Re: [PATCH] powerpc/powernv: Disable native PCIe port management

["Oliver O'Halloran" <oohall@gmail.com>]

On Thu, Nov 14, 2019 at 1:31 AM Bjorn Helgaas <helgaas@kernel.org> wrote:
>
> This is fine, but it feels like sort of a blunt instrument.  Is there
> any practical way to clear pci_host_bridge.native_pcie_hotplug (and
> native_aer if appropriate) for the PHBs in question? That would also
> prevent pciehp from binding.

It is a large hammer, but I don't see a better way to handle it for
the moment. I had another look and my initial assessment was wrong in
that it's the portbus driver which claims the MSI rather than pciehp
itself. The MSI in the PCIe capability is shared between hotplug
events, PMEs, and BW notifications so to make the portbus concept work
the portbus driver needs to own the interrupt. Basicly, pnv_php and
portbus are fundamentally at odds with each other and can't be used
concurrently.

I also think there's some latent issues with the interaction of DPC
and EEH since they operate off the same set of error messages. We
haven't run into any problems yet, but I think that's largely because
we haven't shipped any systems with DPC enabled. In any case, I'd
prefer we disabled portbus until we've fully unpacked what's going on
there.

> We might someday pull portdrv into the PCI core directly instead of as
> a separate driver, and I'm thinking that might be easier if we have
> more specific indications of what the core shouldn't use.

It's not intended to be a permanent change. In the long term I want to
move everything except the initialisation and reset of the PHB out of
firmware and into the kernel so we can use more of the native PCIe
management features.