usb: assign usb3 external hub port peers

Given that root hub port peers are already established, external hub peer
ports can be determined by traversing the device topology:

1/ ascend to the parent hub and find the upstream port_dev

2/ walk ->peer to find the peer port

3/ descend to the peer hub via ->child

4/ find the port with the matching port id

Note that this assumes the port labeling scheme required by the
specification [1].

[1]: usb3 3.1 section 10.3.3

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, 24 insertions, 8 deletions

diff --git a/drivers/usb/core/port.c b/drivers/usb/core/port.c
index 5ecdbf31dfcb..9b7496b52f2a 100644
--- a/drivers/usb/core/port.c
+++ b/drivers/usb/core/port.c
@@ -187,15 +187,18 @@ static void unlink_peers(struct usb_port *left, struct usb_port *right)
         left->peer = NULL;
 }
 
-/* set the default peer port for root hubs */
+/*
+ * Set the default peer port for root hubs, or via the upstream peer
+ * relationship for all other hubs
+ */
 static void find_and_link_peer(struct usb_hub *hub, int port1)
 {
         struct usb_port *port_dev = hub->ports[port1 - 1], *peer;
         struct usb_device *hdev = hub->hdev;
+        struct usb_device *peer_hdev;
+        struct usb_hub *peer_hub;
 
         if (!hdev->parent) {
-                struct usb_hub *peer_hub;
-                struct usb_device *peer_hdev;
                 struct usb_hcd *hcd = bus_to_hcd(hdev->bus);
                 struct usb_hcd *peer_hcd = hcd->shared_hcd;
 
@@ -203,15 +206,28 @@ static void find_and_link_peer(struct usb_hub *hub, int port1)
                         return;
 
                 peer_hdev = peer_hcd->self.root_hub;
-                peer_hub = usb_hub_to_struct_hub(peer_hdev);
-                if (!peer_hub || port1 > peer_hdev->maxchild)
+        } else {
+                struct usb_port *upstream;
+                struct usb_device *parent = hdev->parent;
+                struct usb_hub *parent_hub = usb_hub_to_struct_hub(parent);
+
+                if (!parent_hub)
                         return;
 
-                peer = peer_hub->ports[port1 - 1];
+                upstream = parent_hub->ports[hdev->portnum - 1];
+                if (!upstream || !upstream->peer)
+                        return;
 
-                if (peer)
-                        link_peers(port_dev, peer);
+                peer_hdev = upstream->peer->child;
         }
+
+        peer_hub = usb_hub_to_struct_hub(peer_hdev);
+        if (!peer_hub || port1 > peer_hdev->maxchild)
+                return;
+
+        peer = peer_hub->ports[port1 - 1];
+        if (peer)
+                link_peers(port_dev, peer);
 }
 
 int usb_hub_create_port_device(struct usb_hub *hub, int port1)