linux-kernel - Re: [PATCH] ARM: do not assemble iwmmxt.S with LLVM toolchain

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Message-ID: <20200413211508.GE436020@lunn.ch>
Date:   Mon, 13 Apr 2020 23:15:08 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Nick Desaulniers <ndesaulniers@...gle.com>
Cc:     Arnd Bergmann <arnd@...db.de>,
        Linus Walleij <linus.walleij@...aro.org>,
        Peter Smith <Peter.Smith@....com>,
        Stefan Agner <stefan@...er.ch>,
        David Howells <dhowells@...hat.com>,
        Mauro Carvalho Chehab <mchehab+samsung@...nel.org>,
        Manoj Gupta <manojgupta@...gle.com>,
        Benjamin Gaignard <benjamin.gaignard@...aro.org>,
        "Joel Fernandes (Google)" <joel@...lfernandes.org>,
        Jian Cai <caij2003@...il.com>,
        clang-built-linux <clang-built-linux@...glegroups.com>,
        Ilie Halip <ilie.halip@...il.com>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Russell King <linux@...linux.org.uk>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>,
        Sami Tolvanen <samitolvanen@...gle.com>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        "Steven Rostedt (VMware)" <rostedt@...dmis.org>,
        Jian Cai <jiancai@...gle.com>,
        Doug Anderson <armlinux@...isordat.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Patrick Bellasi <patrick.bellasi@....com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Tejun Heo <tj@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] ARM: do not assemble iwmmxt.S with LLVM toolchain

On Mon, Apr 13, 2020 at 12:20:57PM -0700, Nick Desaulniers wrote:
> On Fri, Apr 10, 2020 at 2:56 AM Arnd Bergmann <arnd@...db.de> wrote:
> >
> > On Fri, Apr 10, 2020 at 1:28 AM Jian Cai <caij2003@...il.com> wrote:
> > >
> > > iwmmxt.S contains XScale instructions LLVM ARM backend does not support.
> > > Skip this file if LLVM integrated assemmbler or LLD is used to build ARM
> > > kernel.
> > >
> > > Signed-off-by: Jian Cai <caij2003@...il.com>
> >
> > It clearly makes sense to limit the Kconfig option to compilers that
> > can actually build it.
> > A few questions though:
> >
> > - Given that Armada XP with its PJ4B was still marketed until fairly
> > recently[1],
> >   wouldn't it make sense to still add support for it? Is it a lot of work?
> 
> Sorry, can you help me verify from that link that PJ4B uses XSCALE?

I think you missed my email. iwmmxt is not Xscale. iwmmxt is an
instruction set of its own, which any ARM processor could implement.

> I
> didn't see references to either in the link provided.  Also, given the
> history of XSCALE as noted by Russell, I'm surprised to see Marvell in
> the mix.

https://en.wikipedia.org/wiki/XScale

	XScale comprises several distinct families: IXP, IXC, IOP, PXA
	and CE.

	Intel sold the PXA family to Marvell Technology Group
	in June 2006.[1] Marvell then extended the brand to include
	processors with other microarchitectures, like ARM's Cortex.

	Andrew