Public bug reported:
Description:
System information:
Machine: Dell XPS 13 Plus 9320
OS: Ubuntu 26.04 LTS (Resolute Raccoon)
Kernel: 7.0.0-22-generic
BIOS: 2.29.0
GPU: Intel Raptor Lake-P Iris Xe Graphics (i915, rev 04)
Session type: Wayland (GNOME)
External monitor: Samsung 43" connected via USB-C to DisplayPort 1.4 passive
cable, running at 3840x2160 @ 120Hz (connector DP-4)
Bug description:
After resume from suspend — consistently reproducible after long suspend
periods (10+ minutes) — the external monitor loses its resolution and display
configuration. The internal laptop display works correctly. Physically
unplugging and replugging the USB-C/DisplayPort cable immediately restores the
correct resolution without any reboot required. Short suspend periods (a few
minutes) sometimes recover correctly, suggesting the issue is related to the
depth of the sleep state reached.
Kernel errors at resume time:
WARNING: drivers/usb/typec/class.c:311 at
typec_altmode_update_active+0x101/0x110 [typec]
Workqueue: events_long ucsi_init_work [typec_ucsi]
RIP: 0010:typec_altmode_update_active+0x101/0x110 [typec]
ucsi_altmode_update_active+0x116/0x1b0 [typec_ucsi]
ucsi_check_altmodes+0x82/0xc0 [typec_ucsi]
ucsi_register_port+0x63a/0x6a0 [typec_ucsi]
ucsi_init+0xdc/0x310 [typec_ucsi]
ucsi_init_work+0x1a/0x90 [typec_ucsi]
i915 0000:00:02.0: [drm] *ERROR* [CONNECTOR:552:DP-4][ENCODER:551:DDI TC3/PHY
TC3][DPRX] Failed to start channel equalization
Root cause analysis:
The UCSI subsystem (typec_ucsi) fails to properly re-negotiate DisplayPort
Alternate Mode after resume from deep suspend. The typec_altmode_update_active
function triggers a kernel WARNING during ucsi_init_work, preventing the i915
driver from completing link training on the USB-C/DisplayPort connection
(DP-4). The physical cable replug forces a clean HPD (Hot Plug Detect) event
that bypasses the failed re-negotiation and restores correct operation.
The issue appears related to the sleep state depth: cat /sys/power/mem_sleep
reports [s2idle]. After short suspensions the system recovers correctly; after
longer ones (10+ minutes) the UCSI firmware loses state and the re-negotiation
fails.
Workarounds attempted (none successful):
options i915 enable_psr=0 enable_dp_mst=0 in /etc/modprobe.d/i915.conf
systemd-sleep hook with sysfs echo detect on the DRM connector
systemd service forcing echo off / echo detect cycle on
/sys/class/drm/card1-DP-4/status
systemd service reloading ucsi_acpi and typec_ucsi modules at resume — triggers
additional kernel WARNINGs in typec_altmode_update_active
Forcing on power management on all Thunderbolt 4 PCI devices via sysfs
Steps to reproduce:
Connect external monitor via USB-C to DisplayPort 1.4 cable
Confirm monitor works correctly at 3840x2160 @ 120Hz
Suspend the system
Wait 10+ minutes
Resume — external monitor shows wrong resolution or black screen
Replug USB-C cable — monitor immediately recovers correct resolution
Thank you for looking into this. I am happy to provide additional logs
or run further tests if needed.
** Affects: linux (Ubuntu)
Importance: Undecided
Status: New
** Tags: dell-xps displayport i915 raptor-lake resume suspend thunderbolt ucsi
usb-c wayland
--
You received this bug notification because you are a member of Ubuntu
Bugs, which is subscribed to Ubuntu.
https://bugs.launchpad.net/bugs/2156501
Title:
i915/UCSI: External monitor loses resolution after suspend/resume on
USB-C to DisplayPort 1.4 — typec_altmode_update_active WARNING
To manage notifications about this bug go to:
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2156501/+subscriptions
--
ubuntu-bugs mailing list
[email protected]
https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
