Implicit feedback on BOSS GT-1, the saga continues...

Mike Oliphant oliphant at nostatic.org
Thu Apr 8 22:54:03 CEST 2021 

Geraldo - the implicit feedback stuff is by no means new - it's been there
for quite some time. The recent changes just refactored it a bit.

Mike

On Thu, Apr 8, 2021 at 1:09 PM Geraldo Nascimento <geraldogabriel at gmail.com>
wrote:

> Em Qui, 8 de abr de 2021 16:42, Mike Oliphant <oliphant at nostatic.org>
> escreveu:
>
>> Hi Geraldo - yes. In fact, that is how I've been operating for the past
>> year or so before the recent implicit feedback changes. I use the GT-1 most
>> every day as a guitar interface and it works perfectly.
>>
>
> Thanks Mike, but I'm not sure I understand. You have been operating with
> implicit feedback sync on the playback for the past year? I thought that
> was a new idea?
>
> The key point here is that with a stock kernel you have to comment out the
> IMPLICIT_FB_SKIP_DEV() entry for the GT-1 for the Roland code inside
> audioformat_implicit_fb_quirk properly kick in.
>
> I was suggesting you try your workaround without adding a
> IMPLICIT_FB_GENERIC_DEV() for your device.
>
>
>> The GT-1 (and I suspect many of the other Roland/BOSS devices) doesn't
>> seem to be quirky at all with regard to implicit feedback setup - it works
>> exactly as the endpoint definitions say it should.
>>
>> Where the GT-1 *does* seem to be quirky is that is doesn't seem to want
>> to send capture data until it receives some playback data - hence my
>> endpoint.c patch.
>>
>
> If that is true then there's definitely a need to rewrite endpoint.c. But
> it could be something else, Mike. One thing is certain: the present kernel
> behaviour is far from the ideal.
>
> I insist: engage implicit feedback sync for the playback, disable it for
> the captures and inspect your dyndbg logs for the failure cases in starting
> JACK that happen when you don't patch endpoint.c.
>
> If you see something related to sync_ep then the problem lies elsewhere,
> specifically inside pcm.c
>
> Although whether this behavior is quirky or typical I don't know. I do
>> know that the GT-1 does not claim to be USB class compliant. It requires
>> custom drivers on Windows and macOS and does not work at all with iOS, so
>> it definitely seems to be somewhat non-standard.
>>
>
> Non-standard to say the least. I really hope that's not the case or it'll
> give Takashi Iwai plenty of headache ;-)
>
>
>> Mike
>>
>> On Thu, Apr 8, 2021 at 12:13 PM Geraldo Nascimento <
>> geraldogabriel at gmail.com> wrote:
>>
>>> Hey Mike, got another question for you, sorry about that.
>>>
>>> If you comment out your GT-1 IMPLICIT_FB_GENERIC_DEV() entry and instead
>>> let audioformat_implicit_fb_quirk() call add_roland_implicit_fb() with
>>> everything else customized your way, your custom endpoint.c etc., does it
>>> still work? And does it work crystal clear?
>>>
>>> I'm sorry about this test this, test that, provide the dyndbg logs
>>> attitude but I'm honestly just trying to help you write the best patch
>>> possible.
>>>
>>> Thank you,
>>> Geraldo
>>>
>>> Em Qui, 8 de abr de 2021 02:05, Geraldo Nascimento <
>>> geraldogabriel at gmail.com> escreveu:
>>>
>>>> Mike, I just realize I missed reply-to-all once again.
>>>>
>>>> In case you were wondering, I was looking for a sync_ep event right in
>>>> the start of the loading of snd-usb-audio. It happens inside pcm.c. If you
>>>> see one of those specifically let me know.
>>>>
>>>> With my Pioneer device, the DDJ-SR2, snd-usb-audio recognized the
>>>> device's implicit feedback EP as sync_ep and that prevented JACK from
>>>> starting.
>>>>
>>>> Em Qua, 7 de abr de 2021 23:47, Mike Oliphant <oliphant at nostatic.org>
>>>>> escreveu:
>>>>>
>>>>>> Hi Geraldo - I had the same thought and I have tried enabling
>>>>>> playback feedback while turning off capture feedback without my endpoint
>>>>>> patch. It doesn't work - at least not on the GT-1. Playback/capture fails
>>>>>> to start.
