[PATCH] Set cpu explicitly in kernel compiles

Tom Rini trini at kernel.crashing.org
Fri May 6 00:23:54 EST 2005

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.

Tom Rini

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