mirror of
https://github.com/AsahiLinux/u-boot
synced 2024-12-14 07:13:03 +00:00
829fb8b5dc
Fix up headings and tables to read better. Signed-off-by: Simon Glass <sjg@chromium.org>
411 lines
13 KiB
ReStructuredText
411 lines
13 KiB
ReStructuredText
U-Boot new uImage source file format (bindings definition)
|
|
==========================================================
|
|
|
|
Introduction
|
|
------------
|
|
|
|
Evolution of the 2.6 Linux kernel for embedded PowerPC systems introduced new
|
|
booting method which requires that hardware description is available to the
|
|
kernel in the form of Flattened Device Tree.
|
|
|
|
Booting with a Flattened Device Tree is much more flexible and is intended to
|
|
replace direct passing of 'struct bd_info' which was used to boot pre-FDT
|
|
kernels.
|
|
|
|
However, U-Boot needs to support both techniques to provide backward
|
|
compatibility for platforms which are not FDT ready. Number of elements
|
|
playing role in the booting process has increased and now includes the FDT
|
|
blob. Kernel image, FDT blob and possibly ramdisk image - all must be placed
|
|
in the system memory and passed to bootm as a arguments. Some of them may be
|
|
missing: FDT is not present for legacy platforms, ramdisk is always optional.
|
|
Additionally, old uImage format has been extended to support multi sub-images
|
|
but the support is limited by simple format of the legacy uImage structure.
|
|
Single binary header 'struct legacy_img_hdr' is not flexible enough to cover all
|
|
possible scenarios.
|
|
|
|
All those factors combined clearly show that there is a need for new, more
|
|
flexible, multi component uImage format.
|
|
|
|
|
|
New uImage format assumptions
|
|
-----------------------------
|
|
|
|
Implementation
|
|
~~~~~~~~~~~~~~
|
|
|
|
Libfdt has been selected for the new uImage format implementation as (1) it
|
|
provides needed functionality, (2) is actively maintained and developed and
|
|
(3) increases code reuse as it is already part of the U-Boot source tree.
|
|
|
|
Terminology
|
|
~~~~~~~~~~~
|
|
|
|
This document defines new uImage structure by providing FDT bindings for new
|
|
uImage internals. Bindings are defined from U-Boot perspective, i.e. describe
|
|
final form of the uImage at the moment when it reaches U-Boot. User
|
|
perspective may be simpler, as some of the properties (like timestamps and
|
|
hashes) will need to be filled in automatically by the U-Boot mkimage tool.
|
|
|
|
To avoid confusion with the kernel FDT the following naming convention is
|
|
proposed for the new uImage format related terms:
|
|
|
|
FIT
|
|
Flattened uImage Tree
|
|
|
|
FIT is formally a flattened device tree (in the libfdt meaning), which
|
|
conforms to bindings defined in this document.
|
|
|
|
.its
|
|
image tree source
|
|
|
|
.itb
|
|
flattened image tree blob
|
|
|
|
Image building procedure
|
|
~~~~~~~~~~~~~~~~~~~~~~~~
|
|
|
|
The following picture shows how the new uImage is prepared. Input consists of
|
|
image source file (.its) and a set of data files. Image is created with the
|
|
help of standard U-Boot mkimage tool which in turn uses dtc (device tree
|
|
compiler) to produce image tree blob (.itb). Resulting .itb file is the
|
|
actual binary of a new uImage::
|
|
|
|
tqm5200.its
|
|
+
|
|
vmlinux.bin.gz mkimage + dtc xfer to target
|
|
eldk-4.2-ramdisk --------------> tqm5200.itb --------------> bootm
|
|
tqm5200.dtb /|\
|
|
|
|
|
'new uImage'
|
|
|
|
Steps:
|
|
|
|
#. Create .its file, automatically filled-in properties are omitted
|
|
|
|
#. Call mkimage tool on a .its file
|
|
|
|
#. mkimage calls dtc to create .itb image and assures that
|
|
missing properties are added
|
|
|
|
#. .itb (new uImage) is uploaded onto the target and used therein
|
|
|
|
|
|
Unique identifiers
|
|
~~~~~~~~~~~~~~~~~~
|
|
|
|
To identify FIT sub-nodes representing images, hashes, configurations (which
|
|
are defined in the following sections), the "unit name" of the given sub-node
|
|
is used as it's identifier as it assures uniqueness without additional
|
|
checking required.
