Re: [PATCH] usb-audio: Fix boot-time crackling for Generic USB Audio device

[Takashi Iwai <tiwai@suse.de>]

On Mon, 20 Jul 2026 04:23:25 +0200,
Zhang Heng wrote:
> 
> 
> > Please add some comment why the device needs this workaround.
> > IIUC, the reason is different from the others in your case.
> > 
> > Also, please verify that the problem is reproduced in the latest
> > upstream kernel, and the workaround works as expected there, too.
> > 
> > 
> > thanks,
> > 
> > Takashi
> 
> >> --- a/sound/usb/quirks.c
> >> +++ b/sound/usb/quirks.c
> >> @@ -1938,6 +1938,10 @@ void snd_usb_endpoint_start_quirk(struct
> snd_usb_endpoint *ep)
> >>   	    ep->type == SND_USB_ENDPOINT_TYPE_SYNC)
> >>   		ep->skip_packets = 4;
> >>
> >> +	if (ep->chip->usb_id == USB_ID(0x1e0b, 0xd01e) &&
> >> +	    ep->type == SND_USB_ENDPOINT_TYPE_SYNC)
> >> +		ep->skip_packets = 4;
> >> +
> 
> Let me update the current status: that piece of code can be
> omitted. I have applied your test patch, but there is no
> change. It might be that your patch has no effect on this
> device. I tested with version v7.2-rc1. To be honest,
> without any modification, the problem becomes a reproducible
> stutter plus crackling noise. After applying my fix, it
> becomes a probabilistic stutter (still with a relatively
> high probability of recurrence), but when there is no
> stutter, there is also no crackling noise. So I am sure
> that this patch is at least useful, but it does not
> perfectly solve the problem. I am still trying to resolve
> the stutter issue, and I wonder if it is due to resource
> contention during boot? This problem only occurs at boot
> time; after entering the system, it disappears.

OK, if the workaround is no solid solution, it's not worth to take.

Have you tried lowlatency=0 option?  If it's an implicit fb and about
the playback, it might stabilize.


thanks,

Takashi