Re: [PATCH 1/2] PCI/DPC: Disable interrupt generation during suspend

[Bjorn Helgaas <helgaas@kernel.org>]

On Sat, Mar 24, 2018 at 02:48:07PM +0100, Lukas Wunner wrote:
> On Thu, Mar 22, 2018 at 02:36:30PM -0500, Bjorn Helgaas wrote:
> > I hope we can avoid adding suspend_late/resume_early callbacks in
> > struct pcie_port_service_driver,
> 
> I'm fairly certain that we cannot avoid adding at least a ->resume_noirq
> callback to struct pcie_port_service_driver to fix a pciehp use case:
> 
> On ->resume_noirq the PCI core walks down the hierarchy to put every
> device in D0 and restore its state (with a few exceptions such as direct
> complete).  However with hotplug ports, it's possible that the user has
> unplugged devices while the system was asleep, or replaced them with
> other devices.  That's a very real use case with Thunderbolt and we're
> handling it poorly or not at all currently.  We need to check if the
> devices below a hotplug port are still there or have been replaced
> (can probably be recognized by looking at vendor/device IDs across the
> entire sub-hierarchy) during the ->resume_noirq phase.  We could mark
> them with pci_dev_set_disconnected(), then skip putting them into D0
> if that flag has been set.

This is definitely a real issue, and I think it affects more than just
Thunderbolt.  We've never handled undocks very well either.

I certainly agree we need a way to handle this; I would just rather do
it by integrating pciehp and the other services more directly into the
PCI core instead of using the port driver.  Maybe we'll need a
short-term ->resume_noirq, but I don't think the port driver is a good
long-term solution.

Bjorn