For optimal power consumption of USB4 routers the XHCI PCIe endpoint used for tunneling must be in D3. Historically this is accomplished by a long list of PCIe IDs that correspond to these endpoints. The linux thunderbolt CM currently uses the `usb4-host-interface` ACPI property to create a device link between the USB4 host router PCIe endpoint and the XHCI PCIe endpoint. The device link will move the devices in out of D3 together. To avoid having to maintain this never ending list of PCIe IDs, use the existence of `usb4-host-interface` property on a USB port as a proxy to allow runtime PM for these controllers. The device links will continue to be created when the CM initializes the USB4 host router and also discovers this property. Link: https://learn.microsoft.com/en-us/windows-hardware/design/component-guidelines/usb4-acpi-requirements#port-mapping-_dsd-for-usb-3x-and-pcie Signed-off-by: Mario Limonciello <mario.limonciello@xxxxxxx> --- RFC v1->PATCH v1 * Move this detection from Thunderbolt CM into USB core --- drivers/usb/core/usb-acpi.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/drivers/usb/core/usb-acpi.c b/drivers/usb/core/usb-acpi.c index 6d93428432f13..f91ab4fd84cf8 100644 --- a/drivers/usb/core/usb-acpi.c +++ b/drivers/usb/core/usb-acpi.c @@ -177,6 +177,15 @@ usb_acpi_find_companion_for_port(struct usb_port *port_dev) port_dev->connect_type = usb_acpi_get_connect_type(handle, pld); ACPI_FREE(pld); } + if (!acpi_dev_get_property(adev, "usb4-host-interface", + ACPI_TYPE_ANY, NULL)) { + struct device *dev = &port_dev->dev; + + while (dev && !dev_is_pci(dev)) + dev = dev->parent; + if (dev) + pm_runtime_allow(dev); + } return adev; } -- 2.34.1
