Public bug reported: [Impact] HP and Dell systems with Intel Panther Lake-H (PTL-H) CPU and eDP panel configured for Panel Replay suffer a permanent black screen after logout from the desktop. Only a hard reboot restores the display.
[Fix] Remove the two erroneous register writes from intel_alpm_disable() so that only the actual enable bits (ALPM_CTL_ALPM_ENABLE and ALPM_CTL_LOBF_ENABLE) are cleared on disable. PORT_ALPM_CTL is no longer touched during the disable path, and ALPM_CTL_ALPM_AUX_LESS_ENABLE is left intact for the subsequent intel_alpm_configure() call during link training. The fix is in linux-next as of 2026-02-27: 008304c9ae75c772d3460040de56e12112cdf5e6 drm/i915/alpm: ALPM disable fixes Patchwork: https://patchwork.freedesktop.org/patch/704253/ [Test Plan] Requires Intel PTL-H system with a Panel Replay + DSC eDP panel (DISPLAY_VER = 20). Click logout button from the top-right menu and then the GDM shows up. [Where problems could occur] It may break Intel i915/xe display driver Panel Replay and PSR functionality on PTL-class hardware (DISPLAY_VER >= 20). If the fix incorrectly omits a necessary cleanup step in intel_alpm_disable(), the ALPM hardware state might not be properly quiesced before subsequent link training, potentially causing Panel Replay or PSR2 to fail to enable at all (black screen at boot or first modeset rather than only on resume). It could also manifest as display corruption, link training failures, or AUX communication errors logged in dmesg on affected hardware. The change is confined to the DISPLAY_VER >= 20 code path; older hardware is not affected. [Other Info] Remaining open issue: a ~20-second GDM login delay after logout (unrelated to ALPM) is tracked upstream at https://gitlab.freedesktop.org/drm/xe/kernel/-/issues/7497 and is outside the scope of this SRU. ** Affects: hwe-next Importance: Undecided Status: New ** Affects: linux (Ubuntu) Importance: Undecided Status: In Progress ** Affects: linux-oem-6.17 (Ubuntu) Importance: Undecided Status: Invalid ** Affects: linux (Ubuntu Noble) Importance: Undecided Status: Invalid ** Affects: linux-oem-6.17 (Ubuntu Noble) Importance: Undecided Assignee: AceLan Kao (acelankao) Status: In Progress ** Affects: linux (Ubuntu Questing) Importance: Undecided Status: In Progress ** Affects: linux-oem-6.17 (Ubuntu Questing) Importance: Undecided Status: Invalid ** Affects: linux (Ubuntu Resolute) Importance: Undecided Status: In Progress ** Affects: linux-oem-6.17 (Ubuntu Resolute) Importance: Undecided Status: Invalid ** Tags: cpl jira-cpl-257 oem-priority ** Also affects: linux-oem-6.17 (Ubuntu Noble) Importance: Undecided Status: New ** Also affects: linux-oem-6.17 (Ubuntu Questing) Importance: Undecided Status: New ** Also affects: linux-oem-6.17 (Ubuntu Resolute) Importance: Undecided Status: New ** Changed in: linux-oem-6.17 (Ubuntu Noble) Status: New => In Progress ** Changed in: linux-oem-6.17 (Ubuntu Noble) Assignee: (unassigned) => AceLan Kao (acelankao) ** Also affects: linux (Ubuntu) Importance: Undecided Status: New ** Changed in: linux (Ubuntu Noble) Status: New => Invalid ** Changed in: linux (Ubuntu Questing) Status: New => In Progress ** Changed in: linux (Ubuntu Resolute) Status: New => In Progress ** Changed in: linux-oem-6.17 (Ubuntu Questing) Status: New => Invalid ** Changed in: linux-oem-6.17 (Ubuntu Resolute) Status: New => Invalid ** Tags added: cpl jira-cpl-257 oem-priority -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/2143100 Title: Got black screen after clicked logout button To manage notifications about this bug go to: https://bugs.launchpad.net/hwe-next/+bug/2143100/+subscriptions -- ubuntu-bugs mailing list [email protected] https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
