[Skiboot] [PATCH v10 16/17] core/opal: Use PCI slot and new APIs for slot states

[Alistair Popple]

On Thu, 12 May 2016 16:13:58 Stewart Smith wrote:
> Alistair Popple <alistair at popple.id.au> writes:
> >> +	rc = slot->ops.set_power_status(slot, *power_state);
> >
> > As we discussed offline there needs to be much better separation of the
> > platform specific parts and the generic parts of setting the power state.
> >
> > At the moment the calls to update device tree, etc. are all in the 
platform
> > specific code but they should really appear here as it will apply to all 
platforms
> > that eventually support hotplug. The platform specific code should only 
deal with
> > platform dependent functions such as actually removing power from the 
slots which
> > is completely different on say an FSP system versus a non-FSP system.
> 
> My thought that is for P9 (as we can change ABI to kernel there :) we
> could *always* hotplug - detect nothing before starting linux, just hotplug
> it all in at runtime.

We probably wouldn't even have to change the ABI would we? Just get skiboot to 
start up with all the slots "powered down" (even if they aren't physically 
powered down) with no device tree entries for anything plugged into the slots. 
Then once the system is up get the kernel to do a hotplug-in of each slot to 
do the scan and get dt entries...

Is PCI bus enumeration a significant part of skiboot startup time?

Regards,

Alistair