From mboxrd@z Thu Jan 1 00:00:00 1970 From: robh@kernel.org (Rob Herring) Date: Wed, 23 May 2018 13:18:00 -0500 Subject: [PATCH 06/11] dts: bindings: Restrict coresight tmc-etr scatter-gather mode In-Reply-To: <1526661567-4578-7-git-send-email-suzuki.poulose@arm.com> References: <1526661567-4578-1-git-send-email-suzuki.poulose@arm.com> <1526661567-4578-7-git-send-email-suzuki.poulose@arm.com> Message-ID: <20180523181800.GA610@rob-hp-laptop> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.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 at vger.kernel.org > Cc: frowand.list at 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