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i bought a new laptop (Lafite III from PC Specialist) and monitor (IIYAMA ProLite B2791QSU-B1 27" WQHD). i installed ubuntu 18.04, connected the monitor via HDMI, and all worked perfectly for a few days.

then i disconnected the laptop from the monitor and used the laptop for a couple of days without the monitor. during this time i did a system update, i don't know if that's relevant. now when i reconnect the laptop to the monitor, the laptop does not detect that the monitor is connected.

any idea what i could do to troubleshoot this?

here are things that i have tried:

  • i deleted file ~/.config/monitors.xml

  • i switched from gdm3 to lightdm and back

  • i logged in under wayland

  • i tried using a different HDMI cable (even though it worked previously with the original HDMI cable)

  • i installed the "Displays" ("monitor Preferences") utility and clicked the "Detect monitors" button

  • i tried running these commands:

    $ sudo xrandr --output HDMI-1 --auto $ sudo xrandr --addmode HDMI-1 1920x1080 $ sudo xrandr --output HDMI-1 --mode 1920x1080 --pos 0x0 xrandr: Configure crtc 1 failed

  • i tried running this command:

    sudo apt-get upgrade xserver-xorg-video-intel -y

  • i plugged the monitor in to a friend's laptop to confirm that the monitor still works correctly


Edit: response to ppoilbarbe

many thanks for getting back to me. i definitely think that you are on to something. unfortunately i have still not been able to get it working after further tinkering based on your comments.

strange indeed that it worked at first. i must have broken something, either by updating the software or by fiddling with the settings. when it first worked i was getting sound out of the monitor speakers.

at boot, i never see any BIOS output at all. on the laptop i first get the logo of the hardware vendor, and then the ubuntu login screen. on the monitor i get nothing at all.

the only sign of life that i ever get from the monitor is if i switch it off and then on again, it displays the iiyama logo, then it thinks for a while, then it says "NO SIGNAL DETECTED!".

near bottom left of the keyboard i do have a blue "Fn" key. and i absolutely monkeyed around with this key during the period that the laptop was disconnected from the monitor. the problem was that i had also used a USB keyboard, and at first the laptop keyboard didn't work - some of the letters were replaced with numbers as marked in blue on the relevant keys. i got it working again with Fn-F4 i think but in the process i tried every combination of Fn-whatever. i don't know if that's what caused my monitor to stop working, but now no amount of monkeying with the Fn key seems to fix the problem.


Edit #2:

so after endless tinkering, the monitor started working again after a reboot. i'm not sure which change fixed it. it's still working now, over a week later, so i will call it resolved.

i have two theories as to what happened:

1) one system update broke it, and another fixed it. since i did many updates along the way, this would mean that the break and the fix both came down within a couple of days, which seems unlikely.

2) i broke it by hitting Fn+F6 (?) (change output) and fixed it later by reversing that operation. the problem with this theory is that it only started working after a reboot, whereas i would expect those function keys to take effect immediately.


here is the output from command uname -a:

$ uname -a
Linux laptop3 4.15.0-46-generic #49-Ubuntu SMP Wed Feb 6 09:33:07 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux

here is the partial output from command xrandr --verbose:

$ xrandr --verbose
Screen 0: minimum 320 x 200, current 1920 x 1080, maximum 8192 x 8192
eDP-1 connected primary 1920x1080+0+0 (0x46) normal (normal left inverted right x axis y axis) 309mm x 173mm
    Identifier: 0x42
    Timestamp:  17775
    Subpixel:   unknown
    Gamma:      1.0:1.0:1.0
    Brightness: 1.0
    Clones:    
    CRTC:       0
    CRTCs:      0 1 2
    Transform:  1.000000 0.000000 0.000000
                0.000000 1.000000 0.000000
                0.000000 0.000000 1.000000
               filter: 
    scaling mode: Full aspect 
        supported: Full, Center, Full aspect
    Broadcast RGB: Automatic 
        supported: Automatic, Full, Limited 16:235
    audio: auto 
        supported: force-dvi, off, auto, on
    non-desktop: 0 
        range: (0, 1)
    link-status: Good 
        supported: Good, Bad
  1920x1080 (0x46) 152.840MHz -HSync -VSync *current +preferred
        h: width  1920 start 2000 end 2060 total 2250 skew    0 clock  67.93KHz
        v: height 1080 start 1086 end 1094 total 1132           

