[Bug 2143100] Re: Got black screen after clicked logout button

This bug is awaiting verification that the linux-azure/6.17.0-1015.15 kernel in -proposed solves the problem. Please test the kernel and update this bug with the results. If the problem is solved, change the tag 'verification-needed-questing-linux-azure' to 'verification-done- questing-linux-azure'. If the problem still exists, change the tag 'verification-needed-questing-linux-azure' to 'verification-failed- questing-linux-azure'. If verification is not done by 5 working days from today, this fix will be dropped from the source code, and this bug will be closed. See https://wiki.ubuntu.com/Testing/EnableProposed for documentation how to enable and use -proposed. Thank you! ** Tags added: kernel-spammed-questing-linux-azure-v2 verification-needed-questing-linux-azure -- You received this bug notification because you are subscribed to linux in Ubuntu. Matching subscriptions: Bgg, Bmail, Nb https://bugs.launchpad.net/bugs/2143100 Title: Got black screen after clicked logout button Status in HWE Next: New Status in linux package in Ubuntu: Fix Released Status in linux-oem-6.17 package in Ubuntu: Invalid Status in linux source package in Noble: Invalid Status in linux-oem-6.17 source package in Noble: Fix Released Status in linux source package in Questing: In Progress Status in linux-oem-6.17 source package in Questing: Invalid Status in linux source package in Resolute: Fix Released Status in linux-oem-6.17 source package in Resolute: Invalid Bug description: [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] Fix the intel_alpm_disable() function in drivers/gpu/drm/i915/display/intel_alpm.c: 1. Remove the PORT_ALPM_CTL write from intel_alpm_disable() — this register must only be written before link training, not during disable. 2. Stop clearing ALPM_CTL_ALPM_AUX_LESS_ENABLE in intel_alpm_disable() — this bit is about mode switching (AUX-Less vs AUX-Wake), not ALPM enable/disable. The fix is in linux-next as of 2026-02-27:   008304c9ae75c772d3460040de56e12112cdf5e6 drm/i915/alpm: ALPM disable fixes In mainline b7.0-rc2   eb4a7139e9737 drm/i915/alpm: ALPM disable fixes Patchwork: https://patchwork.freedesktop.org/patch/704253/ [Test Plan] Requires a system with Intel integrated graphics and an eDP panel that supports Panel Replay (typically recent Intel platforms with Panel Replay-capable eDP displays). Click logout button from the top-right menu and then the GDM shows up. [Where problems could occur] The change modifies the ALPM disable path in the Intel i915 display driver, which is exercised whenever PSR2 or Panel Replay is active on eDP panels. If the removal of the PORT_ALPM_CTL write is incorrect (i.e., if some hardware requires it to be cleared at disable time), ALPM may fail to disable properly, leaving the link in a low-power state that prevents display from recovering. This would manifest as a black screen or display not coming back after suspend/resume. Similarly, if removing the ALPM_CTL_ALPM_AUX_LESS_ENABLE clear has unintended side effects on some panel configurations, the ALPM mode (AUX-Less vs AUX-Wake) could be stuck in the wrong state, causing link training failures or display flicker on affected eDP panels. The fix is reviewed by Intel display maintainers (Reviewed-by: Michał Grzelak), reducing regression risk, but panels with non-standard ALPM implementations may behave differently. [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. To manage notifications about this bug go to: https://bugs.launchpad.net/hwe-next/+bug/2143100/+subscriptions