[Ksummit-2012-discuss] PCI breakout session
James.Bottomley at HansenPartnership.com
Mon Jun 18 07:41:43 UTC 2012
On Mon, 2012-06-18 at 07:42 +1000, Benjamin Herrenschmidt wrote:
> (snip general approval)
> So folks, what should be the format ? Do we organize a mini-summit
> proper with an agenda or we just breakout during KS itself ?
> Ted, does the venue has facilities for us to do something maybe the day
> before ? Or we just do it informally in the corridors ? :-)
> I think the main thing to discuss is rework & cleanup of hotplug which
> is a large impact (PCI boot code as well) if we want to do it properly,
> which means having essentially the same code path overall to deal with
> normal PCI probe and hotplug.
> The main issue I see in term of infrastructure is how we rely on
> initcall "levels" and ordering of things at boot to do things like
> probe, then assign resources, then fixups, then bind drivers. It's
> fragile and doesn't work properly with hotplug, meaning that hotplug
> uses a subtely different ordering (and totally fails to call the final
> The "right" approach is to probably move the resource assignment to
> between the initial scan pass and the "adding" of devices (in our PCI
> stack terminology, adding -> register with the driver model), and
> naturally have the final fixups called right before the latter. But this
> will have some sort of impact on all archs so we probably want to do
> quite a bit of code auditing first.
> Of course that's scary since PCI is so prone to regressions, especially
> on x86 ...
> I have some specific issues with resource allocation on bridges that
> segment the MMIO space in interesting ways (for error handling) that I
> want to discuss and get feedback on how to best deal with.
> Do we start writing an agenda ?
Could we do it on the second mini-summit day? I suspect most of the
arch maintainers will want to be there, since PCI is bound into all our
architectures in some quite unique ways.
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