Re: [PATCH v10 0/6] Re-introduce TX FIFO resize for larger EP bursting

[Pavel Hofman <pavel.hofman@ivitera.com>]

Dne 22. 08. 21 v 21:43 Ferry Toth napsal(a):
> Op 19-08-2021 om 23:04 schreef Pavel Hofman:
>>
>> Dne 19. 08. 21 v 22:10 Ferry Toth napsal(a):
>>> Hi
>>>
>>> Op 19-08-2021 om 09:51 schreef Pavel Hofman:
>>>> Hi,
>>>>
>>>> Dne 18. 08. 21 v 21:07 Ferry Toth napsal(a):
>>>>> Hi,
>>>>>
>>>>> Op 18-08-2021 om 00:00 schreef Ferry Toth:
>>>>>> Hi,
>>>>>>
>>>>>> Op 16-08-2021 om 07:18 schreef Felipe Balbi:
>>>>>>> Hi,
>>>>>>>
>>>>>>> Ferry Toth <fntoth@gmail.com> writes:
>>>>>>>>> Ferry Toth <fntoth@gmail.com> writes:
>>>>>>>>>>>>> Ferry Toth <fntoth@gmail.com> writes:
>>>>>>>>>>>>>>>>>> Hardware name: Intel Corporation Merrifield/BODEGA 
>>>>>>>>>>>>>>>>>> BAY, BIOS 542
>>>>>>>>>>>>>>>>>> 2015.01.21:18.19.48
>>>>>>>>>>>>>>>>>> RIP: 0010:0x500000000
>>>>>>>>>>>>>>>>>> Code: Unable to access opcode bytes at RIP 0x4ffffffd6.
>>>>>>>>>>>>>>>>>> RSP: 0018:ffffa4d00045fc28 EFLAGS: 00010046
>>>>>>>>>>>>>>>>>> RAX: 0000000500000000 RBX: ffff8cd546aed200 RCX: 
>>>>>>>>>>>>>>>>>> 0000000000000000
>>>>>>>>>>>>>>>>>> RDX: 0000000000000000 RSI: ffff8cd547bfcae0 RDI: 
>>>>>>>>>>>>>>>>>> ffff8cd546aed200
>>>>>>>>>>>>>>>>>> RBP: ffff8cd547bfcae0 R08: 0000000000000000 R09: 
>>>>>>>>>>>>>>>>>> 0000000000000001
>>>>>>>>>>>>>>>>>> R10: ffff8cd541fd28c0 R11: 0000000000000000 R12: 
>>>>>>>>>>>>>>>>>> ffff8cd547342828
>>>>>>>>>>>>>>>>>> R13: ffff8cd546aed248 R14: 0000000000000000 R15: 
>>>>>>>>>>>>>>>>>> ffff8cd548b1d000
>>>>>>>>>>>>>>>>>> FS:  0000000000000000(0000) GS:ffff8cd57e200000(0000) 
>>>>>>>>>>>>>>>>>> knlGS:0000000000000000
>>>>>>>>>>>>>>>>>> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>>>>>>>>>>>>>>>>>> CR2: 0000000500000000 CR3: 000000000311e000 CR4: 
>>>>>>>>>>>>>>>>>> 00000000001006f0
>>>>>>>>>>>>>>>>>> Call Trace:
>>>>>>>>>>>>>>>>>>         ? dwc3_remove_requests.constprop.0+0x14d/0x170
>>>>>>>>>>>>>>>>>>         ? __dwc3_gadget_ep_disable+0x7a/0x160
>>>>>>>>>>>>>>>>>>         ? dwc3_gadget_ep_disable+0x3d/0xd0
>>>>>>>>>>>>>>>>>>         ? usb_ep_disable+0x1c/0x
>>>>>>>>>>>>>>>>>>         ? u_audio_stop_capture+0x79/0x120 [u_audio]
>>>>>>>>>>>>>>>>>>         ? afunc_set_alt+0x73/0x80 [usb_f_uac2]
>>>>>>>>>>> So this is triggered by a SetInterface request...
>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>         ? composite_setup+0x224/0x1b90 [libcomposite]
>>>>>>>>>>>>>>>>>>         ? __dwc3_gadget_kick_transfer+0x160/0x400
>>>>>>>>>>>>>>>>>>         ? dwc3_gadget_ep_queue+0xf3/0x1a0
>>>>>>>>>>>>>>>>>>         ? configfs_composite_setup+0x6b/0x90 
>>>>>>>>>>>>>>>>>> [libcomposite]
>>>>>>>>>>>>>>>>>>         ? configfs_composite_setup+0x6b/0x90 
>>>>>>>>>>>>>>>>>> [libcomposite]
>>>>>>>>>>>>>>>>>>         ? dwc3_ep0_interrupt+0x459/0xa40
>>>>>>>>>>>>>>>>>>         ? dwc3_thread_interrupt+0x8ee/0xf40
>>>>>>>>>>>>>>>>>>         ? __schedule+0x235/0x6c0
>>>>>>>>>>>>>>>>>>         ? disable_irq_nosync+0x10/0x10
>>>>>>>>>>>>>>>>>>         ? irq_thread_fn+0x1b/0x60
>>>>>>>>>>>>>>>>>>         ? irq_thread+0xc0/0x160
>>>>>>>>>>>>>>>>>>         ? irq_thread_check_affinity+0x70/0x70
