From patchwork Tue Jun 18 12:54:30 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andrew Murray X-Patchwork-Id: 11001573 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id CBD9513AF for ; Tue, 18 Jun 2019 12:58:42 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id BA4D7289A7 for ; Tue, 18 Jun 2019 12:58:42 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id AEE17289E8; Tue, 18 Jun 2019 12:58:42 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.2 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,MAILING_LIST_MULTI,RCVD_IN_DNSWL_MED autolearn=ham version=3.3.1 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id 5B890289A7 for ; Tue, 18 Jun 2019 12:58:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To: Message-Id:Date:Subject:To:From:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=/V3PChaGhkN3gzL9YP4kqKqvNRdpGCc5MQcL8b+mAg0=; b=D95W7uUqmuqkH/ HrBAyBYtB/g7nPO2WTc6bvvg2amBWLfzuen3ADGwGTAi4AXZtz3WotQ4b1FKlwM2qvtIrKfLLV8CO NmxDfvZFGMiagVd5j+90pSLn0t/NROR5dDlNaUfxe/5XRPv2p2ah+H37UnqZktt+QysiKJn3nKdsr YXMCtDcEMedSnjFoVpo6Y7R+xykQ1xl7pVI9zSfbkMRGUeB+AauyDVQIw/5FrG9w4ue8YCRtcuFQT bGh5914hcXOTefHCzu7+pENCGtfq4xRAlD3/X1r/uiWCpR6r3ifVXmotnUg8woSgAZILAou/g6VWZ /1Io2HdUnBCwVNRwXIEQ==; 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 1hdDh3-0003Vu-Qo; Tue, 18 Jun 2019 12:58:34 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.92 #3 (Red Hat Linux)) id 1hdDdO-0001k7-5Y for linux-arm-kernel@lists.infradead.org; Tue, 18 Jun 2019 12:54:47 +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 6F5C5804; Tue, 18 Jun 2019 05:54:45 -0700 (PDT) Received: from e119886-lin.cambridge.arm.com (unknown [10.37.6.20]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 8054D3F246; Tue, 18 Jun 2019 05:54:44 -0700 (PDT) From: Andrew Murray To: Mathieu Poirier , Suzuki K Poulose , Alexander Shishkin Subject: [PATCH v1 2/5] coresight: etm4x: use explicit barriers on enable/disable Date: Tue, 18 Jun 2019 13:54:30 +0100 Message-Id: <20190618125433.9739-3-andrew.murray@arm.com> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20190618125433.9739-1-andrew.murray@arm.com> References: <20190618125433.9739-1-andrew.murray@arm.com> MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190618_055446_293500_0ADB3823 X-CRM114-Status: GOOD ( 11.56 ) 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: 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 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. 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 --- 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 da7cf74d612b..ae623415c431 100644 --- a/drivers/hwtracing/coresight/coresight-etm4x.c +++ b/drivers/hwtracing/coresight/coresight-etm4x.c @@ -187,6 +187,10 @@ static int etm4_enable_hw(struct etmv4_drvdata *drvdata) dev_err(drvdata->dev, "timeout while waiting for Idle Trace Status\n"); + /* As recommended by 4.3.7 of ARM IHI 0064D */ + dsb(sy); + isb(); + done: CS_LOCK(drvdata->base); @@ -453,7 +457,8 @@ 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 */ + dsb(sy); isb(); writel_relaxed(control, drvdata->base + TRCPRGCTLR);