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 mathieu.poirier@linaro.org Cc: Mike Leach mike.leach@linaro.org Cc: Mark Rutland mark.rutland@arm.com Cc: John Horley john.horley@arm.com Cc: Robert Walker robert.walker@arm.com Cc: devicetree@vger.kernel.org Cc: frowand.list@gmail.com Cc: Rob Herring robh@kernel.org Signed-off-by: Suzuki K Poulose suzuki.poulose@arm.com
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 robh@kernel.org