From: Shenwei Wang <shenwei.wang@xxxxxxx>
[ Upstream commit 9025944fddfed5966c8f102f1fe921ab3aee2c12 ]
Two dma_wmb() are added in the XDP TX path to ensure proper ordering of
descriptor and buffer updates:
1. A dma_wmb() is added after updating the last BD to make sure
the updates to rest of the descriptor are visible before
transferring ownership to FEC.
2. A dma_wmb() is also added after updating the bdp to ensure these
updates are visible before updating txq->bd.cur.
3. Start the xmit of the frame immediately right after configuring the
tx descriptor.
Fixes: 6d6b39f180b8 ("net: fec: add initial XDP support")
Signed-off-by: Shenwei Wang <shenwei.wang@xxxxxxx>
Reviewed-by: Wei Fang <wei.fang@xxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
drivers/net/ethernet/freescale/fec_main.c | 17 +++++++++++------
1 file changed, 11 insertions(+), 6 deletions(-)
diff --git a/drivers/net/ethernet/freescale/fec_main.c b/drivers/net/ethernet/freescale/fec_main.c
index 577d94821b3e7..38e5b5abe067c 100644
--- a/drivers/net/ethernet/freescale/fec_main.c
+++ b/drivers/net/ethernet/freescale/fec_main.c
@@ -3834,6 +3834,11 @@ static int fec_enet_txq_xmit_frame(struct fec_enet_private *fep,
index = fec_enet_get_bd_index(last_bdp, &txq->bd);
txq->tx_skbuff[index] = NULL;
+ /* Make sure the updates to rest of the descriptor are performed before
+ * transferring ownership.
+ */
+ dma_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.
*/
@@ -3843,8 +3848,14 @@ static int fec_enet_txq_xmit_frame(struct fec_enet_private *fep,
/* If this was the last BD in the ring, start at the beginning again. */
bdp = fec_enet_get_nextdesc(last_bdp, &txq->bd);
+ /* Make sure the update to bdp are performed before txq->bd.cur. */
+ dma_wmb();
+
txq->bd.cur = bdp;
+ /* Trigger transmission start */
+ writel(0, txq->bd.reg_desc_active);
+
return 0;
}
@@ -3873,12 +3884,6 @@ static int fec_enet_xdp_xmit(struct net_device *dev,
sent_frames++;
}
- /* Make sure the update to bdp and tx_skbuff are performed. */
- wmb();
-
- /* Trigger transmission start */
- writel(0, txq->bd.reg_desc_active);
-
__netif_tx_unlock(nq);
return sent_frames;
--
2.39.2
