linux-kernel - Re: [PATCH v11] asus-wmi: Add support for custom fan curves

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Message-ID: <ef22aa1f-288a-4e5a-0210-d62c7fc89307@redhat.com>
Date:   Tue, 28 Sep 2021 13:44:32 +0200
From:   Hans de Goede <hdegoede@...hat.com>
To:     Bastien Nocera <hadess@...ess.net>,
        "Luke D. Jones" <luke@...nes.dev>, linux-kernel@...r.kernel.org
Cc:     pobrn@...tonmail.com, linux@...ck-us.net,
        platform-driver-x86@...r.kernel.org
Subject: Re: [PATCH v11] asus-wmi: Add support for custom fan curves

Hi,

On 9/28/21 1:36 PM, Bastien Nocera wrote:
> On Wed, 2021-09-08 at 11:22 +1200, Luke D. Jones wrote:
>> Add support for custom fan curves found on some ASUS ROG laptops.
>>
>> These laptops have the ability to set a custom curve for the CPU
>> and GPU fans via two ACPI methods.
>>
>> This patch adds two pwm<N> attributes to the hwmon sysfs,
>> pwm1 for CPU fan, pwm2 for GPU fan. Both are under the hwmon of the
>> name `asus_custom_fan_curve`. There is no safety check of the set
>> fan curves - this must be done in userspace.
>>
>> The fans have settings [1,2,3] under pwm<N>_enable:
>> 1. Enable and write settings out
>> 2. Disable and use factory fan mode
>> 3. Same as 2, additionally restoring default factory curve.
>>
>> Use of 2 means that the curve the user has set is still stored and
>> won't be erased, but the laptop will be using its default auto-fan
>> mode. Re-enabling the manual mode then activates the curves again.
>>
>> Notes:
>> - pwm<N>_enable = 0 is an invalid setting.
>> - pwm is actually a percentage and is scaled on writing to device.
> 
> I was trying to update:
> https://gitlab.freedesktop.org/hadess/power-profiles-daemon/-/merge_requests/80
> but I don't understand what files I need to check for what values to
> detect whether custom fan curves were used.
> 
> Can you help me out here?

How to deal with this is actually one of my remaining questions too.

I've not looked at the new code closely yet, but if I understand
things correctly, the now code basically only allows to set 1
custom profile and setting that profile overrides the last
profile set through /sys/firmware/acpi/platform_profile.

And any write to /sys/firmware/acpi/platform_profile will
overwrite / replace the last custom set profile (if any) with
the one matching the requested platform-profile.

So basically users of custom fan profiles are expected to
disable power-profiles-daemon or at least to refrain from
making any platform_profile changes.

And if power-profile-daemon is actually active and
makes a change then any custom settings will be thrown away,
IOW p-p-d will always win. So I believe that it no longer needs
to check for custom profiles, since any time it requests a
standard profile that will overwrite any custom profile
which may be present.

Luke, do I have that right ?

> Also, was this patch accepted in the pdx86 tree?

No, I still need to find/make some time to review it and
I still have the same question as you :)

Regards,

Hans