Kernel BUG sometimes during pluging in a DP Splitter

[Michael]

Sometimes, during plugging in a DP -> 2x HDMI splitter, I get a kernel BUG with a NULL pointer dereference. Most times it works, through.

I'm using Ubuntu 20.04

I've a 1920x1200 (eDP) display in my laptop, and a 2560x1440 and a 1920x1080 display on the splitter.

Its a Intel(R) Core(TM) i5-8250U CPU platform.
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ProblemType: Bug
ApportVersion: 2.20.11-0ubuntu22
Architecture: amd64
DistroRelease: Ubuntu 20.04
HibernationDevice: RESUME=/dev/mapper/sda5_crypt
MachineType: Default string Default string
Package: linux-meta (not installed)
ProcFB: 0 i915drmfb
ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-5.4.0-21-generic root=UUID=df422beb-6d13-4575-9b30-ad00e25a7d35 ro noquiet nosplash
ProcVersionSignature: Ubuntu 5.4.0-21.25-generic 5.4.27
PulseList: Error: command ['pacmd', 'list'] failed with exit code 1: No PulseAudio daemon running, or not running as session daemon.
RelatedPackageVersions:
 linux-restricted-modules-5.4.0-21-generic N/A
 linux-backports-modules-5.4.0-21-generic N/A
 linux-firmware 1.187
Tags: focal
Uname: Linux 5.4.0-21-generic x86_64
UpgradeStatus: No upgrade log present (probably fresh install)
UserGroups: audio mythtv
WpaSupplicantLog:

_MarkForUpload: True
dmi.bios.date: 01/11/2019
dmi.bios.vendor: American Megatrends Inc.
dmi.bios.version: 5.12
dmi.board.asset.tag: Default string
dmi.board.name: Default string
dmi.board.vendor: Default string
dmi.board.version: Default string
dmi.chassis.asset.tag: Default string
dmi.chassis.type: 3
dmi.chassis.vendor: Default string
dmi.chassis.version: Default string
dmi.modalias: dmi:bvnAmericanMegatrendsInc.:bvr5.12:bd01/11/2019:svnDefaultstring:pnDefaultstring:pvrDefaultstring:rvnDefaultstring:rnDefaultstring:rvrDefaultstring:cvnDefaultstring:ct3:cvrDefaultstring:
dmi.product.family: Default string
dmi.product.name: Default string
dmi.product.sku: Default string
dmi.product.version: Default string
dmi.sys.vendor: Default string

[Michael (3-ueuntu-4)]

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[Michael (3-ueuntu-4)]

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[Michael (3-ueuntu-4)]

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[Michael (3-ueuntu-4)]

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[Michael (3-ueuntu-4)]

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[Michael (3-ueuntu-4)]

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[Michael (3-ueuntu-4)]

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[Michael (3-ueuntu-4)]

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[Michael (3-ueuntu-4)]

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[Michael (3-ueuntu-4)]

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[Michael (3-ueuntu-4)]

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[Michael (3-ueuntu-4)]

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[Michael (3-ueuntu-4)]

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[Michael (3-ueuntu-4)]

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[Michael (3-ueuntu-4)]

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[Michael (3-ueuntu-4)]

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[Michael (3-ueuntu-4)]

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[Ubuntu Kernel Bot (ubuntu-kernel-bot)]

This change was made by a bot.

[Kai-Heng Feng (kaihengfeng)]

Please test latest mainline kernel:
https://kernel.ubuntu.com/~kernel-ppa/mainline/v5.6/

[Po-Hsu Lin (cypressyew)]

Marked as Incomplete as per request in comment #23

[Michael (3-ueuntu-4)]

Sorry, didn't see the request :-/

I just tried with 5.8 from HWE. After my frist reconnect, I got a

[350240.293152] failed hdr00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

(nothing else!) in dmesg, nothing about the external monitors in xrandr.

At the second try (no restart), they work again.

3th try works, put spits a

350562.536195] i915 0000:00:02.0: DP-7: EDID is invalid:
[350562.536197] [00] BAD 00 ff ff ff ff ff ff 00 ff ff ff ff ff ff ff ff
[350562.536198] [00] BAD ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
[350562.536199] [00] BAD ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
[350562.536199] [00] BAD ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
[350562.536200] [00] BAD ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
[350562.536200] [00] BAD ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
[350562.536201] [00] BAD ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
[350562.536202] [00] BAD ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff

[Michael (3-ueuntu-4)]

4th try: Works, but

[350616.380035] [drm:drm_dp_check_act_status [drm_kms_helper]] *ERROR* Failed to get ACT after 3000ms, last status: 00
[350619.421657] [drm:drm_dp_check_act_status [drm_kms_helper]] *ERROR* Failed to get ACT after 3000ms, last status: 00

So something seems to be still flacky. I'll try it later again.

[Po-Hsu Lin (cypressyew)]

Hi,
thanks for trying this out.
If this is still reproducible, please give the latest mainline kernel [1] a try to see if you issue exists in the upstream kernel. Instructions could be found in [2]

Please flip the bug status back to confirmed after your test.
Thank you!

[1] https://kernel.ubuntu.com/~kernel-ppa/mainline/v5.12-rc5/
[2] https://wiki.ubuntu.com/Kernel/MainlineBuilds

[Launchpad Janitor (janitor)]

[Expired for linux (Ubuntu) because there has been no activity for 60 days.]