>>>>>>>>>>>>>>>>>>         ? irq_forced_thread_fn+0x70/0x70
>>>>>>>>>>>>>>>>>>         ? kthread+0x122/0x140
>>>>>>>>>>>>>>>>>>         ? set_kthread_struct+0x40/0x40
>>>>>>>>>>>>>>>>>>         ? ret_from_fork+0x22/0x30
>>>>>>>>>>>>>>>>> Do you mind enabling dwc3 traces and collecting them? 
>>>>>>>>>>>>>>>>> Trying to figure
>>>>>>>>>>>>>>>>> out how we got here.
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> I'll try if I can get the same error by booting with USB 
>>>>>>>>>>>>>>>> in host mode
>>>>>>>>>>>>>>>> and then switch to device mode. If so I can enable 
>>>>>>>>>>>>>>>> traces and collect as
>>>>>>>>>>>>>>>> you explained me before.
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> I'll try before monday, as then I fly for a holiday and 
>>>>>>>>>>>>>>>> will not be
>>>>>>>>>>>>>>>> available before rc5.
>>>>>>>>>>>>>>> you can enable all of those with kernel cmdline :-)
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> https://www.kernel.org/doc/html/latest/admin-guide/kernel-parameters.html 
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> you need ftrace_dump_on_oops=1 and also need the correct 
>>>>>>>>>>>>>>> options on
>>>>>>>>>>>>>>> trace_buf_size and trace_event.
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>> On Edison-Arduino I have a switch to go to device mode, 
>>>>>>>>>>>>>> after which
>>>>>>>>>>>>>> udev triggers a script configure gadgets through configfs.
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> I tried to log following these instructions:
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> https://www.kernel.org/doc/html/latest/driver-api/usb/dwc3.html#reporting-bugs 
>>>>>>>>>>>>>> <https://www.kernel.org/doc/html/latest/driver-api/usb/dwc3.html#reporting-bugs> 
>>>>>>>>>>>>>>
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> Unfortunately the kernel crashes so badly I can not get to 
>>>>>>>>>>>>>> the ` cp
>>>>>>>>>>>>>> /t/trace /root/trace.txt` line (after a while the watchdog 
>>>>>>>>>>>>>> kicks).
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> What to do next?
>>>>>>>>>>>>> Pass ftrace_dump_on_oops to kernel cmdline.
>>>>>>>>>>>>>
>>>>>>>>>>>> No sure if I did this right, on oops everything is pushed to 
>>>>>>>>>>>> console
>>>>>>>>>>>> (115k2 serial), I hope nothing essential is lost.
>>>>>>>>>>>>
>>>>>>>>>>>> I copied the screen buffer to file see attached.
>>>>>>>>>>> Thank you, I bet it took quite a some time :-) Anyway, 
>>>>>>>>>>> looking at
>>>>>>>>>>> the logs around Set Interface requests, we can track every 
>>>>>>>>>>> endpoint
>>>>>>>>>>> that's disabled. I'll take a guess and assume we're failing 
>>>>>>>>>>> at the last
>>>>>>>>>>> Set Interface, that means we should have something odd with 
>>>>>>>>>>> ep6in, but
>>>>>>>>>>> everything looks fine in the trace output:
>>>>>>>>>>>
>>>>>>>>>>> [   75.823107] irq/14-d-596       0d... 42789194us : 
>>>>>>>>>>> dwc3_gadget_ep_enable: ep6in: mps 192/346 streams 16 burst 0 
>>>>>>>>>>> ring 0/0 flags E:swbp:<
>>>>>>>>>>> [   75.835472] irq/14-d-596       0d... 42789198us : 
>>>>>>>>>>> dwc3_alloc_request: ep6in: req 0000000002c71409 length 0/0 
>>>>>>>>>>> zsI ==> 0
