LG monitor not detected via HDMI on a Thinkpad T480

miguelsvieira · Post by **miguelsvieira** » Tue Sep 01, 2020 11:20 am

Hi folks, I'm a happy longtime user of LMDE, and am having trouble with an external monitor (LG, model 23MB35PH) on a Thinkpad T480 laptop: it doesn't get detected (even though that monitor works on a PC, and a TV works on the laptop's same HDMI port); any help is very appreciated!

I'm running LMDE 4. Output of inxi -Fxxxrz:

Code: Select all

System:    Host: t480 Kernel: 4.19.0-10-amd64 x86_64 bits: 64 compiler: gcc v: 8.3.0 Desktop: Cinnamon 4.6.7 wm: muffin 4.6.3 
           dm: LightDM 1.26.0 Distro: LMDE 4 Debbie base: Debian 10.2 buster 
Machine:   Type: Laptop System: LENOVO product: 20L6S9UY00 v: ThinkPad T480 serial: <filter> Chassis: type: 10 
           serial: <filter> 
           Mobo: LENOVO model: 20L6S9UY00 v: SDK0J40697 WIN serial: <filter> UEFI: LENOVO v: N24ET59W (1.34 ) date: 06/02/2020 
Battery:   ID-1: BAT0 charge: 19.8 Wh condition: 19.8/24.0 Wh (82%) volts: 12.9/11.6 model: SANYO 01AV419 type: Li-ion 
           serial: <filter> status: Full cycles: 89 
           ID-2: BAT1 charge: 20.8 Wh condition: 20.8/23.9 Wh (87%) volts: 12.8/11.4 model: LGC 01AV490 type: Li-poly 
           serial: <filter> status: Full cycles: 200 
CPU:       Topology: Quad Core model: Intel Core i5-8350U bits: 64 type: MT MCP arch: Kaby Lake rev: A L2 cache: 6144 KiB 
           flags: lm nx pae sse sse2 sse3 sse4_1 sse4_2 ssse3 vmx bogomips: 30336 
           Speed: 800 MHz min/max: 400/3600 MHz Core speeds (MHz): 1: 800 2: 801 3: 800 4: 800 5: 800 6: 800 7: 800 8: 801 
Graphics:  Device-1: Intel UHD Graphics 620 vendor: Lenovo driver: i915 v: kernel bus ID: 00:02.0 chip ID: 8086:5917 
           Display: x11 server: X.Org 1.20.4 driver: modesetting unloaded: fbdev,vesa resolution: 1920x1080~60Hz 
           OpenGL: renderer: Mesa DRI Intel UHD Graphics 620 (Kabylake GT2) v: 4.5 Mesa 18.3.6 compat-v: 3.0 
           direct render: Yes 
Audio:     Device-1: Intel Sunrise Point-LP HD Audio vendor: Lenovo driver: snd_hda_intel v: kernel bus ID: 00:1f.3 
           chip ID: 8086:9d71 
           Sound Server: ALSA v: k4.19.0-10-amd64 
Network:   Device-1: Intel Ethernet I219-LM vendor: Lenovo driver: e1000e v: 3.2.6-k port: efa0 bus ID: 00:1f.6 
           chip ID: 8086:15d7 
           IF: enp0s31f6 state: down mac: <filter> 
           Device-2: Intel Wireless 8265 / 8275 driver: iwlwifi v: kernel port: efa0 bus ID: 03:00.0 chip ID: 8086:24fd 
           IF: wlp3s0 state: up mac: <filter> 
Drives:    Local Storage: total: 223.57 GiB used: 81.22 GiB (36.3%) 
           ID-1: /dev/sda vendor: SanDisk model: SSD PLUS 240GB size: 223.57 GiB speed: 6.0 Gb/s serial: <filter> rev: 04RL 
           scheme: GPT 
Partition: ID-1: / size: 23.42 GiB used: 10.83 GiB (46.2%) fs: ext4 dev: /dev/sda3 
           ID-2: /home size: 195.03 GiB used: 70.39 GiB (36.1%) fs: ext4 dev: /dev/sda2 
Sensors:   System Temperatures: cpu: 45.0 C mobo: N/A 
           Fan Speeds (RPM): cpu: 0 
Repos:     No active apt repos in: /etc/apt/sources.list 
           Active apt repos in: /etc/apt/sources.list.d/official-package-repositories.list 
           1: deb http://mint-packages.c3sl.ufpr.br debbie main upstream import backport
           2: deb http://ftp.br.debian.org/debian/ buster main contrib non-free
           3: deb http://ftp.br.debian.org/debian/ buster-updates main contrib non-free
           4: deb http://security.debian.org/ buster/updates main contrib non-free
           5: deb http://ftp.br.debian.org/debian/ buster-backports main contrib non-free
           Active apt repos in: /etc/apt/sources.list.d/skype-stable.list 
           1: deb [arch=amd64] https://repo.skype.com/deb stable main
Info:      Processes: 243 Uptime: 16m Memory: 15.54 GiB used: 941.4 MiB (5.9%) Init: systemd v: 241 runlevel: 5 Compilers: 
           gcc: 8.3.0 alt: 8 Shell: bash v: 5.0.3 running in: gnome-terminal inxi: 3.0.32

I'm using the HDMI port on both the laptop and the monitor (no adapters, just a regular HDMI cable). When I connect the cable to the laptop, the monitor displays a "no signal" message; nothing happens on the laptop. Running xrandr --verbose gives me the same output before and after connecting the cable (always listing HDMI as "disconnected"):

