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Documentation: dt: chosen properties for arm64 kdump

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Add documentation for DT properties:
	linux,usable-memory-range
	linux,elfcorehdr
used by arm64 kdump. Those are, respectively, a usable memory range
allocated to crash dump kernel and the elfcorehdr's location within it.

Signed-off-by: James Morse <james.morse@arm.com>
[takahiro.akashi@linaro.org: update the text due to recent changes ]
Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Cc: devicetree@vger.kernel.org
Cc: Rob Herring <robh+dt@kernel.org>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
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James Morse 2017-04-03 11:26:06 +09:00 committed by Catalin Marinas
parent 0ceb7d887e
commit fcbd4bb71e
1 changed files with 45 additions and 0 deletions
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45
Documentation/devicetree/bindings/chosen.txt
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@ -52,3 +52,48 @@ This property is set (currently only on PowerPC, and only needed on
book3e) by some versions of kexec-tools to tell the new kernel that it
is being booted by kexec, as the booting environment may differ (e.g.
a different secondary CPU release mechanism)
linux,usable-memory-range
-------------------------
This property (arm64 only) holds a base address and size, describing a
limited region in which memory may be considered available for use by
the kernel. Memory outside of this range is not available for use.
This property describes a limitation: memory within this range is only
valid when also described through another mechanism that the kernel
would otherwise use to determine available memory (e.g. memory nodes
or the EFI memory map). Valid memory may be sparse within the range.
e.g.
/ {
chosen {
linux,usable-memory-range = <0x9 0xf0000000 0x0 0x10000000>;
};
};
The main usage is for crash dump kernel to identify its own usable
memory and exclude, at its boot time, any other memory areas that are
part of the panicked kernel's memory.
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
----------------
This property (currently used only on arm64) holds the memory range,
the address and the size, of the elf core header which mainly describes
the panicked kernel's memory layout as PT_LOAD segments of elf format.
e.g.
/ {
chosen {
linux,elfcorehdr = <0x9 0xfffff000 0x0 0x800>;
};
};
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.