[dpdk-dev] [PATCH 03/10] net/enetc: batch process enetc clean Tx ring calls

[Hemant Agrawal <hemant.agrawal@nxp.com>]

From: Alex Marginean <alexandru.marginean@nxp.com>

Each call to enetc_clean_tx_ring will cost at least 150-200 CPU cycles
even if no clean-up is done, due to the CI register read.
We're only calling it once at the end of the function, on the assumption
that software is slower than hardware and hardware completed sending older
frames out by now.
We're also cleaning up the ring before kicking off Tx for the new batch to
minimize chances of contention on the Tx ring.

Signed-off-by: Alex Marginean <alexandru.marginean@nxp.com>
---
 drivers/net/enetc/enetc_rxtx.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/net/enetc/enetc_rxtx.c b/drivers/net/enetc/enetc_rxtx.c
index 395f5ecf4..958e3a21d 100644
--- a/drivers/net/enetc/enetc_rxtx.c
+++ b/drivers/net/enetc/enetc_rxtx.c
@@ -76,7 +76,6 @@ enetc_xmit_pkts(void *tx_queue,
 
 	start = 0;
 	while (nb_pkts--) {
-		enetc_clean_tx_ring(tx_ring);
 		tx_ring->q_swbd[i].buffer_addr = tx_pkts[start];
 		txbd = ENETC_TXBD(*tx_ring, i);
 		tx_swbd = &tx_ring->q_swbd[i];
@@ -92,6 +91,14 @@ enetc_xmit_pkts(void *tx_queue,
 			i = 0;
 	}
 
+	/* we're only cleaning up the Tx ring here, on the assumption that
+	 * software is slower than hardware and hardware completed sending
+	 * older frames out by now.
+	 * We're also cleaning up the ring before kicking off Tx for the new
+	 * batch to minimize chances of contention on the Tx ring
+	 */
+	enetc_clean_tx_ring(tx_ring);
+
 	tx_ring->next_to_use = i;
 	enetc_wr_reg(tx_ring->tcir, i);
 	return start;
-- 
2.17.1