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From:   Elson Roy Serrao <quic_eserrao@quicinc.com>
To:     gregkh@linuxfoundation.org, Thinh.Nguyen@synopsys.com
Cc:     linux-kernel@vger.kernel.org, linux-usb@vger.kernel.org,
        quic_wcheng@quicinc.com, quic_jackp@quicinc.com,
        Elson Roy Serrao <quic_eserrao@quicinc.com>
Subject: [PATCH v2] usb: dwc3: gadget: Reset num TRBs before giving back the request
Date:   Thu,  1 Jun 2023 14:27:30 -0700
Message-Id: <1685654850-8468-1-git-send-email-quic_eserrao@quicinc.com>
Precedence: bulk

Consider a scenario where cable disconnect happens when there is an active
usb reqest queued to the UDC. As part of the disconnect we would issue an
end transfer with no interrupt-on-completion before giving back this
request. Since we are giving back the request without skipping TRBs the
num_trbs field of dwc3_request still holds the stale value previously used.
Function drivers re-use same request for a given bind-unbind session and
hence their dwc3_request context gets preserved across cable
disconnect/connect. When such a request gets re-queued after cable connect,
we would increase the num_trbs field on top of the previous stale value
thus incorrectly representing the number of TRBs used. Fix this by
resetting num_trbs field before giving back the request.

Fixes: 09fe1f8d7e2f ("usb: dwc3: gadget: track number of TRBs per request")
Signed-off-by: Elson Roy Serrao <quic_eserrao@quicinc.com>
---
Changes in v2:
 - Addressed Thinh's comment to reset num_trbs in dwc3_gadget_del_and_unmap_request
   rather than calling skip_trbs.
 - Modify the commit message to match the modification.

 drivers/usb/dwc3/gadget.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
index 578804d..0ded919 100644
--- a/drivers/usb/dwc3/gadget.c
+++ b/drivers/usb/dwc3/gadget.c
@@ -198,6 +198,7 @@ static void dwc3_gadget_del_and_unmap_request(struct dwc3_ep *dep,
 	list_del(&req->list);
 	req->remaining = 0;
 	req->needs_extra_trb = false;
+	req->num_trbs = 0;
 
 	if (req->request.status == -EINPROGRESS)
 		req->request.status = status;
-- 
2.7.4