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 <20210824201433.11385-2-ftoth@exalondelft.nl>
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From:   Felipe Balbi <balbi@kernel.org>
To:     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>,
        Ferry Toth <fntoth@gmail.com>
Subject: Re: [PATCH v1 2/3] Revert "usb: gadget: f_uac2: add adaptive sync
 support for capture"
Date:   Wed, 25 Aug 2021 08:53:57 +0300
In-reply-to: <20210824201433.11385-2-ftoth@exalondelft.nl>
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Ferry Toth <ftoth@exalondelft.nl> writes:

> This reverts commit 40c73b30546e759bedcec607fedc2d4be954508f.
>
> 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>

Signed-off-by?

-- 
balbi