[Feature Request] Allow setting fan speed by writing to sysfs

[MilesBHuff]

Distribution (run cat /etc/os-release):

NAME="Manjaro Linux"
ID=manjaro
ID_LIKE=arch
BUILD_ID=rolling
PRETTY_NAME="Manjaro Linux"
ANSI_COLOR="32;1;24;144;200"
HOME_URL="https://manjaro.org/"
DOCUMENTATION_URL="https://wiki.manjaro.org/"
SUPPORT_URL="https://manjaro.org/"
BUG_REPORT_URL="https://bugs.manjaro.org/"
LOGO=manjarolinux

Related Application and/or Package Version (run apt policy $PACKAGE NAME):
system76-acpi-dkms 1.0.2+1+g0bc966c-1

Issue/Bug Description:
I am unable to set my fan speeds via the settings files exposed by system76-acpi-dkms.

Steps to reproduce (if you know):

sudo pwmconfig
# You can also try `echo`ing to the fan settings directly;  in all cases, you get "permission denied".

Expected behavior:
The fan settings exposed by system76-acpi-dkms should be changeable.

Other Notes:
This is a complaint I have seen semi-commonly on the Internet in general, and Reddit in particular. It's definitely not just me wanting this functionality.

[jacobgkau]

The fan speed is controlled by the fan curve in the firmware: https://github.com/system76/ec/blob/16778e4a41477498eaf5791cae57ae404515973e/src/board/system76/oryp7/board.mk

You can change the fan curve by changing the values in that file before you build firmware-open.

Leaving this open as a feature request, but wanted to let you know in case you weren't aware.

[Raikiri]

I definitely agree that this is a much-needed feature. I'd love if there was a good API to change those curves in runtime or at least in bios.

Hopefully if/when merged, this one should be used : system76/ec#63

[MilesBHuff]

@Raikiri

I'd love if there was a good API to change those curves in runtime or at least in bios.

Providing a sysfs interface for setting fan speeds would inherently allow changing the curves in runtime. (Not literally, but close-enough, since you could pretty easily use a program like fancontrol to handle that for you.)
If you want the entire curve exposed in the OS, that's a whole other matter altogether, and should be raised as a separate issue, as it is outside the scope of this request. I see you have already raised that issue here: system76/firmware-open#570.

Hopefully if/when merged, this one should be used : system76/ec#63

This issue (#9) is correct as-written, and in the correct place. Adding to sysfs is the domain of system76-acpi-dkms, not of ec. If and when any code is merged, it will be done separately for each issue. These issues may overlap, but they do not supercede each other, and each pertains to a somewhat vastly different scope.

[curiousercreative]

@MilesBHuff so I've actually got this working for myself, it's spread across three repos, so not the easiest thing to pull and run for yourself. Unfortunately, after sinking my time into this I have to say that what pwmcontrol and fancontrol gave me were far less smooth fan speed transitions. So now I'm genuinely curious how folks are using these for themselves. What are the use cases and how do you manage it? I didn't try any GUI apps, though I think that's probably desirable. Until a couple years ago when I migrated to Pop! I had great experiences on macOS with iStat Menus (primarily with my 2009-2010 Mac Pro towers). It did a terrific job of allowing multiple profiles that you could have triggered by specific temperature sensor values and it always did a great job of smoothly transitioning. With pwmcontrol and fancontrol I only found an AVERAGE configuration setting and no sub second interval option. Contrast this with our EC fans that are on a <100ms interval with discrete averaging for declining fan speeds vs rising speeds.

• ACPI DKMS PR
• Coreboot (ACPI) PR
• EC (ACPI and Fan controller) PR - This is the PR that would be impacted based discussion

[curiousercreative]

@MilesBHuff No promises, but I think this will get your machine in a similar state as mine to verify the sysfs pwm interface

1. Fetch, build and install system76-acpi-dkms (check for errors in last step)

   git clone git@github.com:pop-os/system76-acpi-dkms.git
   cd system76-acpi-dkms
   
   git remote add curiouser git@github.com:curiousercreative/system76-acpi-dkms.git
   git fetch curiouser
   git checkout curiouser/master
   
   sudo dpkg-buildpackage  -b -uc -us
   sudo dpkg -i ../system76-acpi-dkms_1.0.2_amd64.deb

2. Get firmware codebase in the right state, omit the clone if you already have it

   git clone git@github.com:system76/firmware-open.git
   cd firmware-open
   
   git remote add curiouser git@github.com:curiousercreative/firmware-open.git
   git fetch curiouser acpi-fans
   git checkout curiouser/acpi-fans
   
   ./scripts/update.sh

3. If you have previously flashed your EC with mods that you want to preserve (fan curve, etc) then you'll want to merge one of these two branches into your personal EC branch: EC smooths ACPI pwm values or EC doesn't smooth ACPI pwm values (good for pwmconfig detection, but your own your own for smoothing)
4. Build and flash firmware (including EC)

   ./scripts/build.sh YOUR_MODEL_HERE
   ./scripts/flash.sh YOUR_MODEL_HERE

5. After the computer shuts down, wait a few moments and boot back up. Log in and open a terminal. You need to determine which hwmon directory is "system76_acpi". Do the below until you determine it, let's say it's "hwmon3".

   sudo su
   cat /sys/class/hwmon/hwmon3/name # system76_acpi
   
   cat /sys/class/hwmon/hwmon3/pwm1 # 0
   echo 255 > /sys/class/hwmon/hwmon3/pwm1
   cat /sys/class/hwmon/hwmon3/pwm1 # 255

If you can't find "system76_acpi" hwmon, then we need to debug step 1. If you get a permission denied error when writing to pwm sysfs, then the install in step 1 probably failed. If you can write, but the value remains 0 in read back and the fans don't respond, then our firmware is to blame and requires debugging.

[MilesBHuff]

@curiousercreative Wow, thanks! I will plan to give that a try. I doubt I'll have time to look at it before this weekend, though.