Re: [Linaro-acpi] [RFC] ACPI on arm64 TODO List

Linda Knippers
2015-01-15T17:45:36Z

On 1/13/2015 7:21 PM, Al Stone wrote:
> On 01/12/2015 12:39 PM, Pavel Machek wrote:
>> On Mon 2015-01-12 14:41:50, Grant Likely wrote:
>>> On Mon, Jan 12, 2015 at 2:23 PM, Pavel Machek <pavel@ucw.cz> wrote:
>>>> On Sat 2015-01-10 14:44:02, Grant Likely wrote:
>>>>> On Wed, Dec 17, 2014 at 10:26 PM, Grant Likely <grant.likely@linaro.org> wrote:
>>>>>> On Tue, Dec 16, 2014 at 11:27 AM, Arnd Bergmann <arnd@arndb.de> wrote:
>>>>>>> On Monday 15 December 2014 19:18:16 Al Stone wrote:
>>>>>>>> 7. Why is ACPI required?
>>>>>>>> * Problem:
>>>>>>>> * arm64 maintainers still haven't been convinced that ACPI is
>>>>>>>> necessary.
>>>>>>>> * Why do hardware and OS vendors say ACPI is required?
>>>>>>>> * Status: Al & Grant collecting statements from OEMs to be posted
>>>>>>>> publicly early in the new year; firmware summit for broader
>>>>>>>> discussion planned.
>>>>>>>
>>>>>>> I was particularly hoping to see better progress on this item. It
>>>>>>> really shouldn't be that hard to explain why someone wants this feature.
>>>>>>
>>>>>> I've written something up in as a reply on the firmware summit thread.
>>>>>> I'm going to rework it to be a standalone document and post it
>>>>>> publicly. I hope that should resolve this issue.
>>>>>
>>>>> I've posted an article on my blog, but I'm reposting it here because
>>>>> the mailing list is more conducive to discussion...
>>>>>
>>>>> http://www.secretlab.ca/archives/151
>>>>
>>>> Unfortunately, I seen the blog post before the mailing list post, so
>>>> here's reply in blog format.
>>>>
>>>> Grant Likely published article about ACPI and ARM at
>>>>
>>>> http://www.secretlab.ca/archives/151
>>>>
>>>> . He acknowledges systems with ACPI are harder to debug, but because
>>>> Microsoft says so, we have to use ACPI (basically).
>>>
>>> Please reread the blog post. Microsoft is a factor, but it is not the
>>> primary driver by any means.
>>
>> Ok, so what is the primary reason? As far as I could tell it is
>> "Microsoft wants ACPI" and "hardware people want Microsoft" and
>> "fragmentation is bad so we do ACPI" (1) (and maybe "someone at RedHat
>> says they want ACPI" -- but RedHat people should really speak for
>> themselves.)
>
> I have to say I found this statement fascinating.
>
> I have been seconded to Linaro from Red Hat for over two years now,
> working on getting ACPI running, first as a prototype on an ARMv7 box,
> then on ARMv8. I have been working with Grant since very early on when
> some of us first started talking about ARM servers in the enterprise
> market, and what sorts of standards, if any, would be needed to build an
> ecosystem.
>
> This is the first time in at least two years that I have had someone
> ask for Red Hat to speak up about ACPI on ARM servers; it's usually
> quite the opposite, as in "will you Red Hat folks please shut up about
> this already?" :).
>
> For all the reasons Grant has already mentioned, my Customers need to
> have ACPI on ARM servers for them to be successful in their business.
> I view my job as providing what my Customers need to be successful.
> So, here I am. I want ACPI on ARMv8 for my Customers.

I want that too, even for platforms that might not ever run Windows.

-- ljk

>
>> You snipped quite a lot of reasons why ACPI is inferior that were
>> below this line in email.
>>
>> Pavel
>>
>> (1) ignoring fact that it causes fragmentation between servers and phones.
>>
>
> I see this very differently. This is a "fact" only when viewed from
> the perspective of having two different technologies that can do very
> similar things.
>
> In my opinion, the issue is that these are two very, very different
> markets; technologies are only relevant as the tools to be used to be
> successful in those markets.
>
> Just on a surface level, phones are expected to be completely replaced
> every 18 months or less -- new hardware, new version of the OS, new
> everything. That's the driving force in the market.
>
> A server does not change that quickly; it is probable that the hardware
> will change, but it is unlikely to change at that speed. It can take
> 18 months just for some of the certification testing needed for new
> hardware or software. Further, everything from the kernel on up is
> expected to be stable for a long time -- as long as 25 years, in some
> cases I have worked on. "New" can be a bad word in this environment.
>
> Best I can tell, I need different tool sets to do well in each of these
> environments -- one that allows me to move quickly for phones, and one
> that allows me to carefully control change for servers. I personally
> don't see that as fragmentation, but as using the right tool for the
> job. If I'm building a phone, I want the speed and flexibility of DT.
> If I'm building a server, I want the long term stability of ACPI.
>