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From:   John Stultz <john.stultz@linaro.org>
To:     linux-kernel@vger.kernel.org
Cc:     Anurag Kumar Vulisha <anurag.kumar.vulisha@xilinx.com>,
        Felipe Balbi <felipe.balbi@linux.intel.com>,
        Fei Yang <fei.yang@intel.com>,
        Thinh Nguyen <thinhn@synopsys.com>,
        Tejas Joglekar <tejas.joglekar@synopsys.com>,
        Andrzej Pietrasiewicz <andrzej.p@collabora.com>,
        Greg KH <gregkh@linuxfoundation.org>,
        Linux USB List <linux-usb@vger.kernel.org>,
        stable <stable@vger.kernel.org>,
        John Stultz <john.stultz@linaro.org>
Subject: [PATCH] usb: dwc3: Check for IOC/LST bit in both event->status and TRB->ctrl fields
Date:   Tue, 23 Jul 2019 20:27:35 +0000
Message-Id: <20190723202735.113381-1-john.stultz@linaro.org>
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From: Anurag Kumar Vulisha <anurag.kumar.vulisha@xilinx.com>

The present code in dwc3_gadget_ep_reclaim_completed_trb() will check
for IOC/LST bit in the event->status and returns if IOC/LST bit is
set. This logic doesn't work if multiple TRBs are queued per
request and the IOC/LST bit is set on the last TRB of that request.
Consider an example where a queued request has multiple queued TRBs
and IOC/LST bit is set only for the last TRB. In this case, the Core
generates XferComplete/XferInProgress events only for the last TRB
(since IOC/LST are set only for the last TRB). As per the logic in
dwc3_gadget_ep_reclaim_completed_trb() event->status is checked for
IOC/LST bit and returns on the first TRB. This makes the remaining
TRBs left unhandled.
To aviod this, changed the code to check for IOC/LST bits in both
event->status & TRB->ctrl. This patch does the same.

At a practical level, this patch resolves USB transfer stalls seen
with adb on dwc3 based Android devices after functionfs gadget
added scatter-gather support around v4.20.

Cc: Felipe Balbi <felipe.balbi@linux.intel.com>
Cc: Fei Yang <fei.yang@intel.com>
Cc: Thinh Nguyen <thinhn@synopsys.com>
Cc: Tejas Joglekar <tejas.joglekar@synopsys.com>
Cc: Andrzej Pietrasiewicz <andrzej.p@collabora.com>
Cc: Greg KH <gregkh@linuxfoundation.org>
Cc: Linux USB List <linux-usb@vger.kernel.org>
Cc: stable <stable@vger.kernel.org>
Tested-By: Tejas Joglekar <tejas.joglekar@synopsys.com>
Reviewed-by: Thinh Nguyen <thinhn@synopsys.com>
Signed-off-by: Anurag Kumar Vulisha <anurag.kumar.vulisha@xilinx.com>
[jstultz: forward ported to mainline, added note to commit log]
Signed-off-by: John Stultz <john.stultz@linaro.org>
---
Just wanted to send this out so we're all looking at the same thing.
Not sure if its correct, but it seems to solve the adb stalls I've
been seeing for awhile.

 thanks
 -john

 drivers/usb/dwc3/gadget.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
index c9cecb3a9670..1d9701dde69b 100644
--- a/drivers/usb/dwc3/gadget.c
+++ b/drivers/usb/dwc3/gadget.c
@@ -2394,7 +2394,12 @@ static int dwc3_gadget_ep_reclaim_completed_trb(struct dwc3_ep *dep,
 	if (event->status & DEPEVT_STATUS_SHORT && !chain)
 		return 1;
 
-	if (event->status & DEPEVT_STATUS_IOC)
+	if ((event->status & DEPEVT_STATUS_IOC) &&
+	    (trb->ctrl & DWC3_TRB_CTRL_IOC))
+		return 1;
+
+	if ((event->status & DEPEVT_STATUS_LST) &&
+	    (trb->ctrl & DWC3_TRB_CTRL_LST))
 		return 1;
 
 	return 0;
-- 
2.17.1