>>>>>>
>>>>>
>>>>> Would you mind sharing the dyndbg logs for the failure case from the
>>>>> point you connect the device, and trying to start JACK?
>>>>>
>>>>> Sometimes failures elucidate more than success cases.
>>>>>
>>>>>
>>>>>> Speaking of testing, if you (or anyone else following this
>>>>>> discussion) have one of these Roland/BOSS devices, it would be great if you
>>>>>> could try testing with playback feedback enabled and my endpoint.c
>>>>>> workaround.
>>>>>>
>>>>>
>>>>> I don't have the hardware, but I'm sure it works. The problem is that
>>>>> endpoint.c code really shouldn't be disabled unless all the other options
>>>>> fail, and even then, I'm not so sure the maintainers will be so willing to
>>>>> disable it. So let's keep some other options on the table by debugging a
>>>>> little further.
>>>>>
>>>>> Thank you,
>>>>> Geraldo
>>>>>
>>>>>
>>>>>> Mike
>>>>>>
>>>>>> On Wed, Apr 7, 2021 at 7:21 PM Geraldo Nascimento <
>>>>>> geraldogabriel at gmail.com> wrote:
>>>>>>
>>>>>>> Thanks, Mike, one thing I can tell you right off the bat is that if
>>>>>>> you turn implicit feedback sync on for both endpoints at the same time like
>>>>>>> you mentioned, without your workaround inside endpoint.c, they most likely
>>>>>>> will stall because they would both be waiting for each other to start.
>>>>>>>
>>>>>>> Have you tried engaging the generic implicit feedback sync just for
>>>>>>> the playback, thereby commenting out the capture implicit feedback entries,
>>>>>>> and re-enabling snd_usb_endpoint_implicit_feedback_sink(ep) inside
>>>>>>> endpoint.c? Does playback still fail to start?
>>>>>>>
>>>>>>> If you choose to perform this simple test please share with us the
>>>>>>> test's dyndbg logs right from the moment you turn on the device, not just
>>>>>>> after you start jackd.
>>>>>>>
>>>>>>> Sorry for the endless do-this, do-that. Such is the pace of
>>>>>>> teledebugging
>>>>>>>
>>>>>>>
>>>>>>> Em Qua, 7 de abr de 2021 21:38, Mike Oliphant <oliphant at nostatic.org>
>>>>>>> escreveu:
>>>>>>>
>>>>>>>> Geraldo - here is the dmesg output when starting up jackd for
>>>>>>>> capture/playback:
>>>>>>>>
>>>>>>>> With my patch:
>>>>>>>>
>>>>>>>> [  136.734081] usb 3-1.2: Open EP 0x8e, iface=2:1, idx=0
>>>>>>>> [  136.734088] usb 3-1.2:   channels=2, rate=44100, format=S32_LE,
>>>>>>>> period_bytes=256, periods=2, implicit_fb=0
>>>>>>>> [  136.734092] usb 3-1.2: Setting usb interface 2:0 for EP 0x8e
>>>>>>>> [  136.734233] usb 3-1.2: Setting usb interface 2:1 for EP 0x8e
>>>>>>>> [  136.734381] usb 3-1.2: 2:1 Set sample rate 44100, clock 0
>>>>>>>> [  136.734388] usb 3-1.2: Setting params for data EP 0x8e, pipe
>>>>>>>> 0x70480
>>>>>>>> [  136.734394] usb 3-1.2: Set up 12 URBS, ret=0
>>>>>>>> [  136.734466] usb 3-1.2: Open EP 0xd, iface=1:1, idx=0
>>>>>>>> [  136.734468] usb 3-1.2:   channels=2, rate=44100, format=S32_LE,
>>>>>>>> period_bytes=256, periods=2, implicit_fb=1
>>>>>>>> [  136.734471] usb 3-1.2: Reopened EP 0x8e (count 1)
>>>>>>>> [  136.734473] usb 3-1.2: Setting usb interface 1:0 for EP 0xd
>>>>>>>> [  136.734605] usb 3-1.2: Setting usb interface 1:1 for EP 0xd
>>>>>>>> [  136.734762] usb 3-1.2: 1:1 Set sample rate 44100, clock 0
>>>>>>>> [  136.734774] usb 3-1.2: Setting params for data EP 0xd, pipe
>>>>>>>> 0x68400
>>>>>>>> [  136.734781] usb 3-1.2: Set up 12 URBS, ret=0
