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Wed, 21 Mar 2018 18:56:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=codeaurora.org; s=default; t=1521658582; bh=2H9QFEk86A9ARflRws4pF/kG3G744iXzzqx4++hiQfI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=FOSpMyrq2fQreCRT3PgrYJD7GoHXuxdkvoEovT/i9DgzBl3cJdY52WzimStAJNk5L 0OFo1hWhs2qW7vEhlKVnnc8n1QdiqQmGb9nHxBS//AYNAfLbJXhx17eIhwF2/llhp0 1MokASVdJDSDxMYCzgH4Ryq3Ekc50rjS+TdmKryc= DMARC-Filter: OpenDMARC Filter v1.3.2 smtp.codeaurora.org 5484060F61 Authentication-Results: pdx-caf-mail.web.codeaurora.org; dmarc=none (p=none dis=none) header.from=codeaurora.org Authentication-Results: pdx-caf-mail.web.codeaurora.org; spf=none smtp.mailfrom=okaya@codeaurora.org From: Sinan Kaya To: jeffrey.t.kirsher@intel.com Subject: [PATCH REPOST v4 2/7] ixgbe: eliminate duplicate barriers on weakly-ordered archs Date: Wed, 21 Mar 2018 14:56:06 -0400 Message-Id: <1521658572-26354-3-git-send-email-okaya@codeaurora.org> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1521658572-26354-1-git-send-email-okaya@codeaurora.org> References: <1521658572-26354-1-git-send-email-okaya@codeaurora.org> MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20180321_115631_301746_AC0AB24D X-CRM114-Status: GOOD ( 12.26 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: sulrich@codeaurora.org, netdev@vger.kernel.org, timur@codeaurora.org, linux-kernel@vger.kernel.org, Sinan Kaya , intel-wired-lan@lists.osuosl.org, linux-arm-msm@vger.kernel.org, linux-arm-kernel@lists.infradead.org Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org X-Virus-Scanned: ClamAV using ClamSMTP Code includes wmb() followed by writel() in multiple places. 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 Reviewed-by: Alexander Duyck --- drivers/net/ethernet/intel/ixgbe/ixgbe_main.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c index 0da5aa2..58ed70f 100644 --- a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c +++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c @@ -1692,7 +1692,7 @@ void ixgbe_alloc_rx_buffers(struct ixgbe_ring *rx_ring, u16 cleaned_count) * such as IA-64). */ wmb(); - writel(i, rx_ring->tail); + writel_relaxed(i, rx_ring->tail); } } @@ -2453,7 +2453,7 @@ static int ixgbe_clean_rx_irq(struct ixgbe_q_vector *q_vector, * know there are new descriptors to fetch. */ wmb(); - writel(ring->next_to_use, ring->tail); + writel_relaxed(ring->next_to_use, ring->tail); xdp_do_flush_map(); } @@ -8078,7 +8078,7 @@ static int ixgbe_tx_map(struct ixgbe_ring *tx_ring, ixgbe_maybe_stop_tx(tx_ring, DESC_NEEDED); 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 @@ -10014,7 +10014,7 @@ static void ixgbe_xdp_flush(struct net_device *dev) * are new descriptors to fetch. */ wmb(); - writel(ring->next_to_use, ring->tail); + writel_relaxed(ring->next_to_use, ring->tail); return; }