linux-kernel - [PATCH] usb: dwc3: gadget: Clear req->needs_extra

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Message-Id: <20181221232005.5301-1-jackp@codeaurora.org>
Date:   Fri, 21 Dec 2018 15:20:05 -0800
From:   Jack Pham <jackp@...eaurora.org>
To:     Felipe Balbi <balbi@...nel.org>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        Jack Pham <jackp@...eaurora.org>
Subject: [PATCH] usb: dwc3: gadget: Clear req->needs_extra_trb flag on cleanup

OUT endpoint requests may somtimes have this flag set when
preparing to be submitted to HW indicating that there is an
additional TRB chained to the request for alignment purposes.
If that request is removed before the controller can execute the
transfer (e.g. ep_dequeue/ep_disable), the request will not go
through the dwc3_gadget_ep_cleanup_completed_request() handler
and will not have its needs_extra_trb flag cleared when
dwc3_gadget_giveback() is called.  This same request could be
later requeued for a new transfer that does not require an
extra TRB and if it is successfully completed, the cleanup
and TRB reclamation will incorrectly process the additional TRB
which belongs to the next request, and incorrectly advances the
TRB dequeue pointer, thereby messing up calculation of the next
requeust's actual/remaining count when it completes.

The right thing to do here is to ensure that the flag is cleared
before it is given back to the function driver.  A good place
to do that is in dwc3_gadget_del_and_unmap_request().

Signed-off-by: Jack Pham <jackp@...eaurora.org>
---
Hi Felipe,

There's probably zero chance this is making it to 4.20, so if you take
this after 4.21-rc1 so be it. But should this be Cc: stable? If so it
needs to be sent separately for <= 4.19 as needs_extra_trb was previously
req->unaligned and req->zero.

Thanks,
Jack

 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 2ecde30ad0b7..e97b14f444c8 100644
--- a/drivers/usb/dwc3/gadget.c
+++ b/drivers/usb/dwc3/gadget.c
@@ -177,6 +177,7 @@ static void dwc3_gadget_del_and_unmap_request(struct dwc3_ep *dep,
 	req->started = false;
 	list_del(&req->list);
 	req->remaining = 0;
+	req->needs_extra_trb = false;

 	if (req->request.status == -EINPROGRESS)
 		req->request.status = status;
-- 
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