linux-kernel - Re: [PATCH v2 1/2] usb: dwc3: Not set DWC3_EP_END_TRANSFER

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Date:   Mon, 14 Feb 2022 18:44:33 +0000
From:   Thinh Nguyen <Thinh.Nguyen@...opsys.com>
To:     Daehwan Jung <dh10.jung@...sung.com>,
        Felipe Balbi <balbi@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
CC:     "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>,
        "quic_wcheng@...cinc.com" <quic_wcheng@...cinc.com>,
        "quic_jackp@...cinc.com" <quic_jackp@...cinc.com>,
        Thinh Nguyen <Thinh.Nguyen@...opsys.com>
Subject: Re: [PATCH v2 1/2] usb: dwc3: Not set DWC3_EP_END_TRANSFER_PENDING in
 ep cmd fails

Hi,

Daehwan Jung wrote:
> It always sets DWC3_EP_END_TRANSFER_PENDING in dwc3_stop_active_transfer
> even if dwc3_send_gadget_ep_cmd fails. It can cause some problems like

How does it fail? Timed out?

> skipping clear stall commmand or giveback from dequeue. We fix to set it
> only when ep cmd success. Additionally, We clear DWC3_EP_TRANSFER_STARTED
> for next trb to start transfer not update transfer.

We shouldn't do this. Things will be out of sync. It may work for 1
scenario, but it won't work for others.

Please help me understand a few things:

1) What is the scenario that triggers this? Is it random?

2) Are there other traffics pending while issuing the End Transfer
command? If so, what transfer type(s)?

3) Have you tried increasing the timeout?

BR,
Thinh


> 
> Signed-off-by: Daehwan Jung <dh10.jung@...sung.com>
> ---
>  drivers/usb/dwc3/gadget.c | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
> index 183b90923f51..3ad3bc5813ca 100644
> --- a/drivers/usb/dwc3/gadget.c
> +++ b/drivers/usb/dwc3/gadget.c
> @@ -2044,6 +2044,12 @@ static int dwc3_gadget_ep_dequeue(struct usb_ep *ep,
>  				dwc3_gadget_move_cancelled_request(r,
>  						DWC3_REQUEST_STATUS_DEQUEUED);
>  
> +			/* If ep cmd fails, then force to giveback cancelled requests here */
> +			if (!(dep->flags & DWC3_EP_END_TRANSFER_PENDING)) {
> +				dep->flags &= ~DWC3_EP_TRANSFER_STARTED;
> +				dwc3_gadget_ep_cleanup_cancelled_requests(dep);
> +			}
> +
>  			dep->flags &= ~DWC3_EP_WAIT_TRANSFER_COMPLETE;
>  
>  			goto out;
> @@ -3645,7 +3651,7 @@ static void dwc3_stop_active_transfer(struct dwc3_ep *dep, bool force,
>  
>  	if (!interrupt)
>  		dep->flags &= ~DWC3_EP_TRANSFER_STARTED;
> -	else
> +	else if (!ret)
>  		dep->flags |= DWC3_EP_END_TRANSFER_PENDING;
>  }
>