From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756942AbeDBTJi (ORCPT ); Mon, 2 Apr 2018 15:09:38 -0400 Received: from smtp.codeaurora.org ([198.145.29.96]:42124 "EHLO smtp.codeaurora.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754430AbeDBTGk (ORCPT ); Mon, 2 Apr 2018 15:06:40 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 smtp.codeaurora.org 83BAA60817 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 Cc: netdev@vger.kernel.org, timur@codeaurora.org, sulrich@codeaurora.org, linux-arm-msm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Sinan Kaya , intel-wired-lan@lists.osuosl.org, linux-kernel@vger.kernel.org Subject: [PATCH v8 2/7] ixgbe: eliminate duplicate barriers on weakly-ordered archs Date: Mon, 2 Apr 2018 15:06:25 -0400 Message-Id: <1522695990-31082-3-git-send-email-okaya@codeaurora.org> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1522695990-31082-1-git-send-email-okaya@codeaurora.org> References: <1522695990-31082-1-git-send-email-okaya@codeaurora.org> MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org memory-barriers.txt has been updated as follows: "When using writel(), a prior wmb() is not needed to guarantee that the cache coherent memory writes have completed before writing to the MMIO region." Remove old IA-64 comments in the code along with unneeded wmb() in front of writel(). There are places in the code where wmb() has been used as a double barrier for CPU and IO in place of smp_wmb() and wmb() as an optimization. For such places, keep the wmb() but replace the following writel() with writel_relaxed() to have a sequence as wmb() writel_relaxed() mmio_wb() Signed-off-by: Sinan Kaya --- drivers/net/ethernet/intel/ixgbe/ixgbe_main.c | 23 ++--------------------- 1 file changed, 2 insertions(+), 21 deletions(-) diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c index afadba9..c17924b 100644 --- a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c +++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c @@ -1696,12 +1696,6 @@ void ixgbe_alloc_rx_buffers(struct ixgbe_ring *rx_ring, u16 cleaned_count) /* update next to alloc since we have filled the ring */ rx_ring->next_to_alloc = i; - /* Force memory writes to complete before letting h/w - * know there are new descriptors to fetch. (Only - * applicable for weak-ordered memory model archs, - * such as IA-64). - */ - wmb(); writel(i, rx_ring->tail); } } @@ -2467,10 +2461,6 @@ static int ixgbe_clean_rx_irq(struct ixgbe_q_vector *q_vector, if (xdp_xmit) { struct ixgbe_ring *ring = adapter->xdp_ring[smp_processor_id()]; - /* Force memory writes to complete before letting h/w - * know there are new descriptors to fetch. - */ - wmb(); writel(ring->next_to_use, ring->tail); xdp_do_flush_map(); @@ -8080,12 +8070,7 @@ static int ixgbe_tx_map(struct ixgbe_ring *tx_ring, /* set the timestamp */ first->time_stamp = jiffies; - /* - * Force memory writes to complete before letting h/w know there - * are new descriptors to fetch. (Only applicable for weak-ordered - * memory model archs, such as IA-64). - * - * We also need this memory barrier to make certain all of the + /* We need this memory barrier to make certain all of the * status bits have been updated before next_to_watch is written. */ wmb(); @@ -8102,7 +8087,7 @@ 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 @@ -10034,10 +10019,6 @@ static void ixgbe_xdp_flush(struct net_device *dev) if (unlikely(!ring)) return; - /* Force memory writes to complete before letting h/w know there - * are new descriptors to fetch. - */ - wmb(); writel(ring->next_to_use, ring->tail); return; -- 2.7.4