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Subject: Re: fsqrt
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Kumar Gala <galak@kernel.crashing.org>
Date: Sat, 08 Jun 2013 09:23:51 +1000
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Cc: Xie Shaohui-B21989 <B21989@freescale.com>,
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On Fri, 2013-06-07 at 14:19 -0500, Kumar Gala wrote:
> > I don't personally have the bandwidth to do a clean implementation (that
> > handles FP exceptions, NaNs, FPSCR, etc...) but I believe it would be
> > valuable if somebody else did (hint hint hint :-) since without this,
> > Fedora ppc64 is basically going to be a non-started on those chips.
> > 
> > BTW. Did you guys (ie. FSL) finally add fsqrt to e6500 or it's still
> > out ? 
> > 
> > Cheers,
> > Ben.
> 
> Pretty sure fsqrt is still out of e6500.

Ok, thinking out loud... looks like we might be able to just use existing 
math-emu for that. From what I can tell, all it needs (other than enabling
the config option), is a call to flush_fp_to_thread(current);

While talking math-emu... we seem to have some duplication between the
code on do_mathemu which can be compiled without CONFIG_MATH_EMULATION and
in this case only just emulates loads/stores/fmr and the code in
arch/powerpc/kernel/softemu8xx.c.

Is there any reason we can't just get rid of the latter ?

Cheers,
Ben.