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

[York Sun]

On 09/26/2013 12:46 PM, Sharma Bhupesh-B45370 wrote:
> 
>> -----Original Message-----
>> From: u-boot-bounces at lists.denx.de [mailto:u-boot-bounces at lists.denx.de]
>> On Behalf Of Scott Wood
>> Sent: Friday, September 27, 2013 12:53 AM
>> To: FengHua
>> Cc: trini; sun york-R58495; u-boot
>> Subject: Re: [U-Boot] When to create a SoC directory for ARM
>>
>> On Thu, 2013-09-26 at 13:23 +0800, FengHua wrote:
>>>> 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.
>>
>> Is the XXX arch-XXX supposed to be an SoC family or a CPU
>> family/architectutre?
>>
> 
> Usually in 'arch/arm/include/asm' we have both:
> - arch-armv7 (Arch specific. Houses stuff common to ARMv7 CPU, e.g. Global timer, SP805 WDT..)
> - arch-mx6 (SoC family specific. Houses stuff like SoC specific IOMUX pads..)
> 
> We should have something similar for LayerScape.
> 
>
If you look closely, you will find arch-armv7 and its sub-arch including
am33xx, at91, exynos, etc.

York