From 88cfb1eefca9a403a76dc3e151adb7565b10e77d Mon Sep 17 00:00:00 2001 From: Julius Werner Date: Tue, 28 Mar 2017 18:11:28 +0200 Subject: firmware: Add coreboot device tree binding documentation 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 Signed-off-by: Thierry Escande Acked-by: Rob Herring Signed-off-by: Greg Kroah-Hartman --- .../devicetree/bindings/firmware/coreboot.txt | 33 ++++++++++++++++++++++ 1 file changed, 33 insertions(+) create mode 100644 Documentation/devicetree/bindings/firmware/coreboot.txt (limited to 'Documentation/devicetree') diff --git a/Documentation/devicetree/bindings/firmware/coreboot.txt b/Documentation/devicetree/bindings/firmware/coreboot.txt new file mode 100644 index 000000000000..4c955703cea8 --- /dev/null +++ b/Documentation/devicetree/bindings/firmware/coreboot.txt @@ -0,0 +1,33 @@ +COREBOOT firmware information + +The device tree node to communicate the location of coreboot's memory-resident +bookkeeping structures to the kernel. Since coreboot itself cannot boot a +device-tree-based kernel (yet), this node needs to be inserted by a +second-stage bootloader (a coreboot "payload"). + +Required properties: + - compatible: Should be "coreboot" + - reg: Address and length of the following two memory regions, in order: + 1.) The coreboot table. This is a list of variable-sized descriptors + that contain various compile- and run-time generated firmware + parameters. It is identified by the magic string "LBIO" in its first + four bytes. + See coreboot's src/commonlib/include/commonlib/coreboot_tables.h for + details. + 2.) The CBMEM area. This is a downward-growing memory region used by + coreboot to dynamically allocate data structures that remain resident. + It may or may not include the coreboot table as one of its members. It + is identified by a root node descriptor with the magic number + 0xc0389481 that resides in the topmost 8 bytes of the area. + See coreboot's src/include/imd.h for details. + +Example: + firmware { + ranges; + + coreboot { + compatible = "coreboot"; + reg = <0xfdfea000 0x264>, + <0xfdfea000 0x16000>; + } + }; -- cgit v1.2.3-59-g8ed1b