[Bug 2084046] Re: [i915] Phantom "Unknown" display detected on Intel Meteor Lake

Hi Justus,

Thanks for bisecting! It really helps. Looking at what you found:

ubuntu-noble 648dd7aa1f69e1ea8eb6fdb8515e86945df2e424
commit b49420d6a1aeb399e5b107fc6eb8584d0860fbd7
Author: Alex Deucher <alexander.deucher@amd.com>
Date: Wed Aug 21 15:11:35 2024 -0400
Subject: video/aperture: optionally match the device in sysfb_disable()
Link: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=b49420d6a1aeb399e5b107fc6eb8584d0860fbd7

I then looked for commits with that Fixes: tag, and came across this:

commit ad604f0a4c040dcb8faf44dc72db25e457c28076
Author: Thomas Zimmermann <tzimmermann@suse.de>
Date: Tue Sep 24 10:41:03 2024 +0200
Subject: firmware/sysfb: Disable sysfb for firmware buffers with unknown parent
Link: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=ad604f0a4c040dcb8faf44dc72db25e457c28076

Looking at

https://lore.kernel.org/dri-devel/SJ1PR11MB6129EFB8CE63D1EF6D932F94B96F2@SJ1PR11MB6129.namprd11.prod.outlook.com/
https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/12160

it mentions phantom displays.

I think we have a good lead on this one.

ubuntu-noble$ git log --grep "firmware/sysfb: Disable sysfb for firmware buffers with unknown parent" origin/master-next
commit a03ade11374b8a4c3a62f6a2ceda679858e8e8ee
Author: Thomas Zimmermann <tzimmermann@suse.de>
Date: Tue Sep 24 10:41:03 2024 +0200

firmware/sysfb: Disable sysfb for firmware buffers with unknown parent

$ git describe --contains a03ade11374b8a4c3a62f6a2ceda679858e8e8ee
fatal: cannot describe 'a03ade11374b8a4c3a62f6a2ceda679858e8e8ee'

ubuntu-oracular$ git log --grep "firmware/sysfb: Disable sysfb for firmware buffers with unknown parent" origin/maste
r-next
commit cd007b66fa1c48f5bbfade6c50079e4423505512
Author: Thomas Zimmermann <tzimmermann@suse.de>
Date: Tue Sep 24 10:41:03 2024 +0200

firmware/sysfb: Disable sysfb for firmware buffers with unknown parent

$ git describe --contains cd007b66fa1c48f5bbfade6c50079e4423505512
fatal: cannot describe 'cd007b66fa1c48f5bbfade6c50079e4423505512'

They are applied to ubuntu-noble and ubuntu-oracular git trees, but not tagged
yet. Possibly available in next SRU cycle?

In the meantime, how about I make you a test kernel you can try with the fix
to double check we actually found the right one.

Let me get some builds going, and I'll write back when they are ready.

Thanks,
Matthew

** Bug watch added: gitlab.freedesktop.org/drm/i915/kernel/-/issues #12160
https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/12160

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https://bugs.launchpad.net/bugs/2084046

Title:
[i915] Phantom "Unknown" display detected on Intel Meteor Lake

Status in linux package in Ubuntu:
Confirmed
Status in linux source package in Noble:
Confirmed
Status in linux source package in Oracular:
Confirmed

Bug description:
Settings is reporting a second display ("Unknown") is connected. This
is on a laptop which has nothing plugged in and only an Intel GPU.

It appears the problem is once again (like bug 2060268) SimpleDRM:

Node: /dev/dri/card0
├───Driver: simpledrm (DRM driver for simple-framebuffer platform devices) version 1.0.0 (0)
--
Node: /dev/dri/card1
├───Driver: i915 (Intel Graphics) version 1.6.0 (0)

Linux version 6.11.0-8-generic (buildd@lcy02-amd64-042) (x86_64-linux-
gnu-gcc-14 (Ubuntu 14.2.0-4ubuntu2) 14.2.0, GNU ld (GNU Binutils for
Ubuntu) 2.43.1) #8-Ubuntu SMP PREEMPT_DYNAMIC Mon Sep 16 13:41:20 UTC
2024 (Ubuntu 6.11.0-8.8-generic 6.11.0)

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