From bc9a2e226ea95e1699f7590845554de095308b75 Mon Sep 17 00:00:00 2001
From: Thinh Nguyen <Thinh.Nguyen@synopsys.com>
Date: Thu, 6 Aug 2020 19:46:35 -0700
Subject: [PATCH] usb: dwc3: gadget: Handle ZLP for sg requests
Git-commit: bc9a2e226ea95e1699f7590845554de095308b75
References: git-fixes
Patch-mainline: v5.9-rc3

Currently dwc3 doesn't handle usb_request->zero for SG requests. This
change checks and prepares extra TRBs for the ZLP for SG requests.

Cc: <stable@vger.kernel.org> # v4.5+
Fixes: 04c03d10e507 ("usb: dwc3: gadget: handle request->zero")
Signed-off-by: Thinh Nguyen <thinhn@synopsys.com>
Signed-off-by: Felipe Balbi <balbi@kernel.org>
Signed-off-by: Oliver Neukum <oneukum@suse.com>
---
 drivers/usb/dwc3/gadget.c |   29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

--- a/drivers/usb/dwc3/gadget.c
+++ b/drivers/usb/dwc3/gadget.c
@@ -1106,6 +1106,35 @@ static void dwc3_prepare_one_trb_sg(stru
 					req->request.stream_id,
 					req->request.short_not_ok,
 					req->request.no_interrupt);
+		} else if (req->request.zero && req->request.length &&
+			   !usb_endpoint_xfer_isoc(dep->endpoint.desc) &&
+			   !rem && !chain) {
+			struct dwc3	*dwc = dep->dwc;
+			struct dwc3_trb *trb;
+
+			req->needs_extra_trb = true;
+
+			/* Prepare normal TRB */
+			dwc3_prepare_one_trb(dep, req, trb_length, true, i);
+
+			/* 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,
+						!req->direction, 1,
+						req->request.stream_id,
+						req->request.short_not_ok,
+						req->request.no_interrupt);
+
+			/* Prepare one more TRB to handle MPS alignment */
+			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);
+			}
 		} else {
 			dwc3_prepare_one_trb(dep, req, trb_length, chain, i);
 		}