Noticeable frame tearing while docked to an external monitor in desktop mode

[murilobnt]

Your system information

• Steam client version: 1719618357
• SteamOS version: 3.6.8
• Opted into Steam client beta?: Yes
• Opted into SteamOS beta?: Yes
• Have you checked for updates in Settings > System?: Yes

Please describe your issue in as much detail as possible:

Since the latest updates (2 days ago) I've been noticing frame tearing that wasn't present before, especially for games such as Garry's Mod (but not restricted to it), in desktop mode docked to an external monitor. A factory reset of Steam OS did not solve it, and everything else (monitor and composer configuration) is triple checked as properly setup. This issue is not present in Gaming mode (still docked to an external monitor). Through investigation, I've discovered that there's a lot of errors in sddm.log (/home/deck/.local/share/sddm.log) related to page flipping. Here's an excerpt of the errors that happens when I launch Garry's Mod:

[06:46:42.185] (WW) X11UserHelper: "(WW) AMDGPU(0): flip queue failed: Invalid argument\n(WW) AMDGPU(0): Page flip failed: Invalid argument\n(EE) AMDGPU(0): present flip failed\n"
[06:46:42.193] (WW) X11UserHelper: "(WW) AMDGPU(0): flip queue failed: Invalid argument\n(WW) AMDGPU(0): Page flip failed: Invalid argument\n"
[06:46:42.193] (WW) X11UserHelper: "(EE) AMDGPU(0): present flip failed\n"
[06:46:42.202] (WW) X11UserHelper: "(WW) AMDGPU(0): flip queue failed: Invalid argument\n(WW) AMDGPU(0): Page flip failed: Invalid argument\n(EE) AMDGPU(0): present flip failed\n"
[06:46:42.210] (WW) X11UserHelper: "(WW) AMDGPU(0): flip queue failed: Invalid argument\n(WW) AMDGPU(0): Page flip failed: Invalid argument\n"

Notice how these errors happen between few milliseconds. Though I'm not sure if it is up to Valve or to AMD to solve this, I'm opening this issue here as it floods the sddm log (at least 90 error messages per second) with errors and produce noticeable tearing.

Steps for reproducing this issue:

1. Go to Desktop mode while docked to an external monitor;
2. Open a game, such as Garry's Mod;
3. Notice the abnormal screen tearing (even with TearFree option set to on for the monitor);
4. Check /home/deck/.local/share/sddm.log for Page flip errors.