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
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https://bugs.launchpad.net/bugs/2156312
Title:
Internal display black screen on Intel Lunar Lake with eDP panel
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