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

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Date:   Mon, 17 Oct 2016 14:53:58 +0300
From:   Felipe Balbi <balbi@...nel.org>
To:     Baolin Wang <baolin.wang@...aro.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,

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?

-- 
balbi

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