[SOLVED] Blank screen on 2nd monitor (hdmi) after installing kernel low latency

[jeancre]

Hi !
First topic for me here ! I tried to find some answers in this sections but all sounds a bit tricky... Thanks for your help !
I use Mint 20.2, and I just installed the lowlatency kernel, useful for audio recordings mostly on reaper using jack. (I used sudo apt install linux-lowlatency)
So, my installed kernels are 5.4.0-91 and 5.4.0-91-lowlatency.
I can switch them when booting.

• With standard kernel selected, everything works just fine, the main screen and hdmi monitor are on.

• With lowlatency, the main screen is working, the hdmi one shows "no signal" for some seconds and remains blank screen.

I saw in some forums that this can be helpful :

Code: Select all

jean@jean-hp:~$ sudo lshw -C video
[sudo] password for jean:       
  *-display                 
       description: VGA compatible controller
       product: HD Graphics 620
       vendor: Intel Corporation
       physical id: 2
       bus info: pci@0000:00:02.0
       version: 02
       width: 64 bits
       clock: 33MHz
       capabilities: pciexpress msi pm vga_controller bus_master cap_list rom
       configuration: driver=i915 latency=0
       resources: irq:130 memory:b2000000-b2ffffff memory:c0000000-cfffffff ioport:5000(size=64) memory:c0000-dffff
  *-display
       description: 3D controller
       product: GM107M [GeForce GTX 950M]
       vendor: NVIDIA Corporation
       physical id: 0
       bus info: pci@0000:01:00.0
       version: a2
       width: 64 bits
       clock: 33MHz
       capabilities: pm msi pciexpress bus_master cap_list rom
       configuration: driver=nvidia latency=0
       resources: irq:134 memory:b3000000-b3ffffff memory:a0000000-afffffff memory:b0000000-b1ffffff ioport:4000(size=128) memory:b4080000-b40fffff

Thanks, all the best !

[SMG]

With lowlatency, the main screen is working, the hdmi one shows "no signal" for some seconds and remains blank screen.

Welcome to the forum, jeancre.

Often times, the HDMI port is run by the Nvidia graphics. It is possible the differences between the two kernels means the Nvidia modules may not be loading at the correct time to work properly.

Please boot into the low-latency kernel and provide the output of SMCGx so we can see if that might be the case. There is a potential fix if that is what is happening.

[jeancre]

Hi SMG !
Thanks for your answer.
So, I did this "inxi" command, with low latency boot !
Thanks !

Code: Select all

jean@jean-hp:~$ inxi -SMCGx
System:    Host: jean-hp Kernel: 5.4.0-91-lowlatency x86_64 bits: 64 compiler: gcc v: 9.3.0 Desktop: Cinnamon 5.0.7 
           Distro: Linux Mint 20.2 Uma base: Ubuntu 20.04 focal 
Machine:   Type: Laptop System: HP product: HP Pavilion Notebook v: Type1ProductConfigId serial: <superuser/root required> 
           Mobo: HP model: 8421 v: 65.09 serial: <superuser/root required> UEFI: Insyde v: F.57 date: 11/13/2017 
CPU:       Topology: Dual Core model: Intel Core i5-7200U bits: 64 type: MT MCP arch: Amber Lake rev: 9 L2 cache: 3072 KiB 
           flags: avx avx2 lm nx pae sse sse2 sse3 sse4_1 sse4_2 ssse3 vmx bogomips: 21599 
           Speed: 800 MHz min/max: 400/3100 MHz Core speeds (MHz): 1: 800 2: 800 3: 800 4: 800 
Graphics:  Device-1: Intel HD Graphics 620 vendor: Hewlett-Packard driver: i915 v: kernel bus ID: 00:02.0 
           Device-2: NVIDIA GM107M [GeForce GTX 950M] vendor: Hewlett-Packard driver: nvidia v: 470.86 bus ID: 01:00.0 
           Display: x11 server: X.Org 1.20.11 driver: modesetting unloaded: fbdev,vesa resolution: 1920x1080~60Hz 
           OpenGL: renderer: Mesa Intel HD Graphics 620 (KBL GT2) v: 4.6 Mesa 21.0.3 direct render: Yes 

[SMG]

So, I did this "inxi" command, with low latency boot !

That is unusual output. I presume the nvidia-prime-applet in the lower right of your screen is showing you are running in On-Demand mode because that is how one gets both the Nvidia and Intel device drivers to load (and it is what you want to be running to have both the laptop screen and HDMI port to work). Is that its current setting?

However, for some reason, neither the nvidia nor nouveau display drivers are loaded or unloaded. Only the Intel display driver is loaded.

Graphics:
Device-1: Intel HD Graphics 620 vendor: Hewlett-Packard driver: i915 v: kernel bus ID: 00:02.0
Device-2: NVIDIA GM107M [GeForce GTX 950M] vendor: Hewlett-Packard driver: nvidia v: 470.86 bus ID: 01:00.0
Display: x11 server: X.Org 1.20.11 driver: modesetting unloaded: fbdev,vesa resolution: 1920x1080~60Hz
OpenGL: renderer: Mesa Intel HD Graphics 620 (KBL GT2) v: 4.6 Mesa 21.0.3 direct render: Yes

Let's have you try the fix for what I thought might be the original issue anyway. It will not hurt your system and may help. Let us know if the fix roblm recommends in the second post addresses the issue for you.

If it does not, please post an updated inxi -Gx and use this command in a terminal to upload the X Server log file to termbin:
cat /var/log/Xorg.0.log | nc termbin.com 9999
It will return with a url address that you can post in your next reply.

[jeancre]

Hi again !
I will apply your recommendations but before to go further, I thought it was important to mention you some settings I did because of some suspend/resume issues. That was before installing the low latency kernel, (so, no idea if it can affect somehow my current issue ).

This forum helps me to fix this issues but I did this commands :

Code: Select all

sudo systemctl stop nvidia-suspend.service
sudo systemctl stop nvidia-hibernate.service
sudo systemctl stop nvidia-resume.service

sudo systemctl disable nvidia-suspend.service
sudo systemctl disable nvidia-hibernate.service
sudo systemctl disable nvidia-resume.service

And this

Code: Select all

sudo rm /lib/systemd/system-sleep/nvidia

As soon as i get your feedback on this, I focus on your last recommendations.

All the best.

[SMG]

Hi again !
I will apply your recommendations but before to go further, I thought it was important to mention you some settings I did because of some suspend/resume issues. That was before installing the low latency kernel, (so, no idea if it can affect somehow my current issue ).

My guess would be those command should affect your system regardless of which kernel you are using. You indicated the external monitor works when using the "normal" kernel, correct? If so, I would not think they should be related to this problem.

[jeancre]

HI SMG !
Solved !
I did add this three lines in this "modules" as roblm recommends, and my monitor turns on on low latency kernel boot.

Thanks again !
Have a nice evening.

Jean-Christophe.