linux-kernel - Re: Old platforms: bring out your dead

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Date:   Sun, 10 Jan 2021 18:35:57 +0100
From:   John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-m68k <linux-m68k@...ts.linux-m68k.org>,
        Sparc kernel list <sparclinux@...r.kernel.org>,
        Linux-sh list <linux-sh@...r.kernel.org>
Subject: Re: Old platforms: bring out your dead

Hi Arnd!

(Please let's have this cross-posted for more visibility. I only learned about this
 while reading Phoronix news)

> I also looked at non-ARM platforms while preparing for my article. Some of
> these look like they are no longer actively maintained or used, but I'm not
> doing anything about those unless the maintainers would like me to:
> 
> * h8300: Steven Rostedt has repeatedly asked about it to be removed
>    or fixed in 2020 with no reply. This was killed before in 2013, added back
>    in 2015 but has been mostly stale again since 2016

As far as I know, Yoshinori Sato is actively maintaining H8300 support, see:

> https://osdn.net/projects/uclinux-h8/

> * c6x: Added in 2011, this has seen very few updates since, but
>     Mark still Acks patches when they come. Like most other DSP platforms,
>     the model of running Linux on a DSP appears to have been obsoleted
>     by using Linux on ARM with on-chip DSP cores running bare-metal code.
> * sparc/sun4m: A patch for removing 32-bit Sun sparc support (not LEON)
>    is currently under review

I don't think this has reached any agreement yet. Multiple people want it to stay.

> * powerpc/cell: I'm the maintainer and I promised to send a patch to remove it.
>    it's in my backlog but I will get to it. This is separate from PS3,
> which is actively
>    maintained and used; spufs will move to ps3
> * powerpc/chrp (32-bit rs6000, pegasos2): last updated in 2009

I'm still using this. Please keep it.

> * powerpc/amigaone: last updated in 2009
> * powerpc/maple: last updated in 2011
> * m68k/{apollo,hp300,sun3,q40} these are all presumably dead and have not
>    seen updates in many years (atari/amiga/mac and coldfire are very much
>    alive)

Dito. I have both sun3 and hp300 machines.

> * mips/jazz: last updated in 2007
> * mips/cobalt: last updated in 2010
> 
> There might be some value in dropping old CPU support on architectures
> and platforms that are almost exclusively used with more modern CPUs.
> If there are only few users, those can still keep using v5.10 or v5.4 stable
> kernels for a few more years. Again, I'm not doing anything about them,
> except mention them since I did the research.
> These are the oldest one by architecture, and they may have reached
> their best-served-by-date:
> 
> * 80486SX/DX: 80386 CPUs were dropped in 2012, and there are
>   indications that 486 have no users either on recent kernels.
>   There is still the Vortex86 family of SoCs, and the oldest of those were
>   486SX-class, but all the modern ones are 586-class.
> * Alpha 2106x: First generation that lacks some of the later features.
>   Since all Alphas are ancient by now, it's hard to tell whether these have
>   any fewer users.

I don't see the point in crippling Alpha support. Does this achieve anything?

> * IA64 Merced: first generation Itanium (2001) was quickly replaced by
>   Itanium II in 2002.
> * MIPS R3000/TX39xx: 32-bit MIPS-II generation, mostly superseded by
>   64-bit MIPS-III (R4000 and higher) starting in 1991. arch/mips still
>   supports these in DECstation and Toshiba Txx9, but it appears that most
>   of those machines are of the 64-bit kind. Later MIPS32 such as 4Kc and
>   later are rather different and widely used.
> * PowerPC 601 (from 1992) just got removed, later 60x, 4xx, 8xx etc
>   are apparently all still used.
> * SuperH SH-2: We discussed removing SH-2 (not J2 or SH-4)
>   support in the past, I don't think there were any objections, but
>   nobody submitted a patch.

Isn't SH-2 basically J-2? I'm not sure what we would gain here.

> * 68000/68328 (Dragonball): these are less capable than the
>   68020+ or the Coldfire MCF5xxx line and similar to the 68360
>   that was removed in 2016.

Adrian

-- 
 .''`.  John Paul Adrian Glaubitz
: :' :  Debian Developer - glaubitz@...ian.org
`. `'   Freie Universitaet Berlin - glaubitz@...sik.fu-berlin.de
  `-    GPG: 62FF 8A75 84E0 2956 9546  0006 7426 3B37 F5B5 F913