.. SPDX-License-Identifier: GPL-2.0
BMIPS DeviceTree Booting
------------------------
Some bootloaders only support a single entry point, at the start of the
kernel image. Other bootloaders will jump to the ELF start address.
Both schemes are supported; CONFIG_BOOT_RAW=y and CONFIG_NO_EXCEPT_FILL=y,
so the first instruction immediately jumps to kernel_entry().
Similar to the arch/arm case (b), a DT-aware bootloader is expected to
set up the following registers:
a0 : 0
a1 : 0xffffffff
a2 : Physical pointer to the device tree block (defined in chapter
II) in RAM. The device tree can be located anywhere in the first
512MB of the physical address space (0x00000000 - 0x1fffffff),
aligned on a 64 bit boundary.
Legacy bootloaders do not use this convention, and they do not pass in a
DT block. In this case, Linux will look for a builtin DTB, selected via
CONFIG_DT_*.
This convention is defined for 32-bit systems only, as there are not
currently any 64-bit BMIPS implementations.
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