Norris Signed-off-by: Zhang Rui

Merge branch 'thermal-core-fix' of .git into next

2014-10-11T01:28:13Z

thermal: step_wise: fix: Prevent from binary overflow when trend is dropping

2014-10-09T02:44:01Z

It turns out that some boards can have instance->lower greater than 0 and when thermal trend is dropping it results with next_target equal to -1. Since the next_target is defined as unsigned long it is interpreted as 0xFFFFFFFF and larger than instance->upper. As a result the next_target is set to instance->upper which ramps up to maximal cooling device target when the temperature is steadily decreasing. Signed-off-by: Lukasz Majewski Signed-off-by: Zhang Rui

thermal: trace: Trace when temperature is above a trip point

2014-07-29T13:28:43Z

Create a new event to trace when the temperature is above a trip point. Use the trace-point when handling non-critical and critical trip pionts. Cc: Zhang Rui Cc: Eduardo Valentin Cc: Steven Rostedt Cc: Frederic Weisbecker Cc: Ingo Molnar Signed-off-by: Punit Agrawal Signed-off-by: Eduardo Valentin

thermal: debug: add debug statement for core and step_wise

2014-01-02T02:52:48Z

To ease debugging thermal problem, add these dynamic debug statements so that user do not need rebuild kernel to see these info. Based on a patch from Zhang Rui for debugging on bugzilla: https://bugzilla.kernel.org/attachment.cgi?id=98671 A sample output after we turn on dynamic debug with the following cmd: # echo 'module thermal_sys +fp' > /sys/kernel/debug/dynamic_debug/control is like: [ 355.147627] update_temperature: thermal thermal_zone0: last_temperature=52000, current_temperature=55000 [ 355.147636] thermal_zone_trip_update: thermal thermal_zone0: Trip1[type=1,temp=79000]:trend=2,throttle=0 [ 355.147644] get_target_state: thermal cooling_device8: cur_state=0 [ 355.147647] thermal_zone_trip_update: thermal cooling_device8: old_target=-1, target=-1 [ 355.147652] get_target_state: thermal cooling_device7: cur_state=0 [ 355.147655] thermal_zone_trip_update: thermal cooling_device7: old_target=-1, target=-1 [ 355.147660] get_target_state: thermal cooling_device6: cur_state=0 [ 355.147663] thermal_zone_trip_update: thermal cooling_device6: old_target=-1, target=-1 [ 355.147668] get_target_state: thermal cooling_device5: cur_state=0 [ 355.147671] thermal_zone_trip_update: thermal cooling_device5: old_target=-1, target=-1 [ 355.147678] thermal_zone_trip_update: thermal thermal_zone0: Trip2[type=0,temp=90000]:trend=1,throttle=0 [ 355.147776] get_target_state: thermal cooling_device0: cur_state=0 [ 355.147783] thermal_zone_trip_update: thermal cooling_device0: old_target=-1, target=-1 [ 355.147792] thermal_zone_trip_update: thermal thermal_zone0: Trip3[type=0,temp=80000]:trend=1,throttle=0 [ 355.147845] get_target_state: thermal cooling_device1: cur_state=0 [ 355.147849] thermal_zone_trip_update: thermal cooling_device1: old_target=-1, target=-1 [ 355.147856] thermal_zone_trip_update: thermal thermal_zone0: Trip4[type=0,temp=70000]:trend=1,throttle=0 [ 355.147904] get_target_state: thermal cooling_device2: cur_state=0 [ 355.147908] thermal_zone_trip_update: thermal cooling_device2: old_target=-1, target=-1 [ 355.147915] thermal_zone_trip_update: thermal thermal_zone0: Trip5[type=0,temp=60000]:trend=1,throttle=0 [ 355.147963] get_target_state: thermal cooling_device3: cur_state=0 [ 355.147967] thermal_zone_trip_update: thermal cooling_device3: old_target=-1, target=-1 [ 355.147973] thermal_zone_trip_update: thermal thermal_zone0: Trip6[type=0,temp=55000]:trend=1,throttle=1 [ 355.148022] get_target_state: thermal cooling_device4: cur_state=0 [ 355.148025] thermal_zone_trip_update: thermal cooling_device4: old_target=-1, target=1 [ 355.148036] thermal_cdev_update: thermal cooling_device4: zone0->target=1 [ 355.169279] thermal_cdev_update: thermal cooling_device4: set to state 1 Signed-off-by: Aaron Lu Acked-by: Eduardo Valentin Signed-off-by: Zhang Rui