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

[York Sun]

On 09/26/2013 03:49 AM, FengHua wrote:
> 
> 
> 
>> -----原始邮件-----
>> 发件人: "sun york-R58495" <R58495 at freescale.com>
>> 发送时间: 2013年9月26日 星期四
>> 收件人: FengHua <fenghua at phytium.com.cn>
>> 抄送: "albert.u.boot" <albert.u.boot at aribaud.net>, trini <trini at ti.com>, "Wood
>>  Scott-B07421" <B07421 at freescale.com>, u-boot <u-boot at lists.denx.de>
>> 主题: Re: [U-Boot] When to create a SoC directory for ARM
>>
>>
>> On Sep 25, 2013, at 10:23 PM, 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.
>>
>>
>> I was thinking to change the include in start.S to
>>
>> #include <asm/arch-armv8/mmu.h>
>>
> 
> The current arch-armv8/mum.h is based on armv8 architecture.
> Maybe just maybe some armv8 processor will not implement some features of it
> for example 64K page size, then it do not works.
> So, maybe it's better to touch a mmu.h file in include/asm/arch_SOC and 
> include arch-armv8/mmu.h or make different implementation.
> 
I think it is OK right now. It can be a subset or superset, as far as
there is no conflict. We will see when we have more SoCs.

York