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

[Peng Fan]

On Tue, Sep 08, 2015 at 07:17:22PM -0700, Stephen Warren wrote:
>On 09/03/2015 03:11 PM, Marek Vasut wrote:
>> On Tuesday, September 01, 2015 at 09:45:12 PM, Stephen Warren wrote:
>>> On 08/30/2015 12:26 AM, Peng Fan wrote:
>>>> Hi Stephen,
>> 
>> Hi,
>> 
>> sorry for the delayed reply, I had to dig into the code myself.
>> 
>>>> 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->d
>>>>>>>> equeue " 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
>> 
>> Yes, that's correct.
>> 
>>> or is it supposed to actually stop the HW performing the transaction on
>>> the USB bus?
>> 
>> No, it's not supposed to kill the transaction in hardware.
>
>OK, the patch seems fine then.
>
>>> 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.
>> 
>> Do we need this for the current release or is this for -next ?
>
>I assume that's a question for Peng?

Since this is a bug fix, I think this patch should be in current release.
Without this patch, boards which want to enable fastboot using ci_udc driver
will hang.

Regards,
Peng.
>

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