1 .. SPDX-License-Identifier: GPL-2.0 1 .. SPDX-License-Identifier: GPL-2.0
2 2
3 BMIPS DeviceTree Booting 3 BMIPS DeviceTree Booting
4 ------------------------ 4 ------------------------
5 5
6 Some bootloaders only support a single entry 6 Some bootloaders only support a single entry point, at the start of the
7 kernel image. Other bootloaders will jump t 7 kernel image. Other bootloaders will jump to the ELF start address.
8 Both schemes are supported; CONFIG_BOOT_RAW= 8 Both schemes are supported; CONFIG_BOOT_RAW=y and CONFIG_NO_EXCEPT_FILL=y,
9 so the first instruction immediately jumps t 9 so the first instruction immediately jumps to kernel_entry().
10 10
11 Similar to the arch/arm case (b), a DT-aware 11 Similar to the arch/arm case (b), a DT-aware bootloader is expected to
12 set up the following registers: 12 set up the following registers:
13 13
14 a0 : 0 14 a0 : 0
15 15
16 a1 : 0xffffffff 16 a1 : 0xffffffff
17 17
18 a2 : Physical pointer to the device t 18 a2 : Physical pointer to the device tree block (defined in chapter
19 II) in RAM. The device tree can be l 19 II) in RAM. The device tree can be located anywhere in the first
20 512MB of the physical address space ( 20 512MB of the physical address space (0x00000000 - 0x1fffffff),
21 aligned on a 64 bit boundary. 21 aligned on a 64 bit boundary.
22 22
23 Legacy bootloaders do not use this conventio 23 Legacy bootloaders do not use this convention, and they do not pass in a
24 DT block. In this case, Linux will look for 24 DT block. In this case, Linux will look for a builtin DTB, selected via
25 CONFIG_DT_*. 25 CONFIG_DT_*.
26 26
27 This convention is defined for 32-bit system 27 This convention is defined for 32-bit systems only, as there are not
28 currently any 64-bit BMIPS implementations. 28 currently any 64-bit BMIPS implementations.
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