From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C2F75C48BD7 for ; Thu, 27 Jun 2019 09:16:27 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 9005B2082F for ; Thu, 27 Jun 2019 09:16:27 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="A3/tU245" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9005B2082F Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender:Content-Type: Content-Transfer-Encoding:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:Date:Message-ID:From: References:To:Subject:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=cjGupCyEeBITH9yYMw7c8GGnPxC/gThf88Vyo59qk/4=; b=A3/tU245XMl3+N/OALA3s0Tra 6B0OSMMMQzmAGY6QyvHMqxYMT/AIvhDLtjTWoVwyMT0pD6HpRAQd8kDv9+FAhVyoTmxs75mSb+N7X fHhRqrLzeSYdEUq/xMjkm61r/Wgk8CLlFJ9eW4P4/bKh0sFufiXJiDTyvPXdqKeYVpqVraQMFq0C+ rVTUQke4VpNxSmUVEGPkzpXpKBAmDxAUuWngtDEdWAWtsKW/hQgFjB3V2HF6pkpRAb+1puw/5VDdp DuCj6F3oGlpy2N9/NYLJPOkAEciDxi/tjWcP61F1DZxXXT/B/FTdKY+x93KjkxXna53FNeza//tRE FEp3CWuLA==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92 #3 (Red Hat Linux)) id 1hgQW0-0006QO-W8; Thu, 27 Jun 2019 09:16:25 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.92 #3 (Red Hat Linux)) id 1hgQVy-0006Py-0m for linux-arm-kernel@lists.infradead.org; Thu, 27 Jun 2019 09:16:23 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 5D4DA2B; Thu, 27 Jun 2019 02:16:19 -0700 (PDT) Received: from [10.1.196.93] (en101.cambridge.arm.com [10.1.196.93]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 4C58C3F718; Thu, 27 Jun 2019 02:16:18 -0700 (PDT) Subject: Re: [PATCH v2 2/5] coresight: etm4x: use explicit barriers on enable/disable To: andrew.murray@arm.com, mathieu.poirier@linaro.org, alexander.shishkin@linux.intel.com References: <20190627083525.37463-1-andrew.murray@arm.com> <20190627083525.37463-3-andrew.murray@arm.com> From: Suzuki K Poulose Message-ID: Date: Thu, 27 Jun 2019 10:16:17 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.1 MIME-Version: 1.0 In-Reply-To: <20190627083525.37463-3-andrew.murray@arm.com> Content-Language: en-US X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190627_021622_135428_76DCFA3F X-CRM114-Status: GOOD ( 22.27 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: coresight@lists.linaro.org, Sudeep.Holla@arm.com, stable@vger.kernel.org, linux-arm-kernel@lists.infradead.org, mike.leach@linaro.org Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi Andrew, On 27/06/2019 09:35, Andrew Murray wrote: > Synchronization is recommended before disabling the trace registers > to prevent any start or stop points being speculative at the point > of disabling the unit (section 7.3.77 of ARM IHI 0064D). > > Synchronization is also recommended after programming the trace > registers to ensure all updates are committed prior to normal code > resuming (section 4.3.7 of ARM IHI 0064D). > > Let's ensure these syncronization points are present in the code > and clearly commented. Please could you also mention why we switched from mb() ? > > Note that we could rely on the barriers in CS_LOCK and > coresight_disclaim_device_unlocked or the context switch to user > space - however coresight may be of use in the kernel. > > Signed-off-by: Andrew Murray > CC: stable@vger.kernel.org > --- > drivers/hwtracing/coresight/coresight-etm4x.c | 7 ++++++- > 1 file changed, 6 insertions(+), 1 deletion(-) > > diff --git a/drivers/hwtracing/coresight/coresight-etm4x.c b/drivers/hwtracing/coresight/coresight-etm4x.c > index c89190d464ab..68e8e3954cef 100644 > --- a/drivers/hwtracing/coresight/coresight-etm4x.c > +++ b/drivers/hwtracing/coresight/coresight-etm4x.c > @@ -188,6 +188,10 @@ static int etm4_enable_hw(struct etmv4_drvdata *drvdata) > dev_err(etm_dev, > "timeout while waiting for Idle Trace Status\n"); > > + /* As recommended by 4.3.7 of ARM IHI 0064D */ nit: It would be good to mention the "section name" to help the reader find the same on a different version of the document. Also within the same version, this is listed in the subsection: "Synchronization when using the memory-mapped interface" Please could you update the comment to reflect the same ? > + dsb(sy); > + isb(); > + > done: > CS_LOCK(drvdata->base); > > @@ -454,7 +458,8 @@ static void etm4_disable_hw(void *info) > control &= ~0x1; > > /* make sure everything completes before disabling */ > - mb(); > + /* As recommended by 7.3.77 of ARM IHI 0064D */ Nit: This refers to completely unrelated section. Shouldn't this be the same as above ? With the above fixed: Reviewed-by: Suzuki K Poulose _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel