[U-Boot] [PATCH 2/2] arm64: add better spin-table support

[york sun]

On 06/24/2016 09:15 PM, Masahiro Yamada wrote:
> Hi York,
>
> 2016-06-21 1:30 GMT+09:00 york sun <york.sun at nxp.com>:
>> On 06/19/2016 03:34 AM, André Przywara wrote:
>>> Hi,
>>>
>>> On 19/06/16 09:57, Masahiro Yamada wrote:
>>>> 2016-06-18 18:40 GMT+09:00 Linus Walleij <linus.walleij at linaro.org>:
>>>>> On Fri, Jun 17, 2016 at 2:51 PM, Masahiro Yamada
>>>>> <yamada.masahiro at socionext.com> wrote:
>>>>>
>>>>>> There are two enable methods supported by ARM64 Linux; psci and
>>>>>> spin-table.  The latter is simpler and easier to use for quick SoC
>>>>>> bring-up.
>>>>>>
>>>>>> So, I used the spin-table for my first ARMv8 SoC porting, but I
>>>>>> found its support in U-Boot was poor.  It is true there exists a
>>>>>> code fragment for the spin code in arch/arm/cpu/armv8/start.S,
>>>>>> but I see some problems:
>>>>>
>>>>> Is part of the motivation for this approach to boot an ARMv8 system
>>>>> without using the ARM Trusted Firmware?
>>>>>
>>>>> Yours,
>>>>> Linus Walleij
>>>>
>>>> Yes, exactly.
>>>>
>>>> It would be the best choice
>>>> to switch over to PSCI with ATF in a long run,
>>>> but, I decided to use spin-table for the initial SoC bring-up
>>>> because of tight schedule.
>>>
>>> So if you don't have an ATF port ready, why not use U-Boot's PSCI
>>> implementation meanwhile? I think there are efforts underway to make
>>> PSCI enablement for random new boards a walk in the park (by making the
>>> PSCI support as generic as possible, CCing Chen-Yu for this).
>>>
>>> IIRC the spin-table boot method was just introduced to cope with cores
>>> that don't have EL3 and thus cannot provide PSCI services the normal way
>>> (and that don't want to or cannot sacrifice EL2 for that).
>>> So I am a bit wary of proliferating this SMP method.
>>>
>>> Wouldn't it be better to help making U-Boot's PSCI stack as easy to use
>>> as possible? I don't see technical reasons that adding PSCI support for
>>> a board should be harder or more involved than adding spin-table support
>>> - in the end you need to tell it about the SMP pen, maybe providing (or
>>> faking?) reset and shutdown for 0.2 compliance.
>>>
>>
>> We have a team working on PSCI for ARMv8. The patches are floating and
>> need some minor fix. With these patches, PSCI will be used instead of
>> spin-table. However, a trusted firmware (or other kind) is required.
>>
>
>
> That's great.
>
>
> So, what should we do about this patch?
>
>
> I admit PSCI with ATF is the best way in the end,
> but I believe having a simpler alternative should not hurt.
>

I support using spin table as alternative. I see you already sent out v2 
patch. It would be easier to maintain if we consolidate existing code 
with generic code.

York