I have verified kernel 3.13.0-37.64 from trusty-proposed and it does fix the problem.
** Tags removed: verification-needed-trusty ** Tags added: verification-done-trusty -- You received this bug notification because you are a member of Kernel Packages, which is subscribed to linux in Ubuntu. https://bugs.launchpad.net/bugs/1369633 Title: 4k laptop eDP display not working on newer laptops Status in HWE Next Project: New Status in “linux” package in Ubuntu: Fix Released Status in “linux” source package in Trusty: Fix Committed Bug description: Impact: Some new laptops with 4k screens are starting to use dp 1.2 only feature of supporting 5.4ghz link rates over displayport which was not turned on until 3.15 even though the plumbing for it was (mostly) there. This should only make more devices work since it has to advertise support for the feature in the dpcd. previously dp 1.2 screens which needed 5.4ghz link rates were forced to use 2.7ghz instead, which would not provide enough bandwidth for some high resolution/high bandwidth screens. It only affects haswell for trusty, broadwell is handled through i915_bdw module which already as this fix and the fix was upstream in 3.15-rc1 so utopic is unaffected. Fix: Allow the 5.4ghz link rate over displayport. This has been tested on an affected OEM laptop with a 4K display that requires 5.4ghz link rate to light up (without it the display never turns on) as well as 2 other haswell machines to be sure it doesn't regress. [ 5.297037] [drm:intel_modeset_stage_output_state] [CONNECTOR:16:eDP-1] to [CRTC:5] [ 5.297038] [drm:intel_modeset_affected_pipes] set mode pipe masks: modeset: 1, prepare: 1, disable: 0 [ 5.297040] [drm:connected_sink_compute_bpp] [CONNECTOR:16:eDP-1] checking for sink bpp constrains [ 5.297042] [drm:intel_dp_compute_config] DP link computation with max lane count 4 max bw 14 pixel clock 533250KHz [ 5.297045] [drm:intel_dp_compute_config] DP link bw 14 lane count 4 clock 540000 bpp 24 [ 5.297046] [drm:intel_dp_compute_config] DP link bw required 1279800 available 1728000 [ 5.297047] [drm:intel_modeset_pipe_config] plane bpp: 24, pipe bpp: 24, dithering: 0 To manage notifications about this bug go to: https://bugs.launchpad.net/hwe-next/+bug/1369633/+subscriptions -- Mailing list: https://launchpad.net/~kernel-packages Post to : kernel-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~kernel-packages More help : https://help.launchpad.net/ListHelp
