[U-Boot] [RFC PATCH 0/21] ARM: start to move SoC code into arch/arm/mach-*

[Simon Glass]

Hi Albert,

On 1 February 2015 at 03:11, Albert ARIBAUD <albert.u.boot at aribaud.net> wrote:
> Hello Simon,
>
> On Sat, 31 Jan 2015 20:20:06 -0700, Simon Glass <sjg at chromium.org>
> wrote:
>> Hi Albert,
>>
>> On 31 January 2015 at 20:02, Albert ARIBAUD <albert.u.boot at aribaud.net> wrote:
>> > Hello Masahiro,
>> >
>> > On Sun, 25 Jan 2015 15:11:02 +0900, Masahiro Yamada
>> > <yamada.m at jp.panasonic.com> wrote:
>> >>
>> >> This series can be applied on the current u-boot/master
>> >> (commit 37b608a52dcb133)
>> >
>> > I'd rather not have all mach-* directories just below arch/arm/. Can't
>> > they be created under arch/arm/soc/ instead? That would give a cleaner
>> > structure IMO.
>>
>> It does save a level and I am forever typing cpu/armv7 to get what
>> feels like nowhere...
>
> That can easily be solved (and tuned to personal taste) with CDPATH, eg.
>
> uboot at lilith:~/src/u-boot-arm (master)$ export CDPATH=arch/arm/cpu:arch/arm
> uboot at lilith:~/src/u-boot-arm (master)$ cd armv
> armv7/  armv8/
> uboot at lilith:~/src/u-boot-arm (master)$ cd armv7
> /home/uboot/src/u-boot-arm/arch/arm/cpu/armv7
> uboot at lilith:~/src/u-boot-arm/arch/arm/cpu/armv7 (master)$
>
> (the u-boot-friendly value of CDPATH can put in a u-boot_env.sh file to
> be sourced along with other u-boot related settings)

I almost never cd into these directories. Mostly I have an editor/IDE
open and I use File->Open to find the files. So this does not help me.
But also I'd say that if the extra levels have no value then why do we
have them at all?

>
>> this is what the kernel does and it does seem convenient.
>
> Well, to me it does not really -- I'm ok with loads of mach-* subdirs
> under a commin parent dir, but what's the benefit of mixing mach-* dirs
> with non-mach-* ones?

If you look at tegra it has its code split between armv7 and arm720t.
This makes it harder to understand what is going on if you are trying
to follow the SPL/U-Boot early boot sequence on tegra. It is nicer to
have all the tegra code under a tegra/ directory regardless of the
particular ARM core.

I think the ARM core name is a convenient way of splitting things up
and has served us well. But now the common elements are more at the
SOC level. Yes the idea of arch/arm/soc/mach-... is more pure from a
hierarchical point of view, but arch/arm/mach-... would be my
preference. I feel that arch/arm is underused now, and U-Boot is
growing so we should try to 'balance' the source tree, making sure
each level of the hierarchy justifies itself with enough
files/subdirs, etc.

$ ls arch/arm
config.mk  cpu  dts  imx-common  include  Kconfig  Kconfig.debug  lib
Makefile  mvebu-common

Note that there are two 'common' directories in there already - see
for example this commit:

commit ea00e59be08989dae905076f4acf3eb297fce552
Author: Stefano Babic <sbabic at denx.de>
Date:   Wed Sep 5 20:16:36 2012 +0000

    MX: set a common place to share code for Freescale i.MX

    Up now only MX5 and MX6 can share code, because they have
    a common source directory in cpu/armv7. Other not armv7
    i.MX can profit of the same shared code. Move these files
    into a directory accessible for all, similar to plat-mxc
    in linux.


One more point is that there is some benefit to using a similar
approach to Linux so long as it is reasonably sensible - familiarity,
less confusing when switching projects.

If we follow this approach then I suspect that arch/arm/cpu will be
only for the 'ARM core' code, not the vendor-specific SOC code built
up around it.

Regards,
Simon