Re: [PATCH 06/11] dts: bindings: Document device tree bindings for ETE

On Mon, Jan 4, 2021 at 11:15 AM Mathieu Poirier
[off-list ref] wrote:

On Mon, Jan 04, 2021 at 02:42:08PM +0000, Suzuki K Poulose wrote:

quoted

Hi Rob,

On 1/3/21 5:02 PM, Rob Herring wrote:

quoted

On Wed, Dec 23, 2020 at 03:33:38PM +0530, Anshuman Khandual wrote:

quoted

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 <redacted>
Cc: Rob Herring <robh@kernel.org>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Anshuman Khandual <redacted>
---
  Documentation/devicetree/bindings/arm/ete.txt | 41 +++++++++++++++++++++++++++
  1 file changed, 41 insertions(+)
  create mode 100644 Documentation/devicetree/bindings/arm/ete.txt

Bindings are in schema format now, please convert this.

Sure, will do that.

quoted

quoted

diff --git a/Documentation/devicetree/bindings/arm/ete.txt b/Documentation/devicetree/bindings/arm/ete.txt
new file mode 100644
index 0000000..b52b507
--- /dev/null
+++ b/Documentation/devicetree/bindings/arm/ete.txt

@@ -0,0 +1,41 @@
+Arm Embedded Trace Extensions
+
+Arm Embedded Trace Extensions (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.
+
+** ETE Required properties:
+
+- compatible : should be one of:
+ "arm,embedded-trace-extensions"
+
+- cpu : the CPU phandle this ETE belongs to.

If this is 1:1 with CPUs, then perhaps it should be a child node of the
CPU nodes.

Yes, it is 1:1 with the CPUs. I have tried to keep this aligned with that of
"coresight-etm4x". The same driver handles both. The only reason why this
was separated from the "coresight.txt" is to describe the new configurations
possible (read, TRBE).

Would it be possible to keep the CPU handle rather than moving things under the
CPU nodes?  ETMv3.x and ETMv4.x are using a handle and as Suzuki points out ETE
and ETMv4.x are sharing the same driver.  Proceeding differently for the ETE
would be terribly confusing.

Yeah, no problem.

Rob

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