[U-Boot] When to create a SoC directory for ARM

[FengHua]

> Date: Wed, 25 Sep 2013 20:10:13 -0500
> From: Scott Wood <scottwood at freescale.com>
> Subject: Re: [U-Boot] When to create a SoC directory for ARM
> To: sun york-R58495 <R58495 at freescale.com>
> Cc: Rini <trini at ti.com>, Wood Scott-B07421 <B07421 at freescale.com>,
> 	"u-boot at lists.denx.de" <u-boot at lists.denx.de>, Tom
> Message-ID: <1380157813.24959.237.camel at snotra.buserror.net>
> Content-Type: text/plain; charset="UTF-8"
> On Wed, 2013-09-25 at 20:04 -0500, sun york-R58495 wrote:
> > On Sep 25, 2013, at 4:52 PM, Scott Wood wrote:
> > 
> > > On Wed, 2013-09-25 at 16:30 -0700, York Sun wrote:
> > >> Dear Wolfgang,
> > >> 
> > >> I failed to find the guideline, here is my question. Pardon me if this
> > >> is a dump question as I am still new to ARM.
> > >> 
> > >> As David Feng post his patch set to add ARMv8 support, I am trying to
> > >> enable it for Freescale implementation. Let's name it as LS2 for this
> > >> discussion. I am thinking to reuse as much as possible for existing
> > >> codes, which include copying some header files from powerpc partially. I
> > >> noticed the SoC field in boards.cfg file and I am wondering how to use
> > >> it effectively. I want to put LS2 specific headers to
> > >> arch/arm/include/asm/arch-ls2. Do I need to copy all files from
> > >> arch/arm/include/asm/arch-armv8/? There aren't many but I see mmu.h is
> > >> included in start.S. I have been searching case like this in ARMv7 but
> > >> didn't see shared header file (maybe I missed it). Please advise.
> > > 
> > > LS2 is (or perhaps more accurately, contains) an implementation of
> > > ARMv8, so you should be using arch-armv8 rather than copying it.
> > 
> > True. But I guess LS2 won't be the only "LS" Freescale is going to
> > make. Where is the best place to put the header file for chassis
> > related registers, like CCSR we have for mpc8xxx.
> Anything that isn't deeply tied to the ARM architecture should probably
> just go in include/.
> >  I am thinking the
> > best place is arch/arm/include/asm/ls2 (or a better name). Like other
> > ARMv7 variants, I am thinking to put ls2 under arch/arm/cpu/armv8/ as
> > well, to host LS-specific code.

> Likewise, if it's specifically tied to armv8 it should go in
> arch/arm/include/asm/arch-armv8, but I'm not sure what would be tied to
> both armv8 and ls2.  Most likely anything LS-specific that needs to go
> under arch/arm/ should go somewhere like arch/arm/include/asm/ls/
> (similar to arch/arm/include/asm/imx-common).

> -Scott
all SOC specific include file should be in arch/arm/include/asm/arch-SOC/ or
some common directory(like include/asm/imx-common). Currently, u-boot only link SOC specific(arch-SOC) include directory.
You could touch a mmu.h file in arch/arm/include/asm/arch-ls2/ and include
arch/arm/include/asm/arch-armv8/mmu.h.
or move arch-armv8/mmu.h to arch/arm/include/asm/ to make it as a generic file.
Maybe we should distinguish architecture specific include directory and SOC
 specific include directory.


-David