Connected to 4k (3840x2160) monitor but I can only select upto 1920x1080 resolution

[NigelT]

Hello all,

I'm a new Pinebook Pro owner, new to this forum and this is my first post.

My PBP is connected to an LG 32UD89-W monitor via USB-C cable.

The cable goes direct from the PBP's USB-C port to the monitors USB-C port.  The USB-C cable is new and came included with the monitor.

It works but I'm limited to 1920x1080 resolution and unable to select the monitor's native 4k resolution.

This LG monitor is the only monitor I have that has a USB-C input (as well as HDMI inputs), and the PBP is the only device I have with a USB-C output.  My other devices (PCs and a Raspberry PI) have HDMI outputs and run this monitor OK at 4k.

The monitor is:
https://www.lg.com/us/monitors/lg-32UD89...ed-monitor

The PBP is running the default Debian OS plus MrFixit's updates as of 10 Jan 2019.

During boot the open sesame splash screen is mirrored on both the built-in panel and the external monitor, and so also is the login/ greeter screen that appears a couple of seconds later.

Once logged into the desktop the monitor resolution is only 1920x1080, not the native 4k/3840x2160.

Control Center->Displays, and xrandr report the resolution as 1920x1080, but do not offer any higher options.

I have turned the built-in panel off so the only output is the external monitor.

I can change resolutions of the monitor from a maximum of 1920x1080, though 1280x720 and 1024x768 to a minimum of 720x480.

However the resolution I want to use, 4k (3840x2160), is not available as an option.

xrandr shows the same mode options as the "Control Center" UI

Code:

rock@Debian-Desktop:~$ xrandr
Screen 0: minimum 320 x 200, current 1920 x 1080, maximum 8192 x 8192
eDP-1 connected (normal left inverted right x axis y axis)
   1920x1080     59.99 +
   1024x768      60.00  
   800x600       60.32    56.25  
   848x480       60.00  
   640x480       59.94  
DP-1 connected primary 1920x1080+0+0 (normal left inverted right x axis y axis) 600mm x 340mm
   1920x1080     60.00*+
   1280x720      60.00  
   1024x768      60.00  
   720x480       59.94  
rock@Debian-Desktop:~$

And this also agrees with

Code:

root@Debian-Desktop:~# cat /sys/devices/platform/display-subsystem/drm/card0/card0-DP-1/modes
1920x1080p60
1280x720p60
1024x768p60
720x480p60
root@Debian-Desktop:~# 

If I connect the same LG monitor to my other PC (via HMDI) or my Raspberry PI4B (via HDMI), it shows more modes (including 3840x2160), and I can select and use 4k resolution on these devices, just not the PBP.

Modes when plugged into a PI4B

Code:

root@raspberrypi:~# cat /sys/devices/platform/soc/soc:gpu/drm/card1/card1-HDMI-A-1/modes
3840x2160
2560x1440
1920x1080
1600x900
1280x1024
1280x800
1152x864
1280x720
1024x768
800x600
720x480
640x480

Something I've noticed on the PBP, but don't know if it is related, is the speeds below in dmesg, is this a negotiated USB-C speed? I wonder if my setup is negotiating a speed too slow for 4k?  (I know very little about about USB-C so am guessing at this)

Code:

root@Debian-Desktop:~# dmesg | grep -i mbps
[    4.274459] cdn-dp fec00000.dp: 1620Mbps x 4lanes
[   32.651935] cdn-dp fec00000.dp: 1620Mbps x 4lanes
[  342.594439] cdn-dp fec00000.dp: 1620Mbps x 4lanes
[ 3255.050333] cdn-dp fec00000.dp: 1620Mbps x 4lanes
[ 3261.161106] cdn-dp fec00000.dp: 1620Mbps x 4lanes
[ 3327.898880] cdn-dp fec00000.dp: 5400Mbps x 4lanes   <==== Note this is 5400 and the rest are 1620
[ 3359.093808] cdn-dp fec00000.dp: 1620Mbps x 4lanes
root@Debian-Desktop:~# 

Another thing I've noticed, but again do not know if it is related.  This monitor's EDID as returned to the PBP via USB-C is an EDID version 1.4 with a preferred mode of 6, whereas the EDID from the same monitor as returned to a Pi4 via HDMI is an EDID version 1.3 with a preferred mode of 10.

EDID as seen by PI4B over HDMI cable

Code:

root@raspberrypi:~# parse-edid < /sys/devices/platform/soc/soc:gpu/drm/card1/card1-HDMI-A-1/edid
Checksum Correct

Section "Monitor"
Identifier "LG Ultra HD"
ModelName "LG Ultra HD"
VendorName "GSM"
# Monitor Manufactured week 7 of 2018
# EDID version 1.3
# Digital Display
DisplaySize 600 340
Gamma 2.20
Option "DPMS" "true"
Horizsync 30-135
VertRefresh 48-61
# Maximum pixel clock is 600MHz
#Not giving standard mode: 1152x864, 60Hz
#Not giving standard mode: 1280x1024, 60Hz
#Not giving standard mode: 1280x720, 60Hz
#Not giving standard mode: 1600x900, 60Hz
#Not giving standard mode: 1920x1080, 60Hz
#Not giving standard mode: 1280x800, 60Hz

