RE: [PATCH] usb: cdns3: Fix dequeue implementation.

[Pawel Laszczak]

>-----Original Message-----
>From: Peter Chen <peter.chen@xxxxxxx>
>Sent: Tuesday, October 8, 2019 9:34 AM
>To: Pawel Laszczak <pawell@xxxxxxxxxxx>
>Cc: felipe.balbi@xxxxxxxxxxxxxxx; gregkh@xxxxxxxxxxxxxxxxxxx; linux-usb@xxxxxxxxxxxxxxx; rogerq@xxxxxx; linux-
>kernel@xxxxxxxxxxxxxxx; jbergsagel@xxxxxx; nsekhar@xxxxxx; nm@xxxxxx; Suresh Punnoose <sureshp@xxxxxxxxxxx>; Rahul Kumar
><kurahul@xxxxxxxxxxx>
>Subject: Re: [PATCH] usb: cdns3: Fix dequeue implementation.
>
>EXTERNAL MAIL
>
>
>On 19-10-07 13:06:18, Pawel Laszczak wrote:
>> Dequeuing implementation in cdns3_gadget_ep_dequeu gets first request from
>
>%s/cdns3_gadget_ep_dequeu/cdns3_gadget_ep_dequeue
>
>> deferred_req_list and changed TRB associated with it to LINK TRB.
>> This approach is incorrect because deferred_req_list contains requests
>> that have not been placed on hardware RING.  In this case driver should
>> just giveback this request to gadget driver.
>>
>> The patch implements new approach that first checks where dequeuing
>> request is located and only when it's on Transfer Ring then changes TRB
>> associated with it to LINK TRB.
>> During processing completed transfers such LINK TRB will be ignored.
>>
>> Reported-by: Peter Chen <peter.chen@xxxxxxx>
>> Signed-off-by: Pawel Laszczak <pawell@xxxxxxxxxxx>
>> Fixes: 7733f6c32e36 ("usb: cdns3: Add Cadence USB3 DRD Driver")
>> ---
>>  drivers/usb/cdns3/gadget.c | 35 ++++++++++++++++++++---------------
>>  1 file changed, 20 insertions(+), 15 deletions(-)
>>
>> diff --git a/drivers/usb/cdns3/gadget.c b/drivers/usb/cdns3/gadget.c
>> index 2ca280f4c054..9050b380ab83 100644
>> --- a/drivers/usb/cdns3/gadget.c
>> +++ b/drivers/usb/cdns3/gadget.c
>> @@ -1145,6 +1145,14 @@ static void cdns3_transfer_completed(struct cdns3_device *priv_dev,
>>  		request = cdns3_next_request(&priv_ep->pending_req_list);
>>  		priv_req = to_cdns3_request(request);
>>
>> +		trb = priv_ep->trb_pool + priv_ep->dequeue;
>> +
>> +		/* Request was dequeued and TRB was changed to TRB_LINK. */
>> +		if (TRB_FIELD_TO_TYPE(trb->control) == TRB_LINK) {
>> +			trace_cdns3_complete_trb(priv_ep, trb);
>> +			cdns3_move_deq_to_next_trb(priv_req);
>> +		}
>
>If the request was dequeued, it should not be at request list, isn't it?

Yes
The dequeued request was removed from pending list but TRB associated with it 
was changed to Link TRB so it should be ignored in cdns3_transfer_completed function. 

Pawel

>
>Peter
>> +
>>  		/* Re-select endpoint. It could be changed by other CPU during
>>  		 * handling usb_gadget_giveback_request.
>>  		 */
>> @@ -2067,6 +2075,7 @@ int cdns3_gadget_ep_dequeue(struct usb_ep *ep,
>>  	struct usb_request *req, *req_temp;
>>  	struct cdns3_request *priv_req;
>>  	struct cdns3_trb *link_trb;
>> +	u8 req_on_hw_ring = 0;
>>  	unsigned long flags;
>>  	int ret = 0;
>>
>> @@ -2083,8 +2092,10 @@ int cdns3_gadget_ep_dequeue(struct usb_ep *ep,
>>
>>  	list_for_each_entry_safe(req, req_temp, &priv_ep->pending_req_list,
>>  				 list) {
>> -		if (request == req)
>> +		if (request == req) {
>> +			req_on_hw_ring = 1;
>>  			goto found;
>> +		}
>>  	}
>>
>>  	list_for_each_entry_safe(req, req_temp, &priv_ep->deferred_req_list,
>> @@ -2096,27 +2107,21 @@ int cdns3_gadget_ep_dequeue(struct usb_ep *ep,
>>  	goto not_found;
>>
>>  found:
>> -
>> -	if (priv_ep->wa1_trb == priv_req->trb)
>> -		cdns3_wa1_restore_cycle_bit(priv_ep);
>> -
>>  	link_trb = priv_req->trb;
>> -	cdns3_move_deq_to_next_trb(priv_req);
>> -	cdns3_gadget_giveback(priv_ep, priv_req, -ECONNRESET);
>> -
>> -	/* Update ring */
>> -	request = cdns3_next_request(&priv_ep->deferred_req_list);
>> -	if (request) {
>> -		priv_req = to_cdns3_request(request);
>>
>> +	/* Update ring only if removed request is on pending_req_list list */
>> +	if (req_on_hw_ring) {
>>  		link_trb->buffer = TRB_BUFFER(priv_ep->trb_pool_dma +
>>  					      (priv_req->start_trb * TRB_SIZE));
>>  		link_trb->control = (link_trb->control & TRB_CYCLE) |
>> -				    TRB_TYPE(TRB_LINK) | TRB_CHAIN | TRB_TOGGLE;
>> -	} else {
>> -		priv_ep->flags |= EP_UPDATE_EP_TRBADDR;
>> +				    TRB_TYPE(TRB_LINK) | TRB_CHAIN;
>> +
>> +		if (priv_ep->wa1_trb == priv_req->trb)
>> +			cdns3_wa1_restore_cycle_bit(priv_ep);
>>  	}
>>
>> +	cdns3_gadget_giveback(priv_ep, priv_req, -ECONNRESET);
>> +
>>  not_found:
>>  	spin_unlock_irqrestore(&priv_dev->lock, flags);
>>  	return ret;
>
>--
>
>Thanks,
>Peter Chen