LG CX HDMI 2.1 40Gbps, HDR, VRR

Graphics / Linux Linux
1

Hello,

I’m experiencing an issue where I’m unable to activate HDR in combination with VRR in KDE Plasma (Wayland) when my laptop is connected to an LG CX TV. Enabling HDR works under specific conditions, but enabling VRR with it causes a driver error.

Error Messages

When I try to enable HDR and VRR at 4K 100Hz/120Hz, I get this error from the KDE display configuration:

Couldn’t apply display configuration: The driver rejected the output configuration

At the same time, dmesg reports the following kernel error:

[drm:nv_drm_gem_alloc_nvkms_memory_ioctl [nvidia_drm]] ERROR [nvidia-drm] [GPU ID 0x00000100] Failed to allocate NVKMS memory for GEM object

System Information

  • GPU: NVIDIA GeForce RTX 3070 Mobile (Intel iGPU is disabled)

  • NVIDIA Driver: 580.82.09

  • CUDA Version: 13.0

  • Desktop Environment: KDE Plasma (Wayland)

  • Monitor: LG CX (Firmware 4.63.25)

  • Interface: HDMI 2.1 (Monitor’s port is limited to 40Gbps)

Troubleshooting and Observations

  • Partial Success (Updated): After updating the monitor’s firmware to 4.63.25, the situation has improved. I can now successfully run 4K at 100Hz with HDR enabled. However, enabling VRR at this resolution and refresh rate still fails. This is an improvement from the previous state, which was limited to 4K 60Hz.

  • Works on Different Monitor: The issue does not occur with an LG C2 TV, which has a full 48Gbps HDMI 2.1 port. HDR and VRR work perfectly on it.

  • Cables Tested: I’ve tested multiple certified HDMI 2.1 cables and also tried connecting via a Thunderbolt to HDMI adapter, but the problem persists.

The monitor firmware update has helped, but the driver still seems unable to handle VRR in combination with a high-bandwidth HDR signal (4K 100Hz) on the LG CX’s 40Gbps connection.

nvidia-bug-report.log.gz (530.8 KB)

2

The C1 in also only 40Gbit hdmi 2.1…

3

My apologies for the mistake. I was in a hurry and using someone else’s monitor. I couldn’t find the model number and guessed it was a LG C1 42. After unmounting the TV to check the back, I can confirm it is an LG C2 42 with 48gbps port. I how ever sure it was a 48 gbps port

5

I contacted Lenovo support and my HDMI port is only 32Gbps bandwidth. there fore i am experience alot of issues. the solution is to not buy a lenovo.

6

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