#
  # (C) Copyright 2014 Google, Inc
  # Simon Glass <sjg@chromium.org>
  #
  # SPDX-License-Identifier:	GPL-2.0+
  #

  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_t 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