FAILED: patch "[PATCH] usb: dwc3: gadget: Fix handling ZLP" failed to apply to 4.19-stable tree

[<gregkh@xxxxxxxxxxxxxxxxxxx>]

The patch below does not apply to the 4.19-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@xxxxxxxxxxxxxxx>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

>From d2ee3ff79e6a3d4105e684021017d100524dc560 Mon Sep 17 00:00:00 2001
From: Thinh Nguyen <Thinh.Nguyen@xxxxxxxxxxxx>
Date: Thu, 6 Aug 2020 19:46:29 -0700
Subject: [PATCH] usb: dwc3: gadget: Fix handling ZLP

The usb_request->zero doesn't apply for isoc. Also, if we prepare a
0-length (ZLP) TRB for the OUT direction, we need to prepare an extra
TRB to pad up to the MPS alignment. Use the same bounce buffer for the
ZLP TRB and the extra pad TRB.

Cc: <stable@xxxxxxxxxxxxxxx> # v4.5+
Fixes: d6e5a549cc4d ("usb: dwc3: simplify ZLP handling")
Fixes: 04c03d10e507 ("usb: dwc3: gadget: handle request->zero")
Signed-off-by: Thinh Nguyen <thinhn@xxxxxxxxxxxx>
Signed-off-by: Felipe Balbi <balbi@xxxxxxxxxx>

diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
index f9231253cbed..df603a817a98 100644
--- a/drivers/usb/dwc3/gadget.c
+++ b/drivers/usb/dwc3/gadget.c
@@ -1199,6 +1199,7 @@ static void dwc3_prepare_one_trb_linear(struct dwc3_ep *dep,
 				req->request.no_interrupt,
 				req->request.is_last);
 	} else if (req->request.zero && req->request.length &&
+		   !usb_endpoint_xfer_isoc(dep->endpoint.desc) &&
 		   (IS_ALIGNED(req->request.length, maxp))) {
 		struct dwc3	*dwc = dep->dwc;
 		struct dwc3_trb	*trb;
@@ -1208,14 +1209,25 @@ static void dwc3_prepare_one_trb_linear(struct dwc3_ep *dep,
 		/* prepare normal TRB */
 		dwc3_prepare_one_trb(dep, req, length, true, 0);
 
-		/* Now prepare one extra TRB to handle ZLP */
+		/* Prepare one extra TRB to handle ZLP */
 		trb = &dep->trb_pool[dep->trb_enqueue];
 		req->num_trbs++;
 		__dwc3_prepare_one_trb(dep, trb, dwc->bounce_addr, 0,
-				false, 1, req->request.stream_id,
+				!req->direction, 1, req->request.stream_id,
 				req->request.short_not_ok,
 				req->request.no_interrupt,
 				req->request.is_last);
+
+		/* Prepare one more TRB to handle MPS alignment for OUT */
+		if (!req->direction) {
+			trb = &dep->trb_pool[dep->trb_enqueue];
+			req->num_trbs++;
+			__dwc3_prepare_one_trb(dep, trb, dwc->bounce_addr, maxp,
+					       false, 1, req->request.stream_id,
+					       req->request.short_not_ok,
+					       req->request.no_interrupt,
+					       req->request.is_last);
+		}
 	} else {
 		dwc3_prepare_one_trb(dep, req, length, false, 0);
 	}
@@ -2690,8 +2702,17 @@ static int dwc3_gadget_ep_cleanup_completed_request(struct dwc3_ep *dep,
 				status);
 
 	if (req->needs_extra_trb) {
+		unsigned int maxp = usb_endpoint_maxp(dep->endpoint.desc);
+
 		ret = dwc3_gadget_ep_reclaim_trb_linear(dep, req, event,
 				status);
+
+		/* Reclaim MPS padding TRB for ZLP */
+		if (!req->direction && req->request.zero && req->request.length &&
+		    !usb_endpoint_xfer_isoc(dep->endpoint.desc) &&
+		    (IS_ALIGNED(req->request.length, maxp)))
+			ret = dwc3_gadget_ep_reclaim_trb_linear(dep, req, event, status);
+
 		req->needs_extra_trb = false;
 	}