|
|
|
|
|
|
Root node properties
|
|
--------------------
|
|
|
|
Root node of the uImage Tree should have the following layout::
|
|
|
|
/ o image-tree
|
|
|- description = "image description"
|
|
|- timestamp = <12399321>
|
|
|- #address-cells = <1>
|
|
|
|
|
o images
|
|
| |
|
|
| o image-1 {...}
|
|
| o image-2 {...}
|
|
| ...
|
|
|
|
|
o configurations
|
|
|- default = "conf-1"
|
|
|
|
|
o conf-1 {...}
|
|
o conf-2 {...}
|
|
...
|
|
|
|
Optional property
|
|
~~~~~~~~~~~~~~~~~
|
|
|
|
description
|
|
Textual description of the uImage
|
|
|
|
Mandatory property
|
|
~~~~~~~~~~~~~~~~~~
|
|
|
|
timestamp
|
|
Last image modification time being counted in seconds since
|
|
1970-01-01 00:00:00 - to be automatically calculated by mkimage tool.
|
|
|
|
Conditionally mandatory property
|
|
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
|
|
|
#address-cells
|
|
Number of 32bit cells required to represent entry and
|
|
load addresses supplied within sub-image nodes. May be omitted when no
|
|
entry or load addresses are used.
|
|
|
|
Mandatory nodes
|
|
~~~~~~~~~~~~~~~
|
|
|
|
images
|
|
This node contains a set of sub-nodes, each of them representing
|
|
single component sub-image (like kernel, ramdisk, etc.). At least one
|
|
sub-image is required.
|
|
|
|
configurations
|
|
Contains a set of available configuration nodes and
|
|
defines a default configuration.
|
|
|
|
|
|
'/images' node
|
|
--------------
|
|
|
|
This node is a container node for component sub-image nodes. Each sub-node of
|
|
the '/images' node should have the following layout::
|
|
|
|
o image-1
|
|
|- description = "component sub-image description"
|
|
|- data = /incbin/("path/to/data/file.bin")
|
|
|- type = "sub-image type name"
|
|
|- arch = "ARCH name"
|
|
|- os = "OS name"
|
|
|- compression = "compression name"
|
|
|- load = <00000000>
|
|
|- entry = <00000000>
|
|
|
|
|
o hash-1 {...}
|
|
o hash-2 {...}
|
|
...
|
|
|
|
Mandatory properties
|
|
~~~~~~~~~~~~~~~~~~~~
|
|
|
|
description
|
|
Textual description of the component sub-image
|
|
|
|
type
|
|
Name of component sub-image type, supported types are:
|
|
|
|
"standalone", "kernel", "kernel_noload", "ramdisk", "firmware", "script",
|
|
"filesystem", "flat_dt" and others (see uimage_type in common/image.c).
|
|
|
|
data
|
|
Path to the external file which contains this node's binary data.
|
|
|
|
compression
|
|
Compression used by included data. Supported compressions
|
|
are "gzip" and "bzip2". If no compression is used compression property
|
|
should be set to "none". If the data is compressed but it should not be
|
|
uncompressed by U-Boot (e.g. compressed ramdisk), this should also be set
|
|
to "none".
|
|
|
|
Conditionally mandatory property
|
|
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
|
|
|
os
|
|
OS name, mandatory for types "kernel". Valid OS names are:
|
|
"openbsd", "netbsd", "freebsd", "4_4bsd", "linux", "svr4", "esix",
|
|
"solaris", "irix", "sco", "dell", "ncr", "lynxos", "vxworks", "psos", "qnx",
|
|
"u-boot", "rtems", "unity", "integrity".
