mirror of
https://github.com/brain-hackers/u-boot-brain
synced 2024-08-19 16:38:53 +09:00
![Andre Przywara](/assets/img/avatar_default.png)
This file apparently hasn't seen an update in a while, so just sync it with reality. Signed-off-by: Andre Przywara <andre.przywara@arm.com>
57 lines
2.3 KiB
Plaintext
57 lines
2.3 KiB
Plaintext
U-Boot for arm64
|
|
|
|
Summary
|
|
=======
|
|
The initial arm64 U-Boot port was developed before hardware was available,
|
|
so the first supported platforms were the Foundation and Fast Model for ARMv8.
|
|
These days U-Boot runs on a variety of 64-bit capable ARM hardware, from
|
|
embedded development boards to servers.
|
|
|
|
Notes
|
|
=====
|
|
|
|
1. U-Boot can run at any exception level it is entered in, it is
|
|
recommened to enter it in EL3 if U-Boot takes some responsibilities of a
|
|
classical firmware (like initial hardware setup, CPU errata workarounds
|
|
or SMP bringup). U-Boot can be entered in EL2 when its main purpose is
|
|
that of a boot loader. It can drop to lower exception levels before
|
|
entering the OS.
|
|
|
|
2. U-Boot for arm64 is compiled with AArch64-gcc. AArch64-gcc
|
|
use rela relocation format, a tool(tools/relocate-rela) by Scott Wood
|
|
is used to encode the initial addend of rela to u-boot.bin. After running,
|
|
the U-Boot will be relocated to destination again.
|
|
|
|
3. Earlier Linux kernel versions required the FDT to be placed at a
|
|
2 MB boundary and within the same 512 MB section as the kernel image,
|
|
resulting in fdt_high to be defined specially.
|
|
Since kernel version 4.2 Linux is more relaxed about the DT location, so it
|
|
can be placed anywhere in memory.
|
|
Please reference linux/Documentation/arm64/booting.txt for detail.
|
|
|
|
4. Spin-table is used to wake up secondary processors. One location
|
|
(or per processor location) is defined to hold the kernel entry point
|
|
for secondary processors. It must be ensured that the location is
|
|
accessible and zero immediately after secondary processor
|
|
enter slave_cpu branch execution in start.S. The location address
|
|
is encoded in cpu node of DTS. Linux kernel store the entry point
|
|
of secondary processors to it and send event to wakeup secondary
|
|
processors.
|
|
Please reference linux/Documentation/arm64/booting.txt for detail.
|
|
|
|
5. Generic board is supported.
|
|
|
|
6. CONFIG_ARM64 instead of CONFIG_ARMV8 is used to distinguish aarch64 and
|
|
aarch32 specific codes.
|
|
|
|
|
|
Contributors
|
|
============
|
|
Tom Rini <trini@ti.com>
|
|
Scott Wood <scottwood@freescale.com>
|
|
York Sun <yorksun@freescale.com>
|
|
Simon Glass <sjg@chromium.org>
|
|
Sharma Bhupesh <bhupesh.sharma@freescale.com>
|
|
Rob Herring <robherring2@gmail.com>
|
|
Sergey Temerkhanov <s.temerkhanov@gmail.com>
|