clock 53.70KHz v: height 432 start 432 end 434 total 447 clock 60.06Hz

DP-1 disconnected (normal left inverted right x axis y axis)
    Identifier: 0x43
    Timestamp:  17775
    Subpixel:   unknown
    Clones:     HDMI-1
    CRTCs:      0 1 2
    Transform:  1.000000 0.000000 0.000000
                0.000000 1.000000 0.000000
                0.000000 0.000000 1.000000
               filter: 
    Broadcast RGB: Automatic 
        supported: Automatic, Full, Limited 16:235
    audio: auto 
        supported: force-dvi, off, auto, on
    non-desktop: 0 
        range: (0, 1)
    link-status: Good 
        supported: Good, Bad
HDMI-1 disconnected (normal left inverted right x axis y axis)
    Identifier: 0x44
    Timestamp:  17775
    Subpixel:   unknown
    Clones:     DP-1
    CRTCs:      0 1 2
    Transform:  1.000000 0.000000 0.000000
                0.000000 1.000000 0.000000
                0.000000 0.000000 1.000000
               filter: 
    aspect ratio: Automatic 
        supported: Automatic, 4:3, 16:9
    Broadcast RGB: Automatic 
        supported: Automatic, Full, Limited 16:235
    audio: auto 
        supported: force-dvi, off, auto, on
    non-desktop: 0 
        range: (0, 1)
    link-status: Good 
        supported: Good, Bad

here is the output from command lspci -v:

$ lspci -v
00:00.0 Host bridge: Intel Corporation Device 3e34 (rev 0b)
    Subsystem: CLEVO/KAPOK Computer Device 1323
    Flags: bus master, fast devsel, latency 0
    Capabilities: <access denied>

00:02.0 VGA compatible controller: Intel Corporation Device 3ea0 (prog-if 00 [VGA controller])
    Subsystem: CLEVO/KAPOK Computer Device 1323
    Flags: bus master, fast devsel, latency 0, IRQ 149
    Memory at 6000000000 (64-bit, non-prefetchable) [size=16M]
    Memory at 4000000000 (64-bit, prefetchable) [size=256M]
    I/O ports at 4000 [size=64]
    [virtual] Expansion ROM at 000c0000 [disabled] [size=128K]
    Capabilities: <access denied>
    Kernel driver in use: i915
    Kernel modules: i915

00:12.0 Signal processing controller: Intel Corporation Device 9df9 (rev 30)
    Subsystem: CLEVO/KAPOK Computer Device 1323
    Flags: bus master, fast devsel, latency 0, IRQ 16
    Memory at 6001109000 (64-bit, non-prefetchable) [size=4K]
    Capabilities: <access denied>
    Kernel driver in use: intel_pch_thermal
    Kernel modules: intel_pch_thermal

00:14.0 USB controller: Intel Corporation Device 9ded (rev 30) (prog-if 30 [XHCI])
    Subsystem: CLEVO/KAPOK Computer Device 1323
    Flags: bus master, medium devsel, latency 0, IRQ 126
    Memory at 6db00000 (64-bit, non-prefetchable) [size=64K]
    Capabilities: <access denied>
    Kernel driver in use: xhci_hcd

00:14.2 RAM memory: Intel Corporation Device 9def (rev 30)
    Subsystem: CLEVO/KAPOK Computer Device 1323
    Flags: bus master, fast devsel, latency 0
    Memory at 6001104000 (64-bit, non-prefetchable) [size=8K]
    Memory at 6001108000 (64-bit, non-prefetchable) [size=4K]
    Capabilities: <access denied>

