From ed2cfb2b3cd8f32419c0abea6cd4648ff99fca86 Mon Sep 17 00:00:00 2001 From: Suzuki K Poulose Date: Wed, 11 Jul 2018 13:40:19 -0600 Subject: dts: bindings: Restrict coresight tmc-etr scatter-gather mode 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 Reviewed-by: Rob Herring Signed-off-by: Suzuki K Poulose Signed-off-by: Mathieu Poirier Signed-off-by: Greg Kroah-Hartman --- Documentation/devicetree/bindings/arm/coresight.txt | 2 ++ 1 file changed, 2 insertions(+) (limited to 'Documentation/devicetree/bindings') diff --git a/Documentation/devicetree/bindings/arm/coresight.txt b/Documentation/devicetree/bindings/arm/coresight.txt index 15ac8e8dcfdf..603d3c62e8c7 100644 --- a/Documentation/devicetree/bindings/arm/coresight.txt +++ b/Documentation/devicetree/bindings/arm/coresight.txt @@ -86,6 +86,8 @@ its hardware characteristcs. * arm,buffer-size: size of contiguous buffer space for TMC ETR (embedded trace router) + * arm,scatter-gather: boolean. Indicates that the TMC-ETR can safely + use the SG mode on this system. Example: -- cgit v1.2.3-55-g7522