Re: [PATCH v4 15/19] dts: bindings: Document device tree bindings for ETE

From: Suzuki K Poulose
Date: Mon Mar 22 2021 - 12:54:17 EST

Hi Rob

On 06/03/2021 21:06, Rob Herring wrote:
On Thu, Feb 25, 2021 at 07:35:39PM +0000, Suzuki K Poulose wrote:
Document the device tree bindings for Embedded Trace Extensions.
ETE can be connected to legacy coresight components and thus
could optionally contain a connection graph as described by
the CoreSight bindings.

Cc: devicetree@xxxxxxxxxxxxxxx
Cc: Mathieu Poirier <mathieu.poirier@xxxxxxxxxx>
Cc: Mike Leach <mike.leach@xxxxxxxxxx>
Cc: Rob Herring <robh@xxxxxxxxxx>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
- Fix out-ports defintion
.../devicetree/bindings/arm/ete.yaml | 71 +++++++++++++++++++
1 file changed, 71 insertions(+)
create mode 100644 Documentation/devicetree/bindings/arm/ete.yaml

diff --git a/Documentation/devicetree/bindings/arm/ete.yaml b/Documentation/devicetree/bindings/arm/ete.yaml
new file mode 100644
index 000000000000..35a42d92bf97
--- /dev/null
+++ b/Documentation/devicetree/bindings/arm/ete.yaml
@@ -0,0 +1,71 @@
+# SPDX-License-Identifier: GPL-2.0-only or BSD-2-Clause
+# Copyright 2021, Arm Ltd
+%YAML 1.2
+$id: "";
+$schema: "";
+title: ARM Embedded Trace Extensions
+ - Suzuki K Poulose <suzuki.poulose@xxxxxxx>
+ - Mathieu Poirier <mathieu.poirier@xxxxxxxxxx>
+description: |
+ Arm Embedded Trace Extension(ETE) is a per CPU trace component that
+ allows tracing the CPU execution. It overlaps with the CoreSight ETMv4
+ architecture and has extended support for future architecture changes.
+ The trace generated by the ETE could be stored via legacy CoreSight
+ components (e.g, TMC-ETR) or other means (e.g, using a per CPU buffer
+ Arm Trace Buffer Extension (TRBE)). Since the ETE can be connected to
+ legacy CoreSight components, a node must be listed per instance, along
+ with any optional connection graph as per the coresight bindings.
+ See bindings/arm/coresight.txt.
+ $nodename:
+ pattern: "^ete([0-9a-f]+)$"
+ compatible:
+ items:
+ - const: arm,embedded-trace-extension
+ cpu:
+ description: |
+ Handle to the cpu this ETE is bound to.
+ $ref: /schemas/types.yaml#/definitions/phandle
+ out-ports:
+ description: |
+ Output connections from the ETE to legacy CoreSight trace bus.
+ $ref: /schemas/graph.yaml#/properties/port



And then you need:

description: what this port is
$ref: /schemas/graph.yaml#/properties/port

Isn't this already covered by the definition of ports ? There are no fixed connections for ETE. It is optional and could be connected to
any legacy CoreSight component. i.e, a "ports" object can have port
objects inside.

Given we have defined out-ports as an object "confirming to the ports"
do we need to describe the individual port nodes ?