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Subject: Re: [PATCH v1 1/3] Revert "usb: gadget: u_audio: add real feedback
 implementation"
To:     Felipe Balbi <balbi@kernel.org>, Ferry Toth <ftoth@exalondelft.nl>
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Jerome Brunet <jbrunet@baylibre.com>,
        Ruslan Bilovol <ruslan.bilovol@gmail.com>,
        Oded Gabbay <oded.gabbay@gmail.com>,
        Cezary Rojewski <cezary.rojewski@intel.com>,
        Mauro Carvalho Chehab <mchehab+huawei@kernel.org>,
        Pawel Laszczak <pawell@cadence.com>,
        Jack Pham <jackp@codeaurora.org>, linux-kernel@vger.kernel.org,
        linux-usb@vger.kernel.org, linux-doc@vger.kernel.org,
        Jonathan Corbet <corbet@lwn.net>,
        Lorenzo Colitti <lorenzo@google.com>,
        Wesley Cheng <wcheng@codeaurora.org>, robh+dt@kernel.org,
        agross@kernel.org, bjorn.andersson@linaro.org,
        frowand.list@gmail.com, devicetree@vger.kernel.org,
        linux-arm-msm@vger.kernel.org, heikki.krogerus@linux.intel.com,
        Thinh Nguyen <Thinh.Nguyen@synopsys.com>,
        Andy Shevchenko <andy.shevchenko@gmail.com>,
        Pavel Hofman <pavel.hofman@ivitera.com>
References: <20210824201433.11385-1-ftoth@exalondelft.nl>
 <87v93u5au9.fsf@kernel.org>
From:   Ferry Toth <fntoth@gmail.com>
Message-ID: <51212e46-a7c0-7d32-a711-0a865e816d33@gmail.com>
Date:   Wed, 25 Aug 2021 09:16:46 +0200
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Hi,
Op 25-08-2021 om 07:53 schreef Felipe Balbi:
> 
> Ferry Toth <ftoth@exalondelft.nl> writes:
> 
>> This reverts commit e89bb4288378b85c82212b60dc98ecda6b3d3a70.
>>
>> The commit is part of a series with commit
>> 24f779dac8f3efb9629adc0e486914d93dc45517 causing a BUG on dwc3
>> hardware, at least on Intel Merrifield platform when configured
>> through configfs:
>> BUG: kernel NULL pointer dereference, address: 0000000000000008
>> ...
>> RIP: 0010:dwc3_gadget_del_and_unmap_request+0x19/0xe0
>> ...
>> Call Trace:
>>   dwc3_remove_requests.constprop.0+0x12f/0x170
>>   __dwc3_gadget_ep_disable+0x7a/0x160
>>   dwc3_gadget_ep_disable+0x3d/0xd0
>>   usb_ep_disable+0x1c/0x70
>>   u_audio_stop_capture+0x79/0x120 [u_audio]
>>   afunc_set_alt+0x73/0x80 [usb_f_uac2]
>>   composite_setup+0x224/0x1b90 [libcomposite]
>>
>> Pavel's suggestion to add
>> `echo "adaptive" > functions/uac2.usb0/c_sync` to the configfs script
>> resolves the issue.
>> Thinh suggests "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."
>>
>> Revert as this is a regression and the kernel shouldn't crash depending
>> on configuration parameters.
>>
>> Reported-by: Ferry Toth <fntoth@gmail.com>
> 
> this should be Signed-off-by ;-)
> 
Indeed. It probably was until I re-worded the commit text.

Will resend tonight v2.