On Fri, Sep 6, 2013 at 6:43 AM, Rafael J. Wysocki <rjw@xxxxxxx> wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
>
> Sometimes we may get a spurious device check or bus check notify for
> a hotplug device and in those cases we should avoid doing all of the
> configuration work needed when something actually changes. To that
> end, check the return value of pci_scan_slot() in enable_slot() and
> bail out early if it is 0.
>
> This turns out to help reduce the amount of diagnostic output from
> the ACPIPHP subsystem and speed up boot on at least one system that
> generates multiple device check notifies for PCIe ports during
> boot.
>
> Reported-by: Alex Williamson <alex.williamson@xxxxxxxxxx>
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
> ---
> drivers/pci/hotplug/acpiphp_glue.c | 35 +++++++++++++++++++++++++++--------
> 1 file changed, 27 insertions(+), 8 deletions(-)
>
> Index: linux-pm/drivers/pci/hotplug/acpiphp_glue.c
> ===================================================================
> --- linux-pm.orig/drivers/pci/hotplug/acpiphp_glue.c
> +++ linux-pm/drivers/pci/hotplug/acpiphp_glue.c
> @@ -542,12 +542,12 @@ static void __ref enable_slot(struct acp
> struct acpiphp_func *func;
> int max, pass;
> LIST_HEAD(add_list);
> + int nr_found;
>
> list_for_each_entry(func, &slot->funcs, sibling)
> acpiphp_bus_add(func_to_handle(func));
>
> - pci_scan_slot(bus, PCI_DEVFN(slot->device, 0));
> -
> + nr_found = pci_scan_slot(bus, PCI_DEVFN(slot->device, 0));
> max = acpiphp_max_busnr(bus);
> for (pass = 0; pass < 2; pass++) {
> list_for_each_entry(dev, &bus->devices, bus_list) {
> @@ -566,8 +566,11 @@ static void __ref enable_slot(struct acp
> }
> }
> }
> -
> __pci_bus_assign_resources(bus, &add_list, NULL);
> + /* Nothing more to do here if there are no new devices on this bus. */
> + if (!nr_found && (slot->flags & SLOT_ENABLED))
> + return;
> +
> acpiphp_sanitize_bus(bus);
> acpiphp_set_hpp_values(bus);
> acpiphp_set_acpi_region(slot);
>
why not just returning early before size bridges and assign unassign resources?
Yinghai
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