dpaa_eth: perform DMA unmapping before read

[ Upstream commit c70fd318 ]

DMA unmapping is required before accessing the HW provided timestamping
information.

Fixes: 4664856e ("dpaa_eth: add support for hardware timestamping")
Signed-off-by: Madalin Bucur <madalin.bucur@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>

drivers/net/ethernet/freescale/dpaa/dpaa_eth.c

@@ -1620,18 +1620,6 @@ static struct sk_buff *dpaa_cleanup_tx_fd(const struct dpaa_priv *priv,
 	skbh = (struct sk_buff **)phys_to_virt(addr);
 	skb = *skbh;
 
-	if (priv->tx_tstamp && skb_shinfo(skb)->tx_flags & SKBTX_HW_TSTAMP) {
-		memset(&shhwtstamps, 0, sizeof(shhwtstamps));
-
-		if (!fman_port_get_tstamp(priv->mac_dev->port[TX], (void *)skbh,
-					  &ns)) {
-			shhwtstamps.hwtstamp = ns_to_ktime(ns);
-			skb_tstamp_tx(skb, &shhwtstamps);
-		} else {
-			dev_warn(dev, "fman_port_get_tstamp failed!\n");
-		}
-	}
-
 	if (unlikely(qm_fd_get_format(fd) == qm_fd_sg)) {
 		nr_frags = skb_shinfo(skb)->nr_frags;
 		dma_unmap_single(dev, addr,
@@ -1654,14 +1642,28 @@ static struct sk_buff *dpaa_cleanup_tx_fd(const struct dpaa_priv *priv,
 			dma_unmap_page(dev, qm_sg_addr(&sgt[i]),
 				       qm_sg_entry_get_len(&sgt[i]), dma_dir);
 		}
-
-		/* Free the page frag that we allocated on Tx */
-		skb_free_frag(phys_to_virt(addr));
 	} else {
 		dma_unmap_single(dev, addr,
 				 skb_tail_pointer(skb) - (u8 *)skbh, dma_dir);
 	}
 
+	/* DMA unmapping is required before accessing the HW provided info */
+	if (priv->tx_tstamp && skb_shinfo(skb)->tx_flags & SKBTX_HW_TSTAMP) {
+		memset(&shhwtstamps, 0, sizeof(shhwtstamps));
+
+		if (!fman_port_get_tstamp(priv->mac_dev->port[TX], (void *)skbh,
+					  &ns)) {
+			shhwtstamps.hwtstamp = ns_to_ktime(ns);
+			skb_tstamp_tx(skb, &shhwtstamps);
+		} else {
+			dev_warn(dev, "fman_port_get_tstamp failed!\n");
+		}
+	}
+
+	if (qm_fd_get_format(fd) == qm_fd_sg)
+		/* Free the page frag that we allocated on Tx */
+		skb_free_frag(phys_to_virt(addr));
+
 	return skb;
 }