>>>>>>>>>>> [   75.846416] irq/14-d-596       0d... 42789202us : 
>>>>>>>>>>> dwc3_ep_queue: ep6in: req 0000000002c71409 length 0/192 zsI 
>>>>>>>>>>> ==> -115
>>>>>>>>>>> [   75.857360] irq/14-d-596       0d... 42789204us : 
>>>>>>>>>>> dwc3_alloc_request: ep6in: req 00000000a324f5d0 length 0/0 
>>>>>>>>>>> zsI ==> 0
>>>>>>>>>>> [   75.868301] irq/14-d-596       0d... 42789206us : 
>>>>>>>>>>> dwc3_ep_queue: ep6in: req 00000000a324f5d0 length 0/192 zsI 
>>>>>>>>>>> ==> -115
>>>>>>>>>>> [   75.879244] irq/14-d-596       0d... 42789209us : 
>>>>>>>>>>> dwc3_event: event (000020c2): ep0in: Transfer Not Ready [0] 
>>>>>>>>>>> (Not Active) [Status Phase]
>>>>>>>>>>> [   75.891880] irq/14-d-596       0d... 42789211us : 
>>>>>>>>>>> dwc3_prepare_trb: ep0in: trb 000000004c0ae319 (E0:D0) buf 
>>>>>>>>>>> 000000001bded000 size 0 ctrl 00000c33 (HLcs:SC:status2)
>>>>>>>>>>> [   75.989131] irq/14-d-596       0d... 42789224us : 
>>>>>>>>>>> dwc3_gadget_ep_cmd: ep0in: cmd 'Start Transfer' [406] params 
>>>>>>>>>>> 00000000 1bded000 00000000 --> status: Successful
>>>>>>>>>>> [   76.096261] irq/14-d-596       0d... 42789272us : 
>>>>>>>>>>> dwc3_event: event (0000c042): ep0in: Transfer Complete (sIL) 
>>>>>>>>>>> [Status Phase]
>>>>>>>>>>> [   76.107834] irq/14-d-596       0d... 42789275us : 
>>>>>>>>>>> dwc3_complete_trb: ep0out: trb 000000004c0ae319 (E0:D0) buf 
>>>>>>>>>>> 000000001bded000 size 0 ctrl 00000c32 (hLcs:SC:status2)
>>>>>>>>>>> [   76.122944] irq/14-d-596       0d... 42789277us : 
>>>>>>>>>>> dwc3_gadget_giveback: ep0out: req 00000000cb1bd3cd length 0/0 
>>>>>>>>>>> zsI ==> 0
>>>>>>>>>>> [   76.134160] irq/14-d-596       0d... 42789280us : 
>>>>>>>>>>> dwc3_prepare_trb: ep0out: trb 000000004c0ae319 (E0:D0) buf 
>>>>>>>>>>> 000000001bded000 size 8 ctrl 00000c23 (HLcs:SC:setup)
>>>>>>>>>>> [   76.231322] irq/14-d-596       0d... 42789292us : 
>>>>>>>>>>> dwc3_gadget_ep_cmd: ep0out: cmd 'Start Transfer' [406] params 
>>>>>>>>>>> 00000000 1bded000 00000000 --> status: Successful
>>>>>>>>>>> [   76.297418] kworker/-23        0d... 42789670us : 
>>>>>>>>>>> dwc3_ep_queue: ep3in: req 0000000029586135 length 0/96 ZsI 
>>>>>>>>>>> ==> -115
>>>>>>>>>>> [   76.308278] kworker/-23        0d... 42789695us : 
>>>>>>>>>>> dwc3_prepare_trb: ep3in: trb 00000000b81213d6 (E1:D0) buf 
>>>>>>>>>>> 0000000003b7a800 size 96 ctrl 00000811 (Hlcs:sC:normal)
>>>>>>>>>>> [   76.395294] kworker/-23        0d... 42789707us : 
>>>>>>>>>>> dwc3_gadget_ep_cmd: ep3in: cmd 'Update Transfer' [60007] 
>>>>>>>>>>> params 00000000 00000000 00000000 --> status: Successful
>>>>>>>>>>> [   76.471900] irq/14-d-596       0d... 42789842us : 
>>>>>>>>>>> dwc3_event: event (0000c040): ep0out: Transfer Complete (sIL) 
>>>>>>>>>>> [Setup Phase]
>>>>>>>>>>> [   76.489308] irq/14-d-596       0d... 42789845us : 
>>>>>>>>>>> dwc3_ctrl_req: Set Interface(Intf = 5, Alt.Setting = 0)
>>>>>>>>>>> [   76.505650] irq/14-d-596       0d... 42789851us : 
>>>>>>>>>>> dwc3_ep_dequeue: ep6in: req 0000000002c71409 length 0/192 zsI 
>>>>>>>>>>> ==> -115
>>>>>>>>>>> [   76.523315] irq/14-d-596       0d... 42789854us : 
>>>>>>>>>>> dwc3_gadget_giveback: ep6in: req 0000000002c71409 length 
