Xilinx Virtex4 FX PPC

[Stephen Neuendorffer]

Note that you should pick one or the other and be consistent.

If you have MATH_EMULATION
in the kernel and use code compiled partly with and partly without
soft-fp,
then you get really strange errors, because (I believe) the soft-fp uses
a different mechanism for emulating the floating point register files
than
the kernel  (I suppose you'll also see the same thing in a system with
floating
point unit and a mixed-up compilation as well).

Steve

> -----Original Message-----
> From: 
> linuxppc-embedded-bounces+stephen=neuendorffer.name at ozlabs.org
>  
> [mailto:linuxppc-embedded-bounces+stephen=neuendorffer.name at oz
labs.org] On Behalf Of Robert Woodworth
> Sent: Monday, August 20, 2007 10:27 AM
> To: Josh Boyer
> Cc: linuxppc-embedded at ozlabs.org
> Subject: Re: Xilinx Virtex4 FX PPC
> 
> On Mon, 2007-08-20 at 11:35 -0500, Josh Boyer wrote:
> > On Mon, 20 Aug 2007 10:00:54 -0600
> > Robert Woodworth <rwoodworth at securics.com> wrote:
> > 
> > > Problem 2:  Build my own rootfs.
> > > If I try to build my own programs (busybox and bash at 
> this point) with
> > > shared libc using the same glibc from my toolchain, I get 
> an "Illegal
> > > instruction" error.  Is my glibc not compatible with my 
> Xilinx PPC 405??
> > > 
> > > 
> > > If I try to build a rootfs with debian ppc packages I 
> have the same
> > > "Illegal instruction" error.
> > > 
> > > 
> > > 
> > > Question 1:
> > > Do I need a special glibc for the Xilinx PPC 405????  
> > > Does a normal PPC glibc have more "advanced" instructions 
> compiled in
> > > that will not work on a Xilinx PPC 405??
> > 
> > Make sure you're building glibc with soft-fp, or make sure you have
> > CONFIG_MATH_EMULATION enabled in your kernel.  The PPC 405 
> doesn't have
> > an FPU.
> > 
> > josh
> 
> 
> CONFIG_MATH_EMULATION fixed it!!
> 
> 
> 
> What are the opinions out there? 
> Kernel fp or glibc soft-fp??
> 
> I don't have a need for floating point in my final application anyway.
> 
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