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This patch adds documentation describing a device tree binding for the coreboot firmware. It is meant to be dynamically added during boot and contains address definitions for the coreboot table (a list of variable-sized descriptors providing information about various compile- and run-time generated firmware parameters) and the CBMEM area (the structure containing most run-time resident memory regions set up by coreboot). These definitions allow kernel drivers to easily access data contained in and pointed to by these regions (such as coreboot's in-memory log). (An example implementation can be seen in the following patch) Signed-off-by: Julius Werner <jwerner@chromium.org> Signed-off-by: Thierry Escande <thierry.escande@collabora.com> Acked-by: Rob Herring <robh@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
34 lines
1.2 KiB
Plaintext
34 lines
1.2 KiB
Plaintext
COREBOOT firmware information
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The device tree node to communicate the location of coreboot's memory-resident
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bookkeeping structures to the kernel. Since coreboot itself cannot boot a
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device-tree-based kernel (yet), this node needs to be inserted by a
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second-stage bootloader (a coreboot "payload").
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Required properties:
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- compatible: Should be "coreboot"
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- reg: Address and length of the following two memory regions, in order:
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1.) The coreboot table. This is a list of variable-sized descriptors
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that contain various compile- and run-time generated firmware
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parameters. It is identified by the magic string "LBIO" in its first
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four bytes.
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See coreboot's src/commonlib/include/commonlib/coreboot_tables.h for
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details.
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2.) The CBMEM area. This is a downward-growing memory region used by
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coreboot to dynamically allocate data structures that remain resident.
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It may or may not include the coreboot table as one of its members. It
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is identified by a root node descriptor with the magic number
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0xc0389481 that resides in the topmost 8 bytes of the area.
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See coreboot's src/include/imd.h for details.
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Example:
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firmware {
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ranges;
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coreboot {
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compatible = "coreboot";
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reg = <0xfdfea000 0x264>,
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<0xfdfea000 0x16000>;
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}
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};
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