linux-kernel - Re: Removing architectures without upstream gcc support

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Date:   Fri, 23 Feb 2018 11:15:43 -0600
From:   Richard Kuo <rkuo@...eaurora.org>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     linux-arch <linux-arch@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-hexagon@...r.kernel.org, Chen Liqin <liqin.linux@...il.com>,
        Lennox Wu <lennox.wu@...il.com>,
        Guan Xuetao <gxt@...c.pku.edu.cn>,
        Guenter Roeck <linux@...ck-us.net>,
        Al Viro <viro@...iv.linux.org.uk>,
        James Hogan <jhogan@...nel.org>, linux-metag@...r.kernel.org,
        Jonas Bonn <jonas@...thpole.se>,
        Stefan Kristiansson <stefan.kristiansson@...nalahti.fi>,
        Stafford Horne <shorne@...il.com>,
        openrisc@...ts.librecores.org, David Howells <dhowells@...hat.com>
Subject: Re: Removing architectures without upstream gcc support

On Thu, Feb 22, 2018 at 11:43:10PM +0100, Arnd Bergmann wrote:
> On Thu, Feb 22, 2018 at 8:17 PM, Richard Kuo <rkuo@...eaurora.org> wrote:
> > On Thu, Feb 22, 2018 at 04:45:06PM +0100, Arnd Bergmann wrote:
> >> * Hexagon is Qualcomm's DSP architecture. It is being actively used
> >>   in all Snapdragon ARM SoCs, but the kernel code appears to be
> >>   the result of a failed research project to make a standalone Hexagon
> >>   SoC without an ARM core. There is some information about the
> >>   project at https://wiki.codeaurora.org/xwiki/bin/Hexagon/ and
> >>   https://unix.stackexchange.com/questions/246243/what-is-was-the-qualcomm-hexagon-comet-board
> >>   There is a port to gcc-4.5 on the project page, which is evidently
> >>   abandoned, but there is an active upstream LLVM port that is
> >>   apparently used to build non-Linux programs.
> >>   I would consider this one a candidate for removal as well, given that
> >>   there were never any machines outside of Qualcomm that used this,
> >>   and they are no longer interested themselves.
> >
> > It's difficult for me to speak to the decisions as I can understand
> > your point of view, but maybe I can speak to some of the status.
> >
> > We still use the port internally for kicking the tools around and other
> > research projects.  As you noticed we're not doing gcc anymore; we're
> > using LLVM for both kernel and userspace.  Yes there have been some
> > caveats but it does work within confines.
> >
> > Time is unfortunately just limited for me to upstream some of my kernel
> > fixes and cleanups, and there are some things that just haven't shown
> > up externally yet.
> >
> > However, as James Hogan mentioned, having it in the tree really has been
> > useful because it gets included in the various upstream changes and
> > fixes, which we appreciate.
> >
> > So hopefully this will help inform the decision a little better.
> >
> > If you have any other questions please let me know.
> 
> Thanks for the clarification! Since you are the maintainer and you
> still consider the port useful, I don't see how anyone else would be
> in a position to demand it to be removed, so we should keep it
> around until you want it gone.
> 
> I still have a few questions:
> 
> - Any idea how we would find out of the status ever changes? E.g. if
>   you decide at some point that you don't find the latest Linux useful
>   any more for your internal work, would you send a patch for removal?

Yes, we can definitely notify everyone if this happens.

 
> - How do I build an llvm based toolchain for Hexagon? Do I need patches
>   on top of the llvm-6 release branch? Where can I find the corresponding
>   binutils-2.30 sources?

The Hexagon LLVM tools available from Qualcomm should have an ABI switch
that's supposed to work for this:

-target hexagon-unknown-linux

Admittedly I haven't tried that one.  I'm unsure about the full upstream
status; I'll check on that, but I think the sketchiest component out of
that bunch is currently going to be the linker.

Let me do some checking on all this the next couple of days and get
a better answer.


Thanks,
Richard Kuo


-- 
Employee of Qualcomm Innovation Center, Inc.
Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, 
a Linux Foundation Collaborative Project