Blackwell cannot do 7680x2160p@240hz via DP2.1 on Linux

[matte-schwartz]

NVIDIA Open GPU Kernel Modules Version

570.133.07

Please confirm this issue does not happen with the proprietary driver (of the same version). This issue tracker is only for bugs specific to the open kernel driver.

• [x] I confirm that this does not happen with the proprietary driver package.

Operating System and Version

CachyOS

Kernel Release

6.13.7-3-cachyos

Please confirm you are running a stable release kernel (e.g. not a -rc). We do not accept bug reports for unreleased kernels.

• [x] I am running on a stable kernel release.

Hardware: GPU

NVIDIA GeForce RTX 5090 (UUID: GPU-addf70ec-1a4e-f8db-39bc-59d1ab271798)

Describe the bug

When connecting my RTX 5090 to my Samsung G95NC running Plasma 6 Wayland, I am unable to utilize my monitor's 7680x2160@240hz modeset via DisplayPort 2.1 on Linux. Instead it caps out at 7680x2160p@60Hz. However, using the same cable on Windows with my 5090 does work at that same full resolution and refresh rate.

Monitor link: https://www.samsung.com/us/computing/monitors/gaming/57-odyssey-neo-g9-dual-4k-uhd-quantum-mini-led-240hz-1ms-hdr-1000-curved-gaming-monitor-ls57cg952nnxza/ DisplayPort 2.1 cable link: https://www.amazon.com/dp/B0DQ7KY639

To Reproduce

1. Connect RTX 5090 to Samsung G95NC via DisplayPort 2.1 cable
2. Make sure the G95NC is in 240Hz mode in the monitor's Menu -> Game -> Refresh Rate and DP 2.1 mode in Menu -> System -> DisplayPort. Ver.
3. Turn on the PC and log into Plasma 6 Wayland

KDE's display settings should report the monitor only supporting a static 60Hz rather than letting you choose between 60Hz and 240Hz like it does on Windows.

Bug Incidence

Always

nvidia-bug-report.log.gz

nvidia-bug-report.log.gz

More Info

Linux screenshot of monitor settings in 240Hz mode:

Windows screenshot of monitor settings in 240Hz mode:

[abchauhan-nv]

Hi @matte-schwartz , Thank you for the report. Tracking this on internal bug - #5185798.

[matte-schwartz]

I booted with drm.debug=0x1e and grabbed a new NVIDIA bug report:

nvidia-bug-report.log.gz

It looks like it's not recognizing 7680x2160@240 as a mode at all in drm_helper_probe_single_connector_modes, although when I probe the edid and decode it with di-edid-decode everything looks fine with the edid itself: edid-decode-240.log

Since I can switch my monitor to a separate 120/60Hz mode with its own edid, and on that mode 120Hz and 60Hz both work, I'm including a readout of that edid too in case it has any useful information about why this 120/60Hz mode works perfectly on Linux while the 240Hz/60Hz mode does not: edid-decode-120.log

[abchauhan-nv]

Can you please check if loading nvidia-modeset with overlay_layers_enabled set to 0 allow 7840x2160@240?

[matte-schwartz]

/sys/module/nvidia_modeset/parameters/enable_overlay_layers:N doesn't appear to have made a difference in the issue.

nvidia-bug-report.log.gz

[matte-schwartz]

I installed plasma-x11 to take a look at nvidia-settings, and this actually might explain things:

Is the driver possibly limited to only UHBR10 on DP2.1 right now? 4 lanes x 10Gbps would make sense if that's the case which would also explain why the 7680x2160@120Hz mode does work, since even Displayport 1.4 can handle that with DSC. 7680x2160p@240Hz requires at least UHBR13.5.

Is there an easy way to check this information on Windows to compare it against Linux via NVIDIA tooling? When I checked with GPU-Z in my 7680x2160@240Hz mode I got but that Link Rate (current) number doesn't really make sense:

[matte-schwartz]

I ended up getting a second DisplayPort 2.1 compatible monitor, the LG 45gx950a-b, which has a maximum resolution/refresh rate of 5120x2160p@165Hz. On this monitor I'm able to select that highest modeset without any issues.

nvidia-bug-report.log.gz

[Sewer56]

I bought and installed a 5080 earlier today and can confirm I have ran into the same issue myself. Same display, different Blackwell card. Tried on latest 575.51.02. Windows driver works as expected, but not Linux.

Not much I can otherwise add, but it does feel a bit disappointing after buying the GPU specifically for DP2.1 support.

[Sewer56]

Potentially worth noting; I use the same display as the person who opened the issue. And (almost) the same cable, just the DP54 certified variant of the cable, rather than the DP80 one; as I needed 3 meters.

[Mattheish]

I have exactly the same issue, with same monitor, GPU and cable. If necessary I can also provide some logs.

[getcontext]

Same here. Tried xrandr to force refresh rate but no luck. Also I can have 8k only on nvidia-open drivers. When I install standard then 1024px resolution

After switching off "Adaptive sync" in my monitor, I was able to set refresh to 120 if this helps anyone.

[Mattheish]

Problem still exists for me under Driver Version: 575.57.08

[Rivelia]

Problem still persists for me as well.

