net: enetc: add Tx checksum offload for i.MX95 ENETC

In addition to supporting Rx checksum offload, i.MX95 ENETC also supports
Tx checksum offload. The transmit checksum offload is implemented through
the Tx BD. To support Tx checksum offload, software needs to fill some
auxiliary information in Tx BD, such as IP version, IP header offset and
size, whether L4 is UDP or TCP, etc.

Same as Rx checksum offload, Tx checksum offload capability isn't defined
in register, so tx_csum bit is added to struct enetc_drvdata to indicate
whether the device supports Tx checksum offload.

Signed-off-by: Wei Fang <[email protected]>
Reviewed-by: Frank Li <[email protected]>
Reviewed-by: Claudiu Manoil <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>

Author: Wei Fang

drivers/net/ethernet/freescale/enetc/enetc.c

@@ -146,6 +146,27 @@ static int enetc_ptp_parse(struct sk_buff *skb, u8 *udp,
 	return 0;
 }
 
+static bool enetc_tx_csum_offload_check(struct sk_buff *skb)
+{
+	switch (skb->csum_offset) {
+	case offsetof(struct tcphdr, check):
+	case offsetof(struct udphdr, check):
+		return true;
+	default:
+		return false;
+	}
+}
+
+static bool enetc_skb_is_ipv6(struct sk_buff *skb)
+{
+	return vlan_get_protocol(skb) == htons(ETH_P_IPV6);
+}
+
+static bool enetc_skb_is_tcp(struct sk_buff *skb)
+{
+	return skb->csum_offset == offsetof(struct tcphdr, check);
+}
+
 static int enetc_map_tx_buffs(struct enetc_bdr *tx_ring, struct sk_buff *skb)
 {
 	bool do_vlan, do_onestep_tstamp = false, do_twostep_tstamp = false;
@@ -163,6 +184,29 @@ static int enetc_map_tx_buffs(struct enetc_bdr *tx_ring, struct sk_buff *skb)
 	dma_addr_t dma;
 	u8 flags = 0;
 
+	enetc_clear_tx_bd(&temp_bd);
+	if (skb->ip_summed == CHECKSUM_PARTIAL) {
+		/* Can not support TSD and checksum offload at the same time */
+		if (priv->active_offloads & ENETC_F_TXCSUM &&
+		    enetc_tx_csum_offload_check(skb) && !tx_ring->tsd_enable) {
+			temp_bd.l3_aux0 = FIELD_PREP(ENETC_TX_BD_L3_START,
+						     skb_network_offset(skb));
+			temp_bd.l3_aux1 = FIELD_PREP(ENETC_TX_BD_L3_HDR_LEN,
+						     skb_network_header_len(skb) / 4);
+			temp_bd.l3_aux1 |= FIELD_PREP(ENETC_TX_BD_L3T,
+						      enetc_skb_is_ipv6(skb));
+			if (enetc_skb_is_tcp(skb))
+				temp_bd.l4_aux = FIELD_PREP(ENETC_TX_BD_L4T,
+							    ENETC_TXBD_L4T_TCP);
+			else
+				temp_bd.l4_aux = FIELD_PREP(ENETC_TX_BD_L4T,
+							    ENETC_TXBD_L4T_UDP);
+			flags |= ENETC_TXBD_FLAGS_CSUM_LSO | ENETC_TXBD_FLAGS_L4CS;
+		} else if (skb_checksum_help(skb)) {
+			return 0;
+		}
+	}
+
 	i = tx_ring->next_to_use;
 	txbd = ENETC_TXBD(*tx_ring, i);
 	prefetchw(txbd);
@@ -173,7 +217,6 @@ static int enetc_map_tx_buffs(struct enetc_bdr *tx_ring, struct sk_buff *skb)
 
 	temp_bd.addr = cpu_to_le64(dma);
 	temp_bd.buf_len = cpu_to_le16(len);
-	temp_bd.lstatus = 0;
 
 	tx_swbd = &tx_ring->tx_swbd[i];
 	tx_swbd->dma = dma;
@@ -594,7 +637,7 @@ static netdev_tx_t enetc_start_xmit(struct sk_buff *skb,
 {
 	struct enetc_ndev_priv *priv = netdev_priv(ndev);
 	struct enetc_bdr *tx_ring;
-	int count, err;
+	int count;
 
