Thread (34 messages) 34 messages, 10 authors, 2020-06-20
STALE2170d
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[PATCH v8 5/5] dt-bindings: chosen: Document linux,low-memory-range for arm64 kdump

From: Chen Zhou <hidden>
Date: 2020-05-21 09:35:28
Also in: kexec, linux-arm-kernel, linux-doc, lkml
Subsystem: open firmware and flattened device tree bindings, the rest · Maintainers: Rob Herring, Krzysztof Kozlowski, Conor Dooley, Linus Torvalds

Add documentation for DT property used by arm64 kdump:
linux,low-memory-range.
"linux,low-memory-range" is an another memory region used for crash
dump kernel devices.

Signed-off-by: Chen Zhou <redacted>
---
 Documentation/devicetree/bindings/chosen.txt | 25 ++++++++++++++++++++
 1 file changed, 25 insertions(+)
diff --git a/Documentation/devicetree/bindings/chosen.txt b/Documentation/devicetree/bindings/chosen.txt
index 45e79172a646..bfe6fb6976e6 100644
--- a/Documentation/devicetree/bindings/chosen.txt
+++ b/Documentation/devicetree/bindings/chosen.txt
@@ -103,6 +103,31 @@ 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.
 
+linux,low-memory-range
+----------------------
+This property (arm64 only) holds a base address and size, describing a
+limited region below 4G. Similar to "linux,usable-memory-range", it is
+an another memory range which may be considered available for use by the
+kernel.
+
+e.g.
+
+/ {
+	chosen {
+		linux,low-memory-range = <0x0 0x70000000 0x0 0x10000000>;
+		linux,usable-memory-range = <0x202f 0xc0000000 0x0 0x40000000>;
+	};
+};
+
+The main usage is for crash dump kernel devices when reserving crashkernel
+above 4G. When reserving crashkernel above 4G, there may be two crash kernel
+regions, one is below 4G, the other is above 4G. In order to distinct from
+the high region, use this property to pass the low region.
+
+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.
+
 linux,elfcorehdr
 ----------------
 
-- 
2.20.1
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