mvpp2: XDP TX support

Add the transmit part of XDP support, which includes:
- support for XDP_TX in mvpp2_xdp()
- .ndo_xdp_xmit hook for AF_XDP and XDP_REDIRECT with mvpp2 as destination

mvpp2_xdp_submit_frame() is a generic function which is called by
mvpp2_xdp_xmit_back() when doing XDP_TX, and by mvpp2_xdp_xmit when
doing AF_XDP or XDP_REDIRECT target.

The buffer allocation has been reworked to be able to map the buffers
as DMA_FROM_DEVICE or DMA_BIDIRECTIONAL depending if native XDP is
in use or not.
Co-developed-by: Sven Auhagen <sven.auhagen@voleatech.de>
Signed-off-by: Sven Auhagen <sven.auhagen@voleatech.de>
Signed-off-by: Matteo Croce <mcroce@microsoft.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/marvell/mvpp2/mvpp2.h

@@ -1082,9 +1082,20 @@ struct mvpp2_rx_desc {
 	};
 };
 
+enum mvpp2_tx_buf_type {
+	MVPP2_TYPE_SKB,
+	MVPP2_TYPE_XDP_TX,
+	MVPP2_TYPE_XDP_NDO,
+};
+
 struct mvpp2_txq_pcpu_buf {
+	enum mvpp2_tx_buf_type type;
+
 	/* Transmitted SKB */
-	struct sk_buff *skb;
+	union {
+		struct xdp_frame *xdpf;
+		struct sk_buff *skb;
+	};
 
 	/* Physical address of transmitted buffer */
 	dma_addr_t dma;