Public bug reported:
== Hardware ==
- Dell XPS 15 9530 (BIOS 1.29.0)
- iGPU: Intel Raptor Lake-P [Iris Xe Graphics] (device ID a7a0, integrated
display version 13.00 stepping E0)
- dGPU: NVIDIA RTX 4060 Max-Q (Optimus, displays driven by iGPU)
- Connected: internal eDP-1 panel (PSR1 capable) + 2x DisplayPort over Dell
Thunderbolt Dock
== Software ==
- Ubuntu Desktop 26.04, snap model `ubuntu-classic-2604-amd64`, grade
`signed` (FDE Enhanced, TPM-sealed LUKS)
- Kernel: 7.0.0-15-generic (pc-kernel snap rev 3419, channel 26.04/stable)
- Bootloader: systemd-boot via signed kernel.efi from pc-kernel snap (Secure
Boot + kernel lockdown active)
== Symptom ==
Recurring display flicker on the eDP panel together with simultaneous USB
re-enumeration ("clink-clong" sound on the Dell TB Dock), USB audio
interruption, and brief Bluetooth (hci0) drop. Episodes last ~1 second and
repeat several
times per day, more frequently when the dGPU activates (e.g. Steam/PRIME
render offload).
PSR debug status during the glitch shows the panel stuck in SRDENT
(Self-Refresh Data Enable) with very high transition rate; counter rises
~500/s. State returns to IDLE when the symptom resolves:
Source PSR/PanelReplay status: SRDENT [0x400f0009] (during glitch)
Source PSR/PanelReplay status: IDLE [0x040b0001] (resolved)
This matches Dell's documented hardware issue for the XPS 15 9530
panel ("LCD Screen on the XPS 15 9530 Randomly Flickers", KB 000218908)
where Dell themselves recommend disabling PSR in the Intel Graphics
Command Center on Windows.
Was not happening on Ubuntu 24.04 with kernel 6.x — regression
introduced by the move to kernel 7.0 and/or pc-kernel snap on 26.04.
== Standard workaround is blocked ==
The well-known workaround `i915.enable_psr=0` cannot be applied on 26.04 with
the current setup:
1. /etc/default/grub does not exist / is not consumed (snap-managed
kernel cmdline).
2. `snap set system system.kernel.cmdline-append="i915.enable_psr=0"` fails
with:
"i915.enable_psr=0" is not allowed in the kernel command line by the gadget
The pc gadget snap (rev 220) gadget.yaml whitelist only permits `quiet`
and `splash`.
3. `system.kernel.dangerous-cmdline-append` is not usable: requires
model grade `dangerous`. This system is grade `signed` (Enhanced FDE).
4. /etc/modprobe.d/i915-disable-psr.conf with `options i915 enable_psr=0` is
ignored: i915 loads from the initrd embedded in kernel.efi (signed) before the
encrypted rootfs is mounted, so the local modprobe.d is never consulted.
Verified by reboot test (enable_psr stays at -1).
5. /sys/module/i915/parameters/enable_psr* are read-only at runtime
(mode 0400 root, write returns Permission denied even with sudo).
6. /sys/kernel/debug/dri/.../i915_edp_psr_debug write is blocked by
kernel lockdown (Secure Boot).
Net result: a user with `signed` Enhanced FDE on this hardware has no
supported way to disable a known-buggy display feature.
== Request ==
Either:
(a) Add the well-known display-related i915 parameters (i915.enable_psr,
i915.enable_fbc, i915.enable_psr2_sel_fetch, i915.enable_dc) to the
kernel-cmdline allow list of the `pc` gadget snap, so users on `signed` FDE
Enhanced systems
can apply standard hardware workarounds; or
(b) Quirk-disable PSR in the i915 driver for the Dell XPS 15 9530 panel (and
similar panels with documented Dell-side PSR issues), in line with Dell's own
Windows guidance.
== Related ==
- LP #2065096 — i915 Display is Laggy/Unresponsive when PSR is enabled (Dell
Latitude 7430/9430, same root cause, 24.04 / kernel 6.8). Workaround there is
i915.enable_psr=0 in GRUB — that escape hatch no longer exists on 26.04 with
`signed` FDE.
- Dell KB 000218908 — XPS 15 9530 random flickering, recommends disabling PSR.
- Discourse: "The pc-kernel snap on 26.04 prevents users from installing
additional firmware" — same family of customisation lock-out issues on 26.04.
ProblemType: Bug
DistroRelease: Ubuntu 26.04
Package: linux-image-7.0.0-15-generic (not installed)
ProcVersionSignature: Ubuntu 7.0.0-15.15-generic 7.0.0
Uname: Linux 7.0.0-15-generic x86_64
NonfreeKernelModules: nvidia_modeset nvidia
ApportVersion: 2.34.0-0ubuntu2
Architecture: amd64
CasperMD5CheckResult: unknown
CurrentDesktop: ubuntu:GNOME
Date: Sat May 9 22:18:19 2026
IwDevWlp0s20f3Link: Not connected.
MachineType: Dell Inc. XPS 15 9530
ProcEnviron:
LANG=es_ES.UTF-8
PATH=(custom, no user)
SHELL=/bin/bash
TERM=xterm-256color
XDG_RUNTIME_DIR=<set>
ProcFB: 0 i915drmfb
ProcKernelCmdLine: snapd_recovery_mode=run console=ttyS0,115200n8 console=tty1
panic=-1 quiet splash snapd.xkb="es,pc105,,"
SourcePackage: linux
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 12/24/2025
dmi.bios.release: 1.29
dmi.bios.vendor: Dell Inc.
dmi.bios.version: 1.29.0
dmi.board.name: 0P6GXD
dmi.board.vendor: Dell Inc.
dmi.board.version: A00
dmi.chassis.type: 10
dmi.chassis.vendor: Dell Inc.
dmi.ec.firmware.release: 1.17
dmi.modalias:
dmi:bvnDellInc.:bvr1.29.0:bd12/24/2025:br1.29:efr1.17:svnDellInc.:pnXPS159530:pvr:rvnDellInc.:rn0P6GXD:rvrA00:cvnDellInc.:ct10:cvr:sku0BEB:pfaXPS:
dmi.product.family: XPS
dmi.product.name: XPS 15 9530
dmi.product.sku: 0BEB
dmi.sys.vendor: Dell Inc.
** Affects: linux (Ubuntu)
Importance: Undecided
Status: New
** Tags: amd64 apport-bug resolute wayland-session
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https://bugs.launchpad.net/bugs/2152105
Title:
i915 PSR causes display+USB+BT glitches on XPS 15 9530; kernel cmdline
whitelist on 26.04 blocks i915.enable_psr=0 workaround
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