From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754861AbeEWSSF (ORCPT ); Wed, 23 May 2018 14:18:05 -0400 Received: from mail-yw0-f196.google.com ([209.85.161.196]:36870 "EHLO mail-yw0-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754658AbeEWSSD (ORCPT ); Wed, 23 May 2018 14:18:03 -0400 X-Google-Smtp-Source: AB8JxZoWzP3GsCmZic4l8YCzm49ojp3LLKgPcG2uOgZvfEQmmzMr8KFUj/SYpmO78S1na99NpunrDg== Date: Wed, 23 May 2018 13:18:00 -0500 From: Rob Herring To: Suzuki K Poulose Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, mathieu.poirier@linaro.org, sudeep.holla@arm.com, frowand.list@gmail.com, coresight@lists.linaro.org, mark.rutland@arm.com, Mike Leach , John Horley , Robert Walker , devicetree@vger.kernel.org Subject: Re: [PATCH 06/11] dts: bindings: Restrict coresight tmc-etr scatter-gather mode Message-ID: <20180523181800.GA610@rob-hp-laptop> References: <1526661567-4578-1-git-send-email-suzuki.poulose@arm.com> <1526661567-4578-7-git-send-email-suzuki.poulose@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1526661567-4578-7-git-send-email-suzuki.poulose@arm.com> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, May 18, 2018 at 05:39:22PM +0100, Suzuki K Poulose wrote: > We are about to add the support for ETR builtin scatter-gather mode > for dealing with large amount of trace buffers. However, on some of > the platforms, using the ETR SG mode can lock up the system due to > the way the ETR is connected to the memory subsystem. > > In SG mode, the ETR performs READ from the scatter-gather table to > fetch the next page and regular WRITE of trace data. If the READ > operation doesn't complete(due to the memory subsystem issues, > which we have seen on a couple of platforms) the trace WRITE > cannot proceed leading to issues. So, we by default do not > use the SG mode, unless it is known to be safe on the platform. > We define a DT property for the TMC node to specify whether we > have a proper SG mode. > > Cc: Mathieu Poirier > Cc: Mike Leach > Cc: Mark Rutland > Cc: John Horley > Cc: Robert Walker > Cc: devicetree@vger.kernel.org > Cc: frowand.list@gmail.com > Cc: Rob Herring > Signed-off-by: Suzuki K Poulose > --- > Documentation/devicetree/bindings/arm/coresight.txt | 2 ++ > drivers/hwtracing/coresight/coresight-tmc.c | 9 ++++++++- > 2 files changed, 10 insertions(+), 1 deletion(-) Reviewed-by: Rob Herring