Code: Select all

Screen 0: minimum 320 x 200, current 1920 x 1080, maximum 8192 x 8192
eDP-1 connected primary 1920x1080+0+0 (0x48) normal (normal left inverted right x axis y axis) 309mm x 173mm
	Identifier: 0x42
	Timestamp:  10971
	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: 
	EDID: 
		00ffffffffffff000daec91400000000
		081a0104951f11780228659759548e27
		1e505400000001010101010101010101
		010101010101b43b804a71383440503c
		680035ad10000018000000fe004e3134
		304843412d4541420a20000000fe0043
		4d4e0a202020202020202020000000fe
		004e3134304843412d4541420a20003e
	scaling mode: Full aspect 
		supported: Full, Center, Full aspect
	Broadcast RGB: Automatic 
		supported: Automatic, Full, Limited 16:235
	link-status: Good 
		supported: Good, Bad
	CONNECTOR_ID: 71 
		supported: 71
	non-desktop: 0 
		range: (0, 1)
  1920x1080 (0x48) 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  60.01Hz
  1920x1080 (0x49) 356.375MHz -HSync +VSync DoubleScan
        h: width  1920 start 2080 end 2288 total 2656 skew    0 clock 134.18KHz
        v: height 1080 start 1081 end 1084 total 1118           clock  60.01Hz
  1920x1080 (0x4a) 266.500MHz +HSync -VSync DoubleScan
        h: width  1920 start 1944 end 1960 total 2000 skew    0 clock 133.25KHz
        v: height 1080 start 1081 end 1084 total 1111           clock  59.97Hz
  1920x1080 (0x4b) 173.000MHz -HSync +VSync
        h: width  1920 start 2048 end 2248 total 2576 skew    0 clock  67.16KHz
        v: height 1080 start 1083 end 1088 total 1120           clock  59.96Hz
  1920x1080 (0x4c) 138.500MHz +HSync -VSync
        h: width  1920 start 1968 end 2000 total 2080 skew    0 clock  66.59KHz
        v: height 1080 start 1083 end 1088 total 1111           clock  59.93Hz
  1680x1050 (0x4d) 146.250MHz -HSync +VSync
        h: width  1680 start 1784 end 1960 total 2240 skew    0 clock  65.29KHz
        v: height 1050 start 1053 end 1059 total 1089           clock  59.95Hz
  1680x1050 (0x4e) 119.000MHz +HSync -VSync
        h: width  1680 start 1728 end 1760 total 1840 skew    0 clock  64.67KHz
        v: height 1050 start 1053 end 1059 total 1080           clock  59.88Hz
  1600x1024 (0x4f) 103.125MHz +HSync +VSync
        h: width  1600 start 1600 end 1656 total 1664 skew    0 clock  61.97KHz
        v: height 1024 start 1024 end 1029 total 1030           clock  60.17Hz
  1400x1050 (0x50) 122.000MHz +HSync +VSync
        h: width  1400 start 1488 end 1640 total 1880 skew    0 clock  64.89KHz
        v: height 1050 start 1052 end 1064 total 1082           clock  59.98Hz
  1600x900 (0x51) 246.000MHz -HSync +VSync DoubleScan
        h: width  1600 start 1728 end 1900 total 2200 skew    0 clock 111.82KHz
        v: height  900 start  901 end  904 total  932           clock  59.99Hz
  1600x900 (0x52) 186.500MHz +HSync -VSync DoubleScan
        h: width  1600 start 1624 end 1640 total 1680 skew    0 clock 111.01KHz
        v: height  900 start  901 end  904 total  926           clock  59.94Hz
  1600x900 (0x53) 118.250MHz -HSync +VSync
        h: width  1600 start 1696 end 1856 total 2112 skew    0 clock  55.99KHz
        v: height  900 start  903 end  908 total  934           clock  59.95Hz
  1600x900 (0x54) 97.500MHz +HSync -VSync
        h: width  1600 start 1648 end 1680 total 1760 skew    0 clock  55.40KHz
        v: height  900 start  903 end  908 total  926           clock  59.82Hz
  1280x1024 (0x55) 108.000MHz +HSync +VSync
        h: width  1280 start 1328 end 1440 total 1688 skew    0 clock  63.98KHz
        v: height 1024 start 1025 end 1028 total 1066           clock  60.02Hz
  1440x900 (0x56) 106.500MHz -HSync +VSync
        h: width  1440 start 1520 end 1672 total 1904 skew    0 clock  55.93KHz
        v: height  900 start  903 end  909 total  934           clock  59.89Hz
  1400x900 (0x57) 103.500MHz -HSync +VSync
        h: width  1400 start 1480 end 1624 total 1848 skew    0 clock  56.01KHz
        v: height  900 start  903 end  913 total  934           clock  59.96Hz
  1400x900 (0x58) 86.500MHz +HSync -VSync
        h: width  1400 start 1448 end 1480 total 1560 skew    0 clock  55.45KHz
        v: height  900 start  903 end  913 total  926           clock  59.88Hz
  1280x960 (0x59) 108.000MHz +HSync +VSync
        h: width  1280 start 1376 end 1488 total 1800 skew    0 clock  60.00KHz
        v: height  960 start  961 end  964 total 1000           clock  60.00Hz
  1440x810 (0x5a) 198.125MHz -HSync +VSync DoubleScan
        h: width  1440 start 1548 end 1704 total 1968 skew    0 clock 100.67KHz
        v: height  810 start  811 end  814 total  839           clock  60.00Hz
  1440x810 (0x5b) 151.875MHz +HSync -VSync DoubleScan
        h: width  1440 start 1464 end 1480 total 1520 skew    0 clock  99.92KHz
        v: height  810 start  811 end  814 total  833           clock  59.97Hz
  1368x768 (0x5c) 85.250MHz -HSync +VSync
        h: width  1368 start 1440 end 1576 total 1784 skew    0 clock  47.79KHz
        v: height  768 start  771 end  781 total  798           clock  59.88Hz
  1368x768 (0x5d) 72.250MHz +HSync -VSync
        h: width  1368 start 1416 end 1448 total 1528 skew    0 clock  47.28KHz
        v: height  768 start  771 end  781 total  790           clock  59.85Hz
  1360x768 (0x5e) 84.750MHz -HSync +VSync
        h: width  1360 start 1432 end 1568 total 1776 skew    0 clock  47.72KHz
        v: height  768 start  771 end  781 total  798           clock  59.80Hz
  1360x768 (0x5f) 72.000MHz +HSync -VSync
