Date:   Mon, 23 Aug 2021 22:50:16 +0000
From:   Thinh Nguyen <Thinh.Nguyen@...opsys.com>
To:     Pavel Hofman <pavel.hofman@...tera.com>,
        Andy Shevchenko <andy.shevchenko@...il.com>
CC:     Ferry Toth <fntoth@...il.com>, Felipe Balbi <balbi@...nel.org>,
        Wesley Cheng <wcheng@...eaurora.org>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "agross@...nel.org" <agross@...nel.org>,
        "bjorn.andersson@...aro.org" <bjorn.andersson@...aro.org>,
        "frowand.list@...il.com" <frowand.list@...il.com>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-arm-msm@...r.kernel.org" <linux-arm-msm@...r.kernel.org>,
        "jackp@...eaurora.org" <jackp@...eaurora.org>,
        "heikki.krogerus@...ux.intel.com" <heikki.krogerus@...ux.intel.com>,
        Ruslan Bilovol <ruslan.bilovol@...il.com>
Subject: Re: [PATCH v10 0/6] Re-introduce TX FIFO resize for larger EP
 bursting

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@...tera.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.

> Again, I am not the author of the patches, my USB knowledge is way
> unsufficient for that. I am trying to make them work as they are
> important and make the existing audio gadget actually usable.
> 

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. :)

Thanks,
Thinh

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