[PATCH 5.13 093/175] usb: cdnsp: Fixed issue with ZLP

[Greg Kroah-Hartman]

From: Pawel Laszczak <pawell@xxxxxxxxxxx>

commit e913aada06830338633fb8524733b0ad3d38a7c1 upstream.

The condition "if (need_zero_pkt && zero_len_trb)" was always false
and it caused that TRB for ZLP was not prepared.

Fix causes that after preparing last TRB in TD, the driver prepares
additional TD with ZLP when a ZLP is required.

Cc: <stable@xxxxxxxxxxxxxxx>
Fixes: 3d82904559f4 ("usb: cdnsp: cdns3 Add main part of Cadence USBSSP DRD Driver")
Signed-off-by: Pawel Laszczak <pawell@xxxxxxxxxxx>
Link: https://lore.kernel.org/r/20210623072728.41275-1-pawell@xxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Peter Chen <peter.chen@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 drivers/usb/cdns3/cdnsp-ring.c |   18 ++++++++----------
 1 file changed, 8 insertions(+), 10 deletions(-)

--- a/drivers/usb/cdns3/cdnsp-ring.c
+++ b/drivers/usb/cdns3/cdnsp-ring.c
@@ -1932,15 +1932,13 @@ int cdnsp_queue_bulk_tx(struct cdnsp_dev
 		}
 
 		if (enqd_len + trb_buff_len >= full_len) {
-			if (need_zero_pkt && zero_len_trb) {
-				zero_len_trb = true;
-			} else {
-				field &= ~TRB_CHAIN;
-				field |= TRB_IOC;
-				more_trbs_coming = false;
-				need_zero_pkt = false;
-				preq->td.last_trb = ring->enqueue;
-			}
+			if (need_zero_pkt)
+				zero_len_trb = !zero_len_trb;
+
+			field &= ~TRB_CHAIN;
+			field |= TRB_IOC;
+			more_trbs_coming = false;
+			preq->td.last_trb = ring->enqueue;
 		}
 
 		/* Only set interrupt on short packet for OUT endpoints. */
@@ -1955,7 +1953,7 @@ int cdnsp_queue_bulk_tx(struct cdnsp_dev
 		length_field = TRB_LEN(trb_buff_len) | TRB_TD_SIZE(remainder) |
 			TRB_INTR_TARGET(0);
 
-		cdnsp_queue_trb(pdev, ring, more_trbs_coming | need_zero_pkt,
+		cdnsp_queue_trb(pdev, ring, more_trbs_coming | zero_len_trb,
 				lower_32_bits(send_addr),
 				upper_32_bits(send_addr),
 				length_field,