usb: xhci-dbg: Display endpoint number and direction in context dump

When CONFIG_XHCI_HCD_DEBUGGING is activated, the XHCI driver can dump
device and input contexts to the console. The endpoint contexts in that
dump are labeled "Endpoint N Context", where N is the XHCI endpoint
index (DCI - 1). This can be very confusing, especially for people who
are not that familiar with the XHCI specification. This patch introduces
an xhci_get_endpoint_address function (as a counterpart to the reverse
xhci_get_endpoint_index), and uses it to additionally display the
endpoint number and direction when dumping contexts, which are much more
commonly used concepts in USB.

Signed-off-by: Julius Werner <jwerner@chromium.org>
Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>
diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
index b4aa79d..9e72caf 100644
--- a/drivers/usb/host/xhci.c
+++ b/drivers/usb/host/xhci.c
@@ -1111,6 +1111,16 @@
 	return index;
 }
 
+/* The reverse operation to xhci_get_endpoint_index. Calculate the USB endpoint
+ * address from the XHCI endpoint index.
+ */
+unsigned int xhci_get_endpoint_address(unsigned int ep_index)
+{
+	unsigned int number = DIV_ROUND_UP(ep_index, 2);
+	unsigned int direction = ep_index % 2 ? USB_DIR_OUT : USB_DIR_IN;
+	return direction | number;
+}
+
 /* Find the flag for this endpoint (for use in the control context).  Use the
  * endpoint index to create a bitmask.  The slot context is bit 0, endpoint 0 is
  * bit 1, etc.