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Opened by Simon Ser@emersion

amdgpu internal page-flip failure with "Mode validation failed for stream update!"

Brief summary of the problem:

gamescope is a compositor that tries to use KMS planes to scan out games. gamescope uses KMS atomic commits to perform page-flips. When running some clients, the atomic commit will succeed, but amdgpu will later internally fail the page-flip.

Since user-space isn't aware of the issue, it freezes, waiting for a page-flip event from the kernel.

Surprisingly enough, the bug goes away when user-space passes DRM_MODE_ATOMIC_ALLOW_MODESET on each commit (though this isn't desirable, it's just a workaround).

Expected behavior: amdgpu should perform all checks needed for a page-flip in the atomic check handler amdgpu_dm_atomic_check. If a game can't be directly scanned out, amdgpu should fail the atomic commit to let user-space know about the failure. In this particular case, it seems like amdgpu could still be capable of scanning out the game (since ALLOW_MODESET makes it work).

Hardware description:

  • CPU: AMD Ryzen 5 3500U
  • GPU: APU (PCI 1002:15d8 Advanced Micro Devices, Inc. [AMD/ATI] Picasso)
  • System Memory: 6GiB
  • Display(s): integrated screen
  • Type of Diplay Connection: eDP

System infomration:

  • Distro name and Version: Arch Linux
  • Kernel version: 5.9.3-arch1-1
  • Custom kernel: N/A
  • AMD package version: N/A

How to reproduce the issue:

  1. Clone gamescope
  2. Apply this patch to stop setting ALLOW_MODESET on all commits: https://l.sr.ht/DHTC.txt
  3. Build gamescope
  4. Run it with Steam and enable use of KMS planes: build/gamescope -e -l -d -- steam -tenfoot -steamos >gamescope.log 2>&1
  5. Start Portal 1 (also reproduces with a lot of other games)
  6. gamescope freezes, dmesg should contain:
[16283.676840] [drm:dc_commit_updates_for_stream [amdgpu]] *ERROR* Mode validation failed for stream update!
[16293.708914] [drm:drm_atomic_helper_wait_for_flip_done [drm_kms_helper]] *ERROR* [CRTC:62:crtc-0] flip_done timed out

Downstream bug: https://github.com/Plagman/gamescope/issues/67

Attached files:

DRM debug dmesg logs: https://l.sr.ht/NVUL.log (also contains errors about the cursor plane, but this is a separate and unrelated issue)

Edited by Simon Ser