[U-Boot] [PATCH] usb: gadget: ci_udc: implement usb_ep_ops dequeue callback

[Stephen Warren <swarren@wwwdotorg.org>]

On 08/30/2015 12:26 AM, Peng Fan wrote:
> Hi Stephen,
> On Fri, Aug 28, 2015 at 08:05:36AM +0800, Peng Fan wrote:
>> Hi Stephen,
>> On Thu, Aug 27, 2015 at 10:06:14AM -0600, Stephen Warren wrote:
>>> On 08/27/2015 05:08 AM, Marek Vasut wrote:
>>>> On Thursday, August 27, 2015 at 01:00:50 PM, Peng Fan wrote:
>>>>> Implement endpoint dequeue callback function.
>>>>>
>>>>> Without this function, uboot will hang when executing fastboot comamnd.
>>>>> See following flow:
>>>>> "fastboot_tx_write_str->fastboot_tx_write->usb_ep_dequeue->ep->ops->dequeue
>>>>> " without implement ci_udc dequeue function, ep->ops->dequeue is NULL, then
>>>>> uboot will hang.
>>>>>
>>>>> Tested on mx6qsabresd board with fastboot enabled.
>>>
>>>>> diff --git a/drivers/usb/gadget/ci_udc.c b/drivers/usb/gadget/ci_udc.c
>>>
>>>>> +static int ci_ep_dequeue(struct usb_ep *_ep, struct usb_request *_req)
>>>
>>>>> +	if (ci_req->req.status == -EINPROGRESS) {
>>>>> +		ci_req->req.status = -ECONNRESET;
>>>>> +		if (ci_req->req.complete)
>>>>> +			ci_req->req.complete(_ep, _req);
>>>>> +	}
>>>
>>> Is there no need to reprogram the HW to abort the transfer?
>>
>> I checked linux udc driver drivers/usb/gadget/udc/fsl_qe_udc.c
>> qe_ep_dequeue->done->usb_gadget_giveback_request->"req->complete(ep, req)"
>> I did not see code to reprogram the HW to abort the transfer.
> 
> Do you have further comments?
> I checked other gadget drivers in drivers/usb/gadget/, I did not see
> drivers that reprogram the HW to abort the transfer. For now, I do not
> think out a scenario to reprogram the HW to abort the transfer

Marek, what are the semantics of this function? Is it supposed to simply
update SW state to make U-Boot not care about the transaction, or is it
supposed to actually stop the HW performing the transaction on the USB bus?

If it's the former, then the patch is likely fine. If it's the latter,
then I think the function does need actually need to do something to
make the HW stop, or we can't implement this particular function.