net: fec: add initial XDP support

This patch adds the initial XDP support to Freescale driver. It supports
XDP_PASS, XDP_DROP and XDP_REDIRECT actions. Upcoming patches will add
support for XDP_TX and Zero Copy features.

This patch also optimizes the RX buffers by using the page pool, which
uses one frame per page for easy management. In the future, it can be
further improved to use two frames per page.

This patch has been tested with the sample apps of "xdpsock" and "xdp2" in
samples/bpf directory for both SKB and Native (XDP) mode. The following
are the testing result comparing with the XDP skb-mode.

 # xdpsock -i eth0
 sock0@eth0:0 rxdrop xdp-drv
                   pps            pkts           1.00
 rx                 198798         1040011
 tx                 0              0

 # xdpsock -S -i eth0         // skb-mode
 sock0@eth0:0 rxdrop xdp-skb
                    pps            pkts           1.00
 rx                 95638          717251
 tx                 0              0

 # xdp2 eth0
 proto 0:     475362 pkt/s
 proto 0:     475549 pkt/s
 proto 0:     475480 pkt/s
 proto 0:     143258 pkt/s

 # xdp2 -S eth0    // skb-mode
 proto 17:      56468 pkt/s
 proto 17:      71999 pkt/s
 proto 17:      72000 pkt/s
 proto 17:      71988 pkt/s

Signed-off-by: Shenwei Wang <shenwei.wang@nxp.com>

drivers/net/ethernet/freescale/fec.h

@@ -346,8 +346,10 @@ struct bufdesc_ex {
  * the skbuffer directly.
  */
 
+#define FEC_ENET_XDP_HEADROOM	(512) /* XDP_PACKET_HEADROOM + NET_IP_ALIGN) */
+
 #define FEC_ENET_RX_PAGES	256
-#define FEC_ENET_RX_FRSIZE	2048
+#define FEC_ENET_RX_FRSIZE	(PAGE_SIZE - FEC_ENET_XDP_HEADROOM)
 #define FEC_ENET_RX_FRPPG	(PAGE_SIZE / FEC_ENET_RX_FRSIZE)
 #define RX_RING_SIZE		(FEC_ENET_RX_FRPPG * FEC_ENET_RX_PAGES)
 #define FEC_ENET_TX_FRSIZE	2048
@@ -517,6 +519,22 @@ struct bufdesc_prop {
 	unsigned char dsize_log2;
 };
 
+struct fec_enet_priv_txrx_info {
+	int	offset;
+	struct	page *page;
+	struct  sk_buff *skb;
+};
+
+struct fec_enet_xdp_stats {
+	u64	xdp_pass;
+	u64	xdp_drop;
+	u64	xdp_xmit;
+	u64	xdp_redirect;
+	u64	xdp_xmit_err;
+	u64	xdp_tx;
+	u64	xdp_tx_err;
+};
+
 struct fec_enet_priv_tx_q {
 	struct bufdesc_prop bd;
 	unsigned char *tx_bounce[TX_RING_SIZE];
@@ -532,7 +550,15 @@ struct fec_enet_priv_tx_q {
 
 struct fec_enet_priv_rx_q {
 	struct bufdesc_prop bd;
-	struct  sk_buff *rx_skbuff[RX_RING_SIZE];
+	struct  fec_enet_priv_txrx_info rx_skb_info[RX_RING_SIZE];
+
+	/* page_pool */
+	struct page_pool *page_pool;
+	struct xdp_rxq_info xdp_rxq;
+	struct fec_enet_xdp_stats stats;
+
+	/* rx queue number, in the range 0-7 */
+	u8 id;
 };
 
 struct fec_stop_mode_gpr {
@@ -644,6 +670,10 @@ struct fec_enet_private {
 
 	struct imx_sc_ipc *ipc_handle;
 
+	/* XDP BPF Program */
+	unsigned long *af_xdp_zc_qps;
+	struct bpf_prog *xdp_prog;
+
 	u64 ethtool_stats[];
 };