ACPI / hotplug / PCI: Make device_is_managed_by_native_pciehp() public
We're about to add runtime PM of hotplug ports, but we need to restrict it
to ports that are handled natively by the OS: If they're handled by the
firmware (which is the case for Thunderbolt on non-Macs), things would
break if the OS put the ports into D3hot behind the firmware's back.
To determine if a hotplug port is handled natively, one has to walk up from
the port to the root bridge and check the cached _OSC Control Field for the
value of the "PCI Express Native Hot Plug control" bit. There's already a
function to do that, device_is_managed_by_native_pciehp(), but it's private
to drivers/pci/hotplug/acpiphp_glue.c and only compiled in if
CONFIG_HOTPLUG_PCI_ACPI is enabled.
Make it public and move it to drivers/pci/pci-acpi.c, so that it is
available in the more general CONFIG_ACPI case.
The function contains a check if the device in question is a hotplug port
and returns false if it's not. The caller we're going to add doesn't need
this as it only calls the function if it actually *is* a hotplug port.
Move the check out of the function into the single existing caller.
Rename it to pciehp_is_native() and add some kerneldoc and polish.
No functional change intended.
Tested-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
diff --git a/drivers/pci/pci-acpi.c b/drivers/pci/pci-acpi.c
index d966d47..ed3daa8 100644
--- a/drivers/pci/pci-acpi.c
+++ b/drivers/pci/pci-acpi.c
@@ -294,6 +294,30 @@ int pci_get_hp_params(struct pci_dev *dev, struct hotplug_params *hpp)
EXPORT_SYMBOL_GPL(pci_get_hp_params);
/**
+ * pciehp_is_native - Check whether a hotplug port is handled by the OS
+ * @pdev: Hotplug port to check
+ *
+ * Walk up from @pdev to the host bridge, obtain its cached _OSC Control Field
+ * and return the value of the "PCI Express Native Hot Plug control" bit.
+ * On failure to obtain the _OSC Control Field return %false.
+ */
+bool pciehp_is_native(struct pci_dev *pdev)
+{
+ struct acpi_pci_root *root;
+ acpi_handle handle;
+
+ handle = acpi_find_root_bridge_handle(pdev);
+ if (!handle)
+ return false;
+
+ root = acpi_pci_find_root(handle);
+ if (!root)
+ return false;
+
+ return root->osc_control_set & OSC_PCI_EXPRESS_NATIVE_HP_CONTROL;
+}
+
+/**
* pci_acpi_wake_bus - Root bus wakeup notification fork function.
* @work: Work item to handle.
*/
