net: netcp: use hw capability to remove FCS word from rx packets

Some of the newer Ethernet switch hw (such as that on k2e/l/g) can
strip the Etherenet FCS from packet at the port 0 egress of the switch.
So use this capability instead of doing it in software.
Signed-off-by: Murali Karicheri <m-karicheri2@ti.com>
Signed-off-by: Sekhar Nori <nsekhar@ti.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/ti/netcp.h

@@ -102,6 +102,8 @@ struct netcp_intf {
 	void			*rx_fdq[KNAV_DMA_FDQ_PER_CHAN];
 	struct napi_struct	rx_napi;
 	struct napi_struct	tx_napi;
+#define ETH_SW_CAN_REMOVE_ETH_FCS	BIT(0)
+	u32			hw_cap;
 
 	/* 64-bit netcp stats */
 	struct netcp_stats	stats;

drivers/net/ethernet/ti/netcp_core.c

@@ -739,8 +739,12 @@ static int netcp_process_one_rx_packet(struct netcp_intf *netcp)
 		dev_dbg(netcp->ndev_dev, "mismatch in packet size(%d) & sum of fragments(%d)\n",
 			pkt_sz, accum_sz);
 
-	/* Remove ethernet FCS from the packet */
-	__pskb_trim(skb, skb->len - ETH_FCS_LEN);
+	/* Newer version of the Ethernet switch can trim the Ethernet FCS
+	 * from the packet and is indicated in hw_cap. So trim it only for
+	 * older h/w
+	 */
+	if (!(netcp->hw_cap & ETH_SW_CAN_REMOVE_ETH_FCS))
+		__pskb_trim(skb, skb->len - ETH_FCS_LEN);
 
 	/* Call each of the RX hooks */
 	p_info.skb = skb;

drivers/net/ethernet/ti/netcp_ethss.c

@@ -122,6 +122,7 @@
 #define MACSL_FULLDUPLEX			BIT(0)
 
 #define GBE_CTL_P0_ENABLE			BIT(2)
+#define ETH_SW_CTL_P0_TX_CRC_REMOVE		BIT(13)
 #define GBE13_REG_VAL_STAT_ENABLE_ALL		0xff
 #define XGBE_REG_VAL_STAT_ENABLE_ALL		0xf
 #define GBE_STATS_CD_SEL			BIT(28)
@@ -2821,7 +2822,7 @@ static int gbe_open(void *intf_priv, struct net_device *ndev)
 	struct netcp_intf *netcp = netdev_priv(ndev);
 	struct gbe_slave *slave = gbe_intf->slave;
 	int port_num = slave->port_num;
-	u32 reg;
+	u32 reg, val;
 	int ret;
 
 	reg = readl(GBE_REG_ADDR(gbe_dev, switch_regs, id_ver));
@@ -2851,7 +2852,12 @@ static int gbe_open(void *intf_priv, struct net_device *ndev)
 	writel(0, GBE_REG_ADDR(gbe_dev, switch_regs, ptype));
 
 	/* Control register */
-	writel(GBE_CTL_P0_ENABLE, GBE_REG_ADDR(gbe_dev, switch_regs, control));
+	val = GBE_CTL_P0_ENABLE;
+	if (IS_SS_ID_MU(gbe_dev)) {
+		val |= ETH_SW_CTL_P0_TX_CRC_REMOVE;
+		netcp->hw_cap = ETH_SW_CAN_REMOVE_ETH_FCS;
+	}
+	writel(val, GBE_REG_ADDR(gbe_dev, switch_regs, control));
 
 	/* All statistics enabled and STAT AB visible by default */
 	writel(gbe_dev->stats_en_mask, GBE_REG_ADDR(gbe_dev, switch_regs,