Documentation/powerpc/booting.rst

1 .. SPDX-License-Identifier: GPL-2.0
4 ------------------
8 was decided to enforce some strict rules regarding the kernel entry and
9 bootloader <-> kernel interfaces, in order to avoid the degeneration that had
10 become the ppc32 kernel entry point and the way a new platform should be added
14 merged architecture for ppc32 and ppc64, new 32-bit platforms and 32-bit
19 of a device-tree whose format is defined after Open Firmware specification.
21 doesn't require the device-tree to represent every device in the system and only
34 Entry point
37 There is one single entry point to the kernel, at the start
38 of the kernel image. That entry point supports two calling
47               bindings to powerpc. Only the 32-bit client interface
54               extract the device-tree and other information from open
55               firmware and build a flattened device-tree as described
56               in b). prom_init() will then re-enter the kernel using
57               the second method. This trampoline code runs in the
61         b) Direct entry with a flattened device-tree block. This entry
66         running one. This method is what I will describe in more
67         details in this document, as method a) is simply standard Open
70         PowerPC platform. The entry point definition then becomes:
72                 r3 : physical pointer to the device-tree block
78                 and a non-1:1 mapping.
80                 r5 : NULL (as to differentiate with method a)
82 Note about SMP entry: Either your firmware puts your other
86 with all CPUs. The way to do that with method b) will be
92 given platform based on the content of the device-tree. Thus, you