 	/* Queue one-step Sync packet if already locked */
 	if (skb->cb[0] & ENETC_F_TX_ONESTEP_SYNC_TSTAMP) {
@@ -627,11 +670,6 @@ static netdev_tx_t enetc_start_xmit(struct sk_buff *skb,
 			return NETDEV_TX_BUSY;
 		}
 
-		if (skb->ip_summed == CHECKSUM_PARTIAL) {
-			err = skb_checksum_help(skb);
-			if (err)
-				goto drop_packet_err;
-		}
 		enetc_lock_mdio();
 		count = enetc_map_tx_buffs(tx_ring, skb);
 		enetc_unlock_mdio();
@@ -3274,6 +3312,7 @@ static const struct enetc_drvdata enetc_pf_data = {
 
 static const struct enetc_drvdata enetc4_pf_data = {
 	.sysclk_freq = ENETC_CLK_333M,
+	.tx_csum = true,
 	.pmac_offset = ENETC4_PMAC_OFFSET,
 	.eth_ops = &enetc4_pf_ethtool_ops,
 };

drivers/net/ethernet/freescale/enetc/enetc.h

@@ -234,6 +234,7 @@ enum enetc_errata {
 
 struct enetc_drvdata {
 	u32 pmac_offset; /* Only valid for PSI which supports 802.1Qbu */
+	u8 tx_csum:1;
 	u64 sysclk_freq;
 	const struct ethtool_ops *eth_ops;
 };
@@ -341,6 +342,7 @@ enum enetc_active_offloads {
 	ENETC_F_QBV			= BIT(9),
 	ENETC_F_QCI			= BIT(10),
 	ENETC_F_QBU			= BIT(11),
+	ENETC_F_TXCSUM			= BIT(12),
 };
 
 enum enetc_flags_bit {

drivers/net/ethernet/freescale/enetc/enetc_hw.h

@@ -558,7 +558,16 @@ union enetc_tx_bd {
 		__le16 frm_len;
 		union {
 			struct {
-				u8 reserved[3];
+				u8 l3_aux0;
+#define ENETC_TX_BD_L3_START	GENMASK(6, 0)
+#define ENETC_TX_BD_IPCS	BIT(7)
+				u8 l3_aux1;
+#define ENETC_TX_BD_L3_HDR_LEN	GENMASK(6, 0)
+#define ENETC_TX_BD_L3T		BIT(7)
+				u8 l4_aux;
+#define ENETC_TX_BD_L4T		GENMASK(7, 5)
+#define ENETC_TXBD_L4T_UDP	1
+#define ENETC_TXBD_L4T_TCP	2
 				u8 flags;
 			}; /* default layout */
 			__le32 txstart;
@@ -582,10 +591,10 @@ union enetc_tx_bd {
 };
 
 enum enetc_txbd_flags {
-	ENETC_TXBD_FLAGS_RES0 = BIT(0), /* reserved */
+	ENETC_TXBD_FLAGS_L4CS = BIT(0), /* For ENETC 4.1 and later */
 	ENETC_TXBD_FLAGS_TSE = BIT(1),
 	ENETC_TXBD_FLAGS_W = BIT(2),
-	ENETC_TXBD_FLAGS_RES3 = BIT(3), /* reserved */
+	ENETC_TXBD_FLAGS_CSUM_LSO = BIT(3), /* For ENETC 4.1 and later */
 	ENETC_TXBD_FLAGS_TXSTART = BIT(4),
 	ENETC_TXBD_FLAGS_EX = BIT(6),
 	ENETC_TXBD_FLAGS_F = BIT(7)

drivers/net/ethernet/freescale/enetc/enetc_pf_common.c

@@ -119,6 +119,9 @@ void enetc_pf_netdev_setup(struct enetc_si *si, struct net_device *ndev,
 
 	ndev->priv_flags |= IFF_UNICAST_FLT;
 
+	if (si->drvdata->tx_csum)
+		priv->active_offloads |= ENETC_F_TXCSUM;
+
 	/* TODO: currently, i.MX95 ENETC driver does not support advanced features */
 	if (!is_enetc_rev1(si)) {
 		ndev->hw_features &= ~(NETIF_F_HW_VLAN_CTAG_FILTER | NETIF_F_LOOPBACK);