Hi everyone,
I've been fighting this one for a while and could use some help — it really looks like a driver regression.
On my laptop the HDMI port is wired to the NVIDIA dGPU. An external monitor is detected perfectly (EDID read, all modes listed, the DRM connector shows connected/enabled/dpms On), but the monitor just sits on "No Signal". The desktop even thinks the screen is on, I can drag windows onto it, yet no image ever comes out. This exact monitor + cable worked on the factory image (older kernel + older NVIDIA driver) and still works on Windows, so the hardware is fine.
My setup:
- Laptop: Acer Nitro ANV15-41, BIOS Insyde V1.20 (no MUX / no "discrete only" option)
- dGPU: GeForce RTX 4050 Laptop / AD107M [10de:28a1] — the HDMI port is wired to this GPU
- iGPU: AMD Radeon 680M [1002:1681] — drives the internal laptop panel
- OS: Ubuntu 26.04, kernel 7.0.0-22-generic, GNOME 50.1 (Wayland; GNOME has no Xorg session anymore)
- NVIDIA driver: 595.71.05 (also tried 580.159.03 — exact same failure)
- nvidia-drm.modeset=1 is active, Secure Boot is off
The most telling clue (this is why I think it's the driver, not the compositor):
Even in a plain Xorg session with the NVIDIA driver driving its OWN HDMI connector (Option "PrimaryGPU" "yes"), the log says the monitor is connected and the mode is validated, but still nothing comes out the cable:
(--) NVIDIA(GPU-0): LG ULTRAWIDE (DFP-0): connected
(--) NVIDIA(GPU-0): LG ULTRAWIDE (DFP-0): Internal TMDS, 600.0 MHz maximum pixel clock
(II) NVIDIA(0): Setting mode "DFP-0:nvidia-auto-select"
(II) NVIDIA(0): Validated MetaModes: "DFP-0:nvidia-auto-select"
(II) NVIDIA(0): Virtual screen size determined to be 2560 x 1080
No NVRM/Xid errors anywhere — it fails silently. The internal panel (on the AMD iGPU) is the only thing that works; anything that needs the NVIDIA GPU to actually scan out a signal stays black.
Stuff I've already tried, so we can skip it:
- Different cable / monitor / both HDMI inputs — all fine on another PC and on Windows
- nvidia_modeset hdmi_deepcolor=0 — no change
- nvidia NVreg_EnableGpuFirmware=0 (GSP off, confirmed "GSP Firmware: N/A") — no change
- Forcing NVIDIA as the primary GPU in mutter (udev mutter-device-preferred-primary) — rendering
does move to NVIDIA (confirmed in glxinfo), but the HDMI still shows no signal
- Kernels 7.0.0-22, 7.0.0-14, and even mainline 6.12 — all fail with driver 580.159.03, so the
driver version (not just the kernel) seems to be the regressed piece
It really looks like the driver's display/scanout path stopped emitting a signal somewhere in the recent driver/kernel combos. Thanks a lot for taking a look! 🙏