>>>>>>>> [  136.734830] usb 3-1.2: Starting data EP 0xd (running 0)
>>>>>>>> [  136.734873] usb 3-1.2: 12 URBs submitted for EP 0xd
>>>>>>>> [  136.734876] usb 3-1.2: Starting data EP 0x8e (running 0)
>>>>>>>> [  136.734906] usb 3-1.2: 12 URBs submitted for EP 0x8e
>>>>>>>> [  136.740627] usb 3-1.2: Starting data EP 0x8e (running 1)
>>>>>>>> [  136.740634] usb 3-1.2: 2:1 Start Capture PCM
>>>>>>>> [  136.740635] usb 3-1.2: 1:1 Start Playback PCM
>>>>>>>>
>>>>>>>>
>>>>>>>> With the unpatched kernel:
>>>>>>>>
>>>>>>>> [  344.813203] usb 3-1.2: Open EP 0x8e, iface=2:1, idx=0
>>>>>>>> [  344.813210] usb 3-1.2:   channels=2, rate=44100, format=S32_LE,
>>>>>>>> period_bytes=256, periods=2, implicit_fb=1
>>>>>>>> [  344.813213] usb 3-1.2: Open EP 0xd, iface=1:1, idx=0
>>>>>>>> [  344.813215] usb 3-1.2:   channels=2, rate=44100, format=S32_LE,
>>>>>>>> period_bytes=256, periods=2, implicit_fb=0
>>>>>>>> [  344.813217] usb 3-1.2: Setting usb interface 2:0 for EP 0x8e
>>>>>>>> [  344.813367] usb 3-1.2: Setting usb interface 2:1 for EP 0x8e
>>>>>>>> [  344.813494] usb 3-1.2: 2:1 Set sample rate 44100, clock 0
>>>>>>>> [  344.813503] usb 3-1.2: Setting params for data EP 0x8e, pipe
>>>>>>>> 0x70580
>>>>>>>> [  344.813509] usb 3-1.2: Set up 12 URBS, ret=0
>>>>>>>> [  344.813513] usb 3-1.2: Setting usb interface 1:0 for EP 0xd
>>>>>>>> [  344.813587] usb 3-1.2: Setting usb interface 1:1 for EP 0xd
>>>>>>>> [  344.813758] usb 3-1.2: 1:1 Set sample rate 44100, clock 0
>>>>>>>> [  344.813765] usb 3-1.2: Setting params for data EP 0xd, pipe
>>>>>>>> 0x68500
>>>>>>>> [  344.813770] usb 3-1.2: Set up 2 URBS, ret=0
>>>>>>>> [  344.813858] usb 3-1.2: Reopened EP 0xd (count 1)
>>>>>>>> [  344.813883] usb 3-1.2: Starting data EP 0xd (running 0)
>>>>>>>> [  344.813899] usb 3-1.2: 2 URBs submitted for EP 0xd
>>>>>>>> [  344.819499] usb 3-1.2: Starting data EP 0x8e (running 0)
>>>>>>>> [  344.819532] usb 3-1.2: 12 URBs submitted for EP 0x8e
>>>>>>>> [  344.819535] usb 3-1.2: Starting data EP 0xd (running 1)
>>>>>>>> [  344.819538] usb 3-1.2: 2:1 Start Capture PCM
>>>>>>>> [  344.819540] usb 3-1.2: 1:1 Start Playback PCM
>>>>>>>> [  344.820663] usb 3-1.2: Stopping data EP 0xd (running 2)
>>>>>>>> [  344.820688] usb 3-1.2: Stopping data EP 0x8e (running 1)
>>>>>>>> [  344.820693] usb 3-1.2: 2:1 Stop Capture PCM
>>>>>>>> [  344.820695] usb 3-1.2: Stopping data EP 0xd (running 1)
>>>>>>>> [  344.820697] usb 3-1.2: 1:1 Stop Playback PCM
>>>>>>>> [  344.833799] usb 3-1.2: Starting data EP 0xd (running 0)
>>>>>>>> [  344.833852] usb 3-1.2: 2 URBs submitted for EP 0xd
>>>>>>>> [  344.833867] usb 3-1.2: Starting data EP 0x8e (running 0)
>>>>>>>> [  344.833888] usb 3-1.2: 12 URBs submitted for EP 0x8e
>>>>>>>> [  344.833890] usb 3-1.2: Starting data EP 0xd (running 1)
>>>>>>>> [  344.833891] usb 3-1.2: 2:1 Start Capture PCM
>>>>>>>> [  344.833893] usb 3-1.2: 1:1 Start Playback PCM
>>>>>>>>
>>>>>>>> On Wed, Apr 7, 2021 at 1:30 PM Geraldo Nascimento <
>>>>>>>> geraldogabriel at gmail.com> wrote:
>>>>>>>>
>>>>>>>>> Em Qua, 7 de abr de 2021 17:16, Mike Oliphant <
>>>>>>>>> oliphant at nostatic.org> escreveu:
>>>>>>>>>
>>>>>>>>>> Hi Geraldo - I don't have that patch applied, but it shouldn't
>>>>>>>>>> make any behavioral difference - it just seems to be simplifying the code.
