netdev - [PATCH net-next V2 7/8] net: fec: don't transfer ownership until descriptor write is complete

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Message-Id: <1454709170-19527-8-git-send-email-troy.kisky@boundarydevices.com>
Date:	Fri,  5 Feb 2016 14:52:49 -0700
From:	Troy Kisky <troy.kisky@...ndarydevices.com>
To:	netdev@...r.kernel.org, davem@...emloft.net, B38611@...escale.com
Cc:	fabio.estevam@...escale.com, l.stach@...gutronix.de,
	andrew@...n.ch, tremyfr@...il.com, linux@....linux.org.uk,
	linux-arm-kernel@...ts.infradead.org, laci@...ndarydevices.com,
	shawnguo@...nel.org, johannes@...solutions.net, arnd@...db.de,
	Troy Kisky <troy.kisky@...ndarydevices.com>
Subject: [PATCH net-next V2 7/8] net: fec: don't transfer ownership until descriptor write is complete

If you don't own it, you shouldn't write to it.

Signed-off-by: Troy Kisky <troy.kisky@...ndarydevices.com>
---
 drivers/net/ethernet/freescale/fec_main.c | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/freescale/fec_main.c b/drivers/net/ethernet/freescale/fec_main.c
index ca2708d..97ca72a 100644
--- a/drivers/net/ethernet/freescale/fec_main.c
+++ b/drivers/net/ethernet/freescale/fec_main.c
@@ -390,6 +390,10 @@ fec_enet_txq_submit_frag_skb(struct fec_enet_priv_tx_q *txq,
 
 		bdp->cbd_bufaddr = cpu_to_fec32(addr);
 		bdp->cbd_datlen = cpu_to_fec16(frag_len);
+		/* Make sure the updates to rest of the descriptor are
+		 * performed before transferring ownership.
+		 */
+		wmb();
 		bdp->cbd_sc = cpu_to_fec16(status);
 	}
 
@@ -499,6 +503,10 @@ static int fec_enet_txq_submit_skb(struct fec_enet_priv_tx_q *txq,
 
 	bdp->cbd_datlen = cpu_to_fec16(buflen);
 	bdp->cbd_bufaddr = cpu_to_fec32(addr);
+	/* Make sure the updates to rest of the descriptor are performed before
+	 * transferring ownership.
+	 */
+	wmb();
 
 	/* Send it on its way.  Tell FEC it's ready, interrupt when done,
 	 * it's the last BD of the frame, and to put the CRC on the end.
@@ -1475,7 +1483,6 @@ rx_processing_done:
 
 		/* Mark the buffer empty */
 		status |= BD_ENET_RX_EMPTY;
-		bdp->cbd_sc = cpu_to_fec16(status);
 
 		if (fep->bufdesc_ex) {
 			struct bufdesc_ex *ebdp = (struct bufdesc_ex *)bdp;
@@ -1484,6 +1491,11 @@ rx_processing_done:
 			ebdp->cbd_prot = 0;
 			ebdp->cbd_bdu = 0;
 		}
+		/* Make sure the updates to rest of the descriptor are
+		 * performed before transferring ownership.
+		 */
+		wmb();
+		bdp->cbd_sc = cpu_to_fec16(status);
 
 		/* Update BD pointer to next entry */
 		bdp = fec_enet_get_nextdesc(bdp, &rxq->bd);
-- 
2.5.0