[Bug 2156312] [NEW] Internal display black screen on Intel Lunar Lake with eDP panel

Public bug reported: [Impact] Internal display goes black after login on Intel Lunar Lake systems with an eDP panel. The external monitor works. The internal display shows as disabled in display settings and cannot be enabled. Hits 100% on affected hardware (3 units, 15/15 attempts). The bug is caused by LOBF (Link Off Between Frames) being enabled on platforms that use the legacy VRR timing generator. Those platforms do not meet the bspec requirement for LOBF (Always-on VRR TG with fixed refresh rate mode). Enabling LOBF incorrectly causes the display to go dark. [Fix] Replace the raw vmin/vmax/flipline comparison with the proper bspec checks: - intel_vrr_always_use_vrr_tg() to gate LOBF on platforms with Always-on VRR TG - intel_vrr_is_fixed_rr() to confirm fixed refresh rate mode Backported from upstream commit 8a517b1e6d8b, merged in v7.1-rc1. [Test Plan] Boot on affected Intel Lunar Lake hardware with an eDP panel. Without patch: internal display is black after login; shows as disabled in display settings. With patch: internal display works normally after login. [Where problems could occur] Could affect intel_alpm.c LOBF configuration logic in the i915 driver. If intel_vrr_always_use_vrr_tg() or intel_vrr_is_fixed_rr() return wrong results on a platform, LOBF would be incorrectly blocked, and Panel Replay power savings would be lost on those machines. The display would still work — it would just not enter LOBF mode. ** Affects: hwe-next Importance: Undecided Status: New ** Affects: linux (Ubuntu) Importance: Undecided Status: Invalid ** Affects: linux-oem-6.17 (Ubuntu) Importance: Undecided Status: Invalid ** Affects: linux (Ubuntu Noble) Importance: Undecided Status: New ** Affects: linux-oem-6.17 (Ubuntu Noble) Importance: Undecided Status: In Progress ** Affects: linux (Ubuntu Questing) Importance: Undecided Status: New ** Affects: linux-oem-6.17 (Ubuntu Questing) Importance: Undecided Status: Invalid ** Affects: linux (Ubuntu Resolute) Importance: Undecided Status: New ** Affects: linux-oem-6.17 (Ubuntu Resolute) Importance: Undecided Status: Invalid ** Tags: cpl jira-cpl-301 jira-somerville-4895 oem-priority somerville ** Also affects: linux-oem-6.17 (Ubuntu) Importance: Undecided Status: New ** Also affects: linux (Ubuntu Noble) Importance: Undecided Status: New ** Also affects: linux-oem-6.17 (Ubuntu Noble) Importance: Undecided Status: New ** Also affects: linux (Ubuntu Resolute) Importance: Undecided Status: New ** Also affects: linux-oem-6.17 (Ubuntu Resolute) Importance: Undecided Status: New ** Also affects: linux (Ubuntu Questing) Importance: Undecided Status: New ** Also affects: linux-oem-6.17 (Ubuntu Questing) Importance: Undecided Status: New ** Tags added: cpl jira-cpl-301 oem-priority ** Tags added: jira-somerville-4895 somerville ** Changed in: linux-oem-6.17 (Ubuntu Questing) Status: New => Invalid ** Changed in: linux-oem-6.17 (Ubuntu Resolute) Status: New => Invalid ** Changed in: linux-oem-6.17 (Ubuntu Noble) Status: New => In Progress ** Changed in: linux-oem-6.17 (Ubuntu) Status: New => Invalid ** Changed in: linux (Ubuntu) Status: New => Invalid -- You received this bug notification because you are subscribed to linux in Ubuntu. Matching subscriptions: Bgg, Bmail, Nb https://bugs.launchpad.net/bugs/2156312 Title: Internal display black screen on Intel Lunar Lake with eDP panel Status in HWE Next: New Status in linux package in Ubuntu: Invalid Status in linux-oem-6.17 package in Ubuntu: Invalid Status in linux source package in Noble: New Status in linux-oem-6.17 source package in Noble: In Progress Status in linux source package in Questing: New Status in linux-oem-6.17 source package in Questing: Invalid Status in linux source package in Resolute: New Status in linux-oem-6.17 source package in Resolute: Invalid Bug description: [Impact] Internal display goes black after login on Intel Lunar Lake systems with an eDP panel. The external monitor works. The internal display shows as disabled in display settings and cannot be enabled. Hits 100% on affected hardware (3 units, 15/15 attempts). The bug is caused by LOBF (Link Off Between Frames) being enabled on platforms that use the legacy VRR timing generator. Those platforms do not meet the bspec requirement for LOBF (Always-on VRR TG with fixed refresh rate mode). Enabling LOBF incorrectly causes the display to go dark. [Fix] Replace the raw vmin/vmax/flipline comparison with the proper bspec checks: - intel_vrr_always_use_vrr_tg() to gate LOBF on platforms with Always-on VRR TG - intel_vrr_is_fixed_rr() to confirm fixed refresh rate mode Backported from upstream commit 8a517b1e6d8b, merged in v7.1-rc1. [Test Plan] Boot on affected Intel Lunar Lake hardware with an eDP panel. Without patch: internal display is black after login; shows as disabled in display settings. With patch: internal display works normally after login. [Where problems could occur] Could affect intel_alpm.c LOBF configuration logic in the i915 driver. If intel_vrr_always_use_vrr_tg() or intel_vrr_is_fixed_rr() return wrong results on a platform, LOBF would be incorrectly blocked, and Panel Replay power savings would be lost on those machines. The display would still work — it would just not enter LOBF mode. To manage notifications about this bug go to: https://bugs.launchpad.net/hwe-next/+bug/2156312/+subscriptions