        h: width  1360 start 1408 end 1440 total 1520 skew    0 clock  47.37KHz
        v: height  768 start  771 end  781 total  790           clock  59.96Hz
  1280x800 (0x60) 174.250MHz -HSync +VSync DoubleScan
        h: width  1280 start 1380 end 1516 total 1752 skew    0 clock  99.46KHz
        v: height  800 start  801 end  804 total  829           clock  59.99Hz
  1280x800 (0x61) 134.250MHz +HSync -VSync DoubleScan
        h: width  1280 start 1304 end 1320 total 1360 skew    0 clock  98.71KHz
        v: height  800 start  801 end  804 total  823           clock  59.97Hz
  1280x800 (0x62) 83.500MHz -HSync +VSync
        h: width  1280 start 1352 end 1480 total 1680 skew    0 clock  49.70KHz
        v: height  800 start  803 end  809 total  831           clock  59.81Hz
  1280x800 (0x63) 71.000MHz +HSync -VSync
        h: width  1280 start 1328 end 1360 total 1440 skew    0 clock  49.31KHz
        v: height  800 start  803 end  809 total  823           clock  59.91Hz
  1152x864 (0x64) 81.620MHz -HSync +VSync
        h: width  1152 start 1216 end 1336 total 1520 skew    0 clock  53.70KHz
        v: height  864 start  865 end  868 total  895           clock  60.00Hz
  1280x720 (0x65) 156.125MHz -HSync +VSync DoubleScan
        h: width  1280 start 1376 end 1512 total 1744 skew    0 clock  89.52KHz
        v: height  720 start  721 end  724 total  746           clock  60.00Hz
  1280x720 (0x66) 120.750MHz +HSync -VSync DoubleScan
        h: width  1280 start 1304 end 1320 total 1360 skew    0 clock  88.79KHz
        v: height  720 start  721 end  724 total  740           clock  59.99Hz
  1280x720 (0x67) 74.500MHz -HSync +VSync
        h: width  1280 start 1344 end 1472 total 1664 skew    0 clock  44.77KHz
        v: height  720 start  723 end  728 total  748           clock  59.86Hz
  1280x720 (0x68) 63.750MHz +HSync -VSync
        h: width  1280 start 1328 end 1360 total 1440 skew    0 clock  44.27KHz
        v: height  720 start  723 end  728 total  741           clock  59.74Hz
  1024x768 (0x69) 133.475MHz -HSync +VSync DoubleScan
        h: width  1024 start 1100 end 1212 total 1400 skew    0 clock  95.34KHz
        v: height  768 start  768 end  770 total  794           clock  60.04Hz
  1024x768 (0x6a) 65.000MHz -HSync -VSync
        h: width  1024 start 1048 end 1184 total 1344 skew    0 clock  48.36KHz
        v: height  768 start  771 end  777 total  806           clock  60.00Hz
  960x720 (0x6b) 117.000MHz -HSync +VSync DoubleScan
        h: width   960 start 1024 end 1128 total 1300 skew    0 clock  90.00KHz
        v: height  720 start  720 end  722 total  750           clock  60.00Hz
  928x696 (0x6c) 109.150MHz -HSync +VSync DoubleScan
        h: width   928 start  976 end 1088 total 1264 skew    0 clock  86.35KHz
        v: height  696 start  696 end  698 total  719           clock  60.05Hz
  896x672 (0x6d) 102.400MHz -HSync +VSync DoubleScan
        h: width   896 start  960 end 1060 total 1224 skew    0 clock  83.66KHz
        v: height  672 start  672 end  674 total  697           clock  60.01Hz
  1024x576 (0x6e) 98.500MHz -HSync +VSync DoubleScan
        h: width  1024 start 1092 end 1200 total 1376 skew    0 clock  71.58KHz
        v: height  576 start  577 end  580 total  597           clock  59.95Hz
  1024x576 (0x6f) 78.375MHz +HSync -VSync DoubleScan
        h: width  1024 start 1048 end 1064 total 1104 skew    0 clock  70.99KHz
        v: height  576 start  577 end  580 total  592           clock  59.96Hz
  1024x576 (0x70) 46.500MHz -HSync +VSync
        h: width  1024 start 1064 end 1160 total 1296 skew    0 clock  35.88KHz
        v: height  576 start  579 end  584 total  599           clock  59.90Hz
  1024x576 (0x71) 42.000MHz +HSync -VSync
        h: width  1024 start 1072 end 1104 total 1184 skew    0 clock  35.47KHz
        v: height  576 start  579 end  584 total  593           clock  59.82Hz
  960x600 (0x72) 96.625MHz -HSync +VSync DoubleScan
        h: width   960 start 1028 end 1128 total 1296 skew    0 clock  74.56KHz
        v: height  600 start  601 end  604 total  622           clock  59.93Hz
  960x600 (0x73) 77.000MHz +HSync -VSync DoubleScan
        h: width   960 start  984 end 1000 total 1040 skew    0 clock  74.04KHz
        v: height  600 start  601 end  604 total  617           clock  60.00Hz
  960x540 (0x74) 86.500MHz -HSync +VSync DoubleScan
        h: width   960 start 1024 end 1124 total 1288 skew    0 clock  67.16KHz
        v: height  540 start  541 end  544 total  560           clock  59.96Hz
  960x540 (0x75) 69.250MHz +HSync -VSync DoubleScan
        h: width   960 start  984 end 1000 total 1040 skew    0 clock  66.59KHz
        v: height  540 start  541 end  544 total  555           clock  59.99Hz
  960x540 (0x76) 40.750MHz -HSync +VSync
        h: width   960 start  992 end 1088 total 1216 skew    0 clock  33.51KHz
        v: height  540 start  543 end  548 total  562           clock  59.63Hz
  960x540 (0x77) 37.250MHz +HSync -VSync
        h: width   960 start 1008 end 1040 total 1120 skew    0 clock  33.26KHz
        v: height  540 start  543 end  548 total  556           clock  59.82Hz
  800x600 (0x78) 81.000MHz +HSync +VSync DoubleScan
        h: width   800 start  832 end  928 total 1080 skew    0 clock  75.00KHz
        v: height  600 start  600 end  602 total  625           clock  60.00Hz
  800x600 (0x79) 40.000MHz +HSync +VSync
        h: width   800 start  840 end  968 total 1056 skew    0 clock  37.88KHz
