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Subject: Re: [PATCH v10 0/6] Re-introduce TX FIFO resize for larger EP
 bursting
To:     Pavel Hofman <pavel.hofman@ivitera.com>,
        Felipe Balbi <balbi@kernel.org>
Cc:     Wesley Cheng <wcheng@codeaurora.org>, gregkh@linuxfoundation.org,
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        linux-arm-msm@vger.kernel.org, jackp@codeaurora.org,
        heikki.krogerus@linux.intel.com, andy.shevchenko@gmail.com,
        Ruslan Bilovol <ruslan.bilovol@gmail.com>
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From:   Ferry Toth <fntoth@gmail.com>
Message-ID: <1fb52c92-9319-c035-722f-695ab34723dd@gmail.com>
Date:   Sun, 22 Aug 2021 21:43:05 +0200
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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.

> Thanks,
> 
> Pavel.