Re: [PATCH v2] usb: dwc3: gadget: Avoid canceling current request for queuing error

[Thinh Nguyen]

Hi,

Wesley Cheng wrote:
> If an error is received when issuing a start or update transfer
> command, the error handler will stop all active requests (including
> the current USB request), and call dwc3_gadget_giveback() to notify
> function drivers of the requests which have been stopped.  Avoid
> having to cancel the current request which is trying to be queued, as
> the function driver will handle the EP queue error accordingly.
> Simply unmap the request as it was done before, and allow previously
> started transfers to be cleaned up.
> 

It looks like you're still letting dwc3 stopping and cancelling all the
active requests instead letting the function driver doing the dequeue.

BTW, what kinds of command and error do you see in your setup and for
what type endpoint? I'm thinking of letting the function driver to
dequeue the requests instead of letting dwc3 automatically
ending/cancelling the queued requests. However, it's a bit tricky to do
that if the error is -ETIMEDOUT since we're not sure if the controller
had already cached the TRBs.

This seems to add more complexity and I don't have a good solution to
it. Since you're already cancelling all the active request anyway, what
do you think of always letting dwc3_gadget_ep_queue() to go through with
success, but report failure through request completion?

Hi Felipe, can you also chime in?

Thanks,
Thinh


> Signed-off-by: Wesley Cheng <wcheng@xxxxxxxxxxxxxx>
> ---
> Changes in v2:
>  - Addressed feedback received by making sure the logic only applies to a req
>    which is being queued, decrementing the enqueue pointer, and only clearing
>    the HWO bit.
> 
>  drivers/usb/dwc3/gadget.c | 75 +++++++++++++++++++++++++++++++++++++++++------
>  1 file changed, 66 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
> index dd80e5c..c8ddbe1 100644
> --- a/drivers/usb/dwc3/gadget.c
> +++ b/drivers/usb/dwc3/gadget.c
> @@ -140,6 +140,29 @@ int dwc3_gadget_set_link_state(struct dwc3 *dwc, enum dwc3_link_state state)
>  }
>  
>  /**
> + * dwc3_ep_dec_trb - decrement a trb index.
> + * @index: Pointer to the TRB index to increment.
> + *
> + * The index should never point to the link TRB. After decrementing,
> + * if index is zero, wrap around to the TRB before the link TRB.
> + */
> +static void dwc3_ep_dec_trb(u8 *index)
> +{
> +	(*index)--;
> +	if (*index < 0)
> +		*index = DWC3_TRB_NUM - 1;
> +}
> +
> +/**
> + * dwc3_ep_dec_enq - decrement endpoint's enqueue pointer
> + * @dep: The endpoint whose enqueue pointer we're decrementing
> + */
> +static void dwc3_ep_dec_enq(struct dwc3_ep *dep)
> +{
> +	dwc3_ep_dec_trb(&dep->trb_enqueue);
> +}
> +
> +/**
>   * dwc3_ep_inc_trb - increment a trb index.
>   * @index: Pointer to the TRB index to increment.
>   *
> @@ -1352,7 +1375,26 @@ static int dwc3_prepare_trbs(struct dwc3_ep *dep)
>  
>  static void dwc3_gadget_ep_cleanup_cancelled_requests(struct dwc3_ep *dep);
>  
> -static int __dwc3_gadget_kick_transfer(struct dwc3_ep *dep)
> +static void dwc3_gadget_ep_revert_trbs(struct dwc3_ep *dep, struct dwc3_request *req)
> +{
> +	int i;
> +
> +	if (!req->trb)
> +		return;
> +
> +	for (i = 0; i < req->num_trbs; i++) {
> +		struct dwc3_trb *trb;
> +
> +		trb = &dep->trb_pool[dep->trb_enqueue];
> +		trb->ctrl &= ~DWC3_TRB_CTRL_HWO;
> +		dwc3_ep_dec_enq(dep);
