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    Subject[PATCH v1 2/2] ACPI: PCI: hotplug: Avoid setting is_hotplug_bridge for PCIe Upstream Ports
    Date
    From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

    It is reported that on some systems pciehp binds to an Upstream Port and
    attempts to operate it which causes devices below the Port to disappear
    from the bus.

    This happens because acpiphp sets is_hotplug_bridge for that Port (after
    receiving a Device Check notification on it from the platform firmware
    via ACPI) during the enumeration of PCI devices and so when
    get_port_device_capability() runs, it sees that is_hotplug_bridge is
    set and adds PCIE_PORT_SERVICE_HP to Port services (which allows pciehp
    to bind to the Port in question).

    Even though this particular problem can be addressed by making the
    portdrv_core checks more robust, it also causes power management to
    work differently on the affected systems which generally is not
    desirable (PCIe Ports with is_hotplug_bridge set have to pass
    additional tests to be allowed to go into the D3hot/cold power
    states which affects runtime PM of devices below these Ports).

    For this reason, amend check_hotplug_bridge() with a PCIe type check
    to prevent it from setting is_hotplug_bridge for Upstream Ports.

    Reported-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
    Suggested-by: Lukas Wunner <lukas@wunner.de>
    Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
    ---
    drivers/pci/hotplug/acpiphp_glue.c | 8 ++++++++
    1 file changed, 8 insertions(+)

    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
    @@ -411,6 +411,14 @@ static void check_hotplug_bridge(struct
    if (dev->is_hotplug_bridge)
    return;

    + /*
    + * In the PCIe case, only Root Ports and Downstream Ports are capable of
    + * accommodating hotplug devices, so avoid marking Upstream Ports as
    + * "hotplug bridges".
    + */
    + if (pci_is_pcie(dev) && pci_pcie_type(dev) == PCI_EXP_TYPE_UPSTREAM)
    + return;
    +
    list_for_each_entry(func, &slot->funcs, sibling) {
    if (PCI_FUNC(dev->devfn) == func->function) {
    dev->is_hotplug_bridge = 1;


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