linux-kernel - Re: [PATCH v2] usb: dwc3: Ignore late xferNotReady event to prevent halt timeout

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Message-ID: <20250807223353.2h6ytbxqkkzijfgx@synopsys.com>
Date: Thu, 7 Aug 2025 22:33:56 +0000
From: Thinh Nguyen <Thinh.Nguyen@...opsys.com>
To: Kuen-Han Tsai <khtsai@...gle.com>
CC: Thinh Nguyen <Thinh.Nguyen@...opsys.com>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        stable <stable@...nel.org>
Subject: Re: [PATCH v2] usb: dwc3: Ignore late xferNotReady event to prevent
 halt timeout

On Thu, Aug 07, 2025, Kuen-Han Tsai wrote:
> During a device-initiated disconnect, the End Transfer command resets
> the event filter, allowing a new xferNotReady event to be generated
> before the controller is fully halted. Processing this late event
> incorrectly triggers a Start Transfer, which prevents the controller
> from halting and results in a DSTS.DEVCTLHLT bit polling timeout.
> 
> Ignore the late xferNotReady event if the controller is already in a
> disconnected state.
> 
> Fixes: 72246da40f37 ("usb: Introduce DesignWare USB3 DRD Driver")
> Cc: stable <stable@...nel.org>
> Signed-off-by: Kuen-Han Tsai <khtsai@...gle.com>
> ---
> Tracing:
> 
> # Stop active transfers by sending End Transfer commands
> dwc3_gadget_ep_cmd: ep1out: cmd 'End Transfer' [20d08] params 00000000 00000000 00000000 --> status: Successful
> dwc3_gadget_ep_cmd: ep1in: cmd 'End Transfer' [40d08] params 00000000 00000000 00000000 --> status: Successful
>  ...
> # Recieve an xferNotReady event on an ISOC IN endpoint
> dwc3_event: event (35d010c6): ep1in: Transfer Not Ready [000035d0] (Not Active)
> dwc3_gadget_ep_cmd: ep1in: cmd 'Start Transfer' [35d60406] params 00000000 ffffb620 00000000 --> status: Successful
> dwc3_gadget_ep_cmd: ep2in: cmd 'End Transfer' [30d08] params 00000000 00000000 00000000 --> status: Timed Out
>  ...
> # Start polling DSTS.DEVCTRLHLT
> dwc3_gadget_run_stop: start polling DWC3_DSTS_DEVCTRLHLT
>  ...
> # HALT timeout and print out the endpoint status for debugging
> dwc3_gadget_run_stop: finish polling DWC3_DSTS_DEVCTRLHLT, is_on=0, reg=0
> dwc3_gadget_ep_status: ep1out: mps 1024/2765 streams 16 burst 5 ring 64/56 flags E:swbp:>
> dwc3_gadget_ep_status: ep1in: mps 1024/1024 streams 16 burst 2 ring 21/64 flags E:swBp:<
> dwc3_gadget_ep_status: ep2out: mps 1024/2765 streams 16 burst 5 ring 56/48 flags e:swbp:>
> 
> ---
> v1 -> v2: Updated the commit ID for the Fixes tag and added the missing !.
> 
>  drivers/usb/dwc3/gadget.c | 9 +++++++++
>  1 file changed, 9 insertions(+)
> 
> diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
> index 25db36c63951..68fa2813e5f4 100644
> --- a/drivers/usb/dwc3/gadget.c
> +++ b/drivers/usb/dwc3/gadget.c
> @@ -3777,6 +3777,15 @@ static void dwc3_gadget_endpoint_transfer_complete(struct dwc3_ep *dep,
>  static void dwc3_gadget_endpoint_transfer_not_ready(struct dwc3_ep *dep,
>  		const struct dwc3_event_depevt *event)
>  {
> +	/*
> +	 * During a device-initiated disconnect, a late xferNotReady event can
> +	 * be generated after the End Transfer command resets the event filter,
> +	 * but before the controller is halted. Ignore it to prevent a new
> +	 * transfer from starting.
> +	 */
> +	if (!dep->dwc->connected)
> +		return;
> +
>  	dwc3_gadget_endpoint_frame_from_event(dep, event);
> 
>  	/*
> --
> 2.50.1.565.gc32cd1483b-goog
> 

Acked-by: Thinh Nguyen <Thinh.Nguyen@...opsys.com>

Thanks,
Thinh