PowerPC G4 support

[Joel Sherrill]

Till Straumann wrote:
> 
> Hi all.
> 
> Is somebody already working on adding G4
> support? If not, I could provide a rudimentary
> implementation:
> 
>  - CPU version recognition etc.
>  - cache initialization.

These sound reaosnable to add as enhancements to
the existing code.

>  - save/restore AltiVec context.
> 
> Are there suggestions regarding the
> implementation of the vector context
> save/restore, i.e. should this go to
> the core code or should it be a user
> extension?

I have always thought that it could be either
part of the FPU context or we could add another
task attribute for vector context.  It should 
definitely be part of the core core though if you
can determine how to turn it on for just altivec CPUs. :)

> Something else that bothers me are the definitions
> 
> #define _IO_BASE        PREP_ISA_IO_BASE
> #define _ISA_MEM_BASE   PREP_ISA_MEM_BASE
> #define PCI_DRAM_OFFSET PREP_PCI_DRAM_OFFSET
> 
> found in lib/libcpu/powerpc/shared/include/io.h
> 
> This should be the business of the BSP rather than
> the CPU library's!

Sounds reasonable to me also.  Could these be provided
by the linker script? This is the most flexible and avoids 
the use of macros.

> -- Till

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