ACPI / hotplug / PCI: Allow slots without new devices to be rescanned

Currently, enable_device() checks the return value of pci_scan_slot()
and returns immediately if that's 0 (meaning that no new functions
have been found in the slot).  However, if one of the functions in
the slot is a bridge, some new devices may appear below it even if
the bridge itself is present continuously, so it generally is
necessary to do the rescan anyway just in case.  [In particular,
that's necessary with the Thunderbolt daisy chaining in which case
new devices may be connected to the existing ones down the chain.]

The correctness of this change relies on the ability of
pcibios_resource_survey_bus() to detect if it has already been called
for the given bus and to skip it if so.  Failure to do that will lead
to resource allocation conflicts.

[rjw: Changelog]
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

1 files changed, 2 insertions, 9 deletions

diff --git a/drivers/pci/hotplug/acpiphp_glue.c b/drivers/pci/hotplug/acpiphp_glue.c
index c7a668e1fc12..21a6269501e1 100644
--- a/drivers/pci/hotplug/acpiphp_glue.c
+++ b/drivers/pci/hotplug/acpiphp_glue.c
@@ -542,18 +542,13 @@ static int __ref enable_device(struct acpiphp_slot *slot)
         struct pci_dev *dev;
         struct pci_bus *bus = slot->bus;
         struct acpiphp_func *func;
-        int num, max, pass;
+        int max, pass;
         LIST_HEAD(add_list);
 
         list_for_each_entry(func, &slot->funcs, sibling)
                 acpiphp_bus_add(func_to_handle(func));
 
-        num = pci_scan_slot(bus, PCI_DEVFN(slot->device, 0));
-        if (num == 0) {
-                /* Maybe only part of funcs are added. */
-                dbg("No new device found\n");
-                goto err_exit;
-        }
+        pci_scan_slot(bus, PCI_DEVFN(slot->device, 0));
 
         max = acpiphp_max_busnr(bus);
         for (pass = 0; pass < 2; pass++) {
@@ -599,8 +594,6 @@ static int __ref enable_device(struct acpiphp_slot *slot)
                 }
         }
 
-
- err_exit:
         return 0;
 }