From patchwork Tue Jun 20 11:04:54 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Zhen Lei X-Patchwork-Id: 105998 Delivered-To: patch@linaro.org Received: by 10.140.91.2 with SMTP id y2csp1307810qgd; Tue, 20 Jun 2017 04:06:57 -0700 (PDT) X-Received: by 10.99.155.1 with SMTP id r1mr31548345pgd.273.1497956817277; Tue, 20 Jun 2017 04:06:57 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1497956817; cv=none; d=google.com; s=arc-20160816; b=DBJYuCfYD0UruUFsvEMo0PhrdOIx54SW5zsFD78O/FlqCgbf0NrSBZkm1ZOfCAWmmQ qoHfFJbQ0A9him8ZsrlO4mHEeUD1yV5zs9h95nkc7HSwWBG9aj7YLXp4DpswhqgVV2Wu VlJb7gULXa9gihUzjyP3YcUy/fEkZuB0nW9hNFnlVYt5FHl0Yx5jsvcwGQ656dtkxsMq AuKZePSbxx/Ix3djsYkehutzS9VCe1Cm0llcvhvSD+U8GWxk9eNfU1vOOebStHNyvPGQ Eb2AUDdMVGXktgOQodKdeueNtzrjgLXySl2EeSXK9f5OAUCxogtMVZDwdtaxl3w01aTl cpHA== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:sender:mime-version:message-id:date:subject:cc :to:from:arc-authentication-results; bh=HS3TMRoKjiCAmloXRKZQS2L4ea6M32GenFzFFA3ROjY=; b=hDskVymjso9X+nKOk/Mc7rqg2cs4sbh2q/1Yx3eFuB2pmNVivxnq6+/hWK34pqWfZg 78QtElagFJpNQMRih7EJXZeL52f1fMqj2SjL/EEtEoKvyw7kUXsKpIgEsXt62S076OY0 J2+YzU7pSmNi3cqYfzCqzVwsLo5Mk6KCCWlBFzl7JXhYJ/4jD4WK/unA3WQ1OJhaWe1S vHELhZ64cpkEntl2bJorzhWW9ZrOOa7EnJmENkDoxkiYvrRh7b0V4xiX0NhXads+USoK oispBJ8rsmvnheDmfOpFn3r07qnKd63uOW+/1mCDnp5X4ILvZ5VhR3sA0StpqBXkt8jK B4tQ== ARC-Authentication-Results: i=1; mx.google.com; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Return-Path: Received: from vger.kernel.org (vger.kernel.org. [209.132.180.67]) by mx.google.com with ESMTP id g6si11054217pln.178.2017.06.20.04.06.56; Tue, 20 Jun 2017 04:06:57 -0700 (PDT) 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; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751656AbdFTLGt (ORCPT + 25 others); Tue, 20 Jun 2017 07:06:49 -0400 Received: from szxga02-in.huawei.com ([45.249.212.188]:8360 "EHLO szxga02-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751007AbdFTLGs (ORCPT ); Tue, 20 Jun 2017 07:06:48 -0400 Received: from 172.30.72.55 (EHLO DGGEML401-HUB.china.huawei.com) ([172.30.72.55]) by dggrg02-dlp.huawei.com (MOS 4.4.6-GA FastPath queued) with ESMTP id APS05685; Tue, 20 Jun 2017 19:06:43 +0800 (CST) Received: from localhost (10.177.23.164) by DGGEML401-HUB.china.huawei.com (10.3.17.32) with Microsoft SMTP Server id 14.3.301.0; Tue, 20 Jun 2017 19:06:35 +0800 From: Zhen Lei To: Will Deacon , Joerg Roedel , linux-arm-kernel , iommu , Robin Murphy , linux-kernel CC: Zefan Li , Xinwei Hu , "Tianhong Ding" , Hanjun Guo , Zhen Lei Subject: [PATCH 1/1] iommu/arm-smmu-v3: replace writel with writel_relaxed in queue_inc_prod Date: Tue, 20 Jun 2017 19:04:54 +0800 Message-ID: <1497956694-11784-1-git-send-email-thunder.leizhen@huawei.com> X-Mailer: git-send-email 1.9.5.msysgit.0 MIME-Version: 1.0 X-Originating-IP: [10.177.23.164] X-CFilter-Loop: Reflected X-Mirapoint-Virus-RAPID-Raw: score=unknown(0), refid=str=0001.0A020201.594901C4.0031, ss=1, re=0.000, recu=0.000, reip=0.000, cl=1, cld=1, fgs=0, ip=0.0.0.0, so=2014-11-16 11:51:01, dmn=2013-03-21 17:37:32 X-Mirapoint-Loop-Id: 63bd0ff14c76460810a099c9f195993f Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This function is protected by spinlock, and the latter will do memory barrier implicitly. So that we can safely use writel_relaxed. In fact, the dmb operation will lengthen the time protected by lock, which indirectly increase the locking confliction in the stress scene. Signed-off-by: Zhen Lei --- drivers/iommu/arm-smmu-v3.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) -- 2.5.0 diff --git a/drivers/iommu/arm-smmu-v3.c b/drivers/iommu/arm-smmu-v3.c index 380969a..d2fbee3 100644 --- a/drivers/iommu/arm-smmu-v3.c +++ b/drivers/iommu/arm-smmu-v3.c @@ -728,7 +728,7 @@ static void queue_inc_prod(struct arm_smmu_queue *q) u32 prod = (Q_WRP(q, q->prod) | Q_IDX(q, q->prod)) + 1; q->prod = Q_OVF(q, q->prod) | Q_WRP(q, prod) | Q_IDX(q, prod); - writel(q->prod, q->prod_reg); + writel_relaxed(q->prod, q->prod_reg); } /*