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From:   Hao Zhang <quic_hazha@quicinc.com>
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CC:     Hao Zhang <quic_hazha@quicinc.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
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Subject: [PATCH v3 3/3] Documentation: trace: Add documentation for Coresight Dummy Trace
Date:   Sat, 22 Apr 2023 15:37:14 +0800
Message-ID: <20230422073714.38844-4-quic_hazha@quicinc.com>
In-Reply-To: <20230422073714.38844-1-quic_hazha@quicinc.com>
References: <20230422073714.38844-1-quic_hazha@quicinc.com>
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Add documentation for Coresight Dummy Trace under trace/coresight.

Signed-off-by: Hao Zhang <quic_hazha@quicinc.com>
---
 .../trace/coresight/coresight-dummy.rst       | 34 +++++++++++++++++++
 1 file changed, 34 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..d0f73253f694
--- /dev/null
+++ b/Documentation/trace/coresight/coresight-dummy.rst
@@ -0,0 +1,34 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+=============================
+Coresight Dummy Trace Module
+=============================
+
+    :Author:   Hao Zhang <quic_hazha@quicinc.com>
+    :Date:     April 2023
+
+Introduction
+---------------------------
+
+Coresight Dummy Trace Module is for the specific devices that kernel
+don't have permission to access or configure, e.g., CoreSight TPDMs
+on Qualcomm platforms. So there need driver to register dummy devices
+as Coresight devices. 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.
+
+Config details
+---------------------------
+
+There are two types of nodes, dummy sink and dummy source. The nodes
+should be observed at the below coresight path::
+
+    ``/sys/bus/coresight/devices``.
+
+e.g.::
+
+    / $ ls -l /sys/bus/coresight/devices | grep dummy
+    dummy0 -> ../../../devices/platform/soc@0/soc@0:dummy_source/dummy0
+    dummy1 -> ../../../devices/platform/soc@0/soc@0:dummy_sink/dummy1
-- 
2.17.1