Thanks Alice, and thanks to Krystian for the analysis on #2161309. I agree this strongly looks like a duplicate of #2161309. The symptom, the hardware class (ThinkPad T480, Intel UHD Graphics 620), and the regression range (7.0.0-27 good, 7.0.0-28 bad) all match, and was reported just a couple days earlier.
On the request to test mainline 7.1.4: I am unable to boot the Ubuntu mainline builds on this machine in a straightforward way. As it's a daily-driver work laptop, Secure Boot is enabled and the UEFI supervisor password is set and not available to me, so I cannot enter firmware setup to disable Secure Boot. The mainline builds ship as linux-image- unsigned, which I think the firmware will reject? Enrolling a Machine Owner Key to sign the mainline vmlinuz seems possible in principle (MOK enrollment does not need the firmware password), but I would rather not add a self-signed key to this machine's key store just for a one-off test. Given that #2161309 already confirms 7.1.4 fixes this on the same model (T480 / UHD 620), and that commit f30fddb4402313aa5301a74d721638d343395269 has been identified as the fix, I am comfortable relying on that confirmation rather than reproducing it on this unit. I can verify the fix on this machine once the SRU lands, by removing the i915.enable_dpcd_backlight=0 workaround and running suspend/resume on the updated kernel. If per-unit confirmation on this exact panel (LG LP140WF6-SPB7) is needed before the SRU, do let me know and I will MOK-sign a mainline 7.1.4 build and report back. In the meantime this machine is running 7.0.0-28 with i915.enable_dpcd_backlight=0 set in the GRUB options, and resume works reliably. -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/2161575 Title: [regression] 7.0.0-28: eDP backlight stays off after resume on ThinkPad T480 (i915 selects DPCD/AUX backlight instead of native PWM) To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2161575/+subscriptions -- ubuntu-bugs mailing list [email protected] https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
