From 1d8fccab29cab59dd75518f5f61209080e1443c7 Mon Sep 17 00:00:00 2001
From: Niklas Cassel <niklas.cassel@axis.com>
Date: Mon, 26 Feb 2018 22:47:07 +0100
Subject: [PATCH 20/21] net: stmmac: use correct barrier between coherent
memory and MMIO
Git-commit: 95eb930a40a0973f9b984d87a4986bb81f897ede
Patch-mainline: v4.17-rc1
References: git-fixes
The last memory barrier in stmmac_xmit()/stmmac_tso_xmit() is placed
between a coherent memory write and a MMIO write:
The own bit is written in First Desc (TSO: MSS desc or First Desc).
<barrier>
The DMA engine is started by a write to the tx desc tail pointer/
enable dma transmission register, i.e. a MMIO write.
This barrier cannot be a simple dma_wmb(), since a dma_wmb() is only
used to guarantee the ordering, with respect to other writes,
to cache coherent DMA memory.
To guarantee that the cache coherent memory writes have completed
before we attempt to write to the cache incoherent MMIO region,
we need to use the more heavyweight barrier wmb().
Signed-off-by: Niklas Cassel <niklas.cassel@axis.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Denis Kirjanov <denis.kirjanov@suse.com>
---
drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index cd54ca7ebe06..23fd6c22778c 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -2985,7 +2985,7 @@ static netdev_tx_t stmmac_tso_xmit(struct sk_buff *skb, struct net_device *dev)
* descriptor and then barrier is needed to make sure that
* all is coherent before granting the DMA engine.
*/
- dma_wmb();
+ wmb();
if (netif_msg_pktdata(priv)) {
pr_info("%s: curr=%d dirty=%d f=%d, e=%d, f_p=%p, nfrags %d\n",
@@ -3214,7 +3214,7 @@ static netdev_tx_t stmmac_xmit(struct sk_buff *skb, struct net_device *dev)
* descriptor and then barrier is needed to make sure that
* all is coherent before granting the DMA engine.
*/
- dma_wmb();
+ wmb();
}
netdev_tx_sent_queue(netdev_get_tx_queue(dev, queue), skb->len);
--
2.16.4