[VxW] powerpc 745 nap/doze mode?

[Kelly Hornsby]

Hello All

I'm trying to find a good way to put my system (Sandpoint 745) into nap or
doze mode.  I can't seem to make the thing go so into power-management mode
and stay there.  I don't know enough about the kernel and the extensions to
the kernel, nor enough about the PPC decrementer interface to decide on the
best way to make the system enter the power management mode, and for it to
recover gracefully when I need for the system to wakeup.

I'm using this Sandpoint-based system (a variant, actually) in an avionics
system that has intermittent power cycles of up to 10 seconds.  I'll use a
capacitor-based voltage supply that will kick in (start
discharging/supplying current) when the primary avionics power voltage goes
below a certain value.  I have a signal that signifies when the voltage from
the main supply is not valid, and I want to doze/nap my PowerPC 745 + MPC
107 when the voltage goes into backup mode.  I only want to refresh memory.
I have no interest in maintaining the PCI bus, because there are no PCI
devices that I must maintain or allow to access memory via the MPC107.

I can disable PCI interrupts just fine from my PCI bus, and from the EPIC,
but I don't know how to easily disable interrupts from the PPC decrementer,
or how this will affect the overall operation of the system.

What is the best way to wakeup the dozing/napping system?  I can do an NMI
with no problem, but what will I need to restore the decrementer? Are there
any gotchas that need to be addressed?

I'm looking for a good document or howto in order to make the nap/doze work,
and perhaps some code snippets to go along with this.  I have the system
running right now in full operation mode, but I'd like to make the system go
into a power-managment mode when I need it to.

I"m using T2.0, but I can go to T2.2 if I need to.

Any hints, suggestions, code snippets, or thoughts are welcome.  Reply here
to the NG if you would.

Thanks.

klh NOSPAM @ cox dot net noBIZ
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