        v: height  600 start  601 end  605 total  628           clock  60.32Hz
  800x600 (0x7a) 36.000MHz +HSync +VSync
        h: width   800 start  824 end  896 total 1024 skew    0 clock  35.16KHz
        v: height  600 start  601 end  603 total  625           clock  56.25Hz
  840x525 (0x7b) 73.125MHz -HSync +VSync DoubleScan
        h: width   840 start  892 end  980 total 1120 skew    0 clock  65.29KHz
        v: height  525 start  526 end  529 total  544           clock  60.01Hz
  840x525 (0x7c) 59.500MHz +HSync -VSync DoubleScan
        h: width   840 start  864 end  880 total  920 skew    0 clock  64.67KHz
        v: height  525 start  526 end  529 total  540           clock  59.88Hz
  864x486 (0x7d) 32.500MHz -HSync +VSync
        h: width   864 start  888 end  968 total 1072 skew    0 clock  30.32KHz
        v: height  486 start  489 end  494 total  506           clock  59.92Hz
  864x486 (0x7e) 30.500MHz +HSync -VSync
        h: width   864 start  912 end  944 total 1024 skew    0 clock  29.79KHz
        v: height  486 start  489 end  494 total  500           clock  59.57Hz
  800x512 (0x7f) 51.562MHz +HSync +VSync DoubleScan
        h: width   800 start  800 end  828 total  832 skew    0 clock  61.97KHz
        v: height  512 start  512 end  514 total  515           clock  60.17Hz
  700x525 (0x80) 61.000MHz +HSync +VSync DoubleScan
        h: width   700 start  744 end  820 total  940 skew    0 clock  64.89KHz
        v: height  525 start  526 end  532 total  541           clock  59.98Hz
  800x450 (0x81) 59.125MHz -HSync +VSync DoubleScan
        h: width   800 start  848 end  928 total 1056 skew    0 clock  55.99KHz
        v: height  450 start  451 end  454 total  467           clock  59.95Hz
  800x450 (0x82) 48.750MHz +HSync -VSync DoubleScan
        h: width   800 start  824 end  840 total  880 skew    0 clock  55.40KHz
        v: height  450 start  451 end  454 total  463           clock  59.82Hz
  640x512 (0x83) 54.000MHz +HSync +VSync DoubleScan
        h: width   640 start  664 end  720 total  844 skew    0 clock  63.98KHz
        v: height  512 start  512 end  514 total  533           clock  60.02Hz
  720x450 (0x84) 53.250MHz -HSync +VSync DoubleScan
        h: width   720 start  760 end  836 total  952 skew    0 clock  55.93KHz
        v: height  450 start  451 end  454 total  467           clock  59.89Hz
  700x450 (0x85) 51.750MHz -HSync +VSync DoubleScan
        h: width   700 start  740 end  812 total  924 skew    0 clock  56.01KHz
        v: height  450 start  451 end  456 total  467           clock  59.96Hz
  700x450 (0x86) 43.250MHz +HSync -VSync DoubleScan
        h: width   700 start  724 end  740 total  780 skew    0 clock  55.45KHz
        v: height  450 start  451 end  456 total  463           clock  59.88Hz
  640x480 (0x87) 54.000MHz +HSync +VSync DoubleScan
        h: width   640 start  688 end  744 total  900 skew    0 clock  60.00KHz
        v: height  480 start  480 end  482 total  500           clock  60.00Hz
  640x480 (0x88) 25.175MHz -HSync -VSync
        h: width   640 start  656 end  752 total  800 skew    0 clock  31.47KHz
        v: height  480 start  490 end  492 total  525           clock  59.94Hz
  720x405 (0x89) 22.500MHz -HSync +VSync
        h: width   720 start  744 end  808 total  896 skew    0 clock  25.11KHz
        v: height  405 start  408 end  413 total  422           clock  59.51Hz
  720x405 (0x8a) 21.750MHz +HSync -VSync
        h: width   720 start  768 end  800 total  880 skew    0 clock  24.72KHz
        v: height  405 start  408 end  413 total  419           clock  58.99Hz
  684x384 (0x8b) 42.625MHz -HSync +VSync DoubleScan
        h: width   684 start  720 end  788 total  892 skew    0 clock  47.79KHz
        v: height  384 start  385 end  390 total  399           clock  59.88Hz
  684x384 (0x8c) 36.125MHz +HSync -VSync DoubleScan
        h: width   684 start  708 end  724 total  764 skew    0 clock  47.28KHz
        v: height  384 start  385 end  390 total  395           clock  59.85Hz
  680x384 (0x8d) 42.375MHz -HSync +VSync DoubleScan
        h: width   680 start  716 end  784 total  888 skew    0 clock  47.72KHz
        v: height  384 start  385 end  390 total  399           clock  59.80Hz
  680x384 (0x8e) 36.000MHz +HSync -VSync DoubleScan
        h: width   680 start  704 end  720 total  760 skew    0 clock  47.37KHz
        v: height  384 start  385 end  390 total  395           clock  59.96Hz
  640x400 (0x8f) 41.750MHz -HSync +VSync DoubleScan
        h: width   640 start  676 end  740 total  840 skew    0 clock  49.70KHz
        v: height  400 start  401 end  404 total  415           clock  59.88Hz
  640x400 (0x90) 35.500MHz +HSync -VSync DoubleScan
        h: width   640 start  664 end  680 total  720 skew    0 clock  49.31KHz
        v: height  400 start  401 end  404 total  411           clock  59.98Hz
  576x432 (0x91) 40.810MHz -HSync +VSync DoubleScan
        h: width   576 start  608 end  668 total  760 skew    0 clock  53.70KHz
        v: height  432 start  432 end  434 total  447           clock  60.06Hz
  640x360 (0x92) 37.250MHz -HSync +VSync DoubleScan
        h: width   640 start  672 end  736 total  832 skew    0 clock  44.77KHz
        v: height  360 start  361 end  364 total  374           clock  59.86Hz
  640x360 (0x93) 31.875MHz +HSync -VSync DoubleScan
        h: width   640 start  664 end  680 total  720 skew    0 clock  44.27KHz
        v: height  360 start  361 end  364 total  370           clock  59.83Hz
  640x360 (0x94) 18.000MHz -HSync +VSync
