https://bugs.kde.org/show_bug.cgi?id=528038
Bug ID: 528038
Summary: Black screen after graphical login when KWin starts on
the secondary GPU (Optimus, i915 panel not on nouveau
card)
Classification: Plasma
Product: plasmashell
Version First 6.8.1
Reported In:
Platform: CachyOS
OS: Linux
Status: REPORTED
Severity: normal
Priority: NOR
Component: Power management & brightness
Assignee: [email protected]
Reporter: [email protected]
Target Milestone: 1.0
Created attachment 197835
--> https://bugs.kde.org/attachment.cgi?id=197835&action=edit
Applying output configuration failed: EACCESS, There are no outputs - creating
placeholder screen, Could not find edid ... VGA-1
STEPS TO REPRODUCE
1. Boot a Dell Inspiron 5420 (Intel HD 4000 + NVIDIA GF108M, Optimus) with
Plasma 6.8.1 on Wayland, plasmalogin as display manager, nouveau for the
NVIDIA GPU.
2. Log in to a Plasma session from the greeter.
OBSERVED RESULT
After authentication the internal panel (LVDS-1) goes dark and stays off; the
session is unusable. The backlight is still on
(/sys/class/backlight/intel_backlight/brightness = 4540/4882), so the panel is
powered but nothing is driving it. Recovering requires switching to a VT
(Ctrl+Alt+F3). The machine rebooted 8 times in 70 minutes because of this.
KWin picks /dev/dri/card0 as its DRM device. Which card is card0 changes
between boots, because the driver that takes over the minor previously owned
by simpledrm is enumerated first:
[drm] Initialized simpledrm 1.0.0 ... on minor 0
[drm] Initialized i915 1.6.0 ... on minor 1
[drm] Initialized nouveau 1.4.2 ... on minor 0
Connector layout: LVDS-1 (1366x768 panel) is only exposed by the Intel GPU
(boot_vga = 1); the NVIDIA GPU only exposes VGA-2. On boots where KWin runs on
card0 (nouveau) there is no connector for the laptop panel at all:
card0-VGA-2 connected (nouveau, no EDID)
card1-LVDS-1 connected (i915, 1366x768)
kwin_wayland[740]: No backend specified, automatically choosing drm
kwin_wayland[740]: drmSetClientCap for Atomic Mode Setting failed. Using
legacy mode on GPU "/dev/dri/card0"
kwin_wayland[740]: Could not find edid for connector DrmConnector(id=45,
gpu="/dev/dri/card0", name="VGA-2", connection="Connected", countMode=5)
kwin_wayland[740]: Invalid framebuffer status:
"GL_FRAMEBUFFER_INCOMPLETE_ATTACHMENT"
kwin_wayland[740]: Applying output configuration failed: EACCESS
On a boot where KWin did pick the Intel card, the saved output configuration
was applied and it disabled the panel and enabled a connector that reports
"connected" without EDID (0 bytes), so again no usable output:
kwin_wayland[737]: ... Using legacy mode on GPU "/dev/dri/card1"
kwin_wayland[737]: Could not find edid for connector DrmConnector(id=45,
gpu="/dev/dri/card1", name="VGA-1", connection="Connected", countMode=5)
kwin_wayland[737]: Applying output configuration failed: EACCESS
~/.config/kwinoutputconfig.json at that point had LVDS-1 disabled and only
VGA-1 enabled, in both the lid-open and lid-closed setups.
EXPECTED RESULT
KWin picks a GPU that can drive the internal panel (the boot_vga device) and
never ends up with zero enabled outputs while a connector is connected.
The unused/EDID-less VGA connector should not replace the internal panel.
```
## Additional information
```
Distribution: CachyOS (Arch-based, rolling)
Kernel: 7.2.7-1-cachyos
KWin/Plasma: 6.8.1 (kwin 6.8.1-2), Wayland session
Display manager: plasmalogin 6.8.1-1
Mesa: 26.2.4
GPUs: 00:02.0 Intel Ivy Bridge HD 4000 (i915, boot_vga=1)
01:00.0 NVIDIA GF108M GT 620M (nouveau, boot_vga=0)
Machine: Dell Inspiron 5420, i5-3210M
No xorg.conf.d GPU config; KWIN_DRM_DEVICES unset on first occurrence.
Workaround: export KWIN_DRM_DEVICES=/dev/dri/<i915 card> (via a udev symlink,
since card numbering changes) and reset kwinoutputconfig.json. With that, KWin
runs on i915, LVDS-1 is enabled at 1366x768 and the session works.
Related report (same hardware, different symptom): bug 528002.
```
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