linux-kernel - Re: [RFC PATCH] usb: dwc3: Poll CMDACT after issuing EndXfer command

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Date: Thu, 25 Apr 2024 09:25:42 +0530
From: Prashanth K <quic_prashk@...cinc.com>
To: Thinh Nguyen <Thinh.Nguyen@...opsys.com>
CC: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Wesley Cheng
	<quic_wcheng@...cinc.com>,
        "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>,
        "linux-usb@...r.kernel.org"
	<linux-usb@...r.kernel.org>
Subject: Re: [RFC PATCH] usb: dwc3: Poll CMDACT after issuing EndXfer command



On 25-04-24 04:06 am, Thinh Nguyen wrote:
> 
> Thanks for the data.
> 
> Ok, I remember now why we did what we did. I just notice the Fixes
> commit you tag: b353eb6dc285 ("usb: dwc3: gadget: Skip waiting for
> CMDACT cleared during endxfer")
> 
> I forgot that at one point we skip CMDACT for End Transfer command.
> Let's not poll for CMDACT for End Transfer command and unconditionally
> wait 1ms. Otherwise we may run into the issue being stuck with CMDACT
> again while SETUP packet is not DMA out again. 1ms should be plenty of
> time for the End Transfer command to complete.
> 
> It should look like this:
> 
> diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
> index f94f68f1e7d2..dad30c6ab19d 100644
> --- a/drivers/usb/dwc3/gadget.c
> +++ b/drivers/usb/dwc3/gadget.c
> @@ -1724,8 +1724,7 @@ static int __dwc3_stop_active_transfer(struct dwc3_ep *dep, bool force, bool int
>          dep->resource_index = 0;
>   
>          if (!interrupt) {
> -               if (!DWC3_IP_IS(DWC3) || DWC3_VER_IS_PRIOR(DWC3, 310A))
> -                       mdelay(1);
> +               mdelay(1);
>                  dep->flags &= ~DWC3_EP_TRANSFER_STARTED;
>          } else if (!ret) {
>                  dep->flags |= DWC3_EP_END_TRANSFER_PENDING;
> 
> Thanks,
> Thinh
> 
> Ps. also please Cc stable.
Thanks for the suggestion, I had tried 1ms initially when encountering 
the issue and it was helping. Then I thought that CMDACT polling was 
better approach. But anyways I echo you, having common solution for all 
controller revisions is the cleaner way. I'll send V2 with mdelay(1).

Thanks again,
Prashanth K