linux-kernel - [RFC PATCH 1/8] dts: binding: coresight: Document graph bindings

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Date:   Fri,  1 Jun 2018 14:16:00 +0100
From:   Suzuki K Poulose <suzuki.poulose@....com>
To:     linux-arm-kernel@...ts.infradead.org
Cc:     mathieu.poirier@...aro.org, sudeep.holla@....com, robh@...nel.org,
        mark.rutland@....com, frowand.list@...il.com, matt.sealey@....com,
        charles.garcia-tobin@....com, john.horley@....com,
        mike.leach@...aro.org, coresight@...ts.linaro.org,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
        Suzuki K Poulose <suzuki.poulose@....com>
Subject: [RFC PATCH 1/8] dts: binding: coresight: Document graph bindings

Before we updat the bindings, document the current graph bindings
and usage of additional properties.

Cc: Mathieu Poirier <mathieu.poirier@...aro.org>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@....com>
---
 .../devicetree/bindings/arm/coresight.txt          | 28 ++++++++++++++++++----
 1 file changed, 24 insertions(+), 4 deletions(-)

diff --git a/Documentation/devicetree/bindings/arm/coresight.txt b/Documentation/devicetree/bindings/arm/coresight.txt
index 15ac8e8..bd36e40 100644
--- a/Documentation/devicetree/bindings/arm/coresight.txt
+++ b/Documentation/devicetree/bindings/arm/coresight.txt
@@ -52,9 +52,7 @@ its hardware characteristcs.
 	  clocks the core of that coresight component. The latter clock
 	  is optional.
 
-	* port or ports: The representation of the component's port
-	  layout using the generic DT graph presentation found in
-	  "bindings/graph.txt".
+	* port or ports: see "Graph bindings for Coresight" below
 
 * Additional required properties for System Trace Macrocells (STM):
 	* reg: along with the physical base address and length of the register
@@ -71,7 +69,7 @@ its hardware characteristcs.
 	  AMBA markee):
 		- "arm,coresight-replicator"
 
-	* port or ports: same as above.
+	* port or ports: see "Graph bindings for Coresight" below.
 
 * Optional properties for ETM/PTMs:
 
@@ -86,6 +84,28 @@ its hardware characteristcs.
 	* arm,buffer-size: size of contiguous buffer space for TMC ETR
 	 (embedded trace router)
 
+Graph bindings for Coresight
+-------------------------------
+
+Coresight components are interconnected to create a data path for the flow of
+trace data generated from the "sources" to their collection points "sink". Each
+coresight component must describe the "input" and "output" connections.
+The connections must be described via generic DT graph bindings as described
+by the "bindings/graph.txt", where each "port" along with an "endpoint" component
+represents a hardware port and the connection.
+
+Since it is possible to have multiple connections for any coresight component with
+a specific direction of data flow, each connection must define the following
+properties to uniquely identify the connection details.
+
+ * Direction of the data flow w.r.t the component :
+   Each input port must have the following property defined at the "endpoint"
+   for the port.
+	"slave-mode"
+
+ * Hardware Port number at the component:
+     -  The hardware port number is assumed to be the address of the "port" component.
+
 
 Example:
 
-- 
2.7.4