>>>>>>>>>>
>>>>>>>>>
>>>>>>>>> Point taken.
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>> The issue is that the BOSS GT-1 *does* need implicit feedback on
>>>>>>>>>> playback to avoid clock timing issues, and the current behavior is
>>>>>>>>>> disabling that feedback.
>>>>>>>>>>
>>>>>>>>>
>>>>>>>>> Mike, would you mind posting some dyndbg logs for both the stock
>>>>>>>>> behaviour and your endpoint.c/generic quirk modified behaviour?
>>>>>>>>>
>>>>>>>>> Just add snd_usb_audio.dyndbg=+p to your kernel options and please
>>>>>>>>> share the logs.
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>> Mike
>>>>>>>>>>
>>>>>>>>>> On Wed, Apr 7, 2021 at 1:04 PM Geraldo Nascimento <
>>>>>>>>>> geraldogabriel at gmail.com> wrote:
>>>>>>>>>>
>>>>>>>>>>> Hey Mike, did you catch the latest patch by Takashi Iwai for
>>>>>>>>>>> capture quirky devices?
>>>>>>>>>>>
>>>>>>>>>>> You can find it here:
>>>>>>>>>>> https://patchwork.kernel.org/project/alsa-devel/patch/20210406113837.32041-1-tiwai@suse.de/
>>>>>>>>>>>
>>>>>>>>>>> Em Qua, 7 de abr de 2021 16:55, Mike Oliphant <
>>>>>>>>>>> oliphant at nostatic.org> escreveu:
>>>>>>>>>>>
>>>>>>>>>>>> I had thought that the recent implicit feedback changes were
>>>>>>>>>>>> fully working
>>>>>>>>>>>> on the BOSS GT-1, but it turns out that I just hadn't tested
>>>>>>>>>>>> well enough.
>>>>>>>>>>>>
>>>>>>>>>>>> Audio playback and capture works, but with periodic dropouts. I
>>>>>>>>>>>> get the
>>>>>>>>>>>> exact same behavior as I did with the quirk to completely
>>>>>>>>>>>> disable implicit
>>>>>>>>>>>> feedback. Without the implicit feedback, you get dropouts from
>>>>>>>>>>>> clock drift
>>>>>>>>>>>> - how bad probably varies from card to card. On mine it is
>>>>>>>>>>>> every second or
>>>>>>>>>>>> so.
>>>>>>>>>>>>
>>>>>>>>>>>> If I switch playback feedback for the GT-1 to generic by doing
>>>>>>>>>>>> "IMPLICIT_FB_GENERIC_DEV(0x0582, 0x01d6)", I get the previous
>>>>>>>>>>>> old behavior,
>>>>>>>>>>>> which is that playback completely fails to start.
>>>>>>>>>>>>
>>>>>>>>>>>> With generic playback feedback, and using my previous patch to
>>>>>>>>>>>> endpoint.c
>>>>>>>>>>>> to avoid playback waiting on capture mentioned here:
>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>>>> https://mailman.alsa-project.org/pipermail/alsa-devel/2020-January/161951.html
>>>>>>>>>>>>
>>>>>>>>>>>> playback and capture work perfectly for me.
>>>>>>>>>>>>
>>>>>>>>>>>

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