Screen flicker on mixed refresh rate external monitor setup

[J0nnyMak0]

I'm connected to 4 external monitors via DP 1.4. The dock only supports 3 monitors @60Hz resulting in the fourth display to be @30Hz. With this setup, I'm seeing the screens flicker (go black for a moment) randomly (not all together). If I force all four monitors to @30Hz then the flicker is gone. WLR_DRM_NO_MODIFIERS=1 doesn't make any difference. Setting adaptive_sync on doesn't help either. Strangely adaptive sync only gets enabled for the @30Hz monitor, even though all monitors have freesync enabled. It would be nice to get rid of the flicker without having to drop all monitors to @30Hz. Nothing in debug log/dmesg/journalctl. I'm using sway built with latest sources.

Edit: Just wanted to add all 4 external monitors are identical.

[zDEFz]

I had flicker too. But for me what helped was to change the gpu mem clock to a higher default one on a AMD 6950xt

[J0nnyMak0]

I had flicker too. But for me what helped was to change the gpu mem clock to a higher default one on a AMD 6950xt

Is there a kernel parameter to set for the amd driver, if I may ask?

[zDEFz]

I had flicker too. But for me what helped was to change the gpu mem clock to a higher default one on a AMD 6950xt

Is there a kernel parameter to set for the amd driver, if I may ask?

No. Kernel parameters didn't allow me to change clocks. Instead I pin clocks so the lowest memclock is never used. Avoid using the lowest memclock with multiple monitors. You can check on AMD, with 'cat /sys/class/drm/card0/device/pp_dpm_mclk'

Here is how I pinned my GPU to never use the 97MHz clock (lowest)
https://github.com/zDEFz/os-base-configurations/blob/main/arch/config/scripts/functions/fixes

One important thing to remember is, you want to run the service the last ! So make sure it runs after your Display Manager. In my case that was emptty. Because otherwise the value is simply not applied, as there is some kind of race condition.

[J0nnyMak0]

Thanks for the reply. In my case, the gpu seems to not be using the lowest clock anyway. Still there is flicker. I was only able to get rid of the flicker by connecting 3 monitors directly to the laptop and one to the dock.