AlaskaLinuxUser's Scratchpad

Recently I was gifted a used tablet from a friend. It is a Vulcan Excursion 10.1″ tablet that came stock with Windows 8.1 and was upgraded to Windows 10. Of course, I love free tablets, but I’m not a Windows fan, so I wiped it and put Ubuntu 21 on it. In case you are interested in doing the same, you can get the atom build from https://linuxiumcomau.blogspot.com/ and they have Ubuntu and Lubuntu builds available.

However, there were a few issues with the tablet once Ubuntu was installed. One of those issues was the sound. For some reason, the sound just didn’t work at all. Yet, for all intents and purposes, it seemed like it was working, just no sound came out. I tried headphones and the speakers, and simply got no audio.

So I got to work. First thing to do was find out what sound card it has, so I used:

$ aplay -l

Which told me the card was recognized as a “bytcr-rt5640”. This also told me the card is recognized, drivers are installed, and it should “work”. So I loaded up alsamixer and made sure it was not muted and was max volume, but still no sound, and did the same in pulseaudio, to make sure it wasn’t an issue there. Still no sound. Armed with the fact that the kernel recognized it and was using it, I jumped online with DuckDuckGo and did some searching. I came across a great mail thread about a bug with this sound card in the Linux kernel:

bytcr_rt5640 sound not working with kernel >= 5.13

https://www.mail-archive.com/ubuntu-bugs%40lists.ubuntu.com/msg5990948.html

It appears that there is some problem with this driver in the newer kernels. I chased down that thread and looked into the issues only to find that it still seems to be a problem. You can read all about the bug here: https://bugs.launchpad.net/ubuntu/+source/linux-meta-hwe-5.13/+bug/1958410

But, for my purposes, the easy thing to do was just to load up Ubuntu with kernel 5.11 and call it a day. Granted, not an actual fix for the problem, but until the kernel modules get fixed, it seemed a very workable solution. I just added these two lines to /etc/default/grub:

GRUB_SAVEDEFAULT=true
GRUB_DEFAULT=saved

And changed the timeout value to 10, giving me ten seconds to choose which kernel options I want at bootup time. After that I ran

$ sudo update-grub

And did a reboot. When the grub menu came up, I chose the advanced options, and then the 5.11 kernel, and everything booted up as normal. Since I chose to save the choice as a default, the tablet always boots up with the 5.11 kernel and I have working sound!

Reading through the bug report, some people had to roll back to kernel 5.4 to get a good working sound, but for me 5.11 seems to work just fine.

Linux – keep it simple.