From ed909de5d3300f473e5ee5a520267c3e04b43b76 Mon Sep 17 00:00:00 2001
From: Andre Przywara <andre.przywara@arm.com>
Date: Mon, 6 Jul 2020 01:40:38 +0100
Subject: [PATCH] net: sun8i_emac: Reduce cache maintenance on TX descriptor
 init

When we initialise the TX descriptors, there is no need yet to clean
them all to memory, as they don't contain any data yet. Later we will
touch and clean each descriptor anyway.
However we tell the MAC about the beginning of the chain, so we have to
clean at least the first descriptor, to make it clear that this is empty
and there are no packets to transfer yet.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Acked-by: Maxime Ripard <mripard@kernel.org>
Tested-by: Amit Singh Tomar <amittomer25@gmail.com> # Pine64+
Reviewed-by: Jagan Teki <jagan@amarulasolutions.com>
---
 drivers/net/sun8i_emac.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/sun8i_emac.c b/drivers/net/sun8i_emac.c
index c567b9e082..335c85f3c2 100644
--- a/drivers/net/sun8i_emac.c
+++ b/drivers/net/sun8i_emac.c
@@ -431,10 +431,10 @@ static void tx_descs_init(struct emac_eth_dev *priv)
 	/* Correcting the last pointer of the chain */
 	desc_p->next =  (uintptr_t)&desc_table_p[0];
 
-	/* Flush all Tx buffer descriptors */
+	/* Flush the first TX buffer descriptor we will tell the MAC about. */
 	flush_dcache_range((uintptr_t)priv->tx_chain,
 			   (uintptr_t)priv->tx_chain +
-			sizeof(priv->tx_chain));
+			   sizeof(priv->tx_chain[0]));
 
 	writel((uintptr_t)&desc_table_p[0], priv->mac_reg + EMAC_TX_DMA_DESC);
 	priv->tx_currdescnum = 0;
-- 
2.39.5