Re: [PATCH v2 3/3] Documentation: trace: Add documentation for Coresight Dummy Trace

From: Hao Zhang
Date: Mon Mar 27 2023 - 02:05:51 EST


Hi Suzuki,

On 3/24/2023 7:00 PM, Suzuki K Poulose wrote:
On 24/03/2023 06:16, Hao Zhang wrote:
Add documentation for Coresight Dummy Trace under trace/coresight.

Signed-off-by: Hao Zhang <quic_hazha@xxxxxxxxxxx>
---
  .../trace/coresight/coresight-dummy.rst       | 58 +++++++++++++++++++
  1 file changed, 58 insertions(+)
  create mode 100644 Documentation/trace/coresight/coresight-dummy.rst

diff --git a/Documentation/trace/coresight/coresight-dummy.rst b/Documentation/trace/coresight/coresight-dummy.rst
new file mode 100644
index 000000000000..819cabab8623
--- /dev/null
+++ b/Documentation/trace/coresight/coresight-dummy.rst
@@ -0,0 +1,58 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+=============================
+Coresight Dummy Trace Module
+=============================
+
+    :Author:   Hao Zhang <quic_hazha@xxxxxxxxxxx>
+    :Date:     March 2023
+
+Introduction
+---------------------------
+
+Coresight Dummy Trace Module is for the specific devices that HLOS don't

Please do not use cryptic abbreviations, please use "kernel"

Sure, I will change it to "kernel".

+have permission to access or configure.

Such as Coresight sink EUD, some
+TPDMs etc.
Say "e.g., CoreSight TPDMs on Qualcomm platforms.:

So there need driver to register dummy devices as Coresight
+devices.

Add:

"It may also be used to define components that may not have any
programming interfaces (e.g, static links), so that paths can
be established in the driver.
"

 Provide Coresight API for dummy device operations, such as
+enabling and disabling dummy devices. Build the Coresight path for dummy
+sink or dummy source for debugging.

I will take your advice in the next version of patch.

I think the following content may not be needed as they are part
of the standard source/sink type devices, nothing specific to
dummy devices.

--- vvvvv ---
+
+Sysfs files and directories
+---------------------------
+
+Root: ``/sys/bus/coresight/devices/dummy<N>``
+
+----
+
+:File:            ``enable_source`` (RW)
+:Notes:
+    - > 0 : enable the datasets of dummy source.
+
+    - = 0 : disable the datasets of dummy source.
+
+:Syntax:
+    ``echo 1 > enable_source``
+
+----
+
+:File:            ``enable_sink`` (RW)
+:Notes:
+    - > 0 : enable the datasets of dummy sink.
+
+    - = 0 : disable the datasets of dummy sink.
+
+:Syntax:
+    ``echo 1 > enable_sink``
+
+----
+

--- You may remove the above ^^^ ----

I will remove the above notes in the next version of patch.

Thanks,
Hao

+Config details
+---------------------------
+
+There are two types of nodes, dummy sink and dummy source. The nodes
+should be observed at the coresight path
+"/sys/bus/coresight/devices".
+e.g.
+/sys/bus/coresight/devices # ls -l | grep dummy
+dummy0 -> ../../../devices/platform/soc@0/soc@0:dummy_source/dummy0
+dummy1 -> ../../../devices/platform/soc@0/soc@0:dummy_sink/dummy1

Suzuki