GSYNC bug regression in 495.44 Ubuntu 21.10

Bug #1950720 reported by berglh
12
This bug affects 2 people
Affects Status Importance Assigned to Milestone
nvidia-graphics-drivers-470 (Ubuntu)
Undecided
Unassigned
nvidia-graphics-drivers-495 (Ubuntu)
Undecided
Unassigned

Bug Description

Similar to bug https://launchpad.net/bugs/1950665, the GSYNC regression bug has returned in 495.44 on Ubuntu 21.10. I have tried the standard kernel and 5.14.1 and 5.14.17, but they are all experiencing the same bug again.

Hardware is:
- NVIDIA GeForce RTX 2080 Super
- Dell 27" S2721DGF G-Sync Compatible monitor
- High quality DisplayPort cable (This was replaced previously under suspicion)

This issue happens at all refresh rates: 60 Hz, 120 Hz, 144 Hz and 165 Hz.

Prior to upgrading to Ubuntu 21.10, I had upgraded to 495.44 on Ubuntu 21.04 and kernel 5.14.1, and this problem was not present.

I then upgraded to Ubuntu 21.10, and the problem didn't seem to be present, but as of today I've noticed again.

I'm not sure what the cause is, but I have tried full driver purges, returned to 470.82, went back to the standard kernel for 21.10 (5.13.0-21-generic), 5.14.1 and 5.14.17, and the problem continues to occur when any GPU accelerated application starts, in some cases when switching between applications (i.e. alt tabbing out of a game). A second or so of no signal occurs as it re-syncs.

I am unsure if X11 has been updated in this time, I know there was work happening on GBM support, wondering if X11 has switched to using this instead of the EGL Streams direct approach that was used previously. Either-way, I'm still running X11 in all of these tests.

Let me know if there are any tests you'd like me to try.

berglh (berglh)
description: updated
description: updated
description: updated
berglh (berglh)
description: updated
Revision history for this message
Daniel van Vugt (vanvugt) wrote :

There's a G-SYNC fix in 470.86:

"Fixed a regression which prevented DisplayPort and HDMI 2.1 variable refresh rate (VRR) G-SYNC Compatible monitors from functioning correctly in variable refresh rate mode, resulting in issues such as flickering."

It's so new that I expect the same bug is still in 495.44. There is no version of 495.xx with a fix that I can find.

Revision history for this message
berglh (berglh) wrote :

Hi Daniel,

Thanks for looking into this. I saw the same commit message in the proposed build for 470.86 by Alberto Milone. Just waiting for this to replace 470.82 after I assume testing is completed.

Revision history for this message
berglh (berglh) wrote :

@vanvugt, I just had a look at the 495.44 download page as I was looking for new driver releases, and this same fix is mentioned on the NVIDIA driver download page: https://www.nvidia.com/Download/driverResults.aspx/181274/en-us

Third from the bottom:
"Fixed a regression which prevented DisplayPort and HDMI 2.1 variable refresh rate (VRR) G-SYNC Compatible monitors from functioning correctly in variable refresh rate mode, resulting in issues such as flickering."

I guess I should try to install it using the NVIDIA installer to see if it's still present?

Revision history for this message
berglh (berglh) wrote :

I installed 495.44 from the NVIDIA website, and it predictably suffers from the same issues as the Ubuntu graphics drivers package. I'm guessing this specific fix is still not addressing the issue in 495.44. I also tried 470.86, and it also has the same issue.

Previously in Ubuntu 21.04, I had downgraded to 460.xx, and the issue was not present. I think my only option is to keybind the AllowFlipping option as a toggle in via a bash script to enable/disable GSYNC when desired. Disabling flipping, which in turn disables GSYNC as far as I can tell, resolves this loss of sync issue. I will just have to wait for future NVIDIA drivers that hopefully fix this regression.

Revision history for this message
punishedsnake (gbisbikis-deactivatedaccount) wrote :

I’m still affected by this issue despite the alleged driver fix. I’ve been running Ubuntu 20.04 for quite some time with a conventional GSYNC monitor and have upgraded to an Asus XG27UQ GSYNC Compatible monitor and this display loses sync if the framerate drops below the VRR threshold and regains sync after blanking out within a few seconds then loses sync again in-game only if the framerate drops below the VRR threshold.

I have tested with the DP cable supplied with the monitor and after
experiencing the issue I then purchased a shorter 1m Comsol DP cable
(DPDP8K01). Both cables are compliant with DP 1.4 spec and support up
to 8K, no adapter is being used, it is plugged directly to the GPU’s DP
port and I have tested all DP ports, the problem still persists.

The behavior has been observed so far first within the game “Doom Eternal” using the Proton Windows-to-Linux compatibility layer within Linux, I then tested it with the game “Black Mesa” which is a native Linux application using OpenGL and observed the same fault, in both cases upon every replication attempt. Disabling GSYNC/Adaptive Sync within the driver or alternatively via the monitor OSD totally prevents the behavior from occurring.

I upgraded to the 495.44 driver from 470.82 with no change in behaviour, I uninstalled this and installed the 470.86 driver in hopes that it would resolve the issue, it has not. This issue is not reproducible under Windows 10, I have tested it thoroughly and the display never blanks out under Windows and I’ve confirmed VRR is engaged via the GSYNC indicator within the driver, this only happens for me on Linux with all the drivers I’ve tried (470.82, 495.44, 470.86).

I still have my conventional GSYNC monitor in my possession, the issue cannot be reproduced under Linux using the Dell S2616DG with GSYNC enabled after swapping back to it when troubleshooting. After swapping back to the XG27UQ I have since also tried driver 460.91, no change in behaviour, problem still persists.

I have already raised this with Nvidia’s Customer Care team and their representative has declined to offer further assistance or an escalation pathway to resolution on the basis that Nvidia’s support channel doesn’t support Linux.

Revision history for this message
Launchpad Janitor (janitor) wrote :

Status changed to 'Confirmed' because the bug affects multiple users.

Changed in nvidia-graphics-drivers-470 (Ubuntu):
status: New → Confirmed
Changed in nvidia-graphics-drivers-495 (Ubuntu):
status: New → Confirmed
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