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[ts-7000] Re: What is needed to have floating point capabilities on 7250

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Subject: [ts-7000] Re: What is needed to have floating point capabilities on 7250?
From: "j.chitte" <>
Date: Wed, 08 Aug 2007 14:10:57 -0000
--- In  "j.chitte" <> wrote:
>
> --- In  Christopher Friedt <cfriedt@> 
> wrote:
> >
> > j.chitte wrote:
> > > I have managed to find some information on the subject which 
> seemed 
> > > to indicate fp emulation could be done but I'd need uclibc 
which 
> in 
> > > itself required a 2.6.x kernel (which is not currently 
supported 
> by 
> > > TS).
> > 
> > This is not the case. uclibc and glibc both have soft-floats, 
it's 
> just 
> > a question of how they're handled. You can do software floating 
> point at 
> > the moment, but it will be quite slow - I think that's the 
> intention of 
> > the warning.
> > 
> 
> Hmm, in view of the complexity of this I may have to see if I can 
> live with that solution.
> 
> > > I need to asses how much customisation effort this is going to 
> imply 
> > > and whether I need to find another way to implement what I need 
> > > without fp.
> > 
> > You could also used fixed point integer arithmetic, and go 
without 
> any 
> > system calls for softfloat - maybe there's even a flag you could 
> pass to 
> > gcc to optimize for fixed-point integer math? It won't be 
terribly 
> fast 
> > though.
> > 
> > > 
> > > Could someone give me details on what is needed to achieve 
softfp 
> on 
> > > 7250?
> > 
> > If you're interested in using something new(er) to speed up FP, 
> then you 
> > probably would want to use the EABI. It speeds up soft-floats by 
a 
> large 
> > factor.
> > 
> > http://www.linuxdevices.com/articles/AT5920399313.html
> > http://wiki.debian.org/ArmEabiPort
> > 
> > I don't know if anyone has actually gotten an eabi kernel / 
> userland 
> > running on the 7[23]xx boards yet, but I'm currently working on 
it. 
> I've 
> > built a toolchain as follows:
> > 
> > USE="-*" crossdev -v \
> > --kernel   2.6.21    \
> > --libc     2.5-r3    \
> > --binutils 2.17      \
> > --gcc      4.2.0     \
> > --target arm-softfloat-linux-gnueabi
> >
> 
> OK, I tried to follow what you posted earlier but glibc failed 
> telling my headers where too old (2.6.20). Is 2.6.21 an minimum 
here 
> or is that possibly a bug? I thought EABI work started around 
2.6.11 .
> 
> I've been having some issues building qemu as well. Odd since I had 
> it working beatifully a few months back.
> 
> Could you cast an eye over this topic if you have a chance?
> http://forums.gentoo.org/viewtopic-p-4162111.html#4162111
> 
> I'm quite interested in your idea of using this as a means of doing 
> "native" arm compiling form gentoo as you suggested.
> 
> Thanks for all your explainations. It's taken some digging but I'm 
> starting to get an overview of the start of the art on all this. 
> 
> js.
>  
> > Both the userland and kernel should either both be compiled w/ 
the 
> EABI 
> > or both not, ... it's possible to have a mixed environment but it 
> would 
> > likely be very complicated.
> > 
> > ... I have yet to get a functional kernel out of EABI though :P I 
> seem 
> > to be hitting the 'invalid machine id' problem in the list's 
> archives, 
> > which leads me to believe that the compiler isn't generating the 
> right 
> > endianness or some other register issue. I probably just need to 
> change 
> > my cflags when compiling linux to point specifically to the 
ep93xx 
> > devices, but haven't touched it for a few days.
> > 
> > 
> > Let us know if you make any interesting progress?
> > 
> > ~/Chris
> >
>

Hi Chris,

I'm hitting a wall here , can you explain something. Since my gentoo 
is almost exactly the same as this setup I tried your example 
crossdev which you reported as working.

USE="-*" crossdev -v  --kernel 2.6.21  --libc 2.5-r4  --binutils 
2.17  --gcc 4.2.0 --target arm-softfloat-linux-gnueabi

I get a thousand and one errors about the headers being too old. 
Presumably you did not get this even though running the same thing.

>In file included from <stdin>:1:
>ports/sysdeps/unix/sysv/linux/arm/eabi/sysdep.h:29:3: error: #error 
Kernel headers are too old

so this seems to be something that has changes in eabi. How can I get 
it to use the code you were able to build?

Sorry if this is a dumb qu. but I'm taking on a lot of new knowlege 
in one hit here and it seems a bit pointless reinventing all that 
you've been through to get to the same point.

TIA. 




 
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