linux-kernel - Re: [PATCH v4 6/8] usb: dwc3: check for requests in started list for stream capable endpoints

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Date:   Mon, 10 Sep 2018 20:13:51 +0000
From:   Thinh Nguyen <Thinh.Nguyen@...opsys.com>
To:     Anurag Kumar Vulisha <anurag.kumar.vulisha@...inx.com>,
        "balbi@...nel.org" <balbi@...nel.org>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>
CC:     "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Thinh.Nguyen@...opsys.com" <Thinh.Nguyen@...opsys.com>,
        "v.anuragkumar@...il.com" <v.anuragkumar@...il.com>
Subject: Re: [PATCH v4 6/8] usb: dwc3: check for requests in started list
 for stream capable endpoints

Hi Anurag,

On 9/8/2018 8:03 AM, Anurag Kumar Vulisha wrote:
> For stream capable endpoints, uas layer can queue mulpile requests on
> single ep with different stream ids. So, there can be multiple pending
> requests waiting to be transferred. This patch changes the code to check
> for any pending requests waiting to be transferred on ep started_list and
> calls __dwc3_gadget_kick_transfer() if any.

Whenever a function driver queues a request, then
__dwc3_gadget_kick_transfer() will be called right? What case exactly is
this for? Scatter gathering? If so, then we probably need further
explanation. (e.g. Why wait to call __dwc3_gadget_kick_transfer() on
XferComplete event rather than sending a START_TRANSFER command for
every prepared TRB whenever we do __dwc3_gadget_kick_transfer()?).

Thanks,
Thinh

>
> Signed-off-by: Anurag Kumar Vulisha <anurag.kumar.vulisha@...inx.com>
> Reviewed-by: Thinh Nguyen <thinhn@...opsys.com>
> ---
>  Changes in v4:
> 	1. None
>
>  Changes in v3:
> 	1. None
>
>  Changes in v2:
> 	1. None
> ---
>  drivers/usb/dwc3/gadget.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
> index 97bfdf0..c50cad8 100644
> --- a/drivers/usb/dwc3/gadget.c
> +++ b/drivers/usb/dwc3/gadget.c
> @@ -2433,6 +2433,9 @@ static void dwc3_gadget_endpoint_transfer_in_progress(struct dwc3_ep *dep,
>  
>  	dwc3_gadget_ep_cleanup_completed_requests(dep, event, status);
>  
> +	if (dep->stream_capable && !list_empty(&dep->started_list))
> +		__dwc3_gadget_kick_transfer(dep);
> +
>  	if (stop) {
>  		dwc3_stop_active_transfer(dep, true);
>  		dep->flags = DWC3_EP_ENABLED;