>>>>>>>>>>> 0/192 zsI ==> -104
>>>>>>>>>>> [   76.541427] irq/14-d-596       0d... 42789857us : 
>>>>>>>>>>> dwc3_free_request: ep6in: req 0000000002c71409 length 0/192 
>>>>>>>>>>> zsI ==> -104
>>>>>>>>>>> [   76.559267] irq/14-d-596       0d... 42789859us : 
>>>>>>>>>>> dwc3_ep_dequeue: ep6in: req 00000000a324f5d0 length 0/192 zsI 
>>>>>>>>>>> ==> -115
>>>>>>>>>>> [   76.576937] irq/14-d-596       0d... 42789861us : 
>>>>>>>>>>> dwc3_gadget_giveback: ep6in: req 00000000a324f5d0 length 
>>>>>>>>>>> 0/192 zsI ==> -104
>>>>>>>>>>> [   76.595046] irq/14-d-596       0d... 42789862us : 
>>>>>>>>>>> dwc3_free_request: ep6in: req 00000000a324f5d0 length 0/192 
>>>>>>>>>>> zsI ==> -104
>>>>>>>>>>> [   76.612892] irq/14-d-596       0d... 42789865us : 
>>>>>>>>>>> dwc3_gadget_ep_disable: ep6in: mps 192/346 streams 16 burst 0 
>>>>>>>>>>> ring 0/0 flags E:swbp:<
>>>>>>>>>>> [   76.665535] irq/14-d-596       0d... 42789873us : 
>>>>>>>>>>> dwc3_event: event (000020c2): ep0in: Transfer Not Ready [0] 
>>>>>>>>>>> (Not Active) [Status Phase]
>>>>>>>>>>> [   76.684716] irq/14-d-596       0d... 42789875us : 
>>>>>>>>>>> dwc3_prepare_trb: ep0in: trb 000000004c0ae319 (E0:D0) buf 
>>>>>>>>>>> 000000001bded000 size 0 ctrl 00000c33 (HLcs:SC:status2)
>>>>>>>>>>> [   76.819195] irq/14-d-596       0d... 42789886us : 
>>>>>>>>>>> dwc3_gadget_ep_cmd: ep0in: cmd 'Start Transfer' [406] params 
>>>>>>>>>>> 00000000 1bded000 00000000 --> status: Successful
>>>>>>>>>>> [   76.926324] irq/14-d-596       0d... 42789930us : 
>>>>>>>>>>> dwc3_event: event (0000c042): ep0in: Transfer Complete (sIL) 
>>>>>>>>>>> [Status Phase]
>>>>>>>>>>> [   76.937892] irq/14-d-596       0d... 42789933us : 
>>>>>>>>>>> dwc3_complete_trb: ep0out: trb 000000004c0ae319 (E0:D0) buf 
>>>>>>>>>>> 000000001bded000 size 0 ctrl 00000c32 (hLcs:SC:status2)
>>>>>>>>>>> [   76.953003] irq/14-d-596       0d... 42789935us : 
>>>>>>>>>>> dwc3_gadget_giveback: ep0out: req 00000000cb1bd3cd length 0/0 
>>>>>>>>>>> zsI ==> 0
>>>>>>>>>>> [   76.964217] irq/14-d-596       0d... 42789938us : 
>>>>>>>>>>> dwc3_prepare_trb: ep0out: trb 000000004c0ae319 (E0:D0) buf 
>>>>>>>>>>> 000000001bded000 size 8 ctrl 00000c23 (HLcs:SC:setup)
>>>>>>>>>>> [   77.061379] irq/14-d-596       0d... 42789950us : 
>>>>>>>>>>> dwc3_gadget_ep_cmd: ep0out: cmd 'Start Transfer' [406] params 
>>>>>>>>>>> 00000000 1bded000 00000000 --> status: Successful
>>>>>>>>>>> [   77.168595] irq/14-d-596       0d... 42790509us : 
>>>>>>>>>>> dwc3_event: event (0000c040): ep0out: Transfer Complete (sIL) 
>>>>>>>>>>> [Setup Phase]
>>>>>>>>>>> [   77.180159] irq/14-d-596       0d... 42790512us : 
>>>>>>>>>>> dwc3_ctrl_req: Get String Descriptor(Index = 18, Length = 255)
>>>>>>>>>>> [   77.190578] irq/14-d-596       0d... 42790537us : 
>>>>>>>>>>> dwc3_prepare_trb: ep0in: trb 000000004c0ae319 (E0:D0) buf 
>>>>>>>>>>> 0000000003b68000 size 36 ctrl 00000c53 (HLcs:SC:data)
>>>>>>>>>>> [   77.287648] irq/14-d-596       0d... 42790550us : 
>>>>>>>>>>> dwc3_gadget_ep_cmd: ep0in: cmd 'Start Transfer' [406] params 
>>>>>>>>>>> 00000000 1bded000 00000000 --> status: Successful
