netdev - [RFC 2/2] ravb: Add Rx checksum offload support

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Message-Id: <20211123133157.21829-3-biju.das.jz@bp.renesas.com>
Date:   Tue, 23 Nov 2021 13:31:57 +0000
From:   Biju Das <biju.das.jz@...renesas.com>
To:     "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>
Cc:     Biju Das <biju.das.jz@...renesas.com>,
        Sergey Shtylyov <s.shtylyov@....ru>,
        Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>,
        Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>,
        netdev@...r.kernel.org, linux-renesas-soc@...r.kernel.org,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Chris Paterson <Chris.Paterson2@...esas.com>,
        Biju Das <biju.das@...renesas.com>
Subject: [RFC 2/2] ravb: Add Rx checksum offload support

TOE has hw support for calculating IP header checkum for IPV4 and
TCP/UDP/ICMP checksum for both IPV4 and IPV6.

This patch adds Rx checksum offload supported by TOE.

Signed-off-by: Biju Das <biju.das.jz@...renesas.com>
---
 drivers/net/ethernet/renesas/ravb.h      |  4 +++
 drivers/net/ethernet/renesas/ravb_main.c | 31 ++++++++++++++++++++++++
 2 files changed, 35 insertions(+)

diff --git a/drivers/net/ethernet/renesas/ravb.h b/drivers/net/ethernet/renesas/ravb.h
index a96552348e2d..d0e5eec0636e 100644
--- a/drivers/net/ethernet/renesas/ravb.h
+++ b/drivers/net/ethernet/renesas/ravb.h
@@ -44,6 +44,10 @@
 #define RAVB_RXTSTAMP_TYPE_ALL	0x00000006
 #define RAVB_RXTSTAMP_ENABLED	0x00000010	/* Enable RX timestamping */
 
+/* GbEthernet TOE hardware checksum values */
+#define TOE_RX_CSUM_OK		0x0000
+#define TOE_RX_CSUM_UNSUPPORTED	0xFFFF
+
 enum ravb_reg {
 	/* AVB-DMAC registers */
 	CCC	= 0x0000,
diff --git a/drivers/net/ethernet/renesas/ravb_main.c b/drivers/net/ethernet/renesas/ravb_main.c
index c2b92c6a6cd2..2533e3401593 100644
--- a/drivers/net/ethernet/renesas/ravb_main.c
+++ b/drivers/net/ethernet/renesas/ravb_main.c
@@ -720,6 +720,33 @@ static void ravb_get_tx_tstamp(struct net_device *ndev)
 	}
 }
 
+static void ravb_rx_csum_gbeth(struct sk_buff *skb)
+{
+	u32 csum_ip_hdr, csum_proto;
+	u8 *hw_csum;
+
+	/* The hardware checksum is contained in sizeof(__sum16) * 2 = 4 bytes
+	 * appended to packet data. First 2 bytes is ip header csum and last
+	 * 2 bytes is protocol csum.
+	 */
+	if (unlikely(skb->len < sizeof(__sum16) * 2))
+		return;
+	hw_csum = skb_tail_pointer(skb) - sizeof(__sum16);
+	csum_proto = csum_unfold((__force __sum16)get_unaligned_le16(hw_csum));
+
+	hw_csum = skb_tail_pointer(skb) - 2 * sizeof(__sum16);
+	csum_ip_hdr = csum_unfold((__force __sum16)get_unaligned_le16(hw_csum));
+
+	skb->ip_summed = CHECKSUM_NONE;
+	if (csum_proto == TOE_RX_CSUM_OK) {
+		if (skb->protocol == htons(ETH_P_IP) && csum_ip_hdr == TOE_RX_CSUM_OK)
+			skb->ip_summed = CHECKSUM_UNNECESSARY;
+		else if (skb->protocol == htons(ETH_P_IPV6) &&
+			 csum_ip_hdr == TOE_RX_CSUM_UNSUPPORTED)
+			skb->ip_summed = CHECKSUM_UNNECESSARY;
+	}
+}
+
 static void ravb_rx_csum(struct sk_buff *skb)
 {
 	u8 *hw_csum;
@@ -805,6 +832,8 @@ static bool ravb_rx_gbeth(struct net_device *ndev, int *quota, int q)
 				skb = ravb_get_skb_gbeth(ndev, entry, desc);
 				skb_put(skb, pkt_len);
 				skb->protocol = eth_type_trans(skb, ndev);
+				if (ndev->features & NETIF_F_RXCSUM)
+					ravb_rx_csum_gbeth(skb);
 				napi_gro_receive(&priv->napi[q], skb);
 				stats->rx_packets++;
 				stats->rx_bytes += pkt_len;
@@ -832,6 +861,8 @@ static bool ravb_rx_gbeth(struct net_device *ndev, int *quota, int q)
 				dev_kfree_skb(skb);
 				priv->rx_1st_skb->protocol =
 					eth_type_trans(priv->rx_1st_skb, ndev);
+				if (ndev->features & NETIF_F_RXCSUM)
+					ravb_rx_csum_gbeth(skb);
 				napi_gro_receive(&priv->napi[q],
 						 priv->rx_1st_skb);
 				stats->rx_packets++;
-- 
2.17.1