        h: width   640 start  664 end  720 total  800 skew    0 clock  22.50KHz
        v: height  360 start  363 end  368 total  376           clock  59.84Hz
  640x360 (0x95) 17.750MHz +HSync -VSync
        h: width   640 start  688 end  720 total  800 skew    0 clock  22.19KHz
        v: height  360 start  363 end  368 total  374           clock  59.32Hz
  512x384 (0x96) 32.500MHz -HSync -VSync DoubleScan
        h: width   512 start  524 end  592 total  672 skew    0 clock  48.36KHz
        v: height  384 start  385 end  388 total  403           clock  60.00Hz
  512x288 (0x97) 23.250MHz -HSync +VSync DoubleScan
        h: width   512 start  532 end  580 total  648 skew    0 clock  35.88KHz
        v: height  288 start  289 end  292 total  299           clock  60.00Hz
  512x288 (0x98) 21.000MHz +HSync -VSync DoubleScan
        h: width   512 start  536 end  552 total  592 skew    0 clock  35.47KHz
        v: height  288 start  289 end  292 total  296           clock  59.92Hz
  480x270 (0x99) 20.375MHz -HSync +VSync DoubleScan
        h: width   480 start  496 end  544 total  608 skew    0 clock  33.51KHz
        v: height  270 start  271 end  274 total  281           clock  59.63Hz
  480x270 (0x9a) 18.625MHz +HSync -VSync DoubleScan
        h: width   480 start  504 end  520 total  560 skew    0 clock  33.26KHz
        v: height  270 start  271 end  274 total  278           clock  59.82Hz
  400x300 (0x9b) 20.000MHz +HSync +VSync DoubleScan
        h: width   400 start  420 end  484 total  528 skew    0 clock  37.88KHz
        v: height  300 start  300 end  302 total  314           clock  60.32Hz
  400x300 (0x9c) 18.000MHz +HSync +VSync DoubleScan
        h: width   400 start  412 end  448 total  512 skew    0 clock  35.16KHz
        v: height  300 start  300 end  301 total  312           clock  56.34Hz
  432x243 (0x9d) 16.250MHz -HSync +VSync DoubleScan
        h: width   432 start  444 end  484 total  536 skew    0 clock  30.32KHz
        v: height  243 start  244 end  247 total  253           clock  59.92Hz
  432x243 (0x9e) 15.250MHz +HSync -VSync DoubleScan
        h: width   432 start  456 end  472 total  512 skew    0 clock  29.79KHz
        v: height  243 start  244 end  247 total  250           clock  59.57Hz
  320x240 (0x9f) 12.587MHz -HSync -VSync DoubleScan
        h: width   320 start  328 end  376 total  400 skew    0 clock  31.47KHz
        v: height  240 start  245 end  246 total  262           clock  60.05Hz
  360x202 (0xa0) 11.250MHz -HSync +VSync DoubleScan
        h: width   360 start  372 end  404 total  448 skew    0 clock  25.11KHz
        v: height  202 start  204 end  206 total  211           clock  59.51Hz
  360x202 (0xa1) 10.875MHz +HSync -VSync DoubleScan
        h: width   360 start  384 end  400 total  440 skew    0 clock  24.72KHz
        v: height  202 start  204 end  206 total  209           clock  59.13Hz
  320x180 (0xa2)  9.000MHz -HSync +VSync DoubleScan
        h: width   320 start  332 end  360 total  400 skew    0 clock  22.50KHz
        v: height  180 start  181 end  184 total  188           clock  59.84Hz
  320x180 (0xa3)  8.875MHz +HSync -VSync DoubleScan
        h: width   320 start  344 end  360 total  400 skew    0 clock  22.19KHz
        v: height  180 start  181 end  184 total  187           clock  59.32Hz
DP-1 disconnected (normal left inverted right x axis y axis)
	Identifier: 0x43
	Timestamp:  10971
	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: 
	Content Protection: Undesired 
		supported: Undesired, Desired, Enabled
	Broadcast RGB: Automatic 
		supported: Automatic, Full, Limited 16:235
	audio: auto 
		supported: force-dvi, off, auto, on
	link-status: Good 
		supported: Good, Bad
	CONNECTOR_ID: 78 
		supported: 78
	non-desktop: 0 
		range: (0, 1)
HDMI-1 disconnected (normal left inverted right x axis y axis)
	Identifier: 0x44
	Timestamp:  10971
	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: 
	Content Protection: Undesired 
		supported: Undesired, Desired, Enabled
	content type: No Data 
		supported: No Data, Graphics, Photo, Cinema, Game
	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
	link-status: Good 
		supported: Good, Bad
	CONNECTOR_ID: 84 
		supported: 84
	non-desktop: 0 
		range: (0, 1)
DP-2 disconnected (normal left inverted right x axis y axis)
	Identifier: 0x45
	Timestamp:  10971
	Subpixel:   unknown
	Clones:     HDMI-2
	CRTCs:      0 1 2
	Transform:  1.000000 0.000000 0.000000
	            0.000000 1.000000 0.000000
	            0.000000 0.000000 1.000000
	           filter: 
	Content Protection: Undesired 
		supported: Undesired, Desired, Enabled
	Broadcast RGB: Automatic 
		supported: Automatic, Full, Limited 16:235
	audio: auto 
		supported: force-dvi, off, auto, on
	link-status: Good 
		supported: Good, Bad
	CONNECTOR_ID: 89 
		supported: 89
	non-desktop: 0 
		range: (0, 1)
HDMI-2 disconnected (normal left inverted right x axis y axis)
	Identifier: 0x46
	Timestamp:  10971
	Subpixel:   unknown
	Clones:     DP-2
	CRTCs:      0 1 2
	Transform:  1.000000 0.000000 0.000000
	            0.000000 1.000000 0.000000
	            0.000000 0.000000 1.000000
	           filter: 
	Content Protection: Undesired 
		supported: Undesired, Desired, Enabled
	content type: No Data 
		supported: No Data, Graphics, Photo, Cinema, Game
	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
	link-status: Good 
		supported: Good, Bad
	CONNECTOR_ID: 94 
		supported: 94
	non-desktop: 0 
		range: (0, 1)

