On Wed, Jan 23, 2019 at 12:07:38PM -0700, Keith Busch wrote:
> Right, so in Alex's case, it looks like we are observing
> pcie_wait_for_link() returning true before the PDC event.
>
> I'm wondering about PDS because if the link is up but Presence reports an
> empty slot, does that matter for any implementations? Or is it perfectly
> fine to enumerate an active link on an empty slot? An empty slot and
> active link doesn't make a lot of sense, but that observation appears to
> be what is reported here.
We allow enumeration with an active link of an allegedly empty slot
because some hardware hardwires PDS to zero, see commit 80696f991424
("PCI: pciehp: Tolerate Presence Detect hardwired to zero").
The brokenness of PCIe hotplug implementations found in the wild is
astonishing.
Thanks,
Lukas
