linux-kernel - Re: [PATCH RESEND v4] arm64: dts: mediatek: mt7986-bpi-r3: Change fan PWM value for mid speed

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Message-ID: <15eb53dd-792d-4bab-84fd-2abd017c0a84@iopsys.eu>
Date: Thu, 9 Oct 2025 11:55:21 +0300
From: Mikhail Kshevetskiy <mikhail.kshevetskiy@...sys.eu>
To: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>,
 Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
 Conor Dooley <conor+dt@...nel.org>, Matthias Brugger
 <matthias.bgg@...il.com>, devicetree@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
 linux-mediatek@...ts.infradead.org
Cc: Frank Wunderlich <frank-w@...lic-files.de>
Subject: Re: [PATCH RESEND v4] arm64: dts: mediatek: mt7986-bpi-r3: Change fan
 PWM value for mid speed

Is there any chances get it merged to linux-6.18?

Regards,
Mikhail Kshevetskiy



On 30.09.2025 14:34, AngeloGioacchino Del Regno wrote:
> Il 30/09/25 04:16, Mikhail Kshevetskiy ha scritto:
>> Popular cheap PWM fans for this machine, like the ones coming in
>> heatsink+fan combos will not work properly at the currently defined
>> medium speed. Trying different pwm setting using a command
>>
>>    echo $value > /sys/devices/platform/pwm-fan/hwmon/hwmon1/pwm1
>>
>> I found:
>>
>>    pwm1 value     fan rotation speed   cpu temperature     notes
>>    -----------------------------------------------------------------
>>      0            maximal              31.5 Celsius        too noisy
>>     40            optimal              35.2 Celsius        no noise
>> hearable
>>     95            minimal
>>     above 95      does not rotate      55.5 Celsius
>>    -----------------------------------------------------------------
>>
>> Thus only cpu-active-high and cpu-active-low modes are usable.
>> I think this is wrong.
>>
>> This patch fixes cpu-active-medium settings for bpi-r3 board.
>>
>> I know, the patch is not ideal as it can break pwm fan for some users.
>> Likely this is the only official mt7986-bpi-r3 heatsink+fan solution
>> available on the market.
>>
>> This patch may not be enough. Users may wants to tweak their
>> thermal_zone0
>> trip points, thus tuning fan rotation speed depending on cpu
>> temperature.
>> That can be done on the base of the following example:
>>
>>    === example =========
>>    # cpu temperature below 25 Celsius degrees, no rotation
>>    echo 25000 > /sys/class/thermal/thermal_zone0/trip_point_4_temp
>>    # cpu temperature in [25..32] Celsius degrees, normal rotation speed
>>    echo 32000 > /sys/class/thermal/thermal_zone0/trip_point_3_temp
>>    # cpu temperature above 50 Celsius degrees, max rotation speed
>>    echo 50000 > /sys/class/thermal/thermal_zone0/trip_point_2_temp
>>    =====================
>>
>> Signed-off-by: Mikhail Kshevetskiy <mikhail.kshevetskiy@...sys.eu>
>> Acked-by: Frank Wunderlich <frank-w@...lic-files.de>
>
> Reviewed-by: AngeloGioacchino Del Regno
> <angelogioacchino.delregno@...labora.com>
>
>