From 95eb930a40a0973f9b984d87a4986bb81f897ede Mon Sep 17 00:00:00 2001 From: Niklas Cassel Date: Mon, 26 Feb 2018 22:47:07 +0100 Subject: [PATCH] net: stmmac: use correct barrier between coherent memory and MMIO 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). 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 Signed-off-by: David S. Miller --- 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 3b5e7b06e796..6dd04f237b2a 100644 --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c @@ -2997,7 +2997,7 @@ 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", @@ -3221,7 +3221,7 @@ 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); -- GitLab