RE: How to use SPE on MPC8541

["Gérard Guével" <gguevel@interfaceconcept.com>]

Andy,

> Your driver runs in kernel space.  The kernel has the SPE bit off.
> The MSR state is process-specific.  If the code executes, the
> MSR bit
> is set.  Why do you want to see if the bit is set?

OK, this is a bad idea to use a driver to check the msr register.

I don't especially want to see if the bit is set, I just want
to improve the board performance for a Linux application :-).

To check the performance, I used the Dhrystone 2.1 benchmark with
the standard glibc (strcpy, strcmp, ...) on one part, and with
the freescale SPE library on the other part (vstrcpy, vstrcmp, ...).

I already verified in the binary elf file that the right functions are
called.
When I run the benchmark, I get the same MIPS with and without SPE code.

I ran the same benchmark on the same board without OS,
with a personal pseudo glibc, I have the same MIPS as under Linux,
with the freescale library, I gain 40% of perf.

That's I want to retreive with the Linux OS.

Regards
Gérard