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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>,
        Ferry Toth <fntoth@gmail.com>,
        Andy Shevchenko <andy.shevchenko@gmail.com>
Cc:     Felipe Balbi <balbi@kernel.org>,
        Wesley Cheng <wcheng@codeaurora.org>,
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        Ruslan Bilovol <ruslan.bilovol@gmail.com>
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From:   Pavel Hofman <pavel.hofman@ivitera.com>
Message-ID: <8020f9af-0269-6f00-c9de-aa614215a5fa@ivitera.com>
Date:   Thu, 26 Aug 2021 15:35:47 +0200
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Dne 26. 08. 21 v 3:18 Thinh Nguyen napsal(a):
> Ferry Toth wrote:
>> Hi
>>
>> Op 24-08-2021 om 07:39 schreef Pavel Hofman:
>>>
>>>
>>> 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.
>>>
>> Edison-Arduino kit 2nd hand with display on ebay ~$100 :-)
>>
> 
> Ferry can correct me if I'm wrong, but I think Edison-Arduino kit only
> supports up to highspeed. Regardless, Edison-Arduino seems to work well
> with the latest Linux kernel.
> 
> I see that there are various development kits with rk3399 that supports
> up to SuperSpeed at reasonable price, but I think they all require some
> effort to bring up to the latest Linux kernel and in device mode.
> 
> Maybe Ferry/Felipe/anyone can provide more recommendations?

Guys, thanks a lot for your recommendations. Andy Shevchenko contacted 
me with Hans de Goede and with their great help one of my Atom Z8350 
noname tablets turned out to support the dwc3 device mode on one of its 
USB3-A ports.

Only highspeed, but that's way better now :-)

Thanks to all,

Pavel.