#Extension block found. Parsing...
#WARNING: I may have missed a mode (CEA mode 97)
#WARNING: I may have missed a mode (CEA mode 96)
#WARNING: I may have missed a mode (CEA mode 93)
#WARNING: I may have missed a mode (CEA mode 94)
#WARNING: I may have missed a mode (CEA mode 95)
Modeline "Mode 10" +hsync -vsync 
Modeline "Mode 0" +hsync +vsync 
Modeline "Mode 1" +hsync -vsync 
Modeline "Mode 2" 148.500 1920 2008 2052 2200 1080 1084 1089 1125 +hsync +vsync
Modeline "Mode 3" 74.250 1920 2008 2052 2200 1080 1084 1089 1125 +hsync +vsync
Modeline "Mode 4" 74.250 1920 2558 2602 2750 1080 1084 1089 1125 +hsync +vsync
Modeline "Mode 5" 74.250 1920 2008 2052 2200 1080 1082 1087 1125 +hsync +vsync interlace
Modeline "Mode 6" 74.250 1280 1390 1420 1650 720 725 730 750 +hsync +vsync
Modeline "Mode 7" 27.027 720 736 798 858 480 489 495 525 -hsync -vsync
Modeline "Mode 8" 27.027 720 736 798 858 480 489 495 525 -hsync -vsync
Modeline "Mode 9" 25.200 640 656 752 800 480 490 492 525 -hsync -vsync
Modeline "Mode 11" +hsync -vsync 
Option "PreferredMode" "Mode 10"
EndSection
root@raspberrypi:~# 

Whereas EDID as seen by PBP over USB-C

Code:

root@Debian-Desktop:~# parse-edid < /sys/devices/platform/display-subsystem/drm/card0/card0-DP-1/edid
Checksum Correct

Section "Monitor"
Identifier "LG Ultra HD"
ModelName "LG Ultra HD"
VendorName "GSM"
# Monitor Manufactured week 7 of 2018
# EDID version 1.4
# Digital Display
DisplaySize 600 340
Gamma 2.20
Option "DPMS" "true"
Horizsync 30-135
VertRefresh 56-61
# Maximum pixel clock is 560MHz
#Not giving standard mode: 1152x864, 60Hz
#Not giving standard mode: 1280x1024, 60Hz
#Not giving standard mode: 1280x720, 60Hz
#Not giving standard mode: 1600x900, 60Hz
#Not giving standard mode: 1920x1080, 60Hz
#Not giving standard mode: 1280x800, 60Hz

#Extension block found. Parsing...
Modeline "Mode 6" +hsync +vsync 
Modeline "Mode 0" +hsync -vsync 
Modeline "Mode 1" +hsync -vsync 
Modeline "Mode 2" 148.500 1920 2008 2052 2200 1080 1084 1089 1125 +hsync +vsync
Modeline "Mode 3" 74.250 1280 1390 1420 1650 720 725 730 750 +hsync +vsync
Modeline "Mode 4" 27.027 720 736 798 858 480 489 495 525 -hsync -vsync
Modeline "Mode 5" 25.200 640 656 752 800 480 490 492 525 -hsync -vsync
Modeline "Mode 7" +hsync -vsync 
Option "PreferredMode" "Mode 6"
EndSection

Is there something extra I need to do to enable 4k / 3840x2160 resolution via USB-C on an external monitor ?

In the meantime I'm going to purchase a USB-C to HDMI adapter and see if that makes a difference.

[Arwen]

From reading the monitor's manual, it does seem like it should work. It's possible it's a software issue on the Pinebook Pro.

If you do buy an adapter, make sure you buy a USB-C to alternate mode Display Port. (Make sure it supports 4 lanes / 4K @ 60hz.) Then use a Display Port to Display Port cable.

In theory you can get a USB-C to alternate mode Display Port, but with a built in active converter to HDMI. However, this makes little sense, because the Pinebook Pro and your monitor have native Display Port options.

Last, if you want 4K @ 60hz, any USB C dock on your Pinebook Pro must be limited to USB 2 speeds. Meaning the two USB 3 lanes would be needed for the video. There are a few out there, either fixed at USB 2 speeds, or have a switch to enable / disable USB 3.

[brownbike]

NigelT, have you made any headway on this? I'm in the same boat, where I'm connection to a 4K monitor over USB-C and I'm only getting 1080 resolution.

[NigelT]

NigelT, have you made any headway on this? I'm in the same boat, where I'm connection to a 4K monitor over USB-C and I'm only getting 1080 resolution.

I didn't manage to get 4k output directly USB-C to USB-C, but I managed to get 4k output via a USB-C to HDMI adapter (adapter in the PBP's USB-C port then an HDMI cable to an HDMI port on the monitor).  Although I found the right third of the external 4k screen to be corrupted if running dual (internal panel + external 4k) displays, but fine if I turned off the internal panel.

The adapter I'm using is https://www.ebuyer.com/797322-xenta-usb-...chdmiadptr

lsusb shows the device ids as 9636:9300

I can't fully recommend that adapter though as I have access to a few other monitors with different native resolutions, 1600x1200 and 1920x1200, and it was unable to run those monitors at their native resolutions (running a 1920x1200 monitor at a sub-optimal 1920x1080) when using the default Debian 9 based OS.  Interestingly I tried the Debian Buster OS (newer kernel) and could use those 1600x1200 and 1920x1200 resolutions (as well as 4k) with the same PBP and same USB-C 9636:9300 adapter - but still no 4k using just a USB-C adapter.

[xmixahlx]

I will find a 4k monitor to test. I am guessing my install and adapter will work based on previous success in testing FHD with audio...