USB: Support for allocating USB 3.0 streams.

Bulk endpoint streams were added in the USB 3.0 specification.  Streams
allow a device driver to overload a bulk endpoint so that multiple
transfers can be queued at once.

The device then decides which transfer it wants to work on first, and can
queue part of a transfer before it switches to a new stream.  All this
switching is invisible to the device driver, which just gets a completion
for the URB.  Drivers that use streams must be able to handle URBs
completing in a different order than they were submitted to the endpoint.

This requires adding new API to set up xHCI data structures to support
multiple queues ("stream rings") per endpoint.  Drivers will allocate a
number of stream IDs before enqueueing URBs to the bulk endpoints of the
device, and free the stream IDs in their disconnect function.  See
Documentation/usb/bulk-streams.txt for details.

The new mass storage device class, USB Attached SCSI Protocol (UASP), uses
these streams API.

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

2 files changed, 71 insertions, 0 deletions

diff --git a/drivers/usb/core/hcd.c b/drivers/usb/core/hcd.c
index 6a05e6934455..3aaee2811f01 100644
--- a/drivers/usb/core/hcd.c
+++ b/drivers/usb/core/hcd.c
@@ -1814,6 +1814,75 @@ void usb_hcd_reset_endpoint(struct usb_device *udev,
         }
 }
 
+/**
+ * usb_alloc_streams - allocate bulk endpoint stream IDs.
+ * @interface:          alternate setting that includes all endpoints.
+ * @eps:                array of endpoints that need streams.
+ * @num_eps:            number of endpoints in the array.
+ * @num_streams:        number of streams to allocate.
+ * @mem_flags:          flags hcd should use to allocate memory.
+ *
+ * Sets up a group of bulk endpoints to have num_streams stream IDs available.
+ * Drivers may queue multiple transfers to different stream IDs, which may
+ * complete in a different order than they were queued.
+ */
+int usb_alloc_streams(struct usb_interface *interface,
+                struct usb_host_endpoint **eps, unsigned int num_eps,
+                unsigned int num_streams, gfp_t mem_flags)
+{
+        struct usb_hcd *hcd;
+        struct usb_device *dev;
+        int i;
+
+        dev = interface_to_usbdev(interface);
+        hcd = bus_to_hcd(dev->bus);
+        if (!hcd->driver->alloc_streams || !hcd->driver->free_streams)
+                return -EINVAL;
+        if (dev->speed != USB_SPEED_SUPER)
+                return -EINVAL;
+
+        /* Streams only apply to bulk endpoints. */
+        for (i = 0; i < num_eps; i++)
+                if (!usb_endpoint_xfer_bulk(&eps[i]->desc))
+                        return -EINVAL;
+
+        return hcd->driver->alloc_streams(hcd, dev, eps, num_eps,
+                        num_streams, mem_flags);
+}
+EXPORT_SYMBOL_GPL(usb_alloc_streams);
+
+/**
+ * usb_free_streams - free bulk endpoint stream IDs.
+ * @interface:  alternate setting that includes all endpoints.
+ * @eps:        array of endpoints to remove streams from.
+ * @num_eps:    number of endpoints in the array.
+ * @mem_flags:  flags hcd should use to allocate memory.
+ *
+ * Reverts a group of bulk endpoints back to not using stream IDs.
+ * Can fail if we are given bad arguments, or HCD is broken.
+ */
+void usb_free_streams(struct usb_interface *interface,
+                struct usb_host_endpoint **eps, unsigned int num_eps,
+                gfp_t mem_flags)
+{
+        struct usb_hcd *hcd;
+        struct usb_device *dev;
+        int i;
+
+        dev = interface_to_usbdev(interface);
+        hcd = bus_to_hcd(dev->bus);
+        if (dev->speed != USB_SPEED_SUPER)
+                return;
+
+        /* Streams only apply to bulk endpoints. */
+        for (i = 0; i < num_eps; i++)
+                if (!usb_endpoint_xfer_bulk(&eps[i]->desc))
+                        return;
+
+        hcd->driver->free_streams(hcd, dev, eps, num_eps, mem_flags);
+}
+EXPORT_SYMBOL_GPL(usb_free_streams);
+
 /* Protect against drivers that try to unlink URBs after the device
  * is gone, by waiting until all unlinks for @udev are finished.
  * Since we don't currently track URBs by device, simply wait until
diff --git a/drivers/usb/host/xhci-pci.c b/drivers/usb/host/xhci-pci.c
index 98a73cd20cc6..d295bbc15eb7 100644
--- a/drivers/usb/host/xhci-pci.c
+++ b/drivers/usb/host/xhci-pci.c
@@ -132,6 +132,8 @@ static const struct hc_driver xhci_pci_hc_driver = {
         .urb_dequeue =          xhci_urb_dequeue,
         .alloc_dev =            xhci_alloc_dev,
         .free_dev =             xhci_free_dev,
+        .alloc_streams =        xhci_alloc_streams,
+        .free_streams =         xhci_free_streams,
         .add_endpoint =         xhci_add_endpoint,
         .drop_endpoint =        xhci_drop_endpoint,
         .endpoint_reset =       xhci_endpoint_reset,