00:16.0 Communication controller: Intel Corporation Device 9de0 (rev 30)
    Subsystem: CLEVO/KAPOK Computer Device 1323
    Flags: bus master, fast devsel, latency 0, IRQ 129
    Memory at 6001107000 (64-bit, non-prefetchable) [size=4K]
    Capabilities: <access denied>
    Kernel driver in use: mei_me
    Kernel modules: mei_me

00:17.0 SATA controller: Intel Corporation Device 9dd3 (rev 30) (prog-if 01 [AHCI 1.0])
    Subsystem: CLEVO/KAPOK Computer Device 1323
    Flags: bus master, 66MHz, medium devsel, latency 0, IRQ 128
    Memory at 6db10000 (32-bit, non-prefetchable) [size=8K]
    Memory at 6db14000 (32-bit, non-prefetchable) [size=256]
    I/O ports at 4080 [size=8]
    I/O ports at 4088 [size=4]
    I/O ports at 4060 [size=32]
    Memory at 6db13000 (32-bit, non-prefetchable) [size=2K]
    Capabilities: <access denied>
    Kernel driver in use: ahci
    Kernel modules: ahci

00:1c.0 PCI bridge: Intel Corporation Device 9dbc (rev f0) (prog-if 00 [Normal decode])
    Flags: bus master, fast devsel, latency 0, IRQ 122
    Bus: primary=00, secondary=01, subordinate=01, sec-latency=0
    I/O behind bridge: 00005000-00005fff
    Memory behind bridge: 6dc00000-6ddfffff
    Prefetchable memory behind bridge: 0000004010000000-00000040101fffff
    Capabilities: <access denied>
    Kernel driver in use: pcieport
    Kernel modules: shpchp

00:1d.0 PCI bridge: Intel Corporation Device 9db0 (rev f0) (prog-if 00 [Normal decode])
    Flags: bus master, fast devsel, latency 0, IRQ 123
    Bus: primary=00, secondary=02, subordinate=02, sec-latency=0
    I/O behind bridge: 00003000-00003fff
    Memory behind bridge: 6da00000-6dafffff
    Capabilities: <access denied>
    Kernel driver in use: pcieport
    Kernel modules: shpchp

00:1d.1 PCI bridge: Intel Corporation Device 9db1 (rev f0) (prog-if 00 [Normal decode])
    Flags: bus master, fast devsel, latency 0, IRQ 124
    Bus: primary=00, secondary=03, subordinate=03, sec-latency=0
    Memory behind bridge: 6d900000-6d9fffff
    Capabilities: <access denied>
    Kernel driver in use: pcieport
    Kernel modules: shpchp

00:1d.4 PCI bridge: Intel Corporation Device 9db4 (rev f0) (prog-if 00 [Normal decode])
    Flags: bus master, fast devsel, latency 0, IRQ 125
    Bus: primary=00, secondary=04, subordinate=04, sec-latency=0
    Memory behind bridge: 6d800000-6d8fffff
    Capabilities: <access denied>
    Kernel driver in use: pcieport
    Kernel modules: shpchp

00:1f.0 ISA bridge: Intel Corporation Device 9d84 (rev 30)
    Subsystem: CLEVO/KAPOK Computer Device 1323
    Flags: bus master, medium devsel, latency 0

00:1f.3 Audio device: Intel Corporation Device 9dc8 (rev 30)
    Subsystem: CLEVO/KAPOK Computer Device 1323
    Flags: bus master, fast devsel, latency 32, IRQ 131
    Memory at 6001100000 (64-bit, non-prefetchable) [size=16K]
    Memory at 6001000000 (64-bit, non-prefetchable) [size=1M]
    Capabilities: <access denied>
    Kernel driver in use: snd_hda_intel
    Kernel modules: snd_hda_intel, snd_soc_skl

00:1f.4 SMBus: Intel Corporation Device 9da3 (rev 30)
    Subsystem: CLEVO/KAPOK Computer Device 1323
    Flags: medium devsel, IRQ 255
    Memory at 6001106000 (64-bit, non-prefetchable) [size=256]
    I/O ports at 4040 [size=32]
    Kernel modules: i2c_i801

