Re: [PATCH] ALSA: usb-audio: Add feedback snap quirk for Mayflower ARC AMP

[Takashi Iwai <tiwai@suse.de>]

On Fri, 09 Oct 2026 13:44:53 +0200,
Dimitri Wegner via B4 Relay wrote:
> 
> From: Dimitri Wegner <d@zerovolt.org>
> 
> The Mayflower ARC AMP DAC (USB ID 0493:4170, MAG Technology front-end)
> at times gets stuck reporting feedback of nominal+1 sample/frame (97
> instead of 96 at 96 kHz) and does not recover. The driver follows this
> feedback, and audible pops occur every 1-2s until the stream is
> restarted.
> 
> Add a quirk for this device that ignores feedback values more than
> 1/128 (~0.8%) away from nominal and uses the nominal rate instead.
> Normal feedback corrections are far smaller than that and pass
> through unchanged. Other devices are not affected.
> 
> Signed-off-by: Dimitri Wegner <d@zerovolt.org>
> ---
> Tested on this DAC at 96 kHz for ~10 weeks on kernels 7.1 and 7.2.
> The pops no longer occur. The quirk triggered ~680 times over that
> period, always with feedback 0x61.0000 against nominal 0x60.0000.

OK, so I assume that dev_warn_ratelimited() isn't too annoying, then.

Applied to for-next branch now.  Thanks.


Takashi