There are no additional displays / devices connected to the laptop.

The monitor is detected and works on a desktop PC running LMDE 3; when connected to the PC, the only quirk is that is that it gives a faulty EDID when running get-edid:

Code: Select all

~$ sudo get-edid | parse-edid 
This is read-edid version 3.0.2. Prepare for some fun.
Attempting to use i2c interface
Looks like no busses have an EDID. Sorry!
Attempting to use the classical VBE interface

	Performing real mode VBE call
	Interrupt 0x10 ax=0x4f00 bx=0x0 cx=0x0
	Function supported
	Call successful

	VBE version 300
	VBE string at 0xc907c "Intel(R) HSW Mobile/Desktop Graphics Chipset Accelerated VGA BIOS"

VBE/DDC service about to be called
	Report DDC capabilities

	Performing real mode VBE call
	Interrupt 0x10 ax=0x4f15 bx=0x0 cx=0x0
	Function supported
	Call successful

	Monitor and video card combination does not support DDC1 transfers
	Monitor and video card combination does not support DDC2 transfers
	0 seconds per 128 byte EDID block transfer
	Screen is not blanked during DDC transfer

Reading next EDID block

VBE/DDC service about to be called
	Read EDID

	Performing real mode VBE call
	Interrupt 0x10 ax=0x4f15 bx=0x1 cx=0x0
	Function supported
	Call failed

The EDID data should not be trusted as the VBE call failed
Error: output block unchanged
I'm sorry nothing was successful. Maybe try some other arguments
if you played with them, or send an email to Matthew Kern <pyrophobicman@gmail.com>.

As I mentioned in the beginning, when I connect a TV to the laptop's HDMI port it works normally, which suggests that the laptop's HDMI port is not broken.

The cable I have been using is the same that works when connecting laptop -> TV, and when connecting desktop PC -> LG monitor; I have also tried a different cable, with the same results.

What I have tried so far:

booting through live USBs (LMDE 3, LMDE 4, Ubuntu 20.04): same result
changing settings under the "Config / Display" section of the BIOS (changing "Boot display device" to "External display", "Boot time extension" to "10 seconds", "Shared display priority" to "HDMI"): tried a few combinations, same result
adding video=... parameter in Grub, as per this post (tried with DP-1, DP-2, HDMI-A-1, HDMI-A-2...): problem remained (in some attempts, the laptop's display got flickering and xrandr output changed)
- also tried some of the previous suggestions in that same post: switching Fn+F7, xset dpms force off
adding acpi_osi=! \"acpi_osi=Windows 2015\" parameter in Grub (following the procedure outlined in this post): same result
updating kernel to 5.4.0: same result
- ...and then creating /usr/share/X11/xorg.conf.d/20-intel.conf as per this post: xrandr listed a new output ("VIRTUAL1", disconnected), but the problem remained
turning the monitor on / off while the laptop is on; turning laptop and monitor on at the same time; turning monitor on 3s after the laptop: same result

Please feel free to ask for logs or additional details...

Post by **SMG** » Tue Sep 01, 2020 9:23 pm

Welcome to the forum, miguelsvieira.

You probably know way more about monitors than I do, but I want to learn more so I did a little research and found something I consider odd and wanted to pass along the links I found in case you might find them helpful.

I pulled up the User Manual for Thinkpad T480 and the section on Using an external display indicates:

Your computer supports the following video resolution, if the external display also supports that resolution.
• Up to 4096 x 2304 pixels / 60 Hz, with an external display connected to the USB-C or USB-C (Thunderbolt 3 compatible) connector
• Up to 4096 x 2160 pixels / 30 Hz with an external display connected to the HDMI connector

This page contains the Download for LG's owner's manual. Near the end of the manual on the specs page it lists the vertical frequency as 56Hz to 61Hz for HDMI. So basically 60Hz, but the Thinkpad manual only lists 30Hz for HDMI. Did you already address that somehow in xrandr or is that a possible reason for the lack of display?

On page 18 of the manual I found: "Note: If you use HDMI PC, it can cause compatibility problem." That's all the note said; I didn't notice any explanation of what that might mean, although perhaps it was on a page I didn't read.

