Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
DMARC-Filter: OpenDMARC Filter v1.3.2 smtp.codeaurora.org 691C860FA8
From:   Sinan Kaya <okaya@codeaurora.org>
To:     netdev@vger.kernel.org, timur@codeaurora.org,
        sulrich@codeaurora.org
Cc:     linux-arm-msm@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org,
        Sinan Kaya <okaya@codeaurora.org>,
        Jeff Kirsher <jeffrey.t.kirsher@intel.com>,
        intel-wired-lan@lists.osuosl.org, linux-kernel@vger.kernel.org
Subject: [PATCH v4 07/17] fm10k: Eliminate duplicate barriers on weakly-ordered archs
Date:   Mon, 19 Mar 2018 22:42:22 -0400
Message-Id: <1521513753-7325-8-git-send-email-okaya@codeaurora.org>
In-Reply-To: <1521513753-7325-1-git-send-email-okaya@codeaurora.org>
References: <1521513753-7325-1-git-send-email-okaya@codeaurora.org>
MIME-Version: 1.0
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

Code includes wmb() followed by writel(). writel() already has a
barrier on some architectures like arm64.

This ends up CPU observing two barriers back to back before executing
the register write.

Since code already has an explicit barrier call, changing writel() to
writel_relaxed().

Signed-off-by: Sinan Kaya <okaya@codeaurora.org>
---
 drivers/net/ethernet/intel/fm10k/fm10k_main.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/intel/fm10k/fm10k_main.c b/drivers/net/ethernet/intel/fm10k/fm10k_main.c
index 8e12aae..eebef01 100644
--- a/drivers/net/ethernet/intel/fm10k/fm10k_main.c
+++ b/drivers/net/ethernet/intel/fm10k/fm10k_main.c
@@ -179,7 +179,7 @@ void fm10k_alloc_rx_buffers(struct fm10k_ring *rx_ring, u16 cleaned_count)
 		wmb();
 
 		/* notify hardware of new descriptors */
-		writel(i, rx_ring->tail);
+		writel_relaxed(i, rx_ring->tail);
 	}
 }
 
@@ -1054,7 +1054,7 @@ static void fm10k_tx_map(struct fm10k_ring *tx_ring,
 
 	/* notify HW of packet */
 	if (netif_xmit_stopped(txring_txq(tx_ring)) || !skb->xmit_more) {
-		writel(i, tx_ring->tail);
+		writel_relaxed(i, tx_ring->tail);
 
 		/* we need this if more than one processor can write to our tail
 		 * at a time, it synchronizes IO on IA64/Altix systems
-- 
2.7.4