PWM fan control not working with Rock5B and upstream kernel

[Qu Wenruo]

在 2025/7/15 18:14, Qu Wenruo 写道:
> 
> 
> 在 2025/7/15 17:19, Nicolas Frattaroli 写道:
>> On Tuesday, 15 July 2025 06:10:45 Central European Summer Time Qu 
>> Wenruo wrote:
>>> Hi,
>>>
>>> My Rock5B board is running edk-rk3588 firmware and (almost) upstream
>>> kernel (6.14.6 kernel from ArchlinuxARM), using upstream dtbs (the
>>> firmware is also switched to device-tree boot mode)
>>
>> Consider using mainline u-boot instead. I think the only ones who
>> insist on edk2 forks are the BSD people, as they don't want to
>> write device drivers. Linux has drivers, so inventing UEFI abstractions
>> for things probably only makes your experience worse.
> 
> Well, having something more user-friendly and more similar to a 
> traditional PC setup is definitely more attractive to end users.
> 
>>
>> Kernel 6.14 is also quite a bit behind and not supported by upstream,
>> you'll likely have a better experience compiling a kernel yourself
>> using defconfig as the base. ALARM likes to roll dice when it comes to
>> their kernel config and then not update their kernels for half a year.
> 
> Thankfully the latest one is 6.15.6, and unfortunately it doesn't make a 
> difference.
> 
> I'm fine compiling kernels for my VMs to run tests, but for the host I'd 
> leave this as the last resort method.
> 
> I'll try the Uboot if required, but no pre-compiled upstream one is not 
> really inviting end users.
> 
>>
>>>
>>> Before that I'm using ACPI mode thus no PMW support, but the firmware's
>>> fan control is working properly although running at a fixed rpm setting.
>>>
>>> But after switching to the upstream kernel and device-tree mode, the pwm
>>> fan control never works.
>>
>> Check /sys/class/pwm, export the pwm associated with the fan in the DT,
>> then manually set a period and duty cycle that corresponds to a period
>> the fan supports. If it doesn't spin, then the problem is likely that
>> there is a disconnect between what Linux thinks the PWM signal is and
>> what it actually is.
> 
> Mind to explain it a little more?
> 
> Not an expert on device-tree, I normally use the board just as a 
> headless VM host.
> 
>>
>> I'm guessing the problem here is that your firmware of choice leaves
>> the clock tree in a bit of a state, and the PWM is clocked from
>> something that's incorrect. If it's not the right clock period for
>> the fan, it won't spin.
> 
> But my bootloader (systemd-boot) is explicitly loading the dtb, not 
> really relying on the one provided by the firmware.
> 
> Or that is not really enough for this case?

I'm a total idiot, the timing when the PWM doesn't work is not the 
change from ACPI to device-tree boot mode, but the timing I switched 
from fanless case to the PWM fan again.

And I plugged the 2pin fan connector to the WRONG PORT!

It's connected to the RTC battery port, I didn't notice until I recheck 
the name of the connector minutes ago.

Really sorry for wasting your time on such a stupid error...

Now it's working again without anything problem.

> 
> Thanks,
> Qu
> 
>>
>> A logic analyzer would be able to tell you definitively whether that's
>> the case.
>>
>>>
>>> `sensors` command detects the fan, and the pwm seems to properly
>>> following the temperature, but the physical fan just do not spin at all:
>>>
>>> center_thermal-virtual-0
>>> Adapter: Virtual device
>>> temp1:        +80.4°C
>>>
>>> bigcore2_thermal-virtual-0
>>> Adapter: Virtual device
>>> temp1:        +84.1°C
>>>
>>> package_thermal-virtual-0
>>> Adapter: Virtual device
>>> temp1:        +81.3°C
>>>
>>> pwmfan-isa-0000
>>> Adapter: ISA adapter
>>> pwm1:            128%  MANUAL CONTROL <<<
>>>
>>> gpu_thermal-virtual-0
>>> Adapter: Virtual device
>>> temp1:        +79.5°C
>>>
>>> littlecore_thermal-virtual-0
>>> Adapter: Virtual device
>>> temp1:        +82.2°C
>>>
>>> bigcore0_thermal-virtual-0
>>> Adapter: Virtual device
>>> temp1:        +83.2°C
>>>
>>>
>>> I'm wondering is this a bug in the upstream PWM code or something else
>>> is missing preventing the fan from working properly.
>>
>> The upstream PWM code definitely works, and has worked for every
>> Rockchip device so far. The PWM fan on my ROCK 5B (mainline u-boot,
>> mainline kernel, mainline TF-A) works just fine.
>>
>>>
>>> Thanks,
>>> Qu
>>>
>>> _______________________________________________
>>> Linux-rockchip mailing list
>>> Linux-rockchip at lists.infradead.org
>>> http://lists.infradead.org/mailman/listinfo/linux-rockchip
>>>
>>
>>
>>
>>
>