7900XTX DSC Issue for 2x 4k 144hz Monitors on Kernels 6.7.7+

Brief summary of the problem:

On kernels >=6.7.7, DSC setup for 2x 4k 144hz monitors is not working properly in both X11 and Wayland. 6.7.6 and below work fine. 2nd monitor works when lowered to 1440p resolution instead of 4k (where it stays blank forever).

Hardware description:

• CPU: AMD Ryzen 9 7950X3D (32) @ 5.76 GHz
• GPU: AMD Radeon RX 7900 XTX
• System Memory: 62.54 GiB
• Display(s): 3840x2160 @ 144.00Hz, 3840x2160 @ 144.00Hz; both are LG 27GP950-B models
• Type of Display Connection: DP 1.4a DSC; 2nd monitor is using DP via USB-C.

System information:

• Distro name and Version: Gentoo 2.14 x86_64
• Kernel version: Linux gentoo 6.7.9-zen1-znver4-o3-pds
• Custom kernel: zen-sources custom (also occurs on Arch packaged zen kernel 6.7.9)
• AMD official driver version: mesa 24.0.2

How to reproduce the issue:

• use kernel 6.7.7+
• have 2x 144hz 4k monitors
• boot
• see that 2nd monitor remains black if both are set to 4k 144hz
• adjust 2nd monitor to 1440p
• see it turn on
• adjust 2nd monitor back to 4k
• see it go black

Attached files:

N/A

Screenshots/video files

Log files (for system lockups / game freezes / crashes)

• Dmesg log (full log)
• Xorg log
• Any other log

No logs at the moment; Using 6.7.6 for daily usage still so I haven't rebuilt 6.7.7+ on my Gentoo system again. Verified the issue happens on both Arch (was testing plasma 6 update) and Gentoo wth 6.7.9 across Wayland (Plasma 6) and X11 (i3wm). Have repeatedly tested and verified the same behaviour across 6.7.7, 6.7.8, and now 6.7.9.

EDIT: Problem exists in 6.8.0/6.8.1 as well.