[RFC PATCH 23/27] net/intel: add special handling for single desc packets

[Bruce Richardson <bruce.richardson@intel.com>]

Within the scalar packets, add a shortcut path for packets that don't
use TSO and have only a single data descriptor.

Signed-off-by: Bruce Richardson <bruce.richardson@intel.com>
---
 drivers/net/intel/common/tx_scalar_fns.h | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/drivers/net/intel/common/tx_scalar_fns.h b/drivers/net/intel/common/tx_scalar_fns.h
index 27791cf138..55502b46ed 100644
--- a/drivers/net/intel/common/tx_scalar_fns.h
+++ b/drivers/net/intel/common/tx_scalar_fns.h
@@ -304,6 +304,28 @@ ci_xmit_pkts(struct ci_tx_queue *txq,
 			ci_txd_enable_checksum(ol_flags, &td_cmd,
 						&td_offset, tx_offload);
 
+		/* special case for single descriptor packet, without TSO offload */
+		if (nb_used == 1 && (ol_flags & (RTE_MBUF_F_TX_TCP_SEG | RTE_MBUF_F_TX_UDP_SEG)) == 0) {
+			txd = &ci_tx_ring[tx_id];
+			tx_id = txe->next_id;
+
+			if (txe->mbuf)
+				rte_pktmbuf_free_seg(txe->mbuf);
+			*txe = (struct ci_tx_entry){ .mbuf = tx_pkt, .last_id = tx_last, .next_id = tx_id };
+
+			/* Setup TX Descriptor */
+			td_cmd |= CI_TX_DESC_CMD_EOP;
+			const uint64_t cmd_type_offset_bsz = CI_TX_DESC_DTYPE_DATA |
+				((uint64_t)td_cmd << CI_TXD_QW1_CMD_S) |
+				((uint64_t)td_offset << CI_TXD_QW1_OFFSET_S) |
+				((uint64_t)tx_pkt->data_len << CI_TXD_QW1_TX_BUF_SZ_S) |
+				((uint64_t)td_tag << CI_TXD_QW1_L2TAG1_S);
+			write_txd(txd, rte_mbuf_data_iova(tx_pkt), cmd_type_offset_bsz);
+
+			txe = &sw_ring[tx_id];
+			goto end_pkt;
+		}
+
 		if (nb_ctx) {
 			/* Setup TX context descriptor if required */
 			uint64_t *ctx_txd = RTE_CAST_PTR(uint64_t *, &ci_tx_ring[tx_id]);
@@ -395,6 +417,7 @@ ci_xmit_pkts(struct ci_tx_queue *txq,
 			txe = txn;
 			m_seg = m_seg->next;
 		} while (m_seg);
+end_pkt:
 		txq->nb_tx_used = (uint16_t)(txq->nb_tx_used + nb_used);
 		txq->nb_tx_free = (uint16_t)(txq->nb_tx_free - nb_used);
 
-- 
2.51.0