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Subject: Re: [PATCH v10 0/6] Re-introduce TX FIFO resize for larger EP
 bursting
To:     Thinh Nguyen <Thinh.Nguyen@synopsys.com>,
        Andy Shevchenko <andy.shevchenko@gmail.com>
Cc:     Ferry Toth <fntoth@gmail.com>, Felipe Balbi <balbi@kernel.org>,
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From:   Pavel Hofman <pavel.hofman@ivitera.com>
Message-ID: <c84135c3-c730-208b-dde8-916c7bde1d73@ivitera.com>
Date:   Tue, 24 Aug 2021 07:39:32 +0200
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Dne 24. 08. 21 v 0:50 Thinh Nguyen napsal(a):
> Pavel Hofman wrote:
>>
>>
>> Dne 23. 08. 21 v 17:21 Andy Shevchenko napsal(a):
>>> On Mon, Aug 23, 2021 at 5:59 PM Pavel Hofman
>>> <pavel.hofman@ivitera.com> wrote:
>>>> 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):
>>>>>>> Op 19-08-2021 om 09:51 schreef Pavel Hofman:
>>>>>>>> Dne 18. 08. 21 v 21:07 Ferry Toth napsal(a):
>>>>>>>>> Op 18-08-2021 om 00:00 schreef Ferry Toth:
>>>
>>> ...
>>>
>>>>>>>>> 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 "${USBDISK}" > functions/mass_storage.usb0/lun.0/file
>>>>>>> ln -s functions/mass_storage.usb0 configs/c.1/
>>>>>>>
>>>>>>> # UAC2 device
>>>>>>> mkdir functions/uac2.usb0
>>>>>>> ln -s functions/uac2.usb0 configs/c.1
>>>>>>> ....
>>>>>>
>>>>>> As you say, could perhaps the reason be that the extra EP-IN added in
>>>>>> those patches (previously 1, now 2 with the default config you use)
>>>>>> exceeds your EP-IN max count or available fifos somehow?  You have a
>>>>>> number of functions initialized. If you change the load order of the
>>>>>> functions, do you get the error later with a different function? Just
>>>>>> guessing...
>>>>>>
>>>>>> You should be able to switch the default async EP-OUT (which
>>>>>> configures the new feedback EP-IN ) to adaptive EP-OUT (which requires
>>>>>> no feedback EP) with c_sync=8 parameter of f_uac2.
>>>>>>
>>>>>> https://urldefense.com/v3/__https://elixir.bootlin.com/linux/v5.14-rc6/source/drivers/usb/gadget/function/f_uac2.c*L47__;Iw!!A4F2R9G_pg!LBySrM_zgMGV0x-zZ7nSrs54yJw1GlnpUVUVxdQE8PeszSMZ6OkFX8lSoigwRbWQzLcU$
>>>>>>
>>>>>> https://urldefense.com/v3/__https://elixir.bootlin.com/linux/v5.14-rc6/source/drivers/usb/gadget/function/f_uac2.c*L830__;Iw!!A4F2R9G_pg!LBySrM_zgMGV0x-zZ7nSrs54yJw1GlnpUVUVxdQE8PeszSMZ6OkFX8lSoigwRfP5TdZC$
>>>>>>
>>>>>> https://urldefense.com/v3/__https://elixir.bootlin.com/linux/v5.14-rc6/source/include/uapi/linux/usb/ch9.h*L453__;Iw!!A4F2R9G_pg!LBySrM_zgMGV0x-zZ7nSrs54yJw1GlnpUVUVxdQE8PeszSMZ6OkFX8lSoigwRejzMbWO$
>>>>>>
>>>>>> 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://urldefense.com/v3/__https://elixir.bootlin.com/linux/v5.14-rc7/source/drivers/usb/gadget/function/f_uac2.c*L1312__;Iw!!A4F2R9G_pg!LBySrM_zgMGV0x-zZ7nSrs54yJw1GlnpUVUVxdQE8PeszSMZ6OkFX8lSoigwRTETcbsN$
>>>
>>>
>>>> In your configfs script:
>>>
>>> Kernel shouldn't crash with any available set of configuration
>>> parameters, right? So, even if the parameter would fix the crash the
>>> series is buggy and has to be reverted in my opinion.
>>
>> Sure, no problem with reverting. I am just trying to start up some
>> troubleshooting. A resource exhaustion was mentioned here, that's why I
>> suggested a way to test the patch with the original number of endpoints
>> allocated. I do not get any crashes on my setup which uses fewer gadget
>> functions. That's why I asked what happens if the functions load order
>> is changed. I am afraid this thread is so complex that the actual
>> problem has been burried in the history.
>>
> 
> As I pointed out previously, the crash is probably because of f_uac2
> prematurely freeing feedback request before its completion.
> usb_ep_dequeue() is asynchronous. dwc2() may treat it as a synchronous
> call so you didn't get a crash.

Thanks for your hint, it greatly helps.
>>
> 
> I'm not sure how easy it is for you to obtain/test a device with dwc3,
> but it would be great to also have it as part of your testing suite. :)

Can you recommend a reasonably priced device with viable kernel updates 
for the testing? Optionally with SS which you mentioned last time? Thanks.

Best regards,

Pavel.