After additional testing I was able to precisely identify the regression
window affecting suspend/resume on this system.

Hardware:
AMD Radeon R9 380 (Tonga)

Driver:
amdgpu

Environment:
Zorin OS 18 (Ubuntu 24.04 base)

Testing methodology:

For each kernel version I performed the following steps:

1. Boot system
2. Confirm kernel version using `uname -r`
3. Suspend the system
4. Resume and verify if the display and keyboard respond normally

Kernel testing results:

6.0 – suspend/resume works normally in X11
6.1 – works
6.2 – works
6.3 – works
6.4 – broken
6.7 – broken
6.9 – broken
6.10 – broken
6.11 – broken
6.12 – broken
6.13 – broken
6.14 – broken

Conclusion:

Last known good kernel: 6.3
First bad kernel: 6.4

Observed behavior:

When resuming from suspend in X11 the display does not return and the
keyboard becomes unresponsive. The system appears to hang until a forced
reboot.

Additional observation:

The system resumes normally under Wayland on all tested kernels.

Relevant log message during resume:

amdgpu: PCI CONFIG reset
[drm:detect_link_and_local_sink [amdgpu]] *ERROR* No EDID read.

This message appears immediately after the GPU reset during the resume
sequence.

The regression window (6.3 → 6.4) seems to coincide with changes in the
AMDGPU display code responsible for display initialization after GPU
reset.

This may indicate an issue related to display link detection or EDID
probing during the resume process.

This information may help narrow down the problematic commit.

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https://bugs.launchpad.net/bugs/2142389

Title:
  amdgpu (R9 380) fails to resume from suspend (deep sleep) – black
  screen, requires hard reboot

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