Messages in this thread | | | Subject | Re: [PATCH V2] thermal/drivers/step_wise: Fix temperature regulation misbehavior | From | Keerthy <> | Date | Fri, 8 Sep 2017 15:21:21 +0530 |
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On Friday 08 September 2017 03:19 PM, Keerthy wrote: > > > On Friday 08 September 2017 02:35 PM, Daniel Lezcano wrote: >> 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 prevening 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. > > Daniel, > > By design this governor is throttling and un-throttling based on the > computed trend. > > Why not add an intermediate trip point with the highest cooling enabled. > Say High alert trip point that allows only the lowest OPP for cpufreq to > operate. > > For example: alert trip is at 100C (where cpufreq cooling kicks in) > critical trip is at 125C(shutdown temperature). > > We have Something like below @110C which allows only the lowest > frequency or lowest 2 frequencies based on experimentation: > > +&cpu_trips { > + cpu_high_alert: cpu_high_alert { > + temperature = <110000>; /* millicelsius */ > + hysteresis = <2000>; /* millicelsius */ > + type = "passive"; > + }; > +}; > + > +&cpu_cooling_maps { > + map1: map1 { > + trip = <&cpu_high_alert>; > + cooling-device = > + <&cpu0 2 THERMAL_NO_LIMIT>; > + }; > +}; > + > > I have seen this problem myself on dra7 platforms. The above will cool > the device post 110C by keeping the cpu frequency at the lowest or lower > values. That way when you are in between 100 - 110C you can still get > highest performance depending on the trend computed and post 110C.
Post 110C cooling is guaranteed by not allowing the cpu frequency hitting the higher values.
> > My 2 cents on this. > > Regards, > Keerthy >> >> Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org> >> --- >> drivers/thermal/step_wise.c | 8 +++++--- >> 1 file changed, 5 insertions(+), 3 deletions(-) >> >> diff --git a/drivers/thermal/step_wise.c b/drivers/thermal/step_wise.c >> index bd2f133..703bd0d 100644 >> --- a/drivers/thermal/step_wise.c >> +++ b/drivers/thermal/step_wise.c >> @@ -95,9 +95,11 @@ static unsigned long get_target_state(struct thermal_instance *instance, >> if (!throttle) >> next_target = THERMAL_NO_TARGET; >> } else { >> - next_target = cur_state - 1; >> - if (next_target > instance->upper) >> - next_target = instance->upper; >> + if (!throttle) { >> + next_target = cur_state - 1; >> + if (next_target > instance->upper) >> + next_target = instance->upper; >> + } >> } >> break; >> case THERMAL_TREND_DROP_FULL: >>
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