From 33da49cd2e2cab9dad56f106204f2a2ae62b26dd Mon Sep 17 00:00:00 2001
From: Ruslan Bukin <br@FreeBSD.org>
Date: Wed, 29 May 2019 16:01:34 +0000
Subject: [PATCH] Don't copy the data from bounce buffer back to the mbuf if
 channel does not use bounce buffering.

Sponsored by:	DARPA, AFRL
---
 sys/dev/xdma/xdma_sg.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/sys/dev/xdma/xdma_sg.c b/sys/dev/xdma/xdma_sg.c
index a78ca5b8d2b..e6c593c7c47 100644
--- a/sys/dev/xdma/xdma_sg.c
+++ b/sys/dev/xdma/xdma_sg.c
@@ -348,7 +348,8 @@ xchan_seg_done(xdma_channel_t *xchan,
 				    BUS_DMASYNC_POSTREAD);
 			bus_dmamap_unload(xchan->dma_tag_bufs, b->map);
 		} else {
-			if (xr->req_type == XR_TYPE_MBUF &&
+			if ((xchan->caps & XCHAN_CAP_NOBUFS) == 0 &&
+			    xr->req_type == XR_TYPE_MBUF &&
 			    xr->direction == XDMA_DEV_TO_MEM)
 				m_copyback(xr->m, 0, st->transferred,
 				    (void *)xr->buf.vaddr);