> +	}
> +
> +	req->num_trbs = 0;
> +}
> +
> +static int __dwc3_gadget_kick_transfer(struct dwc3_ep *dep,
> +				       struct dwc3_request *queued_req)
>  {
>  	struct dwc3_gadget_ep_cmd_params params;
>  	struct dwc3_request		*req;
> @@ -1410,8 +1452,23 @@ static int __dwc3_gadget_kick_transfer(struct dwc3_ep *dep)
>  
>  		dwc3_stop_active_transfer(dep, true, true);
>  
> -		list_for_each_entry_safe(req, tmp, &dep->started_list, list)
> -			dwc3_gadget_move_cancelled_request(req, DWC3_REQUEST_STATUS_DEQUEUED);
> +		/*
> +		 * In order to ensure the logic is applied to a request being
> +		 * queued by dwc3_gadget_ep_queue(), it needs to explicitly
> +		 * check that req is the same as queued_req (request being
> +		 * queued).  If so, then just unmap and decrement the enqueue
> +		 * pointer, as the usb_ep_queue() error handler in the function
> +		 * driver will handle cleaning up the USB request.
> +		 */
> +		list_for_each_entry_safe(req, tmp, &dep->started_list, list) {
> +			if (req == queued_req) {
> +				dwc3_gadget_ep_revert_trbs(dep, req);
> +				dwc3_gadget_del_and_unmap_request(dep, req, ret);
> +			} else {
> +				dwc3_gadget_move_cancelled_request(req,
> +								   DWC3_REQUEST_STATUS_DEQUEUED);
> +			}
> +		}
>  
>  		/* If ep isn't started, then there's no end transfer pending */
>  		if (!(dep->flags & DWC3_EP_END_TRANSFER_PENDING))
> @@ -1546,7 +1603,7 @@ static int dwc3_gadget_start_isoc_quirk(struct dwc3_ep *dep)
>  	dep->start_cmd_status = 0;
>  	dep->combo_num = 0;
>  
> -	return __dwc3_gadget_kick_transfer(dep);
> +	return __dwc3_gadget_kick_transfer(dep, NULL);
>  }
>  
>  static int __dwc3_gadget_start_isoc(struct dwc3_ep *dep)
> @@ -1593,7 +1650,7 @@ static int __dwc3_gadget_start_isoc(struct dwc3_ep *dep)
>  	for (i = 0; i < DWC3_ISOC_MAX_RETRIES; i++) {
>  		dep->frame_number = DWC3_ALIGN_FRAME(dep, i + 1);
>  
> -		ret = __dwc3_gadget_kick_transfer(dep);
> +		ret = __dwc3_gadget_kick_transfer(dep, NULL);
>  		if (ret != -EAGAIN)
>  			break;
>  	}
> @@ -1684,7 +1741,7 @@ static int __dwc3_gadget_ep_queue(struct dwc3_ep *dep, struct dwc3_request *req)
>  		}
>  	}
>  
> -	return __dwc3_gadget_kick_transfer(dep);
> +	return __dwc3_gadget_kick_transfer(dep, req);
>  }
>  
>  static int dwc3_gadget_ep_queue(struct usb_ep *ep, struct usb_request *request,
> @@ -1893,7 +1950,7 @@ int __dwc3_gadget_ep_set_halt(struct dwc3_ep *dep, int value, int protocol)
>  
>  		if ((dep->flags & DWC3_EP_DELAY_START) &&
>  		    !usb_endpoint_xfer_isoc(dep->endpoint.desc))
> -			__dwc3_gadget_kick_transfer(dep);
> +			__dwc3_gadget_kick_transfer(dep, NULL);
>  
>  		dep->flags &= ~DWC3_EP_DELAY_START;
>  	}
> @@ -2992,7 +3049,7 @@ static bool dwc3_gadget_endpoint_trbs_complete(struct dwc3_ep *dep,
>  		(list_empty(&dep->pending_list) || status == -EXDEV))
>  		dwc3_stop_active_transfer(dep, true, true);
>  	else if (dwc3_gadget_ep_should_continue(dep))
> -		if (__dwc3_gadget_kick_transfer(dep) == 0)
> +		if (__dwc3_gadget_kick_transfer(dep, NULL) == 0)
>  			no_started_trb = false;
>  
>  out:
> @@ -3106,7 +3163,7 @@ static void dwc3_gadget_endpoint_command_complete(struct dwc3_ep *dep,
>  
>  	if ((dep->flags & DWC3_EP_DELAY_START) &&
>  	    !usb_endpoint_xfer_isoc(dep->endpoint.desc))
> -		__dwc3_gadget_kick_transfer(dep);
> +		__dwc3_gadget_kick_transfer(dep, NULL);
>  
>  	dep->flags &= ~DWC3_EP_DELAY_START;
>  }
>