I have a Dell laptop with Intel Iris Xe graphics (Raptor Lake / RPL-U) running **Ubuntu 24.04** (kernel 6.8.0-100-generic, Mesa 25.2.8).

My external monitor is a **2560×1080** (21:9 ultrawide).

The monitor works fine at 1920×1080@60Hz, but I cannot force the native resolution 2560×1080 using xrandr — I always get:

xrandr: Configure crtc 1 failed

What I've already tried (all combinations fail with the same error):

- Multiple reduced blanking modelines from `cvt -r 2560 1080 60` (181.25 MHz)

- Even lower clocks: 173 MHz, 170 MHz, 168 MHz, etc.

- Lower refresh rates: 59 Hz, 59.94 Hz, 55 Hz, 50 Hz, 40 Hz, 30 Hz (down to ~106 MHz pixel clock)

- Inverting sync polarities (+hsync/-vsync → -hsync/+vsync)

- Kernel parameters: `i915.enable_psr=0`, `i915.fastboot=1`, `i915.edp_vswing=2` (tried separately and combined)

- Different modelines generated by cvt, gtf, and manual tweaks

Important context:

- I **previously had 2560×1080 working perfectly** on this exact same laptop + same monitor + same cable

- I used a custom xrandr modeline (reduced blanking) that worked at the time

- After breaking GNOME and reinstalling/updating the system, I lost the ability to set it

- The monitor **does not advertise 2560×1080** in EDID (it's a common ultrawide behavior), so custom modelines are required

- HDMI cable is good quality (High Speed HDMI), no adapter

Current xrandr output:

HDMI-1 connected 1920x1080+0+0 (normal left inverted right axis y axis) 800mm x 340mm
1920x1080 59.96*+
... many lower resolutions ...

Example of one modeline I'm trying (the one that used to work):

```bash

xrandr --newmode "2560x1080_60" 181.25 2560 2608 2640 2720 1080 1083 1093 1111 +hsync -vsync

xrandr --addmode HDMI-1 "2560x1080_60"

xrandr --output HDMI-1 --mode "2560x1080_60"

→ Configure crtc 1 failed