nfp: nfdk: implement xdp tx path for NFDK

Due to the different definition of txbuf in NFDK comparing to NFD3,
there're no pre-allocated txbufs for xdp use in NFDK's implementation,
we just use the existed rxbuf and recycle it when xdp tx is completed.

For each packet to transmit in xdp path, we cannot use more than
`NFDK_TX_DESC_PER_SIMPLE_PKT` txbufs, one is to stash virtual address,
and another is for dma address, so currently the amount of transmitted
bytes is not accumulated. Also we borrow the last bit of virtual addr
to indicate a new transmitted packet due to address's alignment
attribution.

Signed-off-by: Yinjun Zhang <yinjun.zhang@corigine.com>
Signed-off-by: Fei Qin <fei.qin@corigine.com>
Signed-off-by: Simon Horman <simon.horman@corigine.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 17 insertions, 0 deletions

diff --git a/drivers/net/ethernet/netronome/nfp/nfdk/nfdk.h b/drivers/net/ethernet/netronome/nfp/nfdk/nfdk.h
index 5107c4f03feb..c41e0975eb73 100644
--- a/drivers/net/ethernet/netronome/nfp/nfdk/nfdk.h
+++ b/drivers/net/ethernet/netronome/nfp/nfdk/nfdk.h
@@ -71,12 +71,29 @@ struct nfp_nfdk_tx_desc {
 	};
 };
 
+/* The device don't make use of the 2 or 3 least significant bits of the address
+ * due to alignment constraints. The driver can make use of those bits to carry
+ * information about the buffer before giving it to the device.
+ *
+ * NOTE: The driver must clear the lower bits before handing the buffer to the
+ * device.
+ *
+ * - NFDK_TX_BUF_INFO_SOP - Start of a packet
+ *   Mark the buffer as a start of a packet. This is used in the XDP TX process
+ *   to stash virtual and DMA address so that they can be recycled when the TX
+ *   operation is completed.
+ */
+#define NFDK_TX_BUF_PTR(val) ((val) & ~(sizeof(void *) - 1))
+#define NFDK_TX_BUF_INFO(val) ((val) & (sizeof(void *) - 1))
+#define NFDK_TX_BUF_INFO_SOP BIT(0)
+
 struct nfp_nfdk_tx_buf {
 	union {
 		/* First slot */
 		union {
 			struct sk_buff *skb;
 			void *frag;
+			unsigned long val;
 		};
 
 		/* 1 + nr_frags next slots */