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From: Alexander Graf <graf@amazon.com>
To: <linux-kernel@vger.kernel.org>
CC: <linux-trace-kernel@vger.kernel.org>, <linux-mm@kvack.org>,
	<devicetree@vger.kernel.org>, <linux-arm-kernel@lists.infradead.org>,
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	"Rob Herring" <robh+dt@kernel.org>, Steven Rostedt <rostedt@goodmis.org>,
	"Andrew Morton" <akpm@linux-foundation.org>, Mark Rutland
	<mark.rutland@arm.com>, "Tom Lendacky" <thomas.lendacky@amd.com>, Ashish
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	<anthony.yznaga@oracle.com>, Usama Arif <usama.arif@bytedance.com>, David
 Woodhouse <dwmw@amazon.co.uk>, Benjamin Herrenschmidt
	<benh@kernel.crashing.org>
Subject: [PATCH v2 17/17] devicetree: Add bindings for ftrace KHO
Date: Fri, 22 Dec 2023 19:51:44 +0000
Message-ID: <20231222195144.24532-12-graf@amazon.com>
In-Reply-To: <20231222195144.24532-1-graf@amazon.com>
References: <20231222193607.15474-1-graf@amazon.com>
 <20231222195144.24532-1-graf@amazon.com>
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With ftrace in KHO, we are creating an ABI between old kernel and new
kernel about the state that they transfer. To ensure that we document
that state and catch any breaking change, let's add its schema to the
common devicetree bindings. This way, we can quickly reason about the
state that gets passed.

Signed-off-by: Alexander Graf <graf@amazon.com>
---
 .../bindings/kho/ftrace/ftrace-array.yaml     | 46 +++++++++++++++
 .../bindings/kho/ftrace/ftrace-cpu.yaml       | 56 +++++++++++++++++++
 .../bindings/kho/ftrace/ftrace.yaml           | 48 ++++++++++++++++
 3 files changed, 150 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/kho/ftrace/ftrace-array.yaml
 create mode 100644 Documentation/devicetree/bindings/kho/ftrace/ftrace-cpu.yaml
 create mode 100644 Documentation/devicetree/bindings/kho/ftrace/ftrace.yaml

diff --git a/Documentation/devicetree/bindings/kho/ftrace/ftrace-array.yaml b/Documentation/devicetree/bindings/kho/ftrace/ftrace-array.yaml
new file mode 100644
index 000000000000..9960fefc292d
--- /dev/null
+++ b/Documentation/devicetree/bindings/kho/ftrace/ftrace-array.yaml
@@ -0,0 +1,46 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/kho/ftrace/ftrace-array.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Ftrace trace array
+
+maintainers:
+  - Alexander Graf <graf@amazon.com>
+
+properties:
+  compatible:
+    enum:
+      - ftrace,array-v1
+
+  trace_flags:
+    $ref: /schemas/types.yaml#/definitions/uint32
+    description:
+      Bitmap of all the trace flags that were enabled in the trace array at the
+      point of serialization.
+
+# Subnodes will be of type "ftrace,cpu-v1", one each per CPU
+additionalProperties: true
+
+required:
+  - compatible
+  - trace_flags
+
+examples:
+  - |
+    ftrace {
+        compatible = "ftrace-v1";
+        events = <1 1 2 2 3 3>;
+
+        global_trace {
+          compatible = "ftrace,array-v1";
+          trace_flags = < 0x3354601 >;
+
+          cpu0 {
+            compatible = "ftrace,cpu-v1";
+            cpu = < 0x00 >;
+            mem = < 0x101000000ULL 0x38ULL 0x101000100ULL 0x1000ULL 0x101000038ULL 0x38ULL 0x101002000ULL 0x1000ULL>;
+          };
+        };
+      };
diff --git a/Documentation/devicetree/bindings/kho/ftrace/ftrace-cpu.yaml b/Documentation/devicetree/bindings/kho/ftrace/ftrace-cpu.yaml
new file mode 100644
index 000000000000..58c715e93f37
--- /dev/null
+++ b/Documentation/devicetree/bindings/kho/ftrace/ftrace-cpu.yaml
@@ -0,0 +1,56 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/kho/ftrace/ftrace-cpu.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Ftrace per-CPU ring buffer contents
+
+maintainers:
+  - Alexander Graf <graf@amazon.com>
+
+properties:
+  compatible:
+    enum:
+      - ftrace,cpu-v1
+
+  cpu:
+    $ref: /schemas/types.yaml#/definitions/uint32
+    description:
+      CPU number of the CPU that this ring buffer belonged to when it was
+      serialized.
+
+  mem:
+    $ref: /schemas/types.yaml#/definitions/uint32-array
+    description:
+      Array of { u64 phys_addr, u64 len } elements that describe a list of ring
+      buffer pages. Each page consists of two elements. The first element
+      describes the location of the struct buffer_page that contains metadata
+      for a given ring buffer page, such as the ring's head indicator. The
+      second element points to the ring buffer data page which contains the raw
+      trace data.
+
+additionalProperties: false
+
+required:
+  - compatible
+  - cpu
+  - mem
+
+examples:
+  - |
+    ftrace {
+        compatible = "ftrace-v1";
+        events = <1 1 2 2 3 3>;
+
+        global_trace {
+          compatible = "ftrace,array-v1";
+          trace_flags = < 0x3354601 >;
+
+          cpu0 {
+            compatible = "ftrace,cpu-v1";
+            cpu = < 0x00 >;
+            mem = < 0x101000000ULL 0x38ULL 0x101000100ULL 0x1000ULL 0x101000038ULL 0x38ULL 0x101002000ULL 0x1000ULL>;
+          };
+        };
+      };
diff --git a/Documentation/devicetree/bindings/kho/ftrace/ftrace.yaml b/Documentation/devicetree/bindings/kho/ftrace/ftrace.yaml
new file mode 100644
index 000000000000..b87a64843af3
--- /dev/null
+++ b/Documentation/devicetree/bindings/kho/ftrace/ftrace.yaml
@@ -0,0 +1,48 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/kho/ftrace/ftrace.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Ftrace core data
+
+maintainers:
+  - Alexander Graf <graf@amazon.com>
+
+properties:
+  compatible:
+    enum:
+      - ftrace-v1
+
+  events:
+    $ref: /schemas/types.yaml#/definitions/uint32-array
+    description:
+      Array of { u32 crc, u32 type } elements. Each element contains a unique
+      identifier for an event, followed by the identifier that this event had
+      in the previous kernel's trace buffers.
+
+# Other child nodes will be of type "ftrace,array-v1". Each of which describe
+# a trace buffer
+additionalProperties: true
+
+required:
+  - compatible
+  - events
+
+examples:
+  - |
+    ftrace {
+        compatible = "ftrace-v1";
+        events = <1 1 2 2 3 3>;
+
+        global_trace {
+          compatible = "ftrace,array-v1";
+          trace_flags = < 0x3354601 >;
+
+          cpu0 {
+            compatible = "ftrace,cpu-v1";
+            cpu = < 0x00 >;
+            mem = < 0x101000000ULL 0x38ULL 0x101000100ULL 0x1000ULL 0x101000038ULL 0x38ULL 0x101002000ULL 0x1000ULL>;
+          };
+        };
+      };
-- 
2.40.1


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