In U-boot, the directory structure, arch/$(ARCH)/cpu/$(CPU)/$(SOC)/
has been adopted except that $(CPU) is missing from some
architectures and $(SOC) is missing from some CPUs.
This structure did not fit very well in some cases.
[1] AT91
AT91 SoC family have been developed across some ARM processor
generations. Generally speaking, some IPs are often re-used in the
same SoC family (same SoC vendor) even when the main processor is
updated. As a result, a SoC-common directory is needed in the upper
level. Currently, AT91 source files are placed as follows:
arch/arm/cpu/arm920t/at91/*
arch/arm/cpu/arm926ejs/at91/*
arch/arm/cpu/armv7/at91/*
arch/arm/cpu/at91-common/*
Once directories are split, the motivation for refactorings across
CPU directories is lost. Some files in arm920t/at91/ and
arm926ejs/at91/ are so similar that they could be merged.
[2] Tegra
Tegra is a little bit special case where different CPUs are used for
SPL and the main U-boot. To obey the arch/$(ARCH)/cpu/$(CPU)/$(SOC)
structure, the source files must be placed across the CPUs,
again SoC-common directory is necessary in the upper level.
Moreover, there are several families in Tegra: Tegra20, Tegra30,
Tegra114, Tegra124. Here again, the tegra-common directory is needed
to contain commonly-used files.
Tegra directories have been sprinkled in the directory structure.
arch/arm/cpu/arm720t/tegra20
arch/arm/cpu/arm720t/tegra30
arch/arm/cpu/arm720t/tegra114
arch/arm/cpu/arm720t/tegra124
arch/arm/cpu/arm720t/tegra-common
arch/arm/cpu/armv7/tegra20
arch/arm/cpu/armv7/tegra30
arch/arm/cpu/armv7/tegra114
arch/arm/cpu/armv7/tegra124
arch/arm/cpu/armv7/tegra-common
arch/arm/cpu/tegra20-common
arch/arm/cpu/tegra30-common
arch/arm/cpu/tegra114-common
arch/arm/cpu/tegra124-common
arch/arm/cpu/tegra-common
As you see, splitting SoC code by the CPU is not going well,
especially for ARM.
Why don't we collect SoC-specific files into a single place?
A good example we can follow is Linux's arch/arm/mach-* structure.
This item was discussed in the following thread:
http://thread.gmane.org/gmane.comp.boot-loaders.u-boot/188548/
Looks like I got some positive responses and we are almost ready to
start this movement.
This commit prepares arch/arm/Makefile for describing machdirs in it.
After this commit, we can move SoC directory to arch/arm/mach-$(SOC)
in simple steps although some cases such as AT91 and Tegra need more
fixes.
What we generally have to do is:
[1] Move files arch/arm/cpu/$(CPU)/$(SOC)/* to arch/arm/mach-$(SOC)/*
[2] Add machine entry into arch/arm/Makefile
[3] Remove "obj-y += $(SOC)" from arch/arm/cpu/$(CPU)/Makefile
[4] Fix the Kconfig file path in arch/arm/Kconfig
[5] Modify MAINTAINERS if necessary
Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
Masahiro Yamada
01f1445630