net: ethernet: ti: am65-cpsw: Add minimal XDP support

This patch adds XDP (eXpress Data Path) support to TI AM65 CPSW
Ethernet driver. The following features are implemented:
- NETDEV_XDP_ACT_BASIC (XDP_PASS, XDP_TX, XDP_DROP, XDP_ABORTED)
- NETDEV_XDP_ACT_REDIRECT (XDP_REDIRECT)
- NETDEV_XDP_ACT_NDO_XMIT (ndo_xdp_xmit callback)

The page pool memory model is used to get better performance.
Below are benchmark results obtained for the receiver with iperf3 default
parameters:
- Without page pool: 495 Mbits/sec
- With page pool: 605 Mbits/sec (actually 610 Mbits/sec, with a 5 Mbits/sec
loss due to extra processing in the hot path to handle XDP).
Signed-off-by: Julien Panis <jpanis@baylibre.com>
Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/ti/am65-cpsw-nuss.h

@@ -14,6 +14,7 @@
 #include <linux/platform_device.h>
 #include <linux/soc/ti/k3-ringacc.h>
 #include <net/devlink.h>
+#include <net/xdp.h>
 #include "am65-cpsw-qos.h"
 
 struct am65_cpts;
@@ -56,10 +57,18 @@ struct am65_cpsw_port {
 	bool				rx_ts_enabled;
 	struct am65_cpsw_qos		qos;
 	struct devlink_port		devlink_port;
+	struct bpf_prog			*xdp_prog;
+	struct xdp_rxq_info		xdp_rxq;
 	/* Only for suspend resume context */
 	u32				vid_context;
 };
 
+enum am65_cpsw_tx_buf_type {
+	AM65_CPSW_TX_BUF_TYPE_SKB,
+	AM65_CPSW_TX_BUF_TYPE_XDP_TX,
+	AM65_CPSW_TX_BUF_TYPE_XDP_NDO,
+};
+
 struct am65_cpsw_host {
 	struct am65_cpsw_common		*common;
 	void __iomem			*port_base;
@@ -80,6 +89,7 @@ struct am65_cpsw_tx_chn {
 	int irq;
 	u32 id;
 	u32 descs_num;
+	unsigned char dsize_log2;
 	char tx_chn_name[128];
 	u32 rate_mbps;
 };
@@ -89,7 +99,10 @@ struct am65_cpsw_rx_chn {
 	struct device *dma_dev;
 	struct k3_cppi_desc_pool *desc_pool;
 	struct k3_udma_glue_rx_channel *rx_chn;
+	struct page_pool *page_pool;
+	struct page **pages;
 	u32 descs_num;
+	unsigned char dsize_log2;
 	int irq;
 };