usb: find internal hub tier mismatch via acpi

ACPI identifies peer ports by setting their 'group_token' and
'group_position' _PLD data to the same value.  If a platform has tier
mismatch [1] , ACPI can override the default (USB3 defined) peer port
association for internal hubs.  External hubs follow the default peer
association scheme.

Location data is cached as an opaque cookie in usb_port_location data.

Note that we only consider the group_token and group_position attributes
from the _PLD data as ACPI specifies that group_token is a unique
identifier.

When we find port location data for a port then we assume that the
firmware will also describe its peer port.  This allows the
implementation to only ever set the peer once.  This leads to a question
about what happens when a pm runtime event occurs while the peer
associations are still resolving.  Since we only ever set the peer
information once, a USB3 port needs to be prevented from suspending
while its ->peer pointer is NULL (implemented in a subsequent patch).

There is always the possibility that firmware mis-identifies the ports,
but there is not much the kernel can do in that case.

[1]: xhci 1.1 appendix D figure 131
[2]: acpi 5 section 6.1.8

[alan]: don't do default peering when acpi data present
Suggested-by: Alan Stern <stern@rowland.harvard.edu>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 2 insertions, 0 deletions

diff --git a/drivers/usb/core/hub.h b/drivers/usb/core/hub.h
index fcad5f9d12f0..048c797f394c 100644
--- a/drivers/usb/core/hub.h
+++ b/drivers/usb/core/hub.h
@@ -84,6 +84,7 @@ struct usb_hub {
  * @port_owner: port's owner
  * @peer: related usb2 and usb3 ports (share the same connector)
  * @connect_type: port's connect type
+ * @location: opaque representation of platform connector location
  * @portnum: port index num based one
  * @power_is_on: port's power state
  * @did_runtime_put: port has done pm_runtime_put().
@@ -94,6 +95,7 @@ struct usb_port {
 	struct usb_dev_state *port_owner;
 	struct usb_port *peer;
 	enum usb_port_connect_type connect_type;
+	usb_port_location_t location;
 	u8 portnum;
 	unsigned power_is_on:1;
 	unsigned did_runtime_put:1;