00:1f.5 Serial bus controller [0c80]: Intel Corporation Device 9da4 (rev 30)
    Subsystem: CLEVO/KAPOK Computer Device 1323
    Flags: bus master, fast devsel, latency 0
    Memory at fe010000 (32-bit, non-prefetchable) [size=4K]

02:00.0 Unassigned class [ff00]: Realtek Semiconductor Co., Ltd. RTL8411B PCI Express Card Reader (rev 01)
    Subsystem: CLEVO/KAPOK Computer RTL8411B PCI Express Card Reader
    Flags: bus master, fast devsel, latency 0, IRQ 127
    Memory at 6da05000 (32-bit, non-prefetchable) [size=4K]
    Expansion ROM at 6da10000 [disabled] [size=64K]
    Capabilities: <access denied>
    Kernel driver in use: rtsx_pci
    Kernel modules: rtsx_pci

02:00.1 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller (rev 12)
    Subsystem: CLEVO/KAPOK Computer RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller
    Flags: bus master, fast devsel, latency 0, IRQ 16
    I/O ports at 3000 [size=256]
    Memory at 6da04000 (64-bit, non-prefetchable) [size=4K]
    Memory at 6da00000 (64-bit, non-prefetchable) [size=16K]
    Capabilities: <access denied>
    Kernel driver in use: r8169
    Kernel modules: r8169

03:00.0 Network controller: Intel Corporation Wireless-AC 9260 (rev 29)
    Subsystem: Intel Corporation Device 0014
    Flags: bus master, fast devsel, latency 0, IRQ 17
    Memory at 6d900000 (64-bit, non-prefetchable) [size=16K]
    Capabilities: <access denied>
    Kernel driver in use: iwlwifi
    Kernel modules: iwlwifi

04:00.0 Non-Volatile memory controller: Samsung Electronics Co Ltd NVMe SSD Controller SM981/PM981 (prog-if 02 [NVM Express])
    Subsystem: Samsung Electronics Co Ltd Device a801
    Flags: bus master, fast devsel, latency 0, IRQ 16, NUMA node 0
    Memory at 6d800000 (64-bit, non-prefetchable) [size=16K]
    Capabilities: <access denied>
    Kernel driver in use: nvme
    Kernel modules: nvme

here is the output from command sudo lshw -C video:

$ sudo lshw -C video
  *-display                 
       description: VGA compatible controller
       product: Intel Corporation
       vendor: Intel Corporation
       physical id: 2
       bus info: pci@0000:00:02.0
       version: 00
       width: 64 bits
       clock: 33MHz
       capabilities: pciexpress msi pm vga_controller bus_master cap_list rom
       configuration: driver=i915 latency=0
       resources: iomemory:600-5ff iomemory:400-3ff irq:149 memory:6000000000-6000ffffff memory:4000000000-400fffffff ioport:4000(size=64) memory:c0000-dffff
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I noticed problems with the i915 driver (the one provided with Ubuntu is a bit outdated). /lib/modules/4.15.0-46-generic/kernel/drivers/gpu/drm/i915/i915.ko is not built for recent i915 firmware.

So maybe some functions do not work as expected (for example since a recent update I did not have sound through HDMI on a nuke PC). But what is strange is that it worked from installation to the first boot without the screen and not after reconnecting.

When you boot with your screen connected via HDMI, do you see BIOS output on both screens ?

Normally they is a key to switch display modes (local screen, external screen, both...). AFAIK It is a combination with blue "FN" (Function) key near the "Windows" key and a blue key cap showing a screen icon (on top row). If so does it changes display behavior ?

  • many thanks for getting back to me. i edited my original post to respond to your remarks. – erik Mar 14 at 13:48
  • hmmm... so, out of boredom, i just did "sudo apt update && sudo apt upgrade" (for like the 100th time in the last few days) and reboot. and the monitor fired up and is working now. very weird. the update messages were about python3 and stuff, i didn't notice anything that seemed likely to fix my problem. my plan now is to never again disconnect, unplug, or update my machine... – erik Mar 14 at 17:16

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