USB: xhci: Performance - move functions that find ep ring.

I've been using perf to measure the top symbols while transferring 1GB of data
on a USB 3.0 drive with dd.  This is using the raw disk with /dev/sdb, with a
block size of 1K.

During performance testing, the top symbol was xhci_triad_to_transfer_ring(), a
function that should return immediately if streams are not enabled for an
endpoint.  It turned out that the functions to find the endpoint ring was
defined in xhci-mem.c and used in xhci-ring.c and xhci-hcd.c.  I moved a copy of
xhci_triad_to_transfer_ring() and xhci_urb_to_transfer_ring() into xhci-ring.c
and declared them static.  I also made a static version of
xhci_urb_to_transfer_ring() in xhci.c.

This improved throughput on a 1GB read of the raw disk with dd from
186MB/s to 195MB/s, and perf reported sampling the xhci_triad_to_transfer_ring()
0.06% of the time, rather than 9.26% of the time.

Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 41 insertions, 0 deletions

diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
index 89ac48534099..f5e0b00cbb83 100644
--- a/drivers/usb/host/xhci.c
+++ b/drivers/usb/host/xhci.c
@@ -916,6 +916,47 @@ dying:
         return -ESHUTDOWN;
 }
 
+/* Get the right ring for the given URB.
+ * If the endpoint supports streams, boundary check the URB's stream ID.
+ * If the endpoint doesn't support streams, return the singular endpoint ring.
+ */
+static struct xhci_ring *xhci_urb_to_transfer_ring(struct xhci_hcd *xhci,
+                struct urb *urb)
+{
+        unsigned int slot_id;
+        unsigned int ep_index;
+        unsigned int stream_id;
+        struct xhci_virt_ep *ep;
+
+        slot_id = urb->dev->slot_id;
+        ep_index = xhci_get_endpoint_index(&urb->ep->desc);
+        stream_id = urb->stream_id;
+        ep = &xhci->devs[slot_id]->eps[ep_index];
+        /* Common case: no streams */
+        if (!(ep->ep_state & EP_HAS_STREAMS))
+                return ep->ring;
+
+        if (stream_id == 0) {
+                xhci_warn(xhci,
+                                "WARN: Slot ID %u, ep index %u has streams, "
+                                "but URB has no stream ID.\n",
+                                slot_id, ep_index);
+                return NULL;
+        }
+
+        if (stream_id < ep->stream_info->num_streams)
+                return ep->stream_info->stream_rings[stream_id];
+
+        xhci_warn(xhci,
+                        "WARN: Slot ID %u, ep index %u has "
+                        "stream IDs 1 to %u allocated, "
+                        "but stream ID %u is requested.\n",
+                        slot_id, ep_index,
+                        ep->stream_info->num_streams - 1,
+                        stream_id);
+        return NULL;
+}
+
 /*
  * Remove the URB's TD from the endpoint ring.  This may cause the HC to stop
  * USB transfers, potentially stopping in the middle of a TRB buffer.  The HC