[Skiboot] [PATCH] Add in new OPAL call to flush the L2 and L3 caches.

[Alistair Popple]

> >> I'd say it should be fairly straightforward to do the purge in the
> >> npu2 creset(). If the current NPU driver in linux expects to get
> >> OPAL_SUCCESS when it does an NPU reset you might be screwed though.
> > 
> > We don't do anything special here in Linux for the NPU so I'd assume it
> > would work as well as it does for everything else. Alexey you were
> > hooking up these resets for pass-through do you know if returning
> > OPAL_PCI_POLL would work in your call paths?
> 
> GPUs are reset from pnv_pci_reset_secondary_bus()+pnv_eeh_bridge_reset()
> which does wait for opal_pci_poll(); in skiboot it is phb4_hreset() and
> this could be the place for the cache purge thingy but I cannot easily
> figure out this state machine in skiboot :-/

Nobody can :-)

Anyway it looks like that deals with a return code of OPAL_PCI_POLL so we 
should be ok to do the cache purge as part of the reset.  I guess knowing this 
I don't feel too strongly either way with respect to implementing this as a 
standalone opal call vs. part of the GPU reset sequence. Alexey/Nick did 
either of you have a preference?

- Alistair
 
> NPUs are reset from pcie_flr() and wait 100ms (then linux waits for
> PCI_COMMAND!=0xffff but this happens immediately).