On Sep 27, 2005, at 10:30, G=E9rard Gu=E9vel wrote:

Hi,

I am running a Linux 2.6.9 on a MPC8541 custom board.

I would like to run a user application which contains
some SPE code extracted from a freescale library.

I compiled the kernel with the CONFIG_SPE set to yes.
The application also compiles and I can run it on the
board.

But it seems the SPE bit from the MSR register
is not set when the process runs.

I tried to use a call to the enable_kernel_spe function
to force the bit, but it is always erased by the kernel (??)
when scheduling task and never set again.

Must I compile the application with some special flags
to instruct the kernel I want to use SPE ?

You say the application runs, right?  So what made you check the SPE =20
bit state?  The kernel keeps SPE disabled by default so it doesn't =20
have to save the upper 32 bits of the registers every context =20
switch.  When a process uses SPE for the first time, an exception is =20
triggered, the kernel enables SPE for that process, and then that =20
process should be able to use SPE every time it gets cpu time.

How are you determining that the SPE bit is not set?  Is your =20
application not executing the SPE instructions?

Andy