[Mattheish]

Just tested again with beta driver version: 580.65.06, kernel version 6.16 and still stuck at 60 Hz

[Sewer56]

We should have bought AMD 🤣

[vonswoopington]

I am having the same issue with driver version 580.76.05 on CachyOS. I have the same monitor and cable as OP and I am using a nvidia 5090 FE.

[bugfixin]

Same issue here - I have a thought that it may be related to DSC (as even 80gbps may not be able to drive the 2x4k@240hz the monitor can handle). I've tried a wide variety of cables which all work in windows and are labeled as "DP2.1 80gbps" cables, including the one that came with the monitor (A samsung LS57CG952NNXZA, AKA G95NC). I can confirm I can get 120HZ refresh rates when I disable VRR in the monitor OSD, but no more. This behavior persists in X and Wayland, with driver version 580.82.07 and on kernels as recent as 6.16.3

I will note that the same cable and monitor works at full 240hz under linux with a 7900XTX so it was surprising to me that it doesn't work with the 5090.

[bugfixin]

I've also tried this with monitor firmware versions 1005.3 and 1007.0.

The monitor OSD has options for "Adaptive sync" [on/off] and when that option is set to "ON", The OSD displays an option for refresh rate [120/240]. This changes the maximum selectable refresh rate in linux, but no combinations allow for 240hz.

Adaptive Sync in Monitor OSD	Refresh Rate selection in Monitor OSD	Maximum mode selectable in linux	Adaptive Sync Selectable in linux
ON	240	7840x2160@60hz	YES
ON	120	7840x2160@120hz	YES
OFF	N/A	7840x2160@120hz	NO

Italics where refresh rate maximums are lower than expected.

I am including the edid-decodes for the different OSD settings (Adaptive sync OFF, Adaptive Sync ON+refresh120, and Adaptive sync ON+refresh240) adaptivesyncoff.log adaptivesyncon-120.log adaptivesyncon-240.log

[AxoyTO]

I can also confirm that this is the case for my setup with RTX 5090 and Samsung Neo G9 57".

Having set the refresh rate to 240Hz on the monitor settings, I can easily get it at 7680x2160 on Windows 11. However, the same settings do not work on Linux. Maximum I can go on Linux is 120Hz.

Driver Version: 575.64.03

[ZlordHUN]

Same issue here.

[Shenmarukai]

Same issue here. Switched from a RTX 3090 to a RTX 5090 expecting to finally be able to run 7680x2160@240hz on my Samsung Neo G9 57" only to end up here after trying to figure out why it wasn't working. 😮‍💨

Driver Version: 580.65.06

[nmahale]

@matte-schwartz Could you please verify if omitting the maximum pixel clock check resolves the issue? You can add the following option to the “Screen” section of the /ext/X11/xorg.conf or the “OutputClass” section of the /usr/share/X11/xorg.conf.d/nvidia-drm-outputclass.conf file:

Option "ModeValidation" "NoMaxPClkCheck"

[matte-schwartz]

Hi @nmahale, I've actually got the monitor boxed up to sell at the moment but if no one else in the thread follows up I will unbox it and try your suggestion during the week.

[vonswoopington]

@matte-schwartz Could you please verify if omitting the maximum pixel clock check resolves the issue? You can add the following option to the “Screen” section of the /ext/X11/xorg.conf or the “OutputClass” section of the /usr/share/X11/xorg.conf.d/nvidia-drm-outputclass.conf file:

Option "ModeValidation" "NoMaxPClkCheck"

I made the change to the 10-nvidia-drm-outputclass.conf file as shown below. I rebooted afterwards but still have no option for 240hz at 7680 x 2160.

Section "OutputClass"
    Identifier "nvidia"
    MatchDriver "nvidia-drm"
    Driver "nvidia"
    Option "AllowEmptyInitialConfiguration"
    ModulePath "/usr/lib/nvidia/xorg"
    ModulePath "/usr/lib/xorg/modules"
    Option "ModeValidation" "NoMaxPClkCheck"
EndSection

CachyOS latest with Nvidia 580.95.05

[matte-schwartz]

you checked that on an x11 session, right? I'd expect that does not change anything on Wayland sessions.

[vonswoopington]

you checked that on an x11 session, right? I'd expect that does not change anything on Wayland sessions.

Thank you for making me double check! It actually is running at 240hz in Plasma (X11) and not Wayland as you mentioned.

screenshot for @nmahale

[nmahale]

Thank you, @vonswoopington and @matte-schwartz , for your assistance. We are actively working to resolve this issue.

[vonswoopington]

Thank you, @vonswoopington and @matte-schwartz , for your assistance. We are actively working to resolve this issue.

Thank you! Please let me know if you need any additional testing done.

[Sewer56]

Seems to work for X11 sessions on my end too- as an extra report.

[getcontext]

Yes it works, however tearing and lagging is a problem for me. On Wayland is much smoother and don't have tearing.

[vonswoopington]

Yes it works, however tearing and lagging is a problem for me. On Wayland is much smoother and don't have tearing.

i can confirm that I get tearing and lagging on x11 at 240hz but not on wayland even at 60hz.