mirror of
https://github.com/AsahiLinux/u-boot
synced 2024-12-12 14:23:00 +00:00
8c8153ead2
Fix typo and whitespace in the document. Signed-off-by: Yu Chien Peter Lin <peterlin@andestech.com> Reviewed-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
48 lines
1.7 KiB
ReStructuredText
48 lines
1.7 KiB
ReStructuredText
.. SPDX-License-Identifier: GPL-2.0+
|
|
|
|
Devicetree in QEMU
|
|
==================
|
|
|
|
For QEMU on ARM, RISC-V and one PPC target, the devicetree is created on-the-fly
|
|
by QEMU. It is intended for use in Linux but can be used by U-Boot also, so long
|
|
as any nodes/properties needed by U-Boot are merged in.
|
|
|
|
When `CONFIG_OF_BOARD` is enabled
|
|
|
|
|
|
Obtaining the QEMU devicetree
|
|
-----------------------------
|
|
|
|
Where QEMU generates its own devicetree to pass to U-Boot you can use
|
|
`-dtb u-boot.dtb` to force QEMU to use U-Boot's in-tree version.
|
|
|
|
To obtain the devicetree that qemu generates, add `-machine dumpdtb=qemu.dtb`,
|
|
e.g.::
|
|
|
|
qemu-system-arm -machine virt -machine dumpdtb=qemu.dtb
|
|
|
|
qemu-system-aarch64 -machine virt -machine dumpdtb=qemu.dtb
|
|
|
|
qemu-system-riscv64 -machine virt -machine dumpdtb=qemu.dtb
|
|
|
|
|
|
Merging in U-Boot nodes/properties
|
|
----------------------------------
|
|
|
|
Various U-Boot features require nodes and properties in the U-Boot devicetree
|
|
and at present QEMU is unaware of these. To use these you must manually merge
|
|
in the appropriate pieces.
|
|
|
|
One way to do this is with dtc. This command runs dtc on each .dtb file in turn,
|
|
to produce a text file. It drops the duplicate header on the qemu one. Then it
|
|
joins them up and runs them through dtc to compile the output::
|
|
|
|
qemu-system-arm -machine virt -machine dumpdtb=qemu.dtb
|
|
cat <(dtc -I dtb qemu.dtb) <(dtc -I dtb u-boot.dtb | grep -v /dts-v1/) | dtc - -o merged.dtb
|
|
|
|
You can then run qemu with the merged devicetree, e.g.::
|
|
|
|
qemu-system-arm -machine virt -nographic -bios u-boot.bin -dtb merged.dtb
|
|
|
|
Note that there seems to be a bug in some versions of qemu where the output of
|
|
dumpdtb does not quite match what is provided to U-Boot.
|