From: Felipe Balbi <balbi@kernel.org>
To: Wesley Cheng <wcheng@codeaurora.org>
Cc: gregkh@linuxfoundation.org, linux-usb@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] usb: dwc3: gadget: Avoid starting DWC3 gadget during UDC unbind
Date: Fri, 17 Sep 2021 08:17:03 +0300 [thread overview]
Message-ID: <87y27vai3p.fsf@kernel.org> (raw)
In-Reply-To: <20210917021852.2037-1-wcheng@codeaurora.org>
Hi,
Wesley Cheng <wcheng@codeaurora.org> writes:
> There is a race present where the DWC3 runtime resume runs in parallel
> to the UDC unbind sequence. This will eventually lead to a possible
> scenario where we are enabling the run/stop bit, without a valid
> composition defined.
>
> Thread#1 (handling UDC unbind):
> usb_gadget_remove_driver()
> -->usb_gadget_disconnect()
> -->dwc3_gadget_pullup(0)
> --> continue UDC unbind sequence
> -->Thread#2 is running in parallel here
>
> Thread#2 (handing next cable connect)
> __dwc3_set_mode()
> -->pm_runtime_get_sync()
> -->dwc3_gadget_resume()
> -->dwc->gadget_driver is NOT NULL yet
> -->dwc3_gadget_run_stop(1)
> --> _dwc3gadget_start()
> ...
>
> Fix this by tracking the pullup disable routine, and avoiding resuming
> of the DWC3 gadget. Once the UDC is re-binded, that will trigger the
> pullup enable routine, which would handle enabling the DWC3 gadget.
>
> Signed-off-by: Wesley Cheng <wcheng@codeaurora.org>
This looks okay to me, but needs to be tested by a few folks ;-)
Acked-by: Felipe Balbi <balbi@kernel.org>
--
balbi
next prev parent reply other threads:[~2021-09-17 5:25 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-17 2:18 [PATCH] usb: dwc3: gadget: Avoid starting DWC3 gadget during UDC unbind Wesley Cheng
2021-09-17 5:17 ` Felipe Balbi [this message]
2021-09-17 6:28 ` Wesley Cheng
2021-09-17 9:37 ` Felipe Balbi
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