Wolfgang Grandegger wrote:
Niklaus Giger wrote:
Am Dienstag, 26. September 2006 22:23 schrieb Wolfgang Grandegger:
Niklaus Giger wrote:
Am Dienstag, 26. September 2006 18:28 schrieb Wolfgang Grandegger:
Philippe Gerum wrote:
On Tue, 2006-09-26 at 16:56 +0200, gilles.chanteperdrix wrote:
OK, but in general, soft-float emulation should be used on systems
without FPU and this is even more important for real-time. This is a
tool chain issue. Niklaus, what tool chain are you using?
In my .config I have
MATH_EMULATION=y
You seem to need that because your compiler generates code with hard FP
instructions. You could check this with:
$ ppc-linux-objdump -d prog|egrep ":\s*[e-f]"
This does not return any match on my system.
Oops, then your compiler seems _not_ to create hard FP instruction,
otherwise you would get:
ppc_82xx-objdump -d latency|egrep ":\s*[e-f]"
latency: file format elf32-powerpc
100036ac: fc 21 f8 28 fsub f1,f1,f31
100036b4: fc 42 f8 28 fsub f2,f2,f31
100036c4: fc 63 f8 28 fsub f3,f3,f31
100036cc: fc 21 f0 24 fdiv f1,f1,f30
100036dc: fc 84 f8 28 fsub f4,f4,f31
...
But looking at the disassembly of the latency program I have code like:
100081bc <_restfpr_28_x>:
100081bc: cb 8b ff e0 lfd f28,-32(r11)
or
1000798c <__floatsidf>:
1000798c: 7c 08 02 a6 mflr r0
10007990: 2f 83 00 00 cmpwi cr7,r3,0
10007994: 94 21 ff c0 stwu r1,-64(r1)
10007998: 90 01 00 44 stw r0,68(r1)
1000799c: 54 60 0f fe rlwinm r0,r3,1,31,31
100079a0: 90 01 00 14 stw r0,20(r1)
100079a4: 40 9e 00 24 bne- cr7,100079c8 <__floatsidf+0x3c>
That's from soft float emulation.
The toolchain is gcc-3.4.4-glibc-2.3.5/powerpc-405-linux-gnu built
using
Dan Kegel crosstool (Version 0.42 if I remember exactly).
Shall I switch to another one?
Maybe (likely) there is nothing wrong with your tool chain.
The ELDK from DENX uses FP soft-emulation for 4xx (http://www.denx.de).
Choose v3.1.1 for Linux 2.4 and v4 for Linux 2.6.
I am breathing only PowerPC code on my Mac PowerBook (running Debian)
and never managed to installed ELDK on it. (And even Detlev as a
Debian developer couldn't recommend a simple way.)
I remember Detlev's pain and frustration.
But I assume that I specifying GLIBC_EXTRA_CONFIG="--without-fp" in
the powerpc-405.dat should be enough to make Dan Kegels crosstool emit
Soft-FPU emulation.
See above.
I will try to run the tests at work where I have installed ELDK 4.0,
but not yet a fully working environment. Therefore it may take some
time to report a result back.
I'm now a bit puzzled why a FP exception occurs. What happens if you
disable MATH_EMULATION
in your kernel (that's what I normally have). It will try the latency
test on my Walnut-Board with CONFIG_XENO_OPT_DEBUG asap.
I'm unable to reproduce the problem of our Sycamore board with Linux 2.6.14:
CPU: AMCC PowerPC 405GPr Rev. B at 333.333 MHz (PLB=133, OPB=66,
EBC=66 MHz)
Internal PCI arbiter enabled, PCI async ext clock used
16 kB I-Cache 16 kB D-Cache
Board: Sycamore - AMCC PPC405GPr Evaluation Board
Wolfgang.
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