>>>>>>>>>>> [   77.333107] irq/14-d-596       0d... 42790557us : 
>>>>>>>>>>> dwc3_event: event (000010c2): ep0in: Transfer Not Ready [0] 
>>>>>>>>>>> (Not Active) [Data Phase]
>>>>>>>>>>> [   77.407223] irq/14-d-596       0d... 42790575us : 
>>>>>>>>>>> dwc3_event: event (000090c2): ep0in: Transfer Not Ready [0] 
>>>>>>>>>>> (Active) [Data Phase]
>>>>>>>>>>> [   77.480985] irq/14-d-596       0d... 42790588us : 
>>>>>>>>>>> dwc3_event: event (0000c042): ep0in: Transfer Complete (sIL) 
>>>>>>>>>>> [Data Phase]
>>>>>>>>>>> [   77.492376] irq/14-d-596       0d... 42790590us : 
>>>>>>>>>>> dwc3_complete_trb: ep0out: trb 000000004c0ae319 (E0:D0) buf 
>>>>>>>>>>> 0000000003b68000 size 0 ctrl 00000c52 (hLcs:SC:data)
>>>>>>>>>>> [   77.507221] irq/14-d-596       0d... 42790595us : 
>>>>>>>>>>> dwc3_gadget_giveback: ep0out: req 00000000cb1bd3cd length 
>>>>>>>>>>> 36/36 ZsI ==> 0
>>>>>>>>>>> [   77.518609] irq/14-d-596       0d... 42790597us : 
>>>>>>>>>>> dwc3_event: event (000020c0): ep0out: Transfer Not Ready [0] 
>>>>>>>>>>> (Not Active) [Status Phase]
>>>>>>>>>>> [   77.531332] irq/14-d-596       0d... 42790598us : 
>>>>>>>>>>> dwc3_prepare_trb: ep0out: trb 000000004c0ae319 (E0:D0) buf 
>>>>>>>>>>> 000000001bded000 size 0 ctrl 00000c43 (HLcs:SC:status3)
>>>>>>>>>>> [   77.628669] irq/14-d-596       0d... 42790609us : 
>>>>>>>>>>> dwc3_gadget_ep_cmd: ep0out: cmd 'Start Transfer' [406] params 
>>>>>>>>>>> 00000000 1bded000 00000000 --> status: Successful
>>>>>>>>>>>
>>>>>>>>>>> Do you mind adding a few prints in dwc3_remove_requests to 
>>>>>>>>>>> tell us which
>>>>>>>>>>> endpoint is being processed? Then we'll know for sure which 
>>>>>>>>>>> one caused
>>>>>>>>>>> the crash.
>>>>>>>>>>>
>>>>>>>>>> I wouldn't mind but am leaving on a holiday, won't have time 
>>>>>>>>>> until 6 aug.
>>>>>>>>> not a problem, we'll still be here when you're back :-)
>>>>>>>> Well, let's go then :-)
>>>>>>>>
>>>>>>>> To get back in the mood I have retested 5.13.0, 5.14.0-rc1, 
>>>>>>>> 5.14.0-rc2
>>>>>>>> and 5.14.0-rc5.
>>>>>>>>
>>>>>>>> I find that 5.13.0 works fine, and the issue starts from 
>>>>>>>> 5.14.0-rc1.
>>>>>>> That's great finding. We have a bisection point. There are a 
>>>>>>> total of
>>>>>>> 13764 commits between v5.13 and v5.14-rc1
>>>>>>>
>>>>>>>     $ git rev-list  --count v5.13..v5.14-rc1
>>>>>>>     13764
>>>>>>>
>>>>>>> git bisect should find the offending commit in at most 14 tries. 
>>>>>>> That's
>>>>>>> not too bad.
>>>>>> I correctly guesstimated that the problem got introduced by the 
>>>>>> usb merge 79160a60
>>>>>>
>>>>>> "Merge tag 'usb-5.14-rc1' of 
>>>>>> git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb"
>>>>>>
>>>>>> 116 commits(7 bisects).
>>>>>>
>>>>>> 24f779dac8f3efb9629adc0e486914d93dc45517 is the first bad commit
>>>>>>
>>>>>> "usb: gadget: f_uac2/u_audio: add feedback endpoint support"
>>>>>>
>>>>>> Ruslan's 3 patches are related to each other so I reverted all 
>>>>>> three 24f779da...e89bb428 and applied the reverts to rc1.
>>>>>>
>>>>>> I can confirm this indeed resolves the problem in rc1.
>>>>>>
>>>>>> Is late now, tomorrow evening I will apply the reverts to rc6.
>>>>>
