linux-kernel - [PATCH] dt-bindings: memory: Document linux,usable-memory property

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Message-Id: <1741874545-19091-1-git-send-email-abhitiwari@linux.microsoft.com>
Date: Thu, 13 Mar 2025 07:02:25 -0700
From: Abhishek Tiwari <abhitiwari@...ux.microsoft.com>
To: robh@...nel.org,
	krzk+dt@...nel.org,
	conor+dt@...nel.org,
	kees@...nel.org,
	tony.luck@...el.com,
	gpiccoli@...lia.com,
	devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux-hardening@...r.kernel.org
Cc: abhitiwari@...rosoft.com,
	Abhishek Tiwari <abhitiwari@...ux.microsoft.com>
Subject: [PATCH] dt-bindings: memory: Document linux,usable-memory property

Add Documentation for linux,usable-memory

Signed-off-by: Abhishek Tiwari <abhitiwari@...ux.microsoft.com>
---
 .../bindings/linux,usable-memory.txt          | 32 +++++++++++++++++++
 1 file changed, 32 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/linux,usable-memory.txt

diff --git a/Documentation/devicetree/bindings/linux,usable-memory.txt b/Documentation/devicetree/bindings/linux,usable-memory.txt
new file mode 100644
index 000000000000..167054d2e9a2
--- /dev/null
+++ b/Documentation/devicetree/bindings/linux,usable-memory.txt
@@ -0,0 +1,32 @@
+linux,usable-memory
+===================
+
+Description
+-----------
+The ``linux,usable-memory`` property can be used to restrict usable memory
+region. This property holds a base address and size, Memory outside of this
+range is not accessible by the kernel. This property is particularly useful
+in specialized hardware platforms where certain memory regions must be
+reserved for specific use.
+
+Common use cases include:
+- Allocating ``ramoops`` region
+- Reserving memory for hardware-specific needs
+- Fake Protecting persistent memory (PMEM)
+
+Valid memory may be sparse within the specified range.
+An example device tree configuration is shown below:
+
+.. code-block:: dts
+/ {
+	&memory {
+		linux,usable-memory = <
+			0x00000000 0x80000000 0x00000000 0x1BA00000
+			0x00000000 0xA1000000 0x00000000 0x2AC00000
+		>;
+	};
+};
+
+While this property does not represent a real hardware, the address
+and the size are expressed in #address-cells and #size-cells,
+respectively, of the root node.
-- 
2.48.1