linux-kernel - Re: [RFC} arm architecture board/feature deprecation timeline

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Message-ID: <upt52224svue5ozyacrzm3qcavkcz7kojyi2yajoqb4y2pgffo@cy437r5ipdbm>
Date: Thu, 15 Aug 2024 14:24:43 -0400
From: Matt Turner <mattst88@...il.com>
To: Arnd Bergmann <arnd@...db.de>, Ard Biesheuvel <ardb@...nel.org>
Cc: linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org, 
	Russell King <linux@...linux.org.uk>, Linus Walleij <linus.walleij@...aro.org>, 
	Richard Earnshaw <richard.earnshaw@....com>, Richard Sandiford <richard.sandiford@....com>, 
	Ramana Radhakrishnan <ramanara@...dia.com>, Nicolas Pitre <nico@...xnic.net>, 
	Krzysztof Kozlowski <krzk@...nel.org>, Mark Brown <broonie@...nel.org>, 
	Kristoffer Ericson <kristoffer.ericson@...il.com>, Robert Jarzmik <robert.jarzmik@...e.fr>, 
	Aaro Koskinen <aaro.koskinen@....fi>, Janusz Krzysztofik <jmkrzyszt@...il.com>, 
	Tony Lindgren <tony@...mide.com>, linux-omap@...r.kernel.org, 
	Nikita Shubin <nikita.shubin@...uefel.me>, linux-samsung-soc@...r.kernel.org, Andrew Lunn <andrew@...n.ch>, 
	Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>, Gregory Clement <gregory.clement@...tlin.com>, 
	"Jeremy J. Peper" <jeremy@...emypeper.com>, debian-arm@...ts.debian.org, 
	Dmitry Torokhov <dmitry.torokhov@...il.com>, Alexandre Torgue <alexandre.torgue@...s.st.com>
Subject: Re: [RFC} arm architecture board/feature deprecation timeline

On 07/31, Arnd Bergmann wrote:
>=== iWMMXt ===
>
>I'm not aware of any remaining users for iWMMXt, and we dropped
>support for ARMv7 PJ4 CPUs (MMP2, Berlin) already, so the
>only supported hardware that even has this is Intel/Marvell
>PXA and MMP1.

pixman had [1][2] iwMMXt paths that I optimized for the XO 1.75 and
would occasionally test on a CuBox over the years.

I'm surprised to see that commit b9920fdd5a75 ("ARM: 9352/1: iwmmxt:
Remove support for PJ4/PJ4B cores") landed with the claim that "there is
no v6/v7 user space that actually makes use of this". A quick Google
search reveals evidence of usage [3]. It doesn't seem like this should
have been backported to the stable branches in any case.

I know that ffmpeg used to have iwMMXt paths as well, but I believe they
were removed a few years ago.

Anyway, I guess it's totally dead now.

[1] https://gitlab.freedesktop.org/pixman/pixman/-/merge_requests/108
[2] https://mattst88.com/blog/2012/07/06/My_time_optimizing_graphics_performance_on_the_OLPC_XO_1.75_laptop/
[3] https://www.phoronix.com/news/MTEzNDQ