Public bug reported:
Package: linux-firmware-amd-graphics
Version affected: 20260319.git217ca6e4-0ubuntu3.1
Release: Ubuntu 26.04 (Resolute)
Hardware: AMD Krackan APU, Radeon 840M/860M integrated GPU
Description:
After upgrading linux-firmware-amd-graphics to
20260319.git217ca6e4-0ubuntu3.1, my laptop stopped resuming reliably
from suspend (s2idle). The first suspend/resume cycle after the upgrade
worked normally, but a second cycle a few minutes later hung completely:
no response to keyboard/mouse/power button, screen stayed black, and the
machine required a physical power cycle to recover.
journalctl -b -1 shows the log terminating abruptly mid-suspend on the
second cycle, with no kernel panic, no amdgpu error, and no other
diagnostic output — consistent with a hard hang rather than a clean
failure or crash.
Reproduction:
1. Suspend the laptop (s2idle), resume — works fine.
2. Wait a few minutes, suspend again, resume — system hangs, no recovery short
of a hard power-off.
Workaround:
Downgrading back to the previous version, 20260319.git217ca6e4-0ubuntu3
(pinned via /etc/apt/preferences.d/), resolved the issue. Suspend/resume
now works reliably across repeated cycles with the older firmware.
Suspected cause / related bug:
This looks related to bug #2147396, which shipped a DMCUB firmware
update (to 4.0.74.0) and a "disable unused PHY" workaround targeting AMD
Rembrandt/Yellow Carp systems, in the same 0ubuntu3.1 upload. That
report explicitly notes the change "could theoretically reintroduce
display issues or be too aggressive with PHY disabling on secondary
display ports, though only Yellow Carp systems are affected." My
hardware is Krackan, not Rembrandt/Yellow Carp, so this appears to be an
undocumented regression of the same fix on a different chip family
rather than the issue #2147396 was written to solve.
Attachments available on request: journalctl -b -1 output, apt-cache
policy linux-firmware-amd-graphics, dmesg.
** Affects: linux-firmware-amd-graphics (Ubuntu)
Importance: Undecided
Status: New
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https://bugs.launchpad.net/bugs/2162104
Title:
linux-firmware-amd-graphics 0ubuntu3.1 DMCUB fix causes suspend hang
on Krackan APU
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