[PATCH] Set cpu explicitly in kernel compiles

[Kumar Gala]

On May 5, 2005, at 9:23 AM, Tom Rini wrote:

> On Thu, May 05, 2005 at 09:00:50AM -0500, Kumar Gala wrote:
>  >
> > On May 5, 2005, at 7:24 AM, Dan Malek wrote:
>  >
> > >
>  > >
>  > >On May 5, 2005, at 1:22 AM, Paul Mackerras wrote:
>  > > > If you think we should have -mcpu=xxx on the command line for 
> 4xx,
>  > > > 44x, 8xx, etc., then that's fine, but that is a separate problem
> > >from
>  > > > what my patch was addressing (one which my patch might make it
> > >easier
>  > > > to fix, though).
>  > >
>  > >I think that is exactly what we want, although I don't know how 
> that is
>  > > separate from the patch you sent.? My original comment was the 
> patch
>  > > fixes the problem for only one of the cpu cores, not all of them.?
> > >Which
>  > > then led into the subsequent suggestion of making the biarch work
>  > > like the past compilers, and we must specific the flags for POWER4
>  > > instead of the other way around.? Without explicit -mcpu flags, 
> the
>  > > existing compiler behavior is just fine .....? but, I guess I'd be
>  > >standing
>  > > in the way of progress to want this :-)
>  >
> > I agree with Dan here.  I think we should go ahead and extend the 
> patch
> > to set -mcpu and -mtune flags for the list of processors we have in
> > "Processor Type".  If I'm building a kernel for e500 or 4xx I might 
> as
> > well get a kernel that is tuned a bit more for the subarch. 
>
>  This is fine.
>
> > Additionally, there should be some expert override ability, so if I
> > really want to do -mcpu=7455 -mtune=7455 I can.
>
> Gack, no!  It's quite a pain to go from CONFIG_FOO="string" into 
> useable
>  Makefile bits that the one we did have back in 2.4 is gone.  That also
>  implies gcc finally knows something about these cores that might be
>  useful, which I don't think is the case, nor is it likely to be.  But 
> if
>  we did want it, we'd probably go the route x86 has.

I'm not saying it has to be done via a CONFIG option, all I'm saying is 
if I want to explicitly use GCC then I would hope we could somehow 
disable it being override.

- kumar