[PATCH 3/7] usb: dwc3: gadget: Handle ZLP for sg requests

[Thinh Nguyen <Thinh.Nguyen@synopsys.com>]

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
Fixes: 04c03d10e507 ("usb: dwc3: gadget: handle request->zero")
Signed-off-by: Thinh Nguyen <thinhn@synopsys.com>
---
 drivers/usb/dwc3/gadget.c | 31 +++++++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)

diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
index c0175dff194e..ced229aeccec 100644
--- a/drivers/usb/dwc3/gadget.c
+++ b/drivers/usb/dwc3/gadget.c
@@ -1137,6 +1137,37 @@ static void dwc3_prepare_one_trb_sg(struct dwc3_ep *dep,
 					req->request.short_not_ok,
 					req->request.no_interrupt,
 					req->request.is_last);
+		} 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,
+					       req->request.is_last);
+
+			/* 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,
+						       req->request.is_last);
+			}
 		} else {
 			dwc3_prepare_one_trb(dep, req, trb_length, chain, i);
 		}
-- 
2.28.0