I originally found specs for the monitor here LG 23MB35PH which didn't quite exactly match what I found in the LG manual, but I noticed something a bit odd. I noticed these specs say HDMI ports quantity is 1, but there is an x and no beside HDMI. There is check and yes for HDCP.

This article, HDCP and Potential Compatibility Issues indicates, "HDCP is relevant when you use a digital HDMI or DVI cable. If every product using these cables supports HDCP, then you shouldn't encounter any problems."

I'm wondering if that's related to the note in the LG manual regarding "can cause compatibility problem"?

jwiz · Post by **jwiz** » Wed Sep 02, 2020 5:39 am

Yep, running linux on notebook technology is a bad idea to begin with.
Something's gonna break for sure.

I've been running linux on various mini pcs (basically notbook tech crammed into a small box) over the years and had all sorts of problems with external displays.
Mainly because the kernel was for some part adressing the wrong (internal) LVDS display instead of the external one.
This issue was thought to be solved with HDMI but it isn't.
Currently, I have a LG HDMI display connected to my Thinkcentre 720q Tiny and on ocaasion I get the 'no signal' issue on boot still.
It usually resolves itself when I reboot the machine.

In the past I used to disable the LVDS display on the kernel line explicitly by setting 'video=LVDS-1:d'
Have you tried that already?

AndyMH · Post by **AndyMH** » Wed Sep 02, 2020 5:40 am

Your xrandr output indicates you have displayport? If so try a DP to HDMI cable. My T430 doesn't have HDMI so I connect to my LG ultrawide via a DP to HDMI cable.

miguelsvieira · Post by **miguelsvieira** » Wed Sep 02, 2020 8:22 pm

Thanks for your help and research, SMG!

SMG wrote: ⤴Tue Sep 01, 2020 9:23 pmSo basically 60Hz, but the Thinkpad manual only lists 30Hz for HDMI. Did you already address that somehow in xrandr or is that a possible reason for the lack of display?

If I understand the T480 manual correctly, that is up to 30Hz: in lower resolutions it should be able to reach 60Hz (on my desktop PC, xrandr says that's the frequency this monitor is running at). I also believe that the fact that xrandr doesn't even list HDMI as connected suggests that the laptop hasn't even got to the point where frequency is an issue (but that's really a guess).

On page 18 of the manual I found: "Note: If you use HDMI PC, it can cause compatibility problem." That's all the note said; I didn't notice any explanation of what that might mean, although perhaps it was on a page I didn't read.

Yeah, that's strange... the manual appears to have been poorly translated from another language.

I originally found specs for the monitor here LG 23MB35PH which didn't quite exactly match what I found in the LG manual, but I noticed something a bit odd. I noticed these specs say HDMI ports quantity is 1, but there is an x and no beside HDMI. There is check and yes for HDCP.

This article, HDCP and Potential Compatibility Issues indicates, "HDCP is relevant when you use a digital HDMI or DVI cable. If every product using these cables supports HDCP, then you shouldn't encounter any problems."

From what I could understand about HDCP, it shouldn't be an issue here: this monitor supports incoming HDCP-encrypted content (from something like a set-top box), but all monitors support regular, non-HDCP content -- which is probably what is being sent by a computer.

miguelsvieira · Post by **miguelsvieira** » Wed Sep 02, 2020 8:27 pm

AndyMH wrote: ⤴Wed Sep 02, 2020 5:40 am Your xrandr output indicates you have displayport? If so try a DP to HDMI cable. My T430 doesn't have HDMI so I connect to my LG ultrawide via a DP to HDMI cable.

Thanks, Andy -- yes, it has DisplayPort output via two USB-C connectors. I don't have an adapter at hand, but if I can't get the HDMI to work I'll buy one (as a last resort).

miguelsvieira · Post by **miguelsvieira** » Wed Sep 02, 2020 8:38 pm

jwiz wrote: ⤴Wed Sep 02, 2020 5:39 am Yep, running linux on notebook technology is a bad idea to begin with.
Something's gonna break for sure. [...] This issue was thought to be solved with HDMI but it isn't.

Surprisingly, the only issues I've had in the laptops I owned were with HDMI connections (VGA has always worked fine). (I might have been on the lucky side with GNU/Linux on laptops, as I've generally had a pretty good experience: my Asus EeePC even ran Linux-libre kernels, and everything worked practically out of the box!)

In the past I used to disable the LVDS display on the kernel line explicitly by setting 'video=LVDS-1:d'
Have you tried that already?

Thanks, just tried that; with "eDP-1" in that parameter (that's what shows up in xrandr) the laptop's display is disabled, but the external monitor still shows a "no signal" message.

jwiz · Post by **jwiz** » Thu Sep 03, 2020 3:31 am

xrandr shows only an X abstraction of your device.

Does your HDMI display get dectected at boot and only fails with X?
Judging from this output kernel doesn't seem to know, what to do with it and falls back to bios modes:
Display: x11 server: X.Org 1.20.4 driver: modesetting unloaded: fbdev,vesa resolution: 1920x1080~60Hz

Post by **SMG** » Thu Sep 03, 2020 9:14 am

jwiz wrote: ⤴Thu Sep 03, 2020 3:31 amJudging from this output kernel doesn't seem to know, what to do with it and falls back to bios modes:
Display: x11 server: X.Org 1.20.4 driver: modesetting unloaded: fbdev,vesa resolution: 1920x1080~60Hz

Modesetting is the display driver I normally see when people have the i915 device driver. What were you expecting to see as a display driver?

