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

Rafael J. Wysocki
2015-05-19T13:02:42Z

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>
---

Changes in Makefile were missing from the previous version.

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!

---
drivers/pci/hotplug/Makefile | 3
drivers/pci/hotplug/pciehp.h | 17 ----
drivers/pci/hotplug/pciehp_acpi.c | 137 --------------------------------------
drivers/pci/hotplug/pciehp_core.c | 10 --
4 files changed, 3 insertions(+), 164 deletions(-)

Index: linux-pm/drivers/pci/hotplug/pciehp_core.c
===================================================================
--- linux-pm.orig/drivers/pci/hotplug/pciehp_core.c
+++ linux-pm/drivers/pci/hotplug/pciehp_core.c
@@ -248,12 +248,9 @@ static int pciehp_probe(struct pcie_devi
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");
Index: linux-pm/drivers/pci/hotplug/pciehp_acpi.c
===================================================================
--- linux-pm.orig/drivers/pci/hotplug/pciehp_acpi.c
+++ /dev/null
@@ -1,137 +0,0 @@
-/*
- * ACPI related functions for PCI Express Hot Plug driver.
- *
- * Copyright (C) 2008 Kenji Kaneshige
- * Copyright (C) 2008 Fujitsu Limited.
- *
- * All rights reserved.
- *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation; either version 2 of the License, or (at
- * your option) any later version.
- *
- * This program is distributed in the hope that it will be useful, but
- * WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
- * NON INFRINGEMENT. See the GNU General Public License for more
- * details.
- *
- * You should have received a copy of the GNU General Public License
- * along with this program; if not, write to the Free Software
- * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
- *
- */
-
-#include <linux/acpi.h>
-#include <linux/pci.h>
-#include <linux/pci_hotplug.h>
-#include <linux/slab.h>
-#include <linux/module.h>
-#include "pciehp.h"
-
-#define PCIEHP_DETECT_PCIE (0)
-#define PCIEHP_DETECT_ACPI (1)
-#define PCIEHP_DETECT_AUTO (2)
-#define PCIEHP_DETECT_DEFAULT PCIEHP_DETECT_AUTO
-
-struct dummy_slot {
- u32 number;
- struct list_head list;
-};
-
-static int slot_detection_mode;
-static char *pciehp_detect_mode;
-module_param(pciehp_detect_mode, charp, 0444);
-MODULE_PARM_DESC(pciehp_detect_mode,
- "Slot detection mode: pcie, acpi, auto\n"
- " pcie - Use PCIe based slot detection\n"
- " acpi - Use ACPI for slot detection\n"
- " auto(default) - Auto select mode. Use acpi option if duplicate\n"
- " slot ids are found. Otherwise, use pcie option\n");
-
-int pciehp_acpi_slot_detection_check(struct pci_dev *dev)
-{
- if (slot_detection_mode != PCIEHP_DETECT_ACPI)
- return 0;
- if (acpi_pci_detect_ejectable(ACPI_HANDLE(&dev->dev)))
- return 0;
- return -ENODEV;
-}
-
-static int __init parse_detect_mode(void)
-{
- if (!pciehp_detect_mode)
- return PCIEHP_DETECT_DEFAULT;
- if (!strcmp(pciehp_detect_mode, "pcie"))
- return PCIEHP_DETECT_PCIE;
- if (!strcmp(pciehp_detect_mode, "acpi"))
- return PCIEHP_DETECT_ACPI;
- if (!strcmp(pciehp_detect_mode, "auto"))
- return PCIEHP_DETECT_AUTO;
- warn("bad specifier '%s' for pciehp_detect_mode. Use default\n",
- pciehp_detect_mode);
- return PCIEHP_DETECT_DEFAULT;
-}
-
-static int __initdata dup_slot_id;
-static int __initdata acpi_slot_detected;
-static struct list_head __initdata dummy_slots = LIST_HEAD_INIT(dummy_slots);
-
-/* Dummy driver for duplicate name detection */
-static int __init dummy_probe(struct pcie_device *dev)
-{
- u32 slot_cap;
- acpi_handle handle;
- struct dummy_slot *slot, *tmp;
- struct pci_dev *pdev = dev->port;
-
- pcie_capability_read_dword(pdev, PCI_EXP_SLTCAP, &slot_cap);
- slot = kzalloc(sizeof(*slot), GFP_KERNEL);
- if (!slot)
- return -ENOMEM;
- slot->number = (slot_cap & PCI_EXP_SLTCAP_PSN) >> 19;
- list_for_each_entry(tmp, &dummy_slots, list) {
- if (tmp->number == slot->number)
- dup_slot_id++;
- }
- list_add_tail(&slot->list, &dummy_slots);
- handle = ACPI_HANDLE(&pdev->dev);
- if (!acpi_slot_detected && acpi_pci_detect_ejectable(handle))
- acpi_slot_detected = 1;
- return -ENODEV; /* dummy driver always returns error */
-}
-
-static struct pcie_port_service_driver __initdata dummy_driver = {
- .name = "pciehp_dummy",
- .port_type = PCIE_ANY_PORT,
- .service = PCIE_PORT_SERVICE_HP,
- .probe = dummy_probe,
-};
-
-static int __init select_detection_mode(void)
-{
- struct dummy_slot *slot, *tmp;
-
- if (pcie_port_service_register(&dummy_driver))
- return PCIEHP_DETECT_ACPI;
- pcie_port_service_unregister(&dummy_driver);
- list_for_each_entry_safe(slot, tmp, &dummy_slots, list) {
- list_del(&slot->list);
- kfree(slot);
- }
- if (acpi_slot_detected && dup_slot_id)
- return PCIEHP_DETECT_ACPI;
- return PCIEHP_DETECT_PCIE;
-}
-
-void __init pciehp_acpi_slot_detection_init(void)
-{
- slot_detection_mode = parse_detect_mode();
- if (slot_detection_mode != PCIEHP_DETECT_AUTO)
- goto out;
- slot_detection_mode = select_detection_mode();
-out:
- if (slot_detection_mode == PCIEHP_DETECT_ACPI)
- info("Using ACPI for slot detection.\n");
-}
Index: linux-pm/drivers/pci/hotplug/pciehp.h
===================================================================
--- linux-pm.orig/drivers/pci/hotplug/pciehp.h
+++ linux-pm/drivers/pci/hotplug/pciehp.h
@@ -167,21 +167,4 @@ static inline const char *slot_name(stru
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 */
Index: linux-pm/drivers/pci/hotplug/Makefile
===================================================================
--- linux-pm.orig/drivers/pci/hotplug/Makefile
+++ linux-pm/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 \