[PATCH] usb: dwc3: Ignore late xferNotReady event to prevent halt timeout

[Kuen-Han Tsai <khtsai@google.com>]

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: 8f608e8ab628 ("usb: dwc3: gadget: remove unnecessary 'dwc' parameter")
Cc: stable <stable@kernel.org>
Signed-off-by: Kuen-Han Tsai <khtsai@google.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:>
---
 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..ad89cbeea761 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