>>>>> With these reverts rc6 works fine as well.
>>>>>
>>>>> So, where do we go from here?
>>>>>
>>>>
>>>> I know the patches have been tested on dwc2 (by me and others).  I 
>>>> do not know if Ruslan or Jerome tested them on dwc3 but probably 
>>>> not. Ruslan has talked about RPi (my case too) and BeagleboneBlack, 
>>>> both with dwc2. Perhaps the dwc2 behaves a bit differently than dwc3?
>>>>
>>>> The patches add a new EP-IN for async feedback. I am sorry I have 
>>>> not followed your long thread (it started as unrelated to uac). Does 
>>>> the problem appear with f_uac1 or f_uac2? Please how have you 
>>>> reached the above problem?
>>>
>>> I'm sorry too. I first believed the issue was related to the patch 
>>> mentioned in the subject line.
>>>
>>> The problem appaers with f_uac2. I bost Edison_Arduino board in host 
>>> mode (there is a switch allowing to select host/device mode). When 
>>> flipping the switch to device mode udev run a script:
>>> But as I am using configfs (excerpt follows) and just disabling the 
>>> last 2 line resolves the issue, I'm guessing uac2 is the issue. Or 
>>> exceeding the available resources.
>>>
>>> # Create directory structure
>>> mkdir "${GADGET_BASE_DIR}"
>>> cd "${GADGET_BASE_DIR}"
>>> mkdir -p configs/c.1/strings/0x409
>>> mkdir -p strings/0x409
>>>
>>> # Serial device
>>> mkdir functions/gser.usb0
>>> ln -s functions/gser.usb0 configs/c.1/
>>> ###
>>>
>>> # Ethernet device
>>> mkdir functions/eem.usb0
>>> echo "${DEV_ETH_ADDR}" > functions/eem.usb0/dev_addr
>>> echo "${HOST_ETH_ADDR}" > functions/eem.usb0/host_addr
>>> ln -s functions/eem.usb0 configs/c.1/
>>>
>>> # Mass Storage device
>>> mkdir functions/mass_storage.usb0
>>> echo 1 > functions/mass_storage.usb0/stall
>>> echo 0 > functions/mass_storage.usb0/lun.0/cdrom
>>> echo 0 > functions/mass_storage.usb0/lun.0/ro
>>> echo 0 > functions/mass_storage.usb0/lun.0/nofua
>>> echo "${USBDISK}" > functions/mass_storage.usb0/lun.0/file
>>> ln -s functions/mass_storage.usb0 configs/c.1/
>>>
>>> # UAC2 device
>>> mkdir functions/uac2.usb0
>>> ln -s functions/uac2.usb0 configs/c.1
>>> ....
>>>
>>
>> As you say, could perhaps the reason be that the extra EP-IN added in 
>> those patches (previously 1, now 2 with the default config you use) 
>> exceeds your EP-IN max count or available fifos somehow?  You have a 
>> number of functions initialized. If you change the load order of the 
>> functions, do you get the error later with a different function? Just 
>> guessing...
>>
>> You should be able to switch the default async EP-OUT (which 
>> configures the new feedback EP-IN ) to adaptive EP-OUT (which requires 
>> no feedback EP) with c_sync=8 parameter of f_uac2.
>>
>> https://elixir.bootlin.com/linux/v5.14-rc6/source/drivers/usb/gadget/function/f_uac2.c#L47 
>>
>>
>> https://elixir.bootlin.com/linux/v5.14-rc6/source/drivers/usb/gadget/function/f_uac2.c#L830 
>>
>>
>> https://elixir.bootlin.com/linux/v5.14-rc6/source/include/uapi/linux/usb/ch9.h#L453 
>>
>>
>> Does that fix the problem?
> 
> Not sure how to do that. Do you mean the module should have a parameter 
> called c_sync? `modinfo` list no parameters for usb_f_uac2.
> 

