PCI: pciehp: Drop pointless ACPI-based "slot detection" check

Jarod Wilson reports that ExpressCard hotplug doesn't work on HP ZBook G2.
The problem turns out to be the ACPI-based "slot detection" code called
from pciehp_probe() which uses questionable heuristics based on what ACPI
objects are present for the PCIe port device to figure out whether 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 ZBook has _RMV.  Of course, Thunderbolt and PCIe
native hotplug need not be mutually exclusive (as they aren't on the
ZBook), 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://lkml.kernel.org/r/1431632038-39917-1-git-send-email-jarod@redhat.com
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>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Jarod Wilson <jarod@redhat.com>
Tested-by: Jarod Wilson <jarod@redhat.com>

drivers/pci/hotplug/Makefile

@@ -61,9 +61,6 @@ pciehp-objs		:=	pciehp_core.o	\
 				pciehp_ctrl.o	\
 				pciehp_pci.o	\
 				pciehp_hpc.o
-ifdef CONFIG_ACPI
-pciehp-objs		+=	pciehp_acpi.o
-endif
 
 shpchp-objs		:=	shpchp_core.o	\
 				shpchp_ctrl.o	\

drivers/pci/hotplug/pciehp.h

@@ -167,21 +167,4 @@ static inline const char *slot_name(struct slot *slot)
 	return hotplug_slot_name(slot->hotplug_slot);
 }
 
-#ifdef CONFIG_ACPI
-#include <linux/pci-acpi.h>
-
-void __init pciehp_acpi_slot_detection_init(void);
-int pciehp_acpi_slot_detection_check(struct pci_dev *dev);
-
-static inline void pciehp_firmware_init(void)
-{
-	pciehp_acpi_slot_detection_init();
-}
-#else
-#define pciehp_firmware_init()				do {} while (0)
-static inline int pciehp_acpi_slot_detection_check(struct pci_dev *dev)
-{
-	return 0;
-}
-#endif				/* CONFIG_ACPI */
 #endif				/* _PCIEHP_H */

drivers/pci/hotplug/pciehp_core.c

@@ -248,12 +248,9 @@ static int pciehp_probe(struct pcie_device *dev)
 	struct slot *slot;
 	u8 occupied, poweron;
 
-	if (pciehp_force)
-		dev_info(&dev->device,
-			 "Bypassing BIOS check for pciehp use on %s\n",
-			 pci_name(dev->port));
-	else if (pciehp_acpi_slot_detection_check(dev->port))
-		goto err_out_none;
+	/* If this is not a "hotplug" service, we have no business here. */
+	if (dev->service != PCIE_PORT_SERVICE_HP)
+		return -ENODEV;
 
 	if (!dev->port->subordinate) {
 		/* Can happen if we run out of bus numbers during probe */
@@ -366,7 +363,6 @@ static int __init pcied_init(void)
 {
 	int retval = 0;
 
-	pciehp_firmware_init();
 	retval = pcie_port_service_register(&hpdriver_portdrv);
 	dbg("pcie_port_service_register = %d\n", retval);
 	info(DRIVER_DESC " version: " DRIVER_VERSION "\n");