[coreboot - Bug #589] (New) X230 eDP panel not detected by libgfxinit but works in Linux

[Jens Moelzer]

Issue #589 has been reported by Jens Moelzer.

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Bug #589: X230 eDP panel not detected by libgfxinit but works in Linux
https://ticket.coreboot.org/issues/589

* Author: Jens Moelzer
* Status: New
* Priority: Normal
* Target version: none
* Start date: 2025-04-09
* Affected versions: 25.03
* Affected hardware: X230 eDP
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I have a X230 with a eDP panel (LP125WF4-SPB1). My FHD mod board is self designed but somewhat similar to the nitrocaster mod (just much simpler). It takes DP_D from the docking port (2 lanes plus AUX plus HDP) and BACKLIGHT_ON + PANEL_BKLT_CTRL from the LVDS connector and connects everything directly to the eDP panel. It is totally passive and has no MCU and no EEPROM. I also attached the schematic (dasher-fhd.pdf).

The panel stays blank until Linux boots and from the debug output it seems libgfxinit does not detect it at all. Once drm/i915 in Linux takes over the panel starts up and works perfectly fine including backlight control. From the log it seems that coreboot/libgfxinit for some reason can't read the EDID but Linux has no problem reading the EDID. An external display attached to the mini-DP port is detected by libgfxinit and does work with coreboot.

I'm using coreboot 25.03 with "ThinkPad X230 eDP Mod (2K/FHD)" as mainboard and libgfxinit with linear framebuffer and edk2 payload. Though I also tried other payloads, gfx initialization settings, various changes to `gma-mainboard.ads`, `devicetree.cb` and other hacks I though worth a try. I also played around a lot with modifications to the VBT (explicitly configuring my panel including DTD, enabling edidless, ...). But nothing made any difference.

Attached you find a coreboot log with Ada debug enabled (cbmem.log) and a full Linux boot log with `drm.debug=0x1ff` (linux.log) from the same boot since I though it might help to see what i915 is doing to get the panel working.

---Files--------------------------------
cbmem.log (58.3 KB)
linux.log (301 KB)
dasher-fhd.pdf (74.4 KB)