Public bug reported: Usually a reboot fixes the problem. I see stuff like this in dmesg.
[15294.887642] [drm:intel_wait_ddi_buf_idle [i915]] *ERROR* Timeout waiting for DDI BUF C idle bit [15295.568309] [drm:intel_dp_link_training_clock_recovery [i915]] *ERROR* too many voltage retries, give up [15295.587193] [drm:intel_wait_ddi_buf_idle [i915]] *ERROR* Timeout waiting for DDI BUF C idle bit [15296.267547] [drm:intel_dp_link_training_clock_recovery [i915]] *ERROR* too many voltage retries, give up [15296.286426] [drm:intel_wait_ddi_buf_idle [i915]] *ERROR* Timeout waiting for DDI BUF C idle bit [15296.886015] [drm:intel_dp_link_training_clock_recovery [i915]] *ERROR* too many voltage retries, give up [15296.886264] [drm:intel_dp_link_training_channel_equalization [i915]] *ERROR* failed to train DP, aborting [15296.898472] [drm:intel_dp_link_training_channel_equalization [i915]] *ERROR* Timed out waiting for DP idle patterns [15296.899688] [drm:intel_wait_ddi_buf_idle [i915]] *ERROR* Timeout waiting for DDI BUF C idle bit [15297.579305] [drm:intel_dp_link_training_clock_recovery [i915]] *ERROR* too many voltage retries, give up [15297.598328] [drm:intel_wait_ddi_buf_idle [i915]] *ERROR* Timeout waiting for DDI BUF C idle bit [15298.279238] [drm:intel_dp_link_training_clock_recovery [i915]] *ERROR* too many voltage retries, give up [15298.298275] [drm:intel_wait_ddi_buf_idle [i915]] *ERROR* Timeout waiting for DDI BUF C idle bit [15298.965500] [drm:intel_dp_link_training_clock_recovery [i915]] *ERROR* too many voltage retries, give up [15298.984539] [drm:intel_wait_ddi_buf_idle [i915]] *ERROR* Timeout waiting for DDI BUF C idle bit [15299.665619] [drm:intel_dp_link_training_clock_recovery [i915]] *ERROR* too many voltage retries, give up [15299.684522] [drm:intel_wait_ddi_buf_idle [i915]] *ERROR* Timeout waiting for DDI BUF C idle bit [15300.367119] [drm:intel_dp_link_training_clock_recovery [i915]] *ERROR* too many voltage retries, give up [15300.386173] [drm:intel_wait_ddi_buf_idle [i915]] *ERROR* Timeout waiting for DDI BUF C idle bit [15301.067203] [drm:intel_dp_link_training_clock_recovery [i915]] *ERROR* too many voltage retries, give up [15301.086097] [drm:intel_wait_ddi_buf_idle [i915]] *ERROR* Timeout waiting for DDI BUF C idle bit [15301.768998] [drm:intel_dp_link_training_clock_recovery [i915]] *ERROR* too many voltage retries, give up [15301.769703] [drm:intel_dp_link_training_channel_equalization [i915]] *ERROR* failed to train DP, aborting [15301.781947] [drm:intel_dp_link_training_channel_equalization [i915]] *ERROR* Timed out waiting for DP idle patterns ProblemType: Bug DistroRelease: Ubuntu 16.04 Package: xserver-xorg-video-intel 2:2.99.917+git20160218-1ubuntu2 ProcVersionSignature: Ubuntu 4.4.0-8.23-generic 4.4.2 Uname: Linux 4.4.0-8-generic x86_64 .tmp.unity.support.test.0: ApportVersion: 2.20-0ubuntu3 Architecture: amd64 BootLog: [[0;32m OK [0m] Started LSB: Speech Dispatcher. CompizPlugins: No value set for `/apps/compiz-1/general/screen0/options/active_plugins' CompositorRunning: compiz CompositorUnredirectDriverBlacklist: '(nouveau|Intel).*Mesa 8.0' CompositorUnredirectFSW: true CurrentDesktop: Unity Date: Tue Mar 1 20:58:27 2016 DistUpgraded: Fresh install DistroCodename: xenial DistroVariant: ubuntu ExtraDebuggingInterest: Yes, including running git bisection searches GraphicsCard: Intel Corporation Haswell-ULT Integrated Graphics Controller [8086:0a16] (rev 09) (prog-if 00 [VGA controller]) Subsystem: Lenovo Haswell-ULT Integrated Graphics Controller [17aa:220c] InstallationDate: Installed on 2016-02-26 (5 days ago) InstallationMedia: Ubuntu 16.04 LTS "Xenial Xerus" - Alpha amd64 (20160224) MachineType: LENOVO 20AQS00500 ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-4.4.0-8-generic root=UUID=bb8da1f1-8970-435e-aeaf-d7e1d9aa8a4e ro quiet splash vt.handoff=7 SourcePackage: xserver-xorg-video-intel UpgradeStatus: No