On Fri, Feb 20, 2015 at 05:04:02PM +0900, Masahiro Yamada wrote:
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
Applied to u-boot/master, thanks!