[PATCH] Behringer UFX1604: get rid of pops and clicks while on 96000hz

[Geraldo]

To clarify: I'm not blaming anyone for introducing an implicit feedback
quirk on a Synchronous endpoint. In fact, I'm almost sure it was somehow
needed at the time. But it isn't anymore. What is needed is to set the
CLOCK_SELECTOR to pin 1 right after we set CLOCK_SOURCE to our desired rate.

Em Qui, 25 de mar de 2021 19:45, Geraldo <geraldogabriel at gmail.com>
escreveu:

> Oh, forgot to mention. Both IN and OUT audio endpoints on the UFX1604 are
> Synchronous. Somehow someone thought it was a good idea to add an implicit
> feedback quirk for it.
>
> I consider this unneeded and pointless. In fact I disengaged the implicit
> feedback quirk on my 5.12-rc4 tree and it runs fine without it.
>
> On Thu, Mar 25, 2021 at 7:39 PM Geraldo <geraldogabriel at gmail.com> wrote:
>
>> Hello everyone!
>>
>> This one has been bugging me for quite a while. I went deep hard in the
>> guts of ALSA to try to solve it, and it turned out to be a minor thing
>> apparently. The problem is old, and every UFX1604 Linux user can attest
>> that it's impossible to use 96000hz in DUPLEX mode without annoying pops
>> and clicks on the capture stream.
>>
>> The fix is simple: after we alter the CLOCK_SOURCE to match our sample
>> rate, let's tell the CLOCK_SELECTOR we want CLOCK_SOURCE 212 (synced to USB
>> SOF) on pin 1. Solves the problem for me, no more pops and clicks while on
>> 96000hz.
>>
>> If you own an UFX1604 please give this patch a good testing. Let me know
>> if it solves the pops and clicks on the input stream for you while on
>> DUPLEX 96000hz.
>>
>> --- clock.c.git 2021-03-22 04:19:55.543485748 -0300
>> +++ clock.c     2021-03-25 19:23:38.597197159 -0300
>> @@ -610,6 +610,13 @@ int snd_usb_set_sample_rate_v2v3(struct
>>         if (err < 0)
>>                 return err;
>>
>> +        if (chip->usb_id == USB_ID(0x1397, 0x0001)) { /* Behringer
>> UFX1604 */
>> +                printk(KERN_WARNING "Setting clock selector for
>> UFX1604");
>> +                err = uac_clock_selector_set_val(chip, 211, 1);
>> +                if (err < 0)
>> +                    return err;
>> +       }
>> +
>>         return get_sample_rate_v2v3(chip, fmt->iface, fmt->altsetting,
>> clock);
>>  }
>>
>>
>