dpaa_eth: enable Rx checksum offload

Use the FMan HW parser L4CV flag to offload Rx checksumming.
Signed-off-by: Madalin Bucur <madalin.bucur@nxp.com>

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

@@ -137,6 +137,13 @@ MODULE_PARM_DESC(tx_timeout, "The Tx timeout in ms");
 /* L4 Type field: TCP */
 #define FM_L4_PARSE_RESULT_TCP	0x20
 
+/* FD status field indicating whether the FM Parser has attempted to validate
+ * the L4 csum of the frame.
+ * Note that having this bit set doesn't necessarily imply that the checksum
+ * is valid. One would have to check the parse results to find that out.
+ */
+#define FM_FD_STAT_L4CV         0x00000004
+
 #define DPAA_SGT_MAX_ENTRIES 16 /* maximum number of entries in SG Table */
 #define DPAA_BUFF_RELEASE_MAX 8 /* maximum number of buffers released at once */
 
@@ -235,6 +242,7 @@ static int dpaa_netdev_init(struct net_device *net_dev,
 	 * For conformity, we'll still declare GSO explicitly.
 	 */
 	net_dev->features |= NETIF_F_GSO;
+	net_dev->features |= NETIF_F_RXCSUM;
 
 	net_dev->priv_flags |= IFF_LIVE_ADDR_CHANGE;
 	/* we do not want shared skbs on TX */
@@ -1526,6 +1534,23 @@ static struct sk_buff *dpaa_cleanup_tx_fd(const struct dpaa_priv *priv,
 	return skb;
 }
 
+static u8 rx_csum_offload(const struct dpaa_priv *priv, const struct qm_fd *fd)
+{
+	/* The parser has run and performed L4 checksum validation.
+	 * We know there were no parser errors (and implicitly no
+	 * L4 csum error), otherwise we wouldn't be here.
+	 */
+	if ((priv->net_dev->features & NETIF_F_RXCSUM) &&
+	    (be32_to_cpu(fd->status) & FM_FD_STAT_L4CV))
+		return CHECKSUM_UNNECESSARY;
+
+	/* We're here because either the parser didn't run or the L4 checksum
+	 * was not verified. This may include the case of a UDP frame with
+	 * checksum zero or an L4 proto other than TCP/UDP
+	 */
+	return CHECKSUM_NONE;
+}
+
 /* Build a linear skb around the received buffer.
  * We are guaranteed there is enough room at the end of the data buffer to
  * accommodate the shared info area of the skb.
@@ -1556,7 +1581,7 @@ static struct sk_buff *contig_fd_to_skb(const struct dpaa_priv *priv,
 	skb_reserve(skb, fd_off);
 	skb_put(skb, qm_fd_get_length(fd));
 
-	skb->ip_summed = CHECKSUM_NONE;
+	skb->ip_summed = rx_csum_offload(priv, fd);
 
 	return skb;
 
@@ -1616,7 +1641,7 @@ static struct sk_buff *sg_fd_to_skb(const struct dpaa_priv *priv,
 			if (WARN_ON(unlikely(!skb)))
 				goto free_buffers;
 
-			skb->ip_summed = CHECKSUM_NONE;
+			skb->ip_summed = rx_csum_offload(priv, fd);
 
 			/* Make sure forwarded skbs will have enough space
 			 * on Tx, if extra headers are added.