Re:

[David Daney <ddaney@caviumnetworks.com>]

On 06/11/2010 07:32 AM, Manuel Lauss wrote:
> Hi,
>
> On Fri, Jun 11, 2010 at 4:06 PM, Jabir M<Jabir_M@pmc-sierra.com>  wrote:
>>     I am working on a FPU-less 34k MIPS platform with linux-2.6.24
>> kernel. After running a Darwin media streaming server on the board
>> for a while, my oprofile results shows high utilization on
>> fpu_emulator_cop1Handler()&  r4k_wait().
>>

r4k_wait() is the idle task, so that indicates there is nothing to do at 
those sample points.

>> wiki page http://www.linux-mips.org/wiki/Floating_point says gcc will
>> use hard float as default and soft float is best suited model for a
>> fpu less processor.  Could anyone kindly help me in understanding use
>> of -msoft-float .
>> Whether I need to compile
>>
>> 1. kernel with -msoft-float ? or

The kernel doesn't use floating point.  So it doesn't matter.

>> 2. Glibc ? or
>> 3. Application ? or
>> 4. All the above ?
>

If you don't want to use the kernel's FP emulator, you need 2 and 3.


> I have fought with this in the past; what you need to do is:
> - build gcc with softfloat support (mipsel-softfloat-linux-gnu triplet
> for example),
> - build a libc with this new compiler,
> - then rebuild all libraries and apps with you new softfloat toolchain.
>
> <plug>
> I have a working softfloat environment for MIPS32 here at [1], it includes a
> complete c/c++ toolchain with gcc-4.4.3.   It's built for mips32r1, no idea if
> it is supposed to work with 34k cores.
> </plug>

34k is mips32r2, which will run r1 code with no problem.

>
> Best regards,
>          Manuel Lauss
>
> [1]  http://mlau.at/files/mips32-linux/
>
>