Bug 215085

Summary:	Audio underrun in CM108 device
Product:	Drivers	Reporter:	Ross Wardrup (minorsecond)
Component:	Sound(ALSA)	Assignee:	Jaroslav Kysela (perex)
Status:	RESOLVED CODE_FIX
Severity:	normal	CC:	styang, tiwai
Priority:	P1
Hardware:	All
OS:	Linux
Kernel Version:	5.15	Subsystem:
Regression:	No	Bisected commit-id:

Description Ross Wardrup 2021-11-20 16:23:46 UTC

I have an audio device (USB soundcard) using the CM108 chipset. When the soundcard is playing audio, I experience an audio underrun error. Audio input is fine. The issue occurs in kernel version 5.15 but does not occur in 5.10.

More info on the device (Digimode-4-Yaesu):

http://xggcomms.com/Yaesu-Interface-Shop(2066629).html

Comment 1 styang 2021-11-30 14:29:24 UTC

Same here, trying to connect an ICOM IC-705 radio and having underrun error when playing audio.

Linux distribution: Arch Linux
Kernel version: 5.14.6
Hardware: Bus 001 Device 032: ID 08bb:2901 Texas Instruments PCM2901 Audio Codec

Comment 2 Jaroslav Kysela 2021-11-30 14:51:04 UTC

Try add lowlatency=n parameter for the snd-usb-audio driver:

  echo "option snd-usb-audio lowlatency=n" /etc/modprobe.d/usb-audio.conf
  reboot

Comment 3 Jaroslav Kysela 2021-11-30 14:51:41 UTC

Typo:

*option = options

Comment 4 styang 2021-11-30 15:10:42 UTC

(In reply to Jaroslav Kysela from comment #2)
> Try add lowlatency=n parameter for the snd-usb-audio driver:
> 
>   echo "option snd-usb-audio lowlatency=n" /etc/modprobe.d/usb-audio.conf
>   reboot

This workaround works for me (after fixing the typo).

BTW, what is the price we pay for setting lowlatency=n?

Comment 5 Takashi Iwai 2021-11-30 15:14:17 UTC

Could you check whether 5.16-rc2 or rc3 kernel works without lowlatency=n?

The low-latency playback support reduces the latency at the start of the PCM playback stream that was added artificially in the earlier kernels.  It's disabled automatically for certain critical cases, but it might miss something.

Comment 6 styang 2021-11-30 16:17:39 UTC

Just checked 5.16-rc3. It works without lowlatency=n.

Comment 7 Ross Wardrup 2021-11-30 22:15:34 UTC

I was able to verify that kernel 5.15 on Gentoo works with the line in usb-audio.conf. I'm unable to check 5.16 as that version isn't available to me yet.

Comment 8 Takashi Iwai 2021-12-01 09:23:20 UTC

I asked Greg to cherry-pick all relevant 5.16 commits into 5.15.x stable, so it'll be available in the future 5.15.x release some time later.