mirror of
https://github.com/smaeul/u-boot.git
synced 2025-10-24 17:48:14 +01:00
bb5a2cf9f9
Some code was not converted by coccinelle, somehow.
I manually fixed up the remaining, and comments, README docs.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
[trini: Add arch/arm/mach-davinci/include/mach/sdmmc_defs.h and
include/fdt_support.h]
Signed-off-by: Tom Rini <trini@konsulko.com>
136 lines
5.5 KiB
Plaintext
136 lines
5.5 KiB
Plaintext
# SPDX-License-Identifier: GPL-2.0+
|
|
#
|
|
# (C) Copyright 2014 Google, Inc
|
|
# Simon Glass <sjg@chromium.org>
|
|
|
|
Background
|
|
----------
|
|
|
|
U-Boot traditionally had a board.c file for each architecture. This introduced
|
|
quite a lot of duplication, with each architecture tending to do
|
|
initialisation slightly differently. To address this, a new 'generic board
|
|
init' feature was introduced in March 2013 (further motivation is
|
|
provided in the cover letter below).
|
|
|
|
All boards and architectures have moved to this as of mid 2016.
|
|
|
|
|
|
What has changed?
|
|
-----------------
|
|
|
|
The main change is that the arch/<arch>/lib/board.c file is removed in
|
|
favour of common/board_f.c (for pre-relocation init) and common/board_r.c
|
|
(for post-relocation init).
|
|
|
|
Related to this, the global_data and bd_info structures now have a core set of
|
|
fields which are common to all architectures. Architecture-specific fields
|
|
have been moved to separate structures.
|
|
|
|
|
|
Further Background
|
|
------------------
|
|
|
|
The full text of the original generic board series is reproduced below.
|
|
|
|
--8<-------------
|
|
|
|
This series creates a generic board.c implementation which contains
|
|
the essential functions of the major arch/xxx/lib/board.c files.
|
|
|
|
What is the motivation for this change?
|
|
|
|
1. There is a lot of repeated code in the board.c files. Any change to
|
|
things like setting up the baud rate requires a change in 10 separate
|
|
places.
|
|
|
|
2. Since there are 10 separate files, adding a new feature which requires
|
|
initialisation is painful since it must be independently added in 10
|
|
places.
|
|
|
|
3. As time goes by the architectures naturally diverge since there is limited
|
|
pressure to compare features or even CONFIG options against similar things
|
|
in other board.c files.
|
|
|
|
4. New architectures must implement all the features all over again, and
|
|
sometimes in subtle different ways. This places an unfair burden on getting
|
|
a new architecture fully functional and running with U-Boot.
|
|
|
|
5. While it is a bit of a tricky change, I believe it is worthwhile and
|
|
achievable. There is no requirement that all code be common, only that
|
|
the code that is common should be located in common/board.c rather than
|
|
arch/xxx/lib/board.c.
|
|
|
|
All the functions of board_init_f() and board_init_r() are broken into
|
|
separate function calls so that they can easily be included or excluded
|
|
for a particular architecture. It also makes it easier to adopt Graeme's
|
|
initcall proposal when it is ready.
|
|
|
|
http://lists.denx.de/pipermail/u-boot/2012-January/114499.html
|
|
|
|
This series removes the dependency on generic relocation. So relocation
|
|
happens as one big chunk and is still completely arch-specific. See the
|
|
relocation series for a proposed solution to this for ARM:
|
|
|
|
http://lists.denx.de/pipermail/u-boot/2011-December/112928.html
|
|
|
|
or Graeme's recent x86 series v2:
|
|
|
|
http://lists.denx.de/pipermail/u-boot/2012-January/114467.html
|
|
|
|
Instead of moving over a whole architecture, this series takes the approach
|
|
of simply enabling generic board support for an architecture. It is then up
|
|
to each board to opt in by defining CONFIG_SYS_GENERIC_BOARD in the board
|
|
config file. If this is not done, then the code will be generated as
|
|
before. This allows both sets of code to co-exist until we are comfortable
|
|
with the generic approach, and enough boards run.
|
|
|
|
ARM is a relatively large board.c file and one which I can test, therefore
|
|
I think it is a good target for this series. On the other hand, x86 is
|
|
relatively small and simple, but different enough that it introduces a
|
|
few issues to be solved. So I have chosen both ARM and x86 for this series.
|
|
After a suggestion from Wolfgang I have added PPC also. This is the
|
|
largest and most feature-full board, so hopefully we have all bases
|
|
covered in this RFC.
|
|
|
|
A generic global_data structure is also required. This might upset a few
|
|
people. Here is my basic reasoning: most fields are the same, all
|
|
architectures include and need it, most global_data.h files already have
|
|
#ifdefs to select fields for a particular SOC, so it is hard to
|
|
see why architecures are different in this area. We can perhaps add a
|
|
way to put architecture-specific fields into a separate header file, but
|
|
for now I have judged that to be counter-productive.
|
|
|
|
Similarly we need a generic bd_info structure, since generic code will
|
|
be accessing it. I have done this in the same way as global_data and the
|
|
same comments apply.
|
|
|
|
There was dicussion on the list about passing gd_t around as a parameter
|
|
to pre-relocation init functions. I think this makes sense, but it can
|
|
be done as a separate change, and this series does not require it.
|
|
|
|
While this series needs to stand on its own (as with the link script
|
|
cleanup series and the generic relocation series) the goal is the
|
|
unification of the board init code. So I hope we can address issues with
|
|
this in mind, rather than focusing too narrowly on particular ARM, x86 or
|
|
PPC issues.
|
|
|
|
I have run-tested ARM on Tegra Seaboard only. To try it out, define
|
|
CONFIG_SYS_GENERIC_BOARD in your board file and rebuild. Most likely on
|
|
x86 and PPC at least it will hang, but if you are lucky it will print
|
|
something first :-)
|
|
|
|
I have run this though MAKEALL with CONFIG_SYS_GENERIC_BOARD on for all
|
|
ARM, PPC and x86 boards. There are a few failures due to errors in
|
|
the board config, which I have sent patches for. The main issue is
|
|
just the difference between __bss_end and __bss_end__.
|
|
|
|
Note: the first group of commits are required for this series to build,
|
|
but could be separated out if required. I have included them here for
|
|
convenience.
|
|
|
|
------------->8--
|
|
|
|
Simon Glass, sjg@chromium.org
|
|
March 2014
|
|
Updated after final removal, May 2016
|