linux-kernel - Re: [PATCH] usb: gadget: udc-core: call udc

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Date:	Tue, 23 Dec 2014 12:31:20 -0600
From:	Felipe Balbi <balbi@...com>
To:	Robert Baldyga <r.baldyga@...sung.com>
CC:	<balbi@...com>, Peter Chen <peter.chen@...escale.com>,
	<gregkh@...uxfoundation.org>, <linux-usb@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <m.szyprowski@...sung.com>,
	<k.opasiak@...sung.com>
Subject: Re: [PATCH] usb: gadget: udc-core: call udc_stop() before gadget
 unbind

On Tue, Dec 23, 2014 at 07:34:15AM +0100, Robert Baldyga wrote:
> Hi Felipe,
> 
> On 12/22/2014 05:34 PM, Felipe Balbi wrote:
> > On Mon, Dec 15, 2014 at 11:05:22AM +0100, Robert Baldyga wrote:
> >> On 12/15/2014 06:13 AM, Peter Chen wrote:
> >>> On Fri, Dec 12, 2014 at 02:17:28PM +0100, Robert Baldyga wrote:
> >>>> As usb function drivers assumes that all usb request will be completed
> >>>> before function unbind call, we should supply such behavior. In some
> >>>> cases ep_disable() won't kill all request effectively, because some
> >>>> IN requests can be in running state. In such situation it's possible
> >>>> to have unbind function called before last request completion, which
> >>>> can cause problems.
> >>>
> >>> Doesn't the function's disable/unbind should call usb_ep_dequeue to make
> >>> sure the transfer has ended?
> >>
> >> USB function drivers like ECM or HID surely doesn't. It looks like
> >> there's assumption that all requests will be completed by UDC driver.
> > 
> > that's a bug on those drivers :-)
> 
> So we can't make assumptions that requests will be completed in
> ep_disable()?

oh, no you can. I misread it.

> >> Function ep_disable() should complete requests in hardware driver, but
> >> at least in DWC2 driver not all requests are completed at this stage
> > 
> > and that's a bug on dwc2 :-)
> 
> I have already found that out. Another UDC drivers simply kill all
> request without waiting for currently running, so I did the same in
> DWC2. Here is my patch:
> http://www.spinics.net/lists/linux-usb/msg118698.html

should be in my pull request already.

> >> (request which are in hardware FIFO are omitted to give them chance to
> >> be transferred). Those requests are forced to complete in udc_stop()
> > 
> > that's wrong, we're disabling the endpoint anyway. Either dwc2 needs to
> > wait_for_completion() or forcibly cancel the request. The bottom line is
> > that control should not exit ep_disable() until all requests have been
> > quiesced.
> 
> So that's not bug in function drivers. They make correct assumption,
> because they expect that requests will be completed in ep_disable().

right :-)

-- 
balbi

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