[linuxsh-dev] SH-5 integration issues

[M. R. B. <mr...@0x...>]

Paul and I have been trying to determine the best fit for the SH-5 port for
2.5.  The problem lies in the SH-5's (and SH-6's) addressing - it's 32-bit
versus 64-bit, so the standard kernel convention for a 64-bit port doesn't
necessarily qualify it as "sh64" (but hey, we're kernel hackers, we can
bend the rules :P).

Moving the SH-5 port in with the sh/ arch is a challenge, but the problem
is trying to plan for structuring future SH processors.  Will the SH-7 and
SH-8 retain the SHmedia instructions and 32-bit addressing?  Or will
Hitachi have a change of mind and switch to 64-bit addressing if the market
calls for it?

If future SH processors are "true" 64-bit machines (well addressing at
least), then it makes sense for the SH-5 and SH-6 to live with the SH-3 and
SH-4 code, but if the SH-7 and SH-8 retain current SHmedia and 32-bit
addressing (e.g. they won't differ "externally" from the SH-5 or SH-6), then
it makes sense for all SHmedia capable processors to live in "sh64".  This is
why we need a bit of clarification (if at all possible) of the plans to stick
with 32-bit addressing, so it'll potentially save us some work down the road.

Is this making sense to people?  We need your insights and suggestions
before we can make the formal proposal of SH-5 inclusion :).

Thanks,

M. R.