linux-kernel - Re: [PATCH v4] usb: dwc3: Wait for control tranfer completed when stopping gadget

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Message-ID: <CAMz4kuLwk3YC83kD-sqeSW9ROPb6qJDxBXTf9eE_UK9rrUGKEg@mail.gmail.com>
Date:   Tue, 18 Oct 2016 10:40:39 +0800
From:   Baolin Wang <baolin.wang@...aro.org>
To:     Felipe Balbi <balbi@...nel.org>
Cc:     Greg KH <gregkh@...uxfoundation.org>,
        Mark Brown <broonie@...nel.org>,
        USB <linux-usb@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4] usb: dwc3: Wait for control tranfer completed when
 stopping gadget

Hi,

On 17 October 2016 at 19:53, Felipe Balbi <balbi@...nel.org> wrote:
>
> Hi,
>
> Baolin Wang <baolin.wang@...aro.org> writes:
>>> Baolin Wang <baolin.wang@...aro.org> writes:
>>>> When we change the USB function with configfs dynamically, we possibly met this
>>>> situation: one core is doing the control transfer, another core is trying to
>>>> unregister the USB gadget from userspace, we must wait for completing this
>>>> control tranfer, or it will hang the controller to set the DEVCTRLHLT flag.
>>>>
>>>> Signed-off-by: Baolin Wang <baolin.wang@...aro.org>
>>>
>>> Can you make sure this still works?
>>
>> With applying this patch, It can work well on my platform, but I have
>> some worries about the risk of accessing 'dwc->ep0state' without lock
>> protection in dwc3_gadget_pullup() function.
>
> hmm, I might be missing something, but I think there's no risk here. If
> anything, a wmb() is probably enough before reading ep0state. No?

OK, I agree with you and I think a wmb() is not useful here.

-- 
Baolin.wang
Best Regards