tree 5cfa55cd668ac328c16efb9849221f09307c6e53
parent c21e3d1e1c50fe0171841b0aa8b0a51e4c3fcd1f
author Oliver O'Halloran <oohall@gmail.com> 1574060153 +1100
committer Greg Kroah-Hartman <gregkh@linuxfoundation.org> 1579763976 +0100

powerpc/powernv: Disable native PCIe port management

commit 9d72dcef891030545f39ad386a30cf91df517fb2 upstream.

On PowerNV the PCIe topology is (currently) managed by the powernv platform
code in Linux in cooperation with the platform firmware. Linux's native
PCIe port service drivers operate independently of both and this can cause
problems.

The main issue is that the portbus driver will conflict with the platform
specific hotplug driver (pnv_php) over ownership of the MSI used to notify
the host when a hotplug event occurs. The portbus driver claims this MSI on
behalf of the individual port services because the same interrupt is used
for hotplug events, PMEs (on root ports), and link bandwidth change
notifications. The portbus driver will always claim the interrupt even if
the individual port service drivers, such as pciehp, are compiled out.

The second, bigger, problem is that the hotplug port service driver
fundamentally does not work on PowerNV. The platform assumes that all
PCI devices have a corresponding arch-specific handle derived from the DT
node for the device (pci_dn) and without one the platform will not allow
a PCI device to be enabled. This problem is largely due to historical
baggage, but it can't be resolved without significant re-factoring of the
platform PCI support.

We can fix these problems in the interim by setting the
"pcie_ports_disabled" flag during platform initialisation. The flag
indicates the platform owns the PCIe ports which stops the portbus driver
from being registered.

This does have the side effect of disabling all port services drivers
that is: AER, PME, BW notifications, hotplug, and DPC. However, this is
not a huge disadvantage on PowerNV since these services are either unused
or handled through other means.

Fixes: 66725152fb9f ("PCI/hotplug: PowerPC PowerNV PCI hotplug driver")
Signed-off-by: Oliver O'Halloran <oohall@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20191118065553.30362-1-oohall@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>