linux-kernel - Re: [PATCH 08/11] x86: document X86_INTEL

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Message-Id: <206b50a2-922f-4a29-8c1a-b8695b19e65c@app.fastmail.com>
Date: Wed, 04 Dec 2024 21:38:05 +0100
From: "Arnd Bergmann" <arnd@...db.de>
To: "Andy Shevchenko" <andy.shevchenko@...il.com>,
 "Arnd Bergmann" <arnd@...nel.org>, "Ferry Toth" <fntoth@...il.com>
Cc: linux-kernel@...r.kernel.org, x86@...nel.org,
 "Thomas Gleixner" <tglx@...utronix.de>, "Ingo Molnar" <mingo@...hat.com>,
 "Borislav Petkov" <bp@...en8.de>,
 "Dave Hansen" <dave.hansen@...ux.intel.com>,
 "H. Peter Anvin" <hpa@...or.com>,
 "Linus Torvalds" <torvalds@...ux-foundation.org>,
 "Andy Shevchenko" <andy@...nel.org>, "Matthew Wilcox" <willy@...radead.org>,
 "Sean Christopherson" <seanjc@...gle.com>,
 "Davide Ciminaghi" <ciminaghi@...dd.com>,
 "Paolo Bonzini" <pbonzini@...hat.com>, kvm@...r.kernel.org
Subject: Re: [PATCH 08/11] x86: document X86_INTEL_MID as 64-bit-only

On Wed, Dec 4, 2024, at 19:55, Andy Shevchenko wrote:
> +Cc: Ferry
>
> On Wed, Dec 4, 2024 at 12:31 PM Arnd Bergmann <arnd@...nel.org> wrote:
>>
>> From: Arnd Bergmann <arnd@...db.de>
>>
>> The X86_INTEL_MID code was originally introduced for the
>> 32-bit Moorestown/Medfield/Clovertrail platform, later the 64-bit
>> Merrifield/Moorefield variant got added, but the final
>
> variant got --> variants were

Fixed

>> Morganfield/Broxton 14nm chips were canceled before they hit
>> the market.
>
> Inaccurate. "Broxton for Mobile", and not "Broxton" in general.

Changed to "but the final Morganfield 14nm platform was canceled
before it hit the market" 

>> To help users understand what the option actually refers to,
>> update the help text, and make it a hard dependency on 64-bit
>> kernels. While they could theoretically run a 32-bit kernel,
>> the devices originally shipped with 64-bit one in 2015, so that
>> was proabably never tested.
>
> probably

Fixed.

> It's all other way around (from SW point of view). For unknown reasons
> Intel decided to release only 32-bit SW and it became the only thing
> that was heavily tested (despite misunderstanding by some developers
> that pointed finger to the HW without researching the issue that
> appears to be purely software in a few cases) _that_ time.  Starting
> ca. 2017 I enabled 64-bit for Merrifield and from then it's being used
> by both 32- and 64-bit builds.
>
> I'm totally fine to drop 32-bit defaults for Merrifield/Moorefield,
> but let's hear Ferry who might/may still have a use case for that.

Ok. I tried to find the oldest Android image and saw it used a 64-bit
kernel, but that must have been after your work then.

>
>> -               Moorestown MID devices
>
> FTR, a year or so ago it was a (weak) interest to revive Medfield, but
> I think it would require too much work even for the person who is
> quite familiar with HW, U-Boot, and Linux kernel, so it is most
> unlikely to happen.

Ok.

>> +
>> +         The only supported devices are the 22nm Merrified (Z34xx) and
>> +         Moorefield (Z35xx) SoC used in Android devices such as the
>> +         Asus Zenfone 2, Asus FonePad 8 and Dell Venue 7.
>
> The list is missing the Intel Edison DIY platform which is probably
> the main user of Intel MID kernels nowadays.

Ah, that explains a lot ;-)

Changed now to

          The only supported devices are the 22nm Merrified (Z34xx) and
          Moorefield (Z35xx) SoC used in the Intel Edison board and
          a small number of Android devices such as the Asus Zenfone 2,
          Asus FonePad 8 and Dell Venue 7.

> ...
>
>> -         Intel MID platforms are based on an Intel processor and chipset which
>> -         consume less power than most of the x86 derivatives.
>
> Why remove this? AFAIK it states the truth.

It seemed irrelevant for users that configure the kernel. I've
put it back now.

Thanks for the review!

     Arnd