Those are configfs params, not available in modinfo.

I checked and the value is "adaptive" 
https://elixir.bootlin.com/linux/v5.14-rc7/source/drivers/usb/gadget/function/f_uac2.c#L1312

In your configfs script:

# UAC2 device
mkdir functions/uac2.usb0
ln -s functions/uac2.usb0 configs/c.1


On the USB Host:
cat /proc/asound/Gadget/stream:
Playback:
   Status: Stop
   Interface 1
     Altset 1
     Format: S16_LE
     Channels: 2
     Endpoint: 0x01 (1 OUT) (ASYNC)
     Rates: 64000
     Data packet interval: 125 us
     Bits: 16
     Channel map: FL FR
     Sync Endpoint: 0x82 (2 IN)
     Sync EP Interface: 1
     Sync EP Altset: 1
     Implicit Feedback Mode: No


lsusb -v -d 1d6b:0104 | | grep EP.*IN
         bEndpointAddress     0x81  EP 1 IN
         bEndpointAddress     0x82  EP 2 IN
         bEndpointAddress     0x83  EP 3 IN

I have additional patches applied which define controls via EP IN 
interrupt mode, not part of that patchset.


Switching to the adaptive mode:
# UAC2 device
mkdir functions/uac2.usb0
echo "adaptive" > functions/uac2.usb0/c_sync
ln -s functions/uac2.usb0 configs/c.1

On the USB Host:
cat /proc/asound/Gadget/stream:
Playback:
   Status: Stop
   Interface 1
     Altset 1
     Format: S16_LE
     Channels: 2
     Endpoint: 0x01 (1 OUT) (ADAPTIVE)
     Rates: 64000
     Data packet interval: 125 us
     Bits: 16
     Channel map: FL FR


lsusb -v -d 1d6b:0104 | grep EP.*IN
         bEndpointAddress     0x81  EP 1 IN
         bEndpointAddress     0x82  EP 2 IN


The feedback EP-IN is gone because the mode is adaptive now.

If you think the new input endpoints should not be created by default 
for resource-compatibility reasons, the adaptive mode can be set by 
default in a fixed patch.

Also the patches defining the new interrupt endpoints can have the 
controls disabled by default (and not allocate the EP-IN). These patches 
on top of the async patches are already accepted by Greg for usb-next 
branch 
https://kernel.googlesource.com/pub/scm/linux/kernel/git/gregkh/usb/+/eaf6cbe0992052a46d93047dc122fad5126aa3bd 
. That's why I was trying to sort out the async patches without 
reverting them as it will call for more reverts.

Thanks,

Pavel.