From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751590AbdFTLGt (ORCPT ); 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 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 Content-Type: text/plain 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 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(-) 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); } /* -- 2.5.0