Graphics:
Device-1: Intel UHD Graphics 620 vendor: Lenovo driver: i915 v: kernel bus ID: 00:02.0 chip ID: 8086:5917
Display: x11 server: X.Org 1.20.4 driver: modesetting unloaded: fbdev,vesa resolution: 1920x1080~60Hz
OpenGL: renderer: Mesa DRI Intel UHD Graphics 620 (Kabylake GT2) v: 4.5 Mesa 18.3.6 compat-v: 3.0
direct render: Yes

miguelsvieira · Post by **miguelsvieira** » Thu Sep 03, 2020 9:26 am

jwiz wrote: ⤴Thu Sep 03, 2020 3:31 am Does your HDMI display get dectected at boot and only fails with X?

As far as I can tell, no -- the behavior of the monitor is the same while booting, before X and after X. I tried setting the BIOS to use the external monitor as the "boot display device", but it still gives me a "no signal" message when booting.

jwiz · Post by **jwiz** » Thu Sep 03, 2020 9:40 am

SMG wrote: ⤴Thu Sep 03, 2020 9:14 am
jwiz wrote: ⤴Thu Sep 03, 2020 3:31 amJudging from this output kernel doesn't seem to know, what to do with it and falls back to bios modes:
Display: x11 server: X.Org 1.20.4 driver: modesetting unloaded: fbdev,vesa resolution: 1920x1080~60Hz
Modesetting is the display driver I normally see when people have the i915 device driver. What were you expecting to see as a display driver?

Graphics:
Device-1: Intel UHD Graphics 620 vendor: Lenovo driver: i915 v: kernel bus ID: 00:02.0 chip ID: 8086:5917
Display: x11 server: X.Org 1.20.4 driver: modesetting unloaded: fbdev,vesa resolution: 1920x1080~60Hz
OpenGL: renderer: Mesa DRI Intel UHD Graphics 620 (Kabylake GT2) v: 4.5 Mesa 18.3.6 compat-v: 3.0
direct render: Yes

Oops, I read that wrong.
Modesetting is on.

jwiz · Post by **jwiz** » Thu Sep 03, 2020 9:53 am

miguelsvieira wrote: ⤴Thu Sep 03, 2020 9:26 am
jwiz wrote: ⤴Thu Sep 03, 2020 3:31 am Does your HDMI display get dectected at boot and only fails with X?
As far as I can tell, no -- the behavior of the monitor is the same while booting, before X and after X. I tried setting the BIOS to use the external monitor as the "boot display device", but it still gives me a "no signal" message when booting.

Could you try:
'for i in /sys/class/drm/card*/enabled; do echo -en "$i\t"; cat $i;done'
and post the output?

miguelsvieira · Post by **miguelsvieira** » Thu Sep 03, 2020 10:08 am

jwiz wrote: ⤴Thu Sep 03, 2020 9:53 am Could you try:
'for i in /sys/class/drm/card*/enabled; do echo -en "$i\t"; cat $i;done'
and post the output?

Sure! Here it is:

Code: Select all

/sys/class/drm/card0-DP-1/enabled	disabled
/sys/class/drm/card0-DP-2/enabled	disabled
/sys/class/drm/card0-eDP-1/enabled	enabled
/sys/class/drm/card0-HDMI-A-1/enabled	disabled
/sys/class/drm/card0-HDMI-A-2/enabled	disabled

jwiz · Post by **jwiz** » Thu Sep 03, 2020 10:13 am

Could you try to force HDMI by putting 'video=HDMI-A-1:e' and 'video=HDMI-A-2:e' onto the kernel line at boot to see if that changes anything?

miguelsvieira · Post by **miguelsvieira** » Thu Sep 03, 2020 11:10 am

jwiz wrote: ⤴Thu Sep 03, 2020 10:13 am Could you try to force HDMI by putting 'video=HDMI-A-1:e' and 'video=HDMI-A-2:e' onto the kernel line at boot to see if that changes anything?

Now xrandr lists them as "connected", with the following modelines:

Code: Select all

   1024x768      60.00  
   800x600       60.32    56.25  
   848x480       60.00  
   640x480       59.94

However, when I enable HDMI-1 or HDMI-2 the monitor still shows the "no signal" message. I also tried adding (to HDMI-2 and HDMI-1) the 1920x1080 modeline this monitor is used at on my desktop, still no changes.

jwiz · Post by **jwiz** » Thu Sep 03, 2020 12:10 pm

No clue atm.
Just for the sake of asking, what happens if you close the lid?
Does the external monitor come up?

miguelsvieira · Post by **miguelsvieira** » Thu Sep 03, 2020 3:32 pm

jwiz wrote: ⤴Thu Sep 03, 2020 12:10 pm Just for the sake of asking, what happens if you close the lid?
Does the external monitor come up?

When the system suspends, nothing changes in the monitor ("no signal" message remains).

Thanks for your effort! Let me know if / when you have any other ideas...

miguelsvieira · Post by **miguelsvieira** » Tue Sep 08, 2020 6:29 pm

Ok, so I've done some other tests and had a slightly better result.

Let me start by the test that failed. I've tried connecting the LG monitor through USB-C, using a hub (very similar to this one); no go, same results.

Now, two successful tests, but with other monitors: succeeded in connecting another Panasonic TV via HDMI, and succeeded with another Samsung monitor via HDMI (but with a female-HDMI-to-male-DVI passive adapter (much like this one), as the monitor had DVI input but no HDMI).

And finally, a small advance in a test with the LG monitor. Aside from HDMI, this monitor also has VGA and DVI input; if I connect it using the monitor's DVI input (via an HDMI cable plus the DVI-HDMI adapter above), the laptop detects the monitor: it shows up in xrandr as HDMI-2 (with adequate modelines, and even EDID when I run xrandr --verbose). However, the monitor still shows a "no signal" message, even after switching inputs in the monitor and turning it off and on again, and disabling and enabling it in xrandr. It's also correctly detected if I plug that HDMI cable + adapter to the USB-C hub (it is then detected as DP-1 or DP-2 output in xrandr), but the "no signal" message remains.

If anyone has ideas of additional things to try, please let me know (I'd love to be able to use this monitor).

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