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Thread-Topic: Re: [PATCH] Fix mt7622.dtsi thermal cpu
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Subject: Re: [PATCH] Fix mt7622.dtsi thermal cpu
From:   Eric Woudstra <ericwouds@gmail.com>
Date:   Wed, 23 Jun 2021 17:35:27 +0200
To:     Daniel Lezcano <daniel.lezcano@linaro.org>
CC:     Rob Herring <robh+dt@kernel.org>,
        Matthias Brugger <matthias.bgg@gmail.com>,
        devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        linux-mediatek@lists.infradead.org, linux-kernel@vger.kernel.org
Message-ID: <56fb5540-fb86-4e6a-a596-1276026b37e5@gmail.com>
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It is only useful to set 1 map with the regulated temperature for cpu frequ=
ency throttling=2E Same as in the kernel document example=2E


It has no us=
e to set frequency scaling on 2 different temperature trip points, as the l=
owest one makes sure the higher one(s) are never reached=2E It can be appli=
ed only at 1 trip point=2E Multiple trip points is only usefully for fan co=
ntrol to make sure the fan is not too noisy when it is not necessary to be =
noisy=2E


The CPU will almost come to a dead stop when it starts to pass t=
he lowest thermal map with frequency throttling=2E 

This is why it is a bu=
g and needs a fix, not only adjustment=2E


There is no fan=2E=2E=2E On t=
he bpi r64=2E


Anyway without throttling at all a kernel build for more th=
en an hour temperature creeps up to 85 degrees=2E

=E2=81=A3Get BlueMail fo=
r Android =E2=80=8B

On Jun 21, 2021, 8:29 PM, at 8:29 PM, Daniel Lezcano <=
daniel=2Elezcano@linaro=2Eorg> wrote:
>On 19/06/2021 14:19, ericwouds@gmail=
=2Ecom wrote:
>> From: Eric Woudstra <ericwouds@gmail=2Ecom>
>> 
>> Cpu-the=
rmal is set to use all frequencies already at 47 degrees=2E 
>> Using the C=
PU at 50 for a minute, the CPU has reached 48 degrees, is 
>> throttled bac=
k to lowest setting, making the mt7622 terrribly slow=2E 
>> Even at this l=
ow speed, the CPU does not cool down lower then 47 so
>> the CPU is stuck a=
t lowest possible frequency until it shut down and
>> stays off for 15 minu=
tes=2E
>> 
>> cooling-device =3D <&cpu0 THERMAL_NO_LIMIT THERMAL_NO_LIMIT>,=

>>                  <&cpu1 THERMAL_NO_LIMIT THERMAL_NO_LIMIT>;
>> 
>> This=
 should not be set al every cooling map=2E It should only be set at
>> the =
highest cooling map=2E Same as in the example:
>> 
>> https://www=2Ekernel=
=2Eorg/doc/Documentation/devicetree/bindings/
>> thermal/thermal=2Etxt  lin=
e 272
>> 
>> But then without the fan and added a third map=2E
>> 
>> Now t=
emperature will be regulated at 87 degrees celcius=2E At
>temperatures
>> l=
ower then 87, all frequencies can be used=2E
>
>47=C2=B0C is really a too l=
ow temperature and this performance drop is
>normal=2E
>
>I would not remov=
e the passive mitigation but try by increasing the CPU
>temp to 70=C2=B0C a=
nd by changing the active trip point to 80=C2=B0C=2E If it works
>fine, try=
 75=C2=B0C and 85=C2=B0C=2E
>
>To test, the thermal killer is dhrystone (on=
e thread per cpu)=2E
>
>With a 75=C2=B0C passive trip point, the step wise =
thermal governor, I think
>the mitigation will happen smoothly providing be=
tter performances, and
>probably the fan won't fire=2E
>
>> Also see the po=
st:
>> 
>> http://forum=2Ebanana-pi=2Eorg/t/bpi-r64-only-10-cpu-speed-at-al=
ready-48-
>> degrees-celcius-speed-not-increasing-anymore/12262
>> 
>> Sign=
ed-off-by: Eric Woudstra <ericwouds@gmail=2Ecom>
>> ---
>>  arch/arm64/boot=
/dts/mediatek/mt7622=2Edtsi | 8 ++++----
>>  1 file changed, 4 insertions(+=
), 4 deletions(-)
>> 
>> diff --git a/arch/arm64/boot/dts/mediatek/mt7622=
=2Edtsi
>b/arch/arm64/boot/dts/mediatek/mt7622=2Edtsi
>> index 890a942ec=2E=
=2Eb779c7aa6 100644
>> --- a/arch/arm64/boot/dts/mediatek/mt7622=2Edtsi
>> =
+++ b/arch/arm64/boot/dts/mediatek/mt7622=2Edtsi
>> @@ -170,14 +170,14 @@ c=
pu-crit {
>>  			cooling-maps {
>>  				map0 {
>>  					trip =3D <&cpu_pass=
ive>;
>> -					cooling-device =3D <&cpu0 THERMAL_NO_LIMIT THERMAL_NO_LIMIT>=
,
>> -							 <&cpu1 THERMAL_NO_LIMIT THERMAL_NO_LIMIT>;
>> +					cooling-d=
evice =3D <&cpu0 0 0>,
>> +							 <&cpu1 0 0>;
>>  				};
>>  
>>  				map=
1 {
>>  					trip =3D <&cpu_active>;
>> -					cooling-device =3D <&cpu0 THE=
RMAL_NO_LIMIT THERMAL_NO_LIMIT>,
>> -							 <&cpu1 THERMAL_NO_LIMIT THERMA=
L_NO_LIMIT>;
>> +					cooling-device =3D <&cpu0 0 0>,
>> +							 <&cpu1 0 =
0>;
>>  				};
>>  
>>  				map2 {
>> 
>
>
>-- 
><http://www=2Elinaro=2Eorg=
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