ENC: AMDGPU Tonga suspend regression identified between kernel 6.3 and 6.4 ( Danilo Machado )

ENC: AMDGPU Tonga suspend regression identified between kernel 6.3 and 6.4 ( Danilo Machado )

[Danilo Machado]

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________________________________
De: Danilo Machado <danilomachado2002@hotmail.com>
Enviado: sexta-feira, 20 de março de 2026 11:06
Para: Alex Deucher <alexdeucher@gmail.com>
Assunto: AMDGPU Tonga suspend regression identified between kernel 6.3 and 6.4 ( Danilo Machado )

danilo@danilo-B450-AORUS-PRO-WIFI:~/kernel-bisect/linux$ git bisect good
b3c98052d46948a8d65d2778c7f306ff38366aac is the first bad commit
commit b3c98052d46948a8d65d2778c7f306ff38366aac
Merge: 4a5fd419952e 4984563823f0
Author: Paolo Bonzini <pbonzini@redhat.com>
Date:   Wed Apr 26 15:56:51 2023 -0400

    Merge tag 'kvm-x86-vmx-6.4' of https://github.com/kvm-x86/linux into HEAD

    KVM VMX changes for 6.4:

     - Fix a bug in emulation of ENCLS in compatibility mode

     - Allow emulation of NOP and PAUSE for L2

     - Misc cleanups

 arch/x86/kvm/vmx/nested.c | 112 ++++++++++++++++++++++++++++++----------------
 arch/x86/kvm/vmx/sgx.c    |   4 +-
 arch/x86/kvm/vmx/vmx.c    |  15 +++++++
 3 files changed, 91 insertions(+), 40 deletions(-)
danilo@danilo-B450-AORUS-PRO-WIFI:~/kernel-bisect/linux$
________________________________
De: Danilo Machado <danilomachado2002@hotmail.com>
Enviado: quinta-feira, 19 de março de 2026 11:18
Para: Alex Deucher <alexdeucher@gmail.com>
Assunto: RE: AMDGPU Tonga suspend regression identified between kernel 6.3 and 6.4


Hello Alex,

I hope you're doing well.

First of all, thank you for your guidance and encouragement regarding the bisect process — it was very helpful and allowed me to narrow down the issue precisely.

I would like to report a regression affecting my GPU, an AMD Radeon R9 380 (Tonga), where HDMI output stops working after suspend/resume. The issue is fully reproducible and was not present in Linux 6.3.

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🔍 Summary

  *   GPU: AMD Radeon R9 380 (Tonga)

  *   CPU: AMD Ryzen 5 5500

  *   RAM: 16 GB

  *   Display: HDMI

  *   Driver: amdgpu (RADV Tonga)

Display server behavior:

  *   X11 → ❌ HDMI “no signal” after resume

  *   Wayland → ✅ Works normally

Kernel status:

  *   Linux 6.3 → ✅ Working correctly

  *   Linux 6.4+ → ❌ Regression present (X11 only)

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⚠️ Problem Description

After resuming from suspend under X11, the system continues running normally, but the HDMI display loses signal completely ("no signal").

The issue is 100% reproducible and requires a reboot to restore video output.

This problem does not occur under Wayland, which strongly suggests an issue in the X11/DRM interaction path or display reinitialization specific to that stack.

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🧪 Bisect Result

A full git bisect was performed between Linux 6.3 (good) and Linux 6.4 (bad).

Result:

First bad commit:
b3c98052d46948a8d65d2778c7f306ff38366aac
Merge tag 'kvm-x86-vmx-6.4'

Last known good:
4a5fd419952e49ef870e9259d815718062871cc1

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🧠 Additional Notes

  *   All intermediate commits tested during bisect (mostly KVM-related) were marked as GOOD.

  *   The regression appears to be introduced indirectly via this merge rather than a direct amdgpu/DRM change.

  *   The behavior strongly suggests a failure in display reinitialization or EDID handling after resume, specifically affecting X11.

Full bisect log available upon request.

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💡 Real-world relevance

Despite being an older GPU, the R9 380 (Tonga) remains a capable and widely used card.

As a practical example, this GPU is still capable of running modern titles (e.g., Resident Evil Requiem via Proton), demonstrating that continued stability and support improvements remain highly relevant.

Given the high cost of newer GPUs, maintaining reliability and fixing regressions on this class of hardware is very important for users.

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📎 Reproduction Steps

  1.  Boot system with HDMI connected

  2.  Log into an X11 session

  3.  Suspend the system

  4.  Resume

  5.  HDMI signal is lost ("no signal")

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🙏 Closing

I hope this bisect result helps narrow down the issue.

Please let me know if I can assist further with testing or provide logs — I would be happy to help in any way possible.

Thank you again for your support and for your work on AMD GPU support.

Best regards,
Danilo Machado




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