linux-image-5.3.0-42-generic regression: no audio output on HP EliteBook 840 G6

[Nico R.]

Symptoms:

no hardware audio output device found by PulseAudio on eoan after I have updated the system yesterday.

Works: linux-image-5.3.0-40-generic
Does not work: linux-image-5.3.0-42-generic

* I suspect this is somewhat related to the recent changes for SkyLake+ platforms between tags Ubuntu-5.3.0-40.32 and Ubuntu-5.3.0-42.34 (I am referring to the repo at <https://git.launchpad.net/~ubuntu-kernel/ubuntu/+source/linux/+git/eoan>).

* I am using the binary package from the Ubuntu repos, not a self-built kernel.

* I can help with bisecting and testing if you like. If you like me to, I need a piece of advice: is <https://wiki.ubuntu.com/Kernel/BuildYourOwnKernel> the proper up-to-date documentation for building my Ubuntu kernel from the sources in the git repo?

What I have tried so far:

I wanted to reload the sound module(s), so I ran the following command:

$ pulseaudio -k ; sudo rmmod snd_hda_intel snd_soc_skl_hda_dsp snd_soc_skl_ssp_clk snd_soc_skl snd_soc_skl_ipc

Then I ran:

# modprobe snd-hda-intel

I found the following in my syslog (not totally sure about when exactly this happened – before or after the rmmod/modprobe):

(see attached file)

Output of ‘sudo lspci -vvnn’ (warning: on 5.3.0-40-generic! Because I am working in parallel and need a functioning audio setup right now; I can try this on another kernel in the evening if absolutely necessary, but this should suffice):

(see attached file)

If more information is necessary for proper debugging, please give me some instructions what to do. Thanks! ☺

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

This bug is missing log files that will aid in diagnosing the problem. While running an Ubuntu kernel (not a mainline or third-party kernel) please enter the following command in a terminal window:

apport-collect 1868061

and then change the status of the bug to 'Confirmed'.

If, due to the nature of the issue you have encountered, you are unable to run this command, please add a comment stating that fact and change the bug status to 'Confirmed'.

This change has been made by an automated script, maintained by the Ubuntu Kernel Team.

[Nico R. (n-roeser)]

I am currently running another kernel and will not be able to quickly provide the information produced by apport-collect. I am quite confident that the information provided by me so far will help with triaging this bug report or requesting further _specific_ details, and therefore I am setting the bug status to 'Confirmed'.

[Nico R. (n-roeser)]

I have started bisecting the eoan kernel <git://kernel.ubuntu.com/ubuntu/ubuntu-eoan.git>/<https://git.launchpad.net/~ubuntu-kernel/ubuntu/+source/linux/+git/eoan>.

Preliminary results:

* Ubuntu-5.3.0-40.32: good,
* Ubuntu-5.3.0-42.34: bad,
* Ubuntu-5.3.0-41.33: bad.

[Nico R. (n-roeser)]

Seems that the problem about audio output has been solved in linux-image-5.3.0-46-generic.