From fcbd4bb71e913d4be7a6d39f622479499bb73bfe Mon Sep 17 00:00:00 2001 From: James Morse Date: Mon, 3 Apr 2017 11:26:06 +0900 Subject: [PATCH] Documentation: dt: chosen properties for arm64 kdump 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 [takahiro.akashi@linaro.org: update the text due to recent changes ] Signed-off-by: AKASHI Takahiro Acked-by: Mark Rutland Cc: devicetree@vger.kernel.org Cc: Rob Herring Signed-off-by: Catalin Marinas --- Documentation/devicetree/bindings/chosen.txt | 45 ++++++++++++++++++++++++++++ 1 file changed, 45 insertions(+) diff --git a/Documentation/devicetree/bindings/chosen.txt b/Documentation/devicetree/bindings/chosen.txt index 6ae9d82..b5e39af 100644 --- a/Documentation/devicetree/bindings/chosen.txt +++ b/Documentation/devicetree/bindings/chosen.txt @@ -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. -- 2.7.4