upgrade log present (probably fresh install) dmi.bios.date: 09/21/2015 dmi.bios.vendor: LENOVO dmi.bios.version: GJET85WW (2.35 ) dmi.board.asset.tag: Not Available dmi.board.name: 20AQS00500 dmi.board.vendor: LENOVO dmi.board.version: Not Defined dmi.chassis.asset.tag: No Asset Information dmi.chassis.type: 10 dmi.chassis.vendor: LENOVO dmi.chassis.version: Not Available dmi.modalias: dmi:bvnLENOVO:bvrGJET85WW(2.35):bd09/21/2015:svnLENOVO:pn20AQS00500:pvrThinkPadT440s:rvnLENOVO:rn20AQS00500:rvrNotDefined:cvnLENOVO:ct10:cvrNotAvailable: dmi.product.name: 20AQS00500 dmi.product.version: ThinkPad T440s dmi.sys.vendor: LENOVO version.compiz: compiz 1:0.9.12.2+16.04.20160209-0ubuntu1 version.ia32-libs: ia32-libs N/A version.libdrm2: libdrm2 2.4.67-1 version.libgl1-mesa-dri: libgl1-mesa-dri 11.1.2-1ubuntu1 version.libgl1-mesa-dri-experimental: libgl1-mesa-dri-experimental N/A version.libgl1-mesa-glx: libgl1-mesa-glx 11.1.2-1ubuntu1 version.xserver-xorg-core: xserver-xorg-core 2:1.17.3-2ubuntu4 version.xserver-xorg-input-evdev: xserver-xorg-input-evdev 1:2.9.2-1ubuntu1 version.xserver-xorg-video-ati: xserver-xorg-video-ati 1:7.6.1-1 version.xserver-xorg-video-intel: xserver-xorg-video-intel 2:2.99.917+git20160218-1ubuntu2 version.xserver-xorg-video-nouveau: xserver-xorg-video-nouveau 1:1.0.12-1 xserver.bootTime: Tue Mar 1 12:11:39 2016 xserver.configfile: default xserver.errors: systemd-logind: failed to get session: PID 832 does not belong to any known session xserver.logfile: /var/log/Xorg.0.log xserver.outputs: product id 12350 vendor AUO xserver.version: 2:1.17.3-2ubuntu4 ** Affects: xserver-xorg-video-intel (Ubuntu) Importance: Undecided Status: New ** Tags: amd64 apport-bug compiz-0.9 ubuntu xenial -- You received this bug notification because you are a member of Desktop Packages, which is subscribed to xserver-xorg-video-intel in Ubuntu. https://bugs.launchpad.net/bugs/1552040 Title: Laptop sometimes doesn't detect external monitor Status in xserver-xorg-video-intel package in Ubuntu: New Bug description: Usually a reboot fixes the problem. I see stuff like this in dmesg. [15294.887642] [drm:intel_wait_ddi_buf_idle [i915]] *ERROR* Timeout waiting for DDI BUF C idle bit [15295.568309] [drm:intel_dp_link_training_clock_recovery [i915]] *ERROR* too many voltage retries, give up [15295.587193] [drm:intel_wait_ddi_buf_idle [i915]] *ERROR* Timeout waiting for DDI BUF C idle bit [15296.267547] [drm:intel_dp_link_training_clock_recovery [i915]] *ERROR* too many voltage retries, give up [15296.286426] [drm:intel_wait_ddi_buf_idle [i915]] *ERROR* Timeout waiting for DDI BUF C idle bit [15296.886015] [drm:intel_dp_link_training_clock_recovery [i915]] *ERROR* too many voltage retries, give up [15296.886264] [drm:intel_dp_link_training_channel_equalization [i915]] *ERROR* failed to train DP, aborting [15296.898472] [drm:intel_dp_link_training_channel_equalization [i915]] *ERROR* Timed out waiting for DP idle patterns [15296.899688] [drm:intel_wait_ddi_buf_idle [i915]] *ERROR* Timeout waiting for DDI BUF C idle bit [15297.579305] [drm:intel_dp_link_training_clock_recovery [i915]] *ERROR* too many voltage retries, give up [15297.598328] [drm:intel_wait_ddi_buf_idle [i915]] *ERROR* Timeout waiting for DDI BUF C idle bit [15298.279238] [drm:intel_dp_link_training_clock_recovery [i915]] *ERROR* too many voltage retries, give up [15298.298275] [drm:intel_wait_ddi_buf_idle [i915]] *ERROR* Timeout waiting for DDI BUF C idle bit [15298.965500] [drm:intel_dp_link_training_clock_recovery [i915]] *ERROR* too many voltage retries, give up [15298.984539] [drm:intel_wait_ddi_buf_idle [i915]] *ERROR* Timeout waiting for DDI BUF C idle bit [15299.665619] [drm:intel_dp_link_training_clock_recovery [i915]] *ERROR* too many voltage retries, give up [15299.684522] [drm:intel_wait_ddi_buf_idle [i915]] *ERROR* Timeout waiting for DDI BUF C idle bit [15300.367119] [drm:intel_dp_link_training_clock_recovery [i915]] *ERROR* too many voltage retries, give up [15300.386173] [drm:intel_wait_ddi_buf_idle [i915]] *ERROR* Timeout waiting for DDI BUF C idle bit [15301.067203] [drm:intel_dp_link_training_clock_recovery [i915]] *ERROR* too many voltage retries, give up [15301.086097] [drm:intel_wait_ddi_buf_idle [i915]] *ERROR* Timeout waiting for DDI BUF C idle bit [15301.768998] [drm:intel_dp_link_training_clock_recovery [i915]] *ERROR* too many voltage retries, give up [15301.769703] [drm:intel_dp_link_training_channel_equalization [i915]] *ERROR* failed to train DP, aborting [15301.781947] [drm:intel_dp_link_training_channel_equalization [i915]] *ERROR* Timed out waiting for DP idle patterns ProblemType: Bug DistroRelease: Ubuntu 16.04 Package: xserver-xorg-video-intel 2:2.99.917+git20160218-1ubuntu2 ProcVersionSignature: Ubuntu 4.4.0-8.23-generic 4.4.2 Uname: Linux 4.4.0-8-generic x86_64 .tmp.unity.support.test.0: ApportVersion: 2.20-0ubuntu3 Architecture: amd64 BootLog: [[0;32m OK [0m] Started LSB: Speech Dispatcher. CompizPlugins: No value set for `/apps/compiz-1/general/screen0/options/active_plugins' CompositorRunning: compiz CompositorUnredirectDriverBlacklist: '(nouveau|Intel).*Mesa 8.0' CompositorUnredirectFSW: true CurrentDesktop: Unity Date: Tue Mar 1 20:58:27 2016 DistUpgraded: Fresh install DistroCodename: xenial DistroVariant: ubuntu ExtraDebuggingInterest: Yes, including running git bisection searches GraphicsCard: Intel Corporation Haswell-ULT Integrated Graphics Controller [8086:0a16] (rev 09) (prog-if 00 [VGA controller]) Subsystem: Lenovo Haswell-ULT Integrated Graphics Controller [17aa:220c] InstallationDate: Installed on 2016-02-26 (5 days ago) InstallationMedia: Ubuntu 16.04 LTS "Xenial Xerus" - Alpha amd64 (20160224) MachineType: LENOVO 20AQS00500 ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-4.4.0-8-generic root=UUID=bb8da1f1-8970-435e-aeaf-d7e1d9aa8a4e ro quiet splash vt.handoff=7 SourcePackage: xserver-xorg-video-intel UpgradeStatus: No upgrade log present (probably fresh install) dmi.bios.date: 09/21/2015 dmi.bios.vendor: LENOVO dmi.bios.version: GJET85WW (2.35 ) dmi.board.asset.tag: Not Available dmi.board.name: 20AQS00500 dmi.board.vendor: LENOVO dmi.board.version: Not Defined dmi.chassis.asset.tag: No Asset Information dmi.chassis.type: 10 dmi.chassis.vendor: LENOVO dmi.chassis.version: Not Available dmi.modalias: dmi:bvnLENOVO:bvrGJET85WW(2.35):bd09/21/2015:svnLENOVO:pn20AQS00500:pvrThinkPadT440s:rvnLENOVO:rn20AQS00500:rvrNotDefined:cvnLENOVO:ct10:cvrNotAvailable: dmi.product.name: 20AQS00500 dmi.product.version: ThinkPad T440s dmi.sys.vendor: LENOVO version.compiz: compiz 1:0.9.12.2+16.04.20160209-0ubuntu1 version.ia32-libs: ia32-libs N/A version.libdrm2: libdrm2 2.4.67-1 version.libgl1-mesa-dri: libgl1-mesa-dri 11.1.2-1ubuntu1 version.libgl1-mesa-dri-experimental: libgl1-mesa-dri-experimental N/A version.libgl1-mesa-glx: libgl1-mesa-glx 11.1.2-1ubuntu1 version.xserver-xorg-core: xserver-xorg-core 2:1.17.3-2ubuntu4 version.xserver-xorg-input-evdev: xserver-xorg-input-evdev 1:2.9.2-1ubuntu1 version.xserver-xorg-video-ati: xserver-xorg-video-ati 1:7.6.1-1 version.xserver-xorg-video-intel: xserver-xorg-video-intel 2:2.99.917+git20160218-1ubuntu2 version.xserver-xorg-video-nouveau: xserver-xorg-video-nouveau 1:1.0.12-1 xserver.bootTime: Tue Mar 1 12:11:39 2016 xserver.configfile: default xserver.errors: systemd-logind: failed to get session: PID 832 does not belong to any known session xserver.logfile: /var/log/Xorg.0.log xserver.outputs: product id 12350 vendor AUO xserver.version: 2:1.17.3-2ubuntu4 To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/xserver-xorg-video-intel/+bug/1552040/+subscriptions -- Mailing list: https://launchpad.net/~desktop-packages Post to : desktop-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~desktop-packages More help : https://help.launchpad.net/ListHelp