Touchpad Lag when Plugged In with Slow Charger


I’ve got an intermittent issue that I’m struggling to debug.

In typical operation, my touchpad is very responsive, and feels smooth. However, occasionally, something happens and it becomes significantly less responsive. Looking at the motion I think it’s still polling at the same rate, however, the mouse pointer updates about 200-500ms after I move my finger on the touchpad. I don’t know the exact difference, but it’s quite noticeable.

I experienced this on a fresh F36 install, and it appeared to happen at random intervals.

Now I’m running the F37 beta with an additional 6.1.0-0.rc0.20221007git4c86114194e6.5.fc38.x86_64 kernel from rawhide. It’s happening less, however, still appears to consistently happen when I plug my laptop into a slow-charging USB-C charger.

I’m using Gnome with Wayland exclusively, and my hardware is a Thinkpad T14 Gen 3 AMD with a 6850U APU. Running the LENOVO 21CFCTO1WW/21CFCTO1WW, BIOS R23ET59W (1.29 ) 09/01/2022 bios, latest as of last week.

I don’t think this is Fedora-specific. I experience a very similar issue on my work laptop, which is a Dell Latitude 5520 with a 13th-gen Intel processor running Ubuntu 22.04. It’s also using Gnome on Wayland. The main difference is that on that laptop, the touchpad is always slow when plugged in, and immediately speeds up when unplugged, and it’s always the exact same two states: either perfectly responsive, or delayed the exact same slow amount.

On my Thinkpad T14 Gen 3 with Fedora, it doesn’t always slow down when plugged in - sometimes it’s completely the same, and sometimes it slows down a tiny amount. Also, when it’s fully laggy, unplugging does not fix the issue - I have to systemctl suspend and resume before it becomes snappy again.

I don’t notice anything in htop when the mouse is lagging vs. not.

The keyboard does not lag when the mouse lags, so I’m fairly sure it’s a touchpad issue, not a display driver issue.

It’s almost most annoying when it very slightly slows down, because then it’s still usable, but I have to adjust my fingers so I can still hit things accurate. And it feels so crisp and snappy when it’s working at its best! Just annoying to have it slightly off.

My question is: where on Wayland can I look for logs related to this? Any tips on if I can enable verbose logging in a touchpad driver, or anything else you’d recommend looking at?

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Experiencing the same issue on my Hp Elitebook G6 with Arch 6.0.8

Ah, I’m glad it’s not just me!

Is there any chance you’ve experienced any other weird touchpad issues?

One that’s happened a few times to me is, seemingly completely randomly, my touchpad will stop registering 1-finger touches, and like, treat 2-finger drags as 1-finger drags, 3-finger as 2-finger, etc. It goes back to normal after 10 seconds - 10 minutes usually.

I haven’t figured out anything about the main issue, the increased latency on touchpad inputs especially after being plugged in, unfortunately.