Re: [PATCH V3 06/14] dts: bindings: Document device tree bindings for ETE

Rob Herring
2021-02-09T19:02:05Z

On Wed, Jan 27, 2021 at 02:25:30PM +0530, Anshuman Khandual wrote:
> From: Suzuki K Poulose <suzuki.poulose@arm.com>
>
> 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@vger.kernel.org
> Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
> Cc: Mike Leach <mike.leach@linaro.org>
> Cc: Rob Herring <robh@kernel.org>
> Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
> Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
> ---
> Changes in V3:
>
> - Fixed all DT yaml semantics problems
>
> Documentation/devicetree/bindings/arm/ete.yaml | 74 ++++++++++++++++++++++++++
> 1 file changed, 74 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 0000000..edc1fe2
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/arm/ete.yaml
> @@ -0,0 +1,74 @@
> +# SPDX-License-Identifier: GPL-2.0-only or BSD-2-Clause
> +# Copyright 2021, Arm Ltd
> +%YAML 1.2
> +---
> +$id: "http://devicetree.org/schemas/arm/ete.yaml#"
> +$schema: "http://devicetree.org/meta-schemas/core.yaml#"
> +
> +title: ARM Embedded Trace Extensions
> +
> +maintainers:
> + - Suzuki K Poulose <suzuki.poulose@arm.com>
> + - Mathieu Poirier <mathieu.poirier@linaro.org>
> +
> +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.
> +
> +properties:
> + $nodename:
> + pattern: "^ete([0-9a-f]+)$"
> + compatible:
> + items:
> + - const: arm,embedded-trace-extension
> +
> + cpu:

We've already established 'cpus' for this purpose.

> + description: |
> + Handle to the cpu this ETE is bound to.
> + $ref: /schemas/types.yaml#/definitions/phandle
> +
> + out-ports:
> + type: object

Replace with: $ref: /schemas/graph.yaml#/properties/ports

> + description: |
> + Output connections from the ETE to legacy CoreSight trace bus.
> + properties:
> + port:
> + $ref: /schemas/graph.yaml#/properties/port

Actually, if only 1 port ever, you can drop 'out-ports' and just have
'port'. Not sure though if the coresight stuff depends on 'out-ports'.

> +
> +required:
> + - compatible
> + - cpu
> +
> +additionalProperties: false
> +
> +examples:
> +
> +# An ETE node without legacy CoreSight connections
> + - |
> + ete0 {
> + compatible = "arm,embedded-trace-extension";
> + cpu = <&cpu_0>;
> + };
> +# An ETE node with legacy CoreSight connections
> + - |
> + ete1 {
> + compatible = "arm,embedded-trace-extension";
> + cpu = <&cpu_1>;
> +
> + out-ports { /* legacy coresight connection */
> + port {
> + ete1_out_port: endpoint {
> + remote-endpoint = <&funnel_in_port0>;
> + };
> + };
> + };
> + };
> +
> +...
> --
> 2.7.4