Re: [PATCH] PCIe / hotplug: Drop pointless ACPI-based "slot detection" check

Rafael J. Wysocki
2015-05-19T13:04:00Z

On Tuesday, May 19, 2015 08:42:00 AM Jarod Wilson wrote:
> On 5/19/2015 7:43 AM, Rafael J. Wysocki wrote:
> > From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> >
> > Jarod Wilson reports that the expresscard hotplug setup doesn't work
> > on HP ZBook G2. The problem turns out to be the ACPI-based "slot
> > detection" code called from pciehp_probe() which tries to use some
> > questionable heuristics based on what ACPI objects are present for
> > the PCIe port device at hand to figure out whether or not to register
> > a hotplug slot for that port.
> >
> > That code is used if there is at least one PCIe port having an ACPI
> > device configuration object related to hotplug (such as _EJ0 or _RMV)
> > and the Thunderbolt port on the affected machine has _RMV. Of course,
> > Thunderbolt and PCIe native hotplug need not be mutually exclusive
> > (as they aren't on the machine in question), so that rule is simply
> > incorrect.
> >
> > Moreover, the ACPI-based "slot detection" check does not add any
> > value if pciehp_probe() is called at all and the service type of the
> > device object it has been called for is PCIE_PORT_SERVICE_HP, because
> > PCIe hotplug services are only registered if the _OSC handshake in
> > acpi_pci_root_add() allows the kernel to control the PCIe native
> > hotplug feature. No more checks need to be carried out to decide
> > whether or not to register a native PCIe hotlug slot in that case.
> >
> > For the above reasons, make pciehp_probe() check if it has been
> > called for the right service type and drop the pointless ACPI-based
> > "slot detection" check from it. Also remove the entire code whose
> > only user is that check (the entire pciehp_acpi.c file goes away
> > as a result) and drop function headers related to it from the
> > internal PCIeHP header file.
> >
> > Link: http://marc.info/?t=143163219300002&r=1&w=2
> > Link: https://bugzilla.kernel.org/show_bug.cgi?id=98581
> > Reported-by: Jarod Wilson <jarod@redhat.com>
> > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> > ---
> >
> > Bjorn, that's -stable material I think. It should be applicable at least
> > since commit 5ba113f7c4fb (PCI: acpiphp: Handle PCIe ports without native
> > hotplug capability) that was shipped in 3.10.
> >
> > Thanks!
>
> I believe you also want to rip the pciehp_acpi.o hunk out of
> drivers/pci/hotplug/Makefile,

Right, just sent an updated patch.

> but I made more or less the exact same
> changes here, and am about to give them a spin on the ZBook 17.

Cool, thanks!

--
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.