netdev - [PATCH v2 08/12] ftgmac100: Move the barrier out of ftgmac100_txdes_set_dma

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Date:   Mon, 10 Apr 2017 11:15:22 +1000
From:   Benjamin Herrenschmidt <benh@...nel.crashing.org>
To:     netdev@...r.kernel.org
Cc:     Benjamin Herrenschmidt <benh@...nel.crashing.org>
Subject: [PATCH v2 08/12] ftgmac100: Move the barrier out of ftgmac100_txdes_set_dma_own()

We'll use variants of this accessor without barriers when
building series of descriptors for fragmented sends

Signed-off-by: Benjamin Herrenschmidt <benh@...nel.crashing.org>
---
 drivers/net/ethernet/faraday/ftgmac100.c | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/drivers/net/ethernet/faraday/ftgmac100.c b/drivers/net/ethernet/faraday/ftgmac100.c
index 8078d65..bdec14f 100644
--- a/drivers/net/ethernet/faraday/ftgmac100.c
+++ b/drivers/net/ethernet/faraday/ftgmac100.c
@@ -483,11 +483,6 @@ static bool ftgmac100_txdes_owned_by_dma(struct ftgmac100_txdes *txdes)
 
 static void ftgmac100_txdes_set_dma_own(struct ftgmac100_txdes *txdes)
 {
-	/*
-	 * Make sure dma own bit will not be set before any other
-	 * descriptor fields.
-	 */
-	wmb();
 	txdes->txdes0 |= cpu_to_le32(FTGMAC100_TXDES0_TXDMA_OWN);
 }
 
@@ -677,6 +672,10 @@ static int ftgmac100_hard_start_xmit(struct sk_buff *skb,
 		}
 	}
 
+	/* Order the previous packet and descriptor udpates
+	 * before setting the OWN bit.
+	 */
+	dma_wmb();
 	ftgmac100_txdes_set_dma_own(txdes);
 
 	/* Update next TX pointer */
-- 
2.9.3