Re: [linuxsh-dev] Preparing for 2.5

[Stuart M. <Stu...@st...>]

On Oct 12,  9:13am, gn...@m1... wrote:
> Subject: [linuxsh-dev] Preparing for 2.5

I'll try and answer some of these, but as a lot of SH-5 progress is still
not public, I'll have to pass on some points.

>  > - What's up for 2.5?  When I met with NIIBE-san at LWE, he mentioned that
>  >   one of the main things he saw for 2.5 was the beginnings of SH5 support.
>  >   The SH5 has a dual-addressing mode, so we'll have to start working on
>  >   64-bit support for the backend, among other things.  Did anyone else have
>  >   agendas for 2.5?  With the new layout/restructuring, hopefully it'll be
>  >   a lot easier to add support for new boards and processors.
> 
> I was a bit optimistic.  At that time, I expected the development
> environment would be available soon to the public.  The real world is
> not like I expected.
> 
> Situation is different.  As of SH-3/SH-4, it's under control of Hitachi.
> For SH-5, it's SuperH, Inc., who is in charge of. 

SH-5 was jointly developed by Hitachi and ST Microelectronics (my
employer). Some time after development started the two companies
decided to form a separate company to licence the SH-5 core, in the
same way ARM and MIPS do. So they formed SuperH Inc as a new company,
with both Hitach and ST as shareholders.

Unfortunatly the formation of the new company has taken longer than
expected, and as effectivly SH-5 is a SuperH product, this has delayed
everything.

Personally, I wish both companies would have allowed open source
developers access before public release. A good model would have been the
way Intel handled the IA-64 and the Trillian Project. This allowed
developers access (admitidy with an NDA) to documentation, simulators etc.,
before public release, and more importantly allowed them to colaborate on
development, safe in the knowledge that when the chip was released, their
code could also be released publically.

However it would have been a big step for two companies who I suspect are
not very aware of the benefits of open source. We're trying, but it is
taking a while!

> For SH-5, it seems for me that it's quite difficult to begin the
> development.  I think that I can't do at my position.  For now,
> there's no publically available development environment, I mean, GCC
> and such.  Even the technical manual of SH-5 CPU is not available for
> public.
> 
> Perhaps, it could be available under NDA with SuperH, Inc.  However,
> it is very very very much difficult at my position (public servant) to
> sign NDA to specific company.
> 
> I won't go the direction to support SH-5, in near future, perhaps never.
> 
> I wish someone with experience could join the SH-5 kernel development.

It looks like a really nice CPU, and should be able to run Linux well.

>From a technical point of view, SH-5 should probably be regarded in the
same way as mips64 and sparc64. It is able to run SH-4 code, but from
a kernel perspective is probably best regarded as a separate CPU, if
you want to get the best out of it.

I wish I could say more, because there has been progress behind the scenes,
but until SuperH Inc. make the architecture public, a lot of other things
can't be made public either.

Stuart