Problem with register cacheing in GDB

[Peter Reilley]

I am making GDB work with the Macraigor Systems Raven
JTAG debug pod under Linux.   I am having a problem making the 
initialization for the 860 PowerPC chip work.   Specifically,
I want to write the immr register.   This register can only
be accessed once after reset, after that, it becomes read only.
That one access must be a write to set the desired value.
If it is a read, then the register is set to read only and you have
lost your chance to write the register.

Is there a way to turn off register caching?   Ideally, you should
be able to turn it off for certain registers that behave in an odd
way.

I have an inelegant way of doing it by fooling with the register_valid
array.   There should be a better way.   Remember, I am coming
in through the JTAG interface so there is no monitor running.

Thanks,
Pete.