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M68k/ColdFire: FPU context initialization
- Date: Mon, 05 Nov 2007 12:11:16 -0600
- From: joel.sherrill at oarcorp.com (Joel Sherrill)
- Subject: M68k/ColdFire: FPU context initialization
Thomas Doerfler wrote:
> we are currently adding FPU support for a ColdFire v4e CPU derivate.
> After reading, re-reading (and reading again) the relevant files in
> cpukit/score/cpu/m68k in the current M68K (with hardware FPU, e.g.
> MC68040) CPU Context management, I have not found, where/how the FPU
> context is initialized for a newly created thread.
> Can somebody please guide me:
> - Is the FPU context in an arbitrary state when a new thread is started?
If the thread is not an FP task, you would prefer to disable the FPU.
If it is FP enabled, then all that you have to initialize is usually
the control registers.
> - Or: Where is the code which defines the initial state of the FPU in a
> new thred?
score/cpu/m68k/rtems/score/cpu.h and score/cpu/m68k/cpu_asm.S
Is the Coldfire FPU similar to the 68881 or is it more RISC like?
Do you have the same type of fsave/restore instructions?
> Any hint appreciated,
> Thomas D?rfler.