|
|
|
|
arch
|
|
Architecture name, mandatory for types: "standalone", "kernel",
|
|
"firmware", "ramdisk" and "fdt". Valid architecture names are: "alpha",
|
|
"arm", "i386", "ia64", "mips", "mips64", "ppc", "s390", "sh", "sparc",
|
|
"sparc64", "m68k", "microblaze", "nios2", "blackfin", "avr32", "st200",
|
|
"sandbox".
|
|
|
|
entry
|
|
entry point address, address size is determined by
|
|
'#address-cells' property of the root node.
|
|
Mandatory for types: "firmware", and "kernel".
|
|
|
|
load
|
|
load address, address size is determined by '#address-cells'
|
|
property of the root node.
|
|
Mandatory for types: "firmware", and "kernel".
|
|
|
|
compatible
|
|
compatible method for loading image.
|
|
Mandatory for types: "fpga", and images that do not specify a load address.
|
|
Supported compatible methods:
|
|
|
|
"u-boot,fpga-legacy"
|
|
the generic fpga loading routine.
|
|
|
|
"u-boot,zynqmp-fpga-ddrauth"
|
|
signed non-encrypted FPGA bitstream for
|
|
Xilinx Zynq UltraScale+ (ZymqMP) device.
|
|
|
|
"u-boot,zynqmp-fpga-enc"
|
|
encrypted FPGA bitstream for Xilinx Zynq
|
|
|
|
UltraScale+ (ZynqMP) device.
|
|
|
|
phase
|
|
U-Boot phase for which the image is intended.
|
|
|
|
"spl"
|
|
image is an SPL image
|
|
|
|
"u-boot"
|
|
image is a U-Boot image
|
|
|
|
Optional nodes:
|
|
|
|
hash-1
|
|
Each hash sub-node represents separate hash or checksum
|
|
calculated for node's data according to specified algorithm.
|
|
|
|
|
|
Hash nodes
|
|
----------
|
|
|
|
::
|
|
|
|
o hash-1
|
|
|- algo = "hash or checksum algorithm name"
|
|
|- value = [hash or checksum value]
|
|
|
|
Mandatory properties
|
|
~~~~~~~~~~~~~~~~~~~~
|
|
|
|
algo
|
|
Algorithm name, supported are "crc32", "md5" and "sha1".
|
|
|
|
value
|
|
Actual checksum or hash value, correspondingly 4, 16 or 20 bytes long.
|
|
|
|
|
|
'/configurations' node
|
|
----------------------
|
|
|
|
The 'configurations' node creates convenient, labeled boot configurations,
|
|
which combine together kernel images with their ramdisks and fdt blobs.
|
|
|
|
The 'configurations' node has the following structure::
|
|
|
|
o configurations
|
|
|- default = "default configuration sub-node unit name"
|
|
|
|
|
o config-1 {...}
|
|
o config-2 {...}
|
|
...
|
|
|
|
|
|
Optional property
|
|
~~~~~~~~~~~~~~~~~
|
|
|
|
default
|
|
Selects one of the configuration sub-nodes as a default configuration.
|
|
|
|
Mandatory nodes
|
|
~~~~~~~~~~~~~~~
|
|
|
|
configuration-sub-node-unit-name
|
|
At least one of the configuration sub-nodes is required.
|
|
|
|
|
|
Configuration nodes
|
|
-------------------
|
|
|
|
Each configuration has the following structure::
|
|
|
|
o config-1
|
|
|- description = "configuration description"
|
|
|- kernel = "kernel sub-node unit name"
|
|
|- fdt = "fdt sub-node unit-name" [, "fdt overlay sub-node unit-name", ...]
|
|
|- loadables = "loadables sub-node unit-name"
|
|
|- script = "
|
|
|- compatible = "vendor,board-style device tree compatible string"
|
|
|
|
|
|
Mandatory properties
|
|
~~~~~~~~~~~~~~~~~~~~
|
|
|
|
description
|
|
Textual configuration description.
|
|
|
|
kernel or firmware
|
|
Unit name of the corresponding kernel or firmware
|
|
(u-boot, op-tee, etc) image. If both "kernel" and "firmware" are specified,
|
|
control is passed to the firmware image.
|
|
|
|
Optional properties
|
|
~~~~~~~~~~~~~~~~~~~
|
|
|
|
fdt
|
|
Unit name of the corresponding fdt blob (component image node of a
|
|
"fdt type"). Additional fdt overlay nodes can be supplied which signify
|
|
that the resulting device tree blob is generated by the first base fdt
|
|
blob with all subsequent overlays applied.
|
|
|
|
fpga
|
|
Unit name of the corresponding fpga bitstream blob
|
|
(component image node of a "fpga type").
|
|
|
|
loadables
|
|
Unit name containing a list of additional binaries to be
|
|
loaded at their given locations. "loadables" is a comma-separated list
|
|
of strings. U-Boot will load each binary at its given start-address and
|
|
may optionally invoke additional post-processing steps on this binary based
|
|
on its component image node type.
|
|
|
|
script
|
|
The image to use when loading a U-Boot script (for use with the
|
|
source command).
|
|
|
|
compatible
|
|
The root compatible string of the U-Boot device tree that
|
|
this configuration shall automatically match when CONFIG_FIT_BEST_MATCH is
|
|
enabled. If this property is not provided, the compatible string will be
|
|
extracted from the fdt blob instead. This is only possible if the fdt is
|
|
not compressed, so images with compressed fdts that want to use compatible
|
|
string matching must always provide this property.
|
|
|
|
The FDT blob is required to properly boot FDT based kernel, so the minimal
|
|
configuration for 2.6 FDT kernel is (kernel, fdt) pair.
|
|
|
|
Older, 2.4 kernel and 2.6 non-FDT kernel do not use FDT blob, in such cases
|
|
'struct bd_info' must be passed instead of FDT blob, thus fdt property *must
|
|
not* be specified in a configuration node.
|
|
|
|
|
|
External data
|
|
-------------
|
|
|
|
The above format shows a 'data' property which holds the data for each image.
|
|
It is also possible for this data to reside outside the FIT itself. This
|
|
allows the FIT to be quite small, so that it can be loaded and scanned
|
|
without loading a large amount of data. Then when an image is needed it can
|
|
be loaded from an external source.
|
|
|
|
In this case the 'data' property is omitted. Instead you can use:
|
|
|
|
data-offset
|
|
offset of the data in a separate image store. The image
|
|
store is placed immediately after the last byte of the device tree binary,
|
|
aligned to a 4-byte boundary.
|
|
|
|
data-size : size of the data in bytes
|
|
|
|
The 'data-offset' property can be substituted with 'data-position', which
|
|
defines an absolute position or address as the offset. This is helpful when
|
|
booting U-Boot proper before performing relocation. Pass '-p [offset]' to
|
|
mkimage to enable 'data-position'.
|
|
|
|
Normal kernel FIT image has data embedded within FIT structure. U-Boot image
|
|
for SPL boot has external data. Existence of 'data-offset' can be used to
|
|
identify which format is used.
|
|
|
|
For FIT image with external data, it would be better to align each blob of data
|
|
to block(512 byte) for block device, so that we don't need to do the copy when
|
|
read the image data in SPL. Pass '-B 0x200' to mkimage to align the FIT
|
|
structure and data to 512 byte, other values available for other align size.
|
|
|
|
Examples
|
|
--------
|
|
|
|
Please see `doc/uImage.FIT/*.its` for actual image source files.
|
|
|
|
.. sectionauthor:: Marian Balakowicz <m8@semihalf.com>
|
|
.. sectionauthor:: External data additions, 25/1/16 Simon Glass <sjg@chromium.org>
|