Re: [PATCH v3] usb: dwc3: gadget: Prevent EP resource conflicts during StartTransfer

[Thinh Nguyen <Thinh.Nguyen@synopsys.com>]

On Wed, Oct 07, 2026, Selvarasu Ganesan wrote:
> 
> Sorry for the format issue. The updated answers as below,
> 
> No, the endpoint completion event is not seen after the -ETIMEDOUT error.
> 
> The proposed fix works well for the __dwc3_gadget_ep_set_halt sequence, 
> where DWC3_EP_END_TRANSFER_PENDING must be set to prevent dwc3_ep_queue 
> from starting a new transfer during a EP transfer timeout.
> 
> But, this is unnecessary for __dwc3_gadget_ep_disable. Since there's no 
> way to clear the pending flag if the interrupt is missed and no 
> dwc3_ep_queue calls occur until the EP is re-enabled, preserving 
> DWC3_EP_END_TRANSFER_PENDING here provides no benefit.
> 
> So, the below changes is not necessary in ep disable,
> 

We still need to keep DWC3_EP_END_TRANSFER_PENDING in ep_disable. That's
for the normal case where the End Transfer completes after ep_disable
returns, which is the original issue. If the command never completes,
the endpoint resource is stuck regardless. Clearing the flag only lead
to a NO_RESOURCE error later.

As for the dwc3_gadget_ep_queue() race during giveback, keeping
DWC3_EP_TRANSFER_STARTED isn't right. We should reject the queue when
the endpoint is disabled. This should be a separate patch:

diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
index ee837235630a..eb6666b7bb98 100644
--- a/drivers/usb/dwc3/gadget.c
+++ b/drivers/usb/dwc3/gadget.c
@@ -1084,6 +1084,8 @@ static int __dwc3_gadget_ep_disable(struct dwc3_ep *dep)
 	reg &= ~DWC3_DALEPENA_EP(dep->number);
 	dwc3_writel(dwc, DWC3_DALEPENA, reg);
 
+	dep->flags &= ~DWC3_EP_ENABLED;
+
 	dwc3_remove_requests(dwc, dep, -ESHUTDOWN);
 
 	dep->stream_capable = false;
@@ -1990,7 +1992,8 @@ static int __dwc3_gadget_ep_queue(struct dwc3_ep *dep, struct dwc3_request *req)
 {
 	struct dwc3		*dwc = dep->dwc;
 
-	if (!dep->endpoint.desc || !dwc->pullups_connected || !dwc->connected) {
+	if (!(dep->flags & DWC3_EP_ENABLED) || !dep->endpoint.desc ||
+	    !dwc->pullups_connected || !dwc->connected) {
 		dev_dbg(dwc->dev, "%s: can't queue to disabled endpoint\n",
 				dep->name);
 		return -ESHUTDOWN;


The End Transfer command not completing is also a separate issue. I
asked you to check whether the command would eventually complete with
the additional code, and it appears it doesn't.

Can you provide some more info on your setup:
 * IP and version
 * connected speed
 * endpoint direction (is it always OUT?)
 * Is there any active transfer
 * tracepoints

Thanks,
Thinh