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Date:   Thu, 22 Feb 2018 15:48:33 -0800
From:   Guenter Roeck <linux@roeck-us.net>
To:     Arnd Bergmann <arnd@arndb.de>
Cc:     linux-arch <linux-arch@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Richard Kuo <rkuo@codeaurora.org>,
        linux-hexagon@vger.kernel.org, Chen Liqin <liqin.linux@gmail.com>,
        Lennox Wu <lennox.wu@gmail.com>,
        Guan Xuetao <gxt@mprc.pku.edu.cn>,
        Al Viro <viro@zeniv.linux.org.uk>,
        James Hogan <jhogan@kernel.org>, linux-metag@vger.kernel.org,
        Jonas Bonn <jonas@southpole.se>,
        Stefan Kristiansson <stefan.kristiansson@saunalahti.fi>,
        Stafford Horne <shorne@gmail.com>,
        openrisc@lists.librecores.org, David Howells <dhowells@redhat.com>
Subject: Re: Removing architectures without upstream gcc support
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On Thu, Feb 22, 2018 at 04:45:06PM +0100, Arnd Bergmann wrote:
> While building the cross-toolchains, I noticed that overall, we can build almost
> all linux target architectures with upstream binutils and gcc these days,
> however there are still some exceptions, and I'd like to find out if anyone
> has objections to removing the ones that do not have upstream support.
> This are the four architectures I found:
> 
> * score (s+core, sunplus core) was a proprietary RISC architecture
>   made by sunplus. It is unclear if they still ship any products based on
>   this architecture, all they list is either ARM Cortex-A9 or an unspecified
>   RISC core that could be any of arm, mips, nds32, arc, xtensa or
>   something completely different. The two maintainers have both left the
>   company many years ago and have not contributed any patches in
>   at least five years. There was an upstream gcc port, which was marked
>   'obsolete' in 2013 and got removed in gcc-5.0.
>   I conclude that this is dead in Linux and can be removed
> 
> * unicore32 was a research project at Peking University with a SoC
>   based on the Intel PXA design. No gcc source code has ever been
>   published, the only toolchain available is a set of binaries that include
>   a gcc-4.4 compiler. The project page at
>   http://mprc.pku.edu.cn/~guanxuetao/linux/ has a TODO list that has
>   not been modified since 2011. The maintainer still Acks patches
>   and has last sent a pull request in 2014 and last sent a patch of
>   his own in 2012 when the project appears to have stalled.
>   I would suggest removing this one.
> 

The above two would be primary removal targets for me; they are all
but impossible to support given the toolchain limitations. Meta
would have been another one, but James is already taking care of it.

Guenter

> * 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.
> 
> * Meta was ImgTec's own architecture and they upstreamed the kernel
>   port just before they acquired MIPS. Apparently Meta was abandoned
>   shortly afterwards and disappeared from imgtec's website in 2014.
>   The maintainer is still fixing bugs in the port, but I could not find
>   any toolchain more recent than
>   https://github.com/img-meta/metag-buildroot/tree/metag-core/toolchain/gcc/4.2.4
>   Not sure about this one, I'd be interested in more background
>   from James Hogan, who probably has an opinion and might have
>   newer toolchain sources.
> 
> * OpenRISC is a RISC architecture with a free license and an
>   active community. It seems to have lost a bit of steam after RISC-V
>   is rapidly taking over that niche, but there are chips out there and
>   the design isn't going away. Listing it here for completeness only
>   because there is no upstream gcc port yet, but this will hopefully
>   change in the future based on
>   https://lists.librecores.org/pipermail/openrisc/2018-January/000958.html
>   and I had no problems locating the gcc-7.x tree for building my
>   toolchains. The port is actively being maintained.
> 
> There are also a couple of architectures that are more or less
> unmaintained but do have working gcc support: FR-V and M32R
> have been orphaned for a while and are not getting updated
> MN10300 is still maintained officially by David Howells but doesn't
> seem any more active than the